(完整版)桥梁毕业设计外文翻译
桥梁毕业设计外文翻译5
附录附录A 外文翻译第一部分英文原文4.2.2 Model that Failed in Punching ShearIt was realized that complete restraint in both the longitudinal and transversedirections is necessary for the development of the internal arching system in the deck slab. With this realization,another half-scale model of a two-girder bridge was built. This model also had a deck slab reinforced only by polypropylene fibres, and was very similar to the previous one, the main difference being that the top flangesof the girders were now interconnected by transverse steel straps lying outside the deck slab. A view of the steel work of this model can be seen in Fig. 4.7.These straps were provided so as to serve as transverse ties to the internal arch in the slab.The 100 mm thick slab of the model with transverse straps failed under a central load of 418 kN in a punching-shear failure mode. As can be seen in Fig. 4.8, the damaged area of the slab was highly localized. It can be appreciated that with such a high failure load, the thin deck slab of the half-scale model could have easily withstood the weights of even the heaviest wheel load of commercial vehicles.The model tests described above and in sub-section 4.2.1 clearly demonstrate that an internal arching action will indeed develop in a deck slab, but only if it is suitably restrained.4.2.3 Edge StiffeningA further appreciation of the deck slab arching action is provided by tests on a scale model of a skew slab-on-girder bridge. As will be discussed in sub-section 4.4.2, one transverse free edge of the deck slab of this model was stiffened by a composite steel channel with its web in the vertical plane. The other free edge was stiffened by a steel channel diaphragm with its web horizontal and connected to the deck slab through shear connectors. The deck slab near the former transverse edge failed in a mode that was a hybrid between punching shear and flexure. Tests near the composite diaphragm led to failure at a much higher load in punching shear (Bakht and Agarwal, 1993).The above tests confirmed yet again that the presence of the internal arching action in deck slabs induces high in-plane force effects which in turn demand stiffer restraint in the plane of the deck than in the out-of-plane direction.4.3 INTERNALLY RESTRAINED DECK SLABSDeck slabs which require embedded reinforcement for strength will now be referred to as internally restrained deck slabs. The state-of-art up to 1986 relating to the quantification and utilization of the beneficial internal arching action in deck slabs with steel reinforcement has been provided by Bakht and Markovic (1986). Their conclusions complemented with up-to-date information are presented in this chapter in a generally chronological order which, however, cannot be adhered to rigidlybecause of the simultaneous occurrence of some developments.4.3.1 Static Tests on Scale ModelsAbout three decades ago, the Structures Research Office of the Ministry of Transportation of Ontario (MTO), Canada, sponsored an extensive laboratory-based research program into the load carrying capacity of deck slabs; this research program was carried out at Queen's University, Kingston, Ontario. Most of this research was conducted through static tests on scale models of slab-on-girder bridges. This pioneering work is reported by Hewitt and Batchelor (1975) and later by Batchelor et al. (1985), and is summarized in the following.The inability of the concrete to sustain tensile strains, which leads to cracking, has been shown to be the main attribute which causes the compressive membrane forces to develop. This phenomenon is illustrated in Fig. 4.9 (a) which shows the part cross-section of slab-on-girder bridge under the action of a concentrated load.The cracking of the concrete, as shown in the figure, results in a net compressive force near the bottom face of the slab at each of the two girder locations. Midway between the girders, the net compressive force moves towards the top of the slab. It can be readily visualized that the transition of the net compressive force from near the top in the middle region, to near the bottom at the supports corresponds to the familiar arching action. Because of this internal arching action, the failure mode of a deck slab under a concentrated load becomes that of punching shear.If the material of the deck slab has the same stress-strain characteristics in both tension and compression, the slab will not crack and, as shown in Fig. 4.9 (b), will not develop the net compressive force and hence the arching action.In the punching shear type of failure, a frustum separates from the rest of the slab, as shown in schematically in Fig. 4.10. It is noted that in most failure tests, the diameter of the lower end of the frustrum extends to the vicinity of the girders.From analytical and confirmatory laboratory studies, it was established that the most significant factor influencing the failure load of a concrete deck slab is the confinement of the panel under consideration. It was concluded that this confinement is provided by the expanse of the slab beyond the loaded area; its degree was founddifficult to assess analytically. A restraint factor, η, was used as an empirical measure of the confinement; its value is equal to zero for the case of no confinement and 1.0 for full confinement.The effect of various parameters on the failure load can be seen in Table 4.1, which lists the theoretical failure loads for various cases. It can be seen that an increase of the restraint factor from 0.0 to 0.5 results in a very large increase in the failure load. The table also emphasizes the fact that neglect of the restraint factor causes a gross underestimation of the failure load.It was concluded that design for flexure leads to the inclusion of large amounts of unnecessary steel reinforcement in the deck slabs, and that even the minimum amount of steel required for crack control against volumetric changes in concrete is adequate to sustain modern-day, and even future, highway vehicles of North America.It was recommended that for new construction, the reinforcement in a deck slab should be in two layers, with each layer consisting of an orthogonal mesh having the same area of reinforcement in each direction. The area of steel reinforcement in each direction of a mesh was suggested to be 0.2% of the effective area of cross-section of the slab. This empirical method of design was recommended for deck slabs with certain constraints.4.3.2 Pulsating Load Tests on Scale ModelsTo study the fatigue strength of deck slabs with reduced reinforcement, five small scale models with different reinforcement ratios in different panels were tested at the Queen's University at Kingston. Details of this study are reported by Batchelor et al. (1978).Experimental investigation confirmed that for loads normally encountered in North America deck slabs with both conventional and recommended reducedreinforcement have large reserve strengths against failure by fatigue. It was confirmed that the reinforcement in the deck slab should be as noted in sub-section 4.3.1. It is recalled that the 0.2% reinforcement requires that the deck slab must have a minimum restraint factor of 0.5.The work of Okada, et al. (1978) also deals with fatigue tests on full scale models of deck slabs and segments of severely cracked slab removed from eight to ten year old bridges. The application of these test results to deck slabs of actual bridges is open to question because test specimens were removed from the original structures in such a way that they did not retain the confinement necessary for the development of the arching action.4.3.3 Field TestingAlong with the studies described in the preceding sub-section, a program of field testing of the deck slabs of in-service bridges was undertaken by the Structures Research Office of the MTO. The testing consisted of subjecting deck slabs to single concentrated loads, simulating wheel loads, and monitoring the load-deflection characteristics of the slab. The testing is reported by Csagoly et al. (1978) and details of the testing equipment are given by Bakht and Csagoly (1979).Values of the restraint factor, η, were back-calculated from measured deflections.A summary of test results, given in Table 4.2, shows that the average value of η in composite bridges is greater than 0.75, while that for non-composite bridges is 0.42. It was concluded that for new construction, the restraint factor, η, can be assumed to have a minimum value of 0.5.Bakht (1981) reports that after the first application of a test load of high magnitude on deck slabs of existing bridges, a small residual deflection was observed in most cases. Subsequent applications of the same load did not result in further residual deflections. It is postulated that the residual deflections are caused by cracking of the concrete which, as discussed earlier, accompanies the development of the internal arching action. The residual deflections after the first cycle of loading suggest that either the slab was never subjected to loads high enough to cause cracking, or the cracks have 'healed' with time.第二部分汉语翻译4.2.2 在冲切剪应力下的实效模型我们已经知道在桥面板内部拱形系统的形成中，不仅纵向而且横向也被完全约束限制是完全必要的。
桥梁工程本科毕业设计外文翻译---混凝土桥梁的结构形式
本科毕业设计外文翻译混凝土桥梁的结构形式院（系、部）名称：专业名称：学生姓名：学生学号：指导教师：The Structure of Concrete BridgePre-stressed concrete has proved to be technically advantageous, economically competitive, and esthetically superior bridges, from very short span structures using standard components to cable-stayed girders and continuous box girders with clear spans of nearly 100aft .Nearly all concrete bridges, even those of relatively short span, are now pre-stressed. Pre-casting, cast-in-place construction, or a combination of the two methods may be used .Both pre-tensioning and post tensioning are employed, often on the same project.In the United States, highway bridges generally must-meet loading ,design ,and construction requirements of the AASHTO Specification .Design requirements for pedestrian crossings and bridges serving other purposes may be established by local or regional codes and specifications .ACI Code provisions are often incorporated by reference .Bridges spans to about 100ft often consist of pre-cast integral-deck units ,which offer low initial cost ,minimum ,maintenance ,and fast easy construction ,with minimum traffic interruption .Such girders are generally pre-tensioned .The units are placed side by side ,and are often post-tensioned laterally at intermediate diaphragm locations ,after which shear keys between adjacent units are filled with non-shrinking mortar .For highway spans ,an asphalt wearing surface may be applied directly to the top of the pre-cast concrete .In some cases ,a cast-in-place slab is placed to provide composite action .The voided slabs are commonly available in depths from 15 to 21 in .and widths of 3 to 4 ft .For a standard highway HS20 loading, they are suitable for spans to about 50 ft, Standard channel sections are available in depths from 21 to 35 in a variety of widths, and are used for spans between about 20 and 60 ft .The hollow box beams-and single-tee girders are intended for longer spans up to about 100 ft.For medium-span highway bridges ,to about 120 ft ,AASHTO standard I beams are generally used .They are intended for use with a composite cast-in-place roadway slab .Such girders often combine pre-tensioning of the pre-cast member with post-tensioning of the composite beam after the deck is placed .In an effort to obtain improved economy ,some states have adopted more refined designs ,such as the State of Washington standard girders.The specially designed pre-cast girders may be used to carry a monorail transit system .The finished guide way of Walt Disney World Monorail features a series of segments, each consisting of six simply supported pre-tensioned beams ,together to from a continuous structure .Typical spans are 100 to 110 ft . Approximately half of the 337 beams used have some combination of vertical and horizontal curvatures and variable super elevation .Allbeams are hollow, a feature achieved by inserting a styro-foam void in the curved beams and by a moving mandrel in straight beam production.Pre-cast girders may not be used for spans much in excess of 120 ft because of the problems of transporting and erecting large, heavy units.On the other hand ,there is a clear trend toward the use of longer spans for bridges .For elevated urban expressways ,long spans facilitate access and minimize obstruction to activities below .Concern for environmental damage has led to the choice of long spans for continuous viaducts . For river crossings, intermediate piers may be impossible because of requirements of navigational clearance.In typical construction of this type, piers are cast-in-place, often using the slip-forming technique .A “hammerhead” section of box girder is often cast at the top of the pier, and construction proceeds in each direction by the balanced cantilever method. Finally, after the closing cast-in-place joint is made at mid-span, the structure is further post-tensioned for full continuity .Shear keys may be used on the vertical faces between segments, and pre-cast are glued with epoxy resin.The imaginative engineering demonstrated by many special techniques has extended the range of concrete construction for bridges far beyond anything that could be conceived just a few years ago .In the United States, twin curved cast-in –place segmental box girders have recently been completed for of span of 310 ft over the Eel River in northern California .Preliminary design has been completed for twin continuous box girders consisting of central 550 ft spans flanked by 390 ft side spans.Another form of pre-stressed concrete bridge well suited to long spans is the cable-stayed box girder .A notable example is the Chaco-Corrientes Bridge in Argentina .The bridges main span of 804 ft is supported by two A-frame towers, with cable stays stretching from tower tops to points along the deck .The deck itself consists of two parallel box girders made of pre-cast sections erected using the cantilever method .The tensioned cables not only provide a vertical reaction component to support the deck ,but also introduce horizontal compression to the box girders ,adding to the post-tensioning force in those members .Stress-ribbon Bridge pioneered many years ago by the German engineer Ulrich Finsterwalder. The stress-ribbon bridge carries a pipeline and pedestrians over the Rhine River with a span of 446 ft .The superstructure erection sequence was to (a) erect two pairs of cables, (b) place pre-cast slabs forming a sidewalk deck and a U under each of the sets of cables, and (c) cast-in-place concrete within the two Us. The pipeline is placed atop supports at railing height, off to one side, which greatly increases the wind speed of the structure.It is appropriate in discussing bridge forms to mention structural esthetics .The time ispast when structures could be designed on the basis of minimum cost and technical advantages alone .Bridge structures in particular are exposed for all to see .To produce a structure that is visually offensive ,as has occurred all too often in the past, is an act professional irresponsibility .Particularly for major spans ,but also for more ordinary structures ,architectural advice should be sought early in conceptual stage of the design process.混凝土梁桥的结构形式事实证明，预应力混凝土结构是在技术上先进、经济上有竞争力、符合审美学的一种先进技术。
桥梁工程毕业设计外文翻译(箱梁)
西南交通大学本科毕业设计(论文）外文资料翻译年级:学号：姓名：专业:指导老师:2013年 6 月外文资料原文：13Box girders13.1 GeneralThe box girder is the most flexible bridge deck form。
It can cover a range of spans from25 m up to the largest non—suspended concrete decks built, of the order of 300 m。
Single box girders may also carry decks up to 30 m wide。
For the longer span beams, beyond about 50 m，they are practically the only feasible deck section. For the shorter spans they are in competition with most of the other deck types discussed in this book.The advantages of the box form are principally its high structural efficiency （5.4），which minimises the prestress force required to resist a given bending moment，and its great torsional strength with the capacity this gives to re—centre eccentric live loads，minimising the prestress required to carry them。
The box form lends itself to many of the highly productive methods of bridge construction that have been progressively refined over the last 50 years，such as precast segmental construction with or without epoxy resin in the joints，balanced cantilever erection either cast in—situ or coupled with precast segmental construction, and incremental launching （Chapter 15)。
道路桥梁专业 中英文对照---毕业设计论文 外文文献翻译
附录一英文翻译原文AUTOMATIC DEFLECTION AND TEMPERATURE MONITORING OFA BALANCED CANTILEVER CONCRETE BRIDGEby Olivier BURDET, Ph.D.Swiss Federal Institute of Technology, Lausanne, SwitzerlandInstitute of Reinforced and Prestressed Concrete SUMMARYThere is a need for reliable monitoring systems to follow the evolution of the behavior of structures over time.Deflections and rotations are values that reflect the overall structure behavior. This paper presents an innovative approach to the measurement of long-term deformations of bridges by use of inclinometers. High precision electronic inclinometers can be used to follow effectively long-term rotations without disruption of the traffic. In addition to their accuracy, these instruments have proven to be sufficiently stable over time and reliable for field conditions. The Mentue bridges are twin 565 m long box-girder post-tensioned concrete highway bridges under construction in Switzerland. The bridges are built by the balanced cantilever method over a deep valley. The piers are 100 m high and the main span is 150 m. A centralized data acquisition system was installed in one bridge during its construction in 1997. Every minute, the system records the rotation and temperature at a number of measuring points. The simultaneous measurement of rotations and concrete temperature at several locations gives a clear idea of the movements induced by thermal conditions. The system will be used in combination with a hydrostatic leveling setup to follow the long-term behavior of the bridge. Preliminary results show that the system performs reliably and that the accuracy of the sensors is excellent.Comparison of the evolution of rotations and temperature indicate that the structure responds to changes in air temperature rather quickly.1.BACKGROUNDAll over the world, the number of structures in service keeps increasing. With the development of traffic and the increased dependence on reliable transportation, it is becoming more and more necessary to foresee and anticipate the deterioration of structures. In particular,for structures that are part of major transportation systems, rehabilitation works need to be carefully planned in order to minimize disruptions of traffic. Automatic monitoring of structures is thus rapidly developing.Long-term monitoring of bridges is an important part of this overall effort to attempt to minimize both the impact and the cost of maintenance and rehabilitation work of major structures. By knowing the rate of deterioration of a given structure, the engineer is able to anticipate and adequately define the timing of required interventions. Conversely, interventions can be delayed until the condition of the structure requires them, without reducing the overall safety of the structure.The paper presents an innovative approach to the measurement of long-term bridge deformations. The use of high precision inclinometers permits an effective, accurate and unobtrusive following of the long-term rotations. The measurements can be performed under traffic conditions. Simultaneous measurement of the temperature at several locations gives a clear idea of the movements induced by thermal conditions and those induced by creep and shrinkage. The system presented is operational since August 1997 in the Mentue bridge, currently under construction in Switzerland. The structure has a main span of 150 m and piers 100 m high.2. LONG-TERM MONITORING OF BRIDGESAs part of its research and service activities within the Swiss Federal Institute of Technology in Lausanne (EPFL), IBAP - Reinforced and Prestressed Concrete has been involved in the monitoring of long-time deformations of bridges and other structures for over twenty-five years [1, 2, 3, 4]. In the past, IBAP has developed a system for the measurement of long-term deformations using hydrostatic leveling [5, 6]. This system has been in successful service in ten bridges in Switzerland for approximately ten years [5,7]. The system is robust, reliable and sufficiently accurate, but it requires human intervention for each measurement, and is not well suited for automatic data acquisition. One additional disadvantage of this system is that it is only easily applicable to box girder bridges with an accessible box.Occasional continuous measurements over periods of 24 hours have shown that the amplitude of daily movements is significant, usually amounting to several millimeters over a couple of hours. This is exemplified in figure 1, where measurements of the twin Lutrive bridges, taken over a period of several years before and after they were strengthened by post-tensioning, areshown along with measurements performed over a period of 24 hours. The scatter observed in the data is primarily caused by thermal effects on the bridges. In the case of these box-girder bridges built by the balanced cantilever method, with a main span of 143.5 m, the amplitude of deformations on a sunny day is of the same order of magnitude than the long term deformation over several years.Instantaneous measurements, as those made by hydrostatic leveling, are not necessarily representative of the mean position of the bridge. This occurs because the position of the bridge at the time of the measurement is influenced by the temperature history over the past several hours and days. Even if every care was taken to perform the measurements early in the morning and at the same period every year, it took a relatively long time before it was realized that the retrofit performed on the Lutrive bridges in 1988 by additional post-tensioning [3, 7,11] had not had the same effect on both of them.Figure 1: Long-term deflections of the Lutrive bridges, compared to deflections measured in a 24-hour period Automatic data acquisition, allowing frequent measurements to be performed at an acceptable cost, is thus highly desirable. A study of possible solutions including laser-based leveling, fiber optics sensors and GPS-positioning was performed, with the conclusion that, provided that their long-term stability can be demonstrated, current types of electronic inclinometers are suitable for automatic measurements of rotations in existing bridges [8].3. MENTUE BRIDGESThe Mentue bridges are twin box-girder bridges that will carry the future A1 motorway from Lausanne to Bern. Each bridge, similar in design, has an overall length of approximately 565 m, and a width of 13.46 m, designed to carry two lanes of traffic and an emergency lane. The bridges cross a deep valley with steep sides (fig. 2). The balanced cantilever design results from a bridge competition. The 100 m high concrete piers were built using climbing formwork, after which the construction of the balanced cantilever started (fig. 3).4. INCLINOMETERSStarting in 1995, IBAP initiated a research project with the goal of investigating the feasibility of a measurement system using inclinometers. Preliminary results indicated that inclinometers offer several advantages for the automatic monitoring of structures. Table 1 summarizes the main properties of the inclinometers selected for this study.One interesting property of measuring a structure’s rotations, is that, for a given ratio of maximum deflection to span length, the maximum rotation is essentially independent from its static system [8]. Since maximal allowable values of about 1/1,000 for long-term deflections under permanent loads are generally accepted values worldwide, developments made for box-girder bridges with long spans, as is the case for this research, are applicable to other bridges, for instance bridges with shorter spans and other types of cross-sections. This is significant because of the need to monitor smaller spans which constitute the majority of all bridges.The selected inclinometers are of type Wyler Zerotronic ±1°[9]. Their accuracy is 1 microradian (μrad), which corresponds to a rotation of one millimeter per kilometer, a very small value. For an intermediate span of a continuous beam with a constant depth, a mid-span deflection of 1/20,000 would induce a maximum rotation of about 150 μrad, or 0.15 milliradians (mrad).One potential problem with electronic instruments is that their measurements may drift overtime. To quantify and control this problem, a mechanical device was designed allowing the inclinometers to be precisely rotated of 180° in an horizontal plane (fig. 4). The drift of each inclinometer can be very simply obtained by comparing the values obtained in the initial and rotated position with previously obtained values. So far, it has been observed that the type of inclinometer used in this project is not very sensitive to drifting.5. INSTRUMENTATION OF THE MENTUE BRIDGESBecause a number of bridges built by the balanced cantilever method have shown an unsatisfactory behavior in service [2, 7,10], it was decided to carefully monitor the evolution of the deformations of the Mentue bridges. These bridges were designed taking into consideration recent recommendations for the choice of the amount of posttensioning [7,10,13]. Monitoring starting during the construction in 1997 and will be pursued after the bridges are opened to traffic in 2001. Deflection monitoring includes topographic leveling by the highway authorities, an hydrostatic leveling system over the entire length of both bridges and a network of inclinometers in the main span of the North bridge. Data collection iscoordinated by the engineer of record, to facilitate comparison of measured values. The information gained from these observations will be used to further enhance the design criteria for that type of bridge, especially with regard to the amount of post-tensioning [7, 10, 11, 12, 13].The automatic monitoring system is driven by a data acquisition program that gathers and stores the data. This system is able to control various types of sensors simultaneously, at the present time inclinometers and thermal sensors. The computer program driving all the instrumentation offers a flexible framework, allowing the later addition of new sensors or data acquisition systems. The use of the development environment LabView [14] allowed to leverage the large user base in the field of laboratory instrumentation and data analysis. The data acquisition system runs on a rather modest computer, with an Intel 486/66 Mhz processor, 16 MB of memory and a 500 MB hard disk, running Windows NT. All sensor data are gathered once per minute and stored in compressed form on the hard disk. The system is located in the box-girder on top of pier 3 (fig. 5). It can withstand severe weather conditions and will restart itself automatically after a power outage, which happened frequently during construction.6. SENSORSFigure 5(a) shows the location of the inclinometers in the main span of the North bridge. The sensors are placed at the axis of the supports (①an d⑤), at 1/4 and 3/4 (③an d④) of the span and at 1/8 of the span for②. In the cross section, the sensors are located on the North web, at a height corresponding to the center of gravity of the section (fig.5a). The sensors are all connected by a single RS-485 cable to the central data acquisition system located in the vicinity of inclinometer ①. Monitoring of the bridge started already during its construction. Inclinometers①,②and③were installed before the span was completed. The resulting measurement were difficult to interpret, however, because of the wide variations of angles induced by the various stages of this particular method of construction.The deflected shape will be determined by integrating the measured rotations along the length of the bridge (fig.5b). Although this integration is in principle straightforward, it has been shown [8, 16] that the type of loading and possible measurement errors need to be carefully taken into account.Thermal sensors were embedded in concrete so that temperature effects could be taken into account for the adjustment of the geometry of the formwork for subsequent casts. Figure 6 shows the layout of thermal sensors in the main span. The measurement sections are located at the same sections than the inclinometers (fig. 5). All sensors were placed in the formwork before concreting and were operational as soon as the formwork was removed, which was required for the needs of the construction. In each section, seven of the nine thermal sensor (indicated in solid black in fig. 6) are now automatically measured by the central data acquisition system.7. RESULTSFigure 7 shows the results of inclinometry measurements performed from the end ofSeptember to the third week of November 1997. All inclinometers performed well during that period. Occasional interruptions of measurement, as observed for example in early October are due to interruption of power to the system during construction operations. The overall symmetry of results from inclinometers seem to indicate that the instruments drift is not significant for that time period. The maximum amplitude of bridge deflection during the observed period, estimated on the basis of the inclinometers results, is around 40 mm. More accurate values will be computed when the method of determination ofdeflections will have been further calibrated with other measurements. Several periods of increase, respectively decrease, of deflections over several days can be observed in the graph. This further illustrates the need for continuous deformation monitoring to account for such effects. The measurement period was .busy. in terms of construction, and included the following operations: the final concrete pours in that span, horizontal jacking of the bridge to compensate some pier eccentricities, as well as the stressing of the continuity post-tensioning, and the de-tensioning of the guy cables (fig. 3). As a consequence, the interpretation of these measurements is quite difficult. It is expected that further measurements, made after the completion of the bridge, will be simpler to interpret.Figure 8 shows a detail of the measurements made in November, while figure.9 shows temperature measurements at the top and bottom of the section at mid-span made during that same period. It is clear that the measured deflections correspond to changes in the temperature. The temperature at the bottom of the section follows closely variations of the air temperature(measured in the shade near the north web of the girder). On the other hand, the temperature at the top of the cross section is less subject to rapid variations. This may be due to the high elevation of the bridge above ground, and also to the fact that, during the measuring period, there was little direct sunshine on the deck. The temperature gradient between top and bottom of the cross section has a direct relationship with short-term variations. It does not, however, appear to be related to the general tendency to decrease in rotations observed in fig. 8.8. FUTURE DEVELOPMENTSFuture developments will include algorithms to reconstruct deflections from measured rotations. To enhance the accuracy of the reconstruction of deflections, a 3D finite element model of the entire structure is in preparation [15]. This model will be used to identify the influence on rotations of various phenomena, such as creep of the piers and girder, differential settlements, horizontal and vertical temperature gradients or traffic loads.Much work will be devoted to the interpretation of the data gathered in the Mentue bridge. The final part of the research project work will focus on two aspects: understanding the very complex behavior of the structure, and determining the most important parameters, to allow a simple and effective monitoring of the bridges deflections.Finally, the research report will propose guidelines for determination of deflections from measured rotations and practical recommendations for the implementation of measurement systems using inclinometers. It is expected that within the coming year new sites will be equipped with inclinometers. Experiences made by using inclinometers to measure deflections during loading tests [16, 17] have shown that the method is very flexible and competitive with other high-tech methods.As an extension to the current research project, an innovative system for the measurement of bridge joint movement is being developed. This system integrates easily with the existing monitoring system, because it also uses inclinometers, although from a slightly different type.9. CONCLUSIONSAn innovative measurement system for deformations of structures using high precision inclinometers has been developed. This system combines a high accuracy with a relatively simple implementation. Preliminary results are very encouraging and indicate that the use of inclinometers to monitor bridge deformations is a feasible and offers advantages. The system is reliable, does not obstruct construction work or traffic and is very easily installed. Simultaneous temperature measurements have confirmed the importance of temperature variations on the behavior of structural concrete bridges.10. REFERENCES[1] ANDREY D., Maintenance des ouvrages d’art: méthodologie de surveillance, PhD Dissertation Nr 679, EPFL, Lausanne, Switzerland, 1987.[2] BURDET O., Load Testing and Monitoring of Swiss Bridges, CEB Information Bulletin Nr 219, Safety and Performance Concepts, Lausanne, Switzerland, 1993.[3] BURDET O., Critères pour le choix de la quantitéde précontrainte découlant de l.observation de ponts existants, CUST-COS 96, Clermont-Ferrand, France, 1996.[4] HASSAN M., BURDET O., FAVRE R., Combination of Ultrasonic Measurements and Load Tests in Bridge Evaluation, 5th International Conference on Structural Faults and Repair, Edinburgh, Scotland, UK, 1993.[5] FAVRE R., CHARIF H., MARKEY I., Observation à long terme de la déformation des ponts, Mandat de Recherche de l’OFR 86/88, Final Report, EPFL, Lausanne, Switzerland, 1990.[6] FAVRE R., MARKEY I., Long-term Monitoring of Bridge Deformation, NATO Research Workshop, Bridge Evaluation, Repair and Rehabilitation, NATO ASI series E: vol. 187, pp. 85-100, Baltimore, USA, 1990.[7] FAVRE R., BURDET O. et al., Enseignements tirés d’essais de charge et d’observations à long terme pour l’évaluation des ponts et le choix de la précontrainte, OFR Report, 83/90, Zürich, Switzerland, 1995.[8] DAVERIO R., Mesures des déformations des ponts par un système d’inclinométrie,Rapport de maîtrise EPFL-IBAP, Lausanne, Switzerland, 1995.[9] WYLER AG., Technical specifications for Zerotronic Inclinometers, Winterthur, Switzerland, 1996.[10] FAVRE R., MARKEY I., Generalization of the Load Balancing Method, 12th FIP Congress, Prestressed Concrete in Switzerland, pp. 32-37, Washington, USA, 1994.[11] FAVRE R., BURDET O., CHARIF H., Critères pour le choix d’une précontrainte: application au cas d’un renforcement, "Colloque International Gestion des Ouvrages d’Art: Quelle Stratégie pour Maintenir et Adapter le Patrimoine, pp. 197-208, Paris, France, 1994. [12] FAVRE R., BURDET O., Wahl einer geeigneten Vorspannung, Beton- und Stahlbetonbau, Beton- und Stahlbetonbau, 92/3, 67, Germany, 1997.[13] FAVRE R., BURDET O., Choix d’une quantité appropriée de précontrain te, SIA D0 129, Zürich, Switzerland, 1996.[14] NATIONAL INSTRUMENTS, LabView User.s Manual, Austin, USA, 1996.[15] BOUBERGUIG A., ROSSIER S., FAVRE R. et al, Calcul non linéaire du béton arméet précontraint, Revue Français du Génie Civil, vol. 1 n° 3, Hermes, Paris, France, 1997. [16] FEST E., Système de mesure par inclinométrie: développement d’un algorithme de calcul des flèches, Mémoire de maîtrise de DEA, Lausanne / Paris, Switzerland / France, 1997.[17] PERREGAUX N. et al., Vertical Displacement of Bridges using the SOFO System: a Fiber Optic Monitoring Method for Structures, 12th ASCE Engineering Mechanics Conference, San Diego, USA, to be published,1998.译文平衡悬臂施工混凝土桥挠度和温度的自动监测作者Olivier BURDET博士瑞士联邦理工学院，洛桑，瑞士钢筋和预应力混凝土研究所概要：我们想要跟踪结构行为随时间的演化，需要一种可靠的监测系统。
(完整版)桥梁毕业设计外文翻译
外文资料The Tenth East Asia-Pacific Conference on Structural Engineering and ConstructionAugust 3-5, 2006, Bangkok, ThailandStructural Rehabilitation of Concrete Bridges with CFRPComposites-Practical Details and ApplicationsRiyad S. ABOUTAHA1, and Nuttawat CHUTARAT2 ABSTRACT: Many old existing bridges are still active in the various highway transportation networks, carrying heavier and faster trucks, in all kinds of environments. Water, salt, and wind have caused damage to these old bridges, and scarcity of maintenance funds has aggravated their conditions. One attempt to restore the original condition; and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP) composites. There appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. In this paper, guidelines for nondestructive evaluation (NDE), nondestructive testing (NDT), and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges are also discussed and presented.KEYWORDS: Concrete deterioration, corrosion of steel, bridge rehabilitation, CFRP composites.1 IntroductionThere are several destructive external environmental factors that limit the service life of bridges. These factors include but not limited to chemical attacks, corrosion of reinforcing steel bars, carbonation of concrete, and chemical reaction of aggregate. If bridges were not well maintained, these factors may lead to a structural deficiency, which reduces the margin of safety, and may result in structural failure. In order to rehabilitate and/or strengthen deteriorated existing bridges, thorough evaluation should be conducted. The purpose of the evaluation is to assess the actual condition of any existing bridge, and generally to examine the remaining strength and load carry capacity of the bridge.1 Associate Professor, Syracuse University, U.S.A.2 Lecturer, Sripatum University, Thailand.One attempt to restore the original condition, and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP) composites.In North America, Europe and Japan, CFRP has been extensively investigated and applied. Several design guides have been developed for strengthening of concrete bridges with CFRP composites. However, there appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. This paper presents guidelines for repair of deteriorated concrete bridges, along with proper detailing. Evaluation, nondestructive testing, and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. Successful application of CFRP composites requires good detailing as the forces developed in the CFRP sheets are transferred by bond at the concrete-CFRP interface. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges will also be discussed and presented.2 Deteriorated Concrete BridgesDurability of bridges is of major concern. Increasing number of bridges are experiencing significant amounts of deterioration prior to reaching their design service life. This premature deterioration considered a problem in terms of the structural integrity and safety of the bridge. In addition, deterioration of a bridge has a considerable magnitude of costs associated with it. In many cases, the root of a deterioration problem is caused by corrosion of steel reinforcement in concrete structures. Concrete normally acts to provide a high degree of protection against corrosion of the embedded reinforcement. However, corrosion will result in those cases that typically experience poor concrete quality, inadequate design or construction, and harsh environmental conditions. If not treated a durability problem, e.g. corrosion, may turn into a strength problem leading to a structural deficiency, as shown in Figure1.Figure1 Corrosion of the steel bars is leading to a structural deficiency3 Non-destructive Testing of Deteriorated Concrete Bridge PiersIn order to design a successful retrofit system, the condition of the existing bridge should be thoroughly evaluated. Evaluation of existing bridge elements or systems involves review of the asbuilt drawings, as well as accurate estimate of the condition of the existing bridge, as shown in Figure2. Depending on the purpose of evaluation, non-destructive tests may involve estimation of strength, salt contents, corrosion rates, alkalinity in concrete, etc.Figure2 Visible concrete distress marked on an elevation of a concrete bridge pier Although most of the non-destructive tests do not cause any damage to existing bridges, some NDT may cause minor local damage (e.g. drilled holes & coring) that should be repaired right after the NDT. These tests are also referred to as partial destructive tests but fall under non-destructive testing.In order to select the most appropriate non-destructive test for a particular case, thepurpose of the test should be identified. In general, there are three types of NDT to investigate: (1) strength, (2) other structural properties, and (3) quality and durability. The strength methods may include; compressive test (e.g. core test/rebound hammer/ ultrasonic pulse velocity), surface hardness test (e.g. rebound hammer), penetration test (e.g. Windsor probe), and pullout test (anchor test).Other structural test methods may include; concrete cover thickness (cover-meter), locating rebars (rebar locator), rebar size (some rebar locators/rebar data scan), concrete moisture (acquameter/moisture meter), cracking (visual test/impact echo/ultrasonic pulse velocity), delamination (hammer test/ ultrasonic pulse velocity/impact echo), flaws and internal cracking (ultrasonic pulse velocity/impact echo), dynamic modulus of elasticity (ultrasonic pulse velocity), Possion’s ratio (ultrasonic pulse velocity), thickness of concrete slab or wall (ultrasonic pulse velocity), CFRP debonding (hammer test/infrared thermographic technique), and stain on concrete surface (visual inspection).Quality and durability test methods may include; rebar corrosion rate –field test, chloride profile field test, rebar corrosion analysis, rebar resistivity test, alkali-silica reactivity field test, concrete alkalinity test (carbonation field test), concrete permeability (field test for permeability).4 Non-destructive Evaluation of Deteriorated Concrete Bridge PiersThe process of evaluating the structural condition of an existing concrete bridge consists of collecting information, e.g. drawings and construction & inspection records, analyzing NDT data, and structural analysis of the bridge. The evaluation process can be summarized as follows: (1) Planning for the assessment, (2) Preliminary assessment, which involves examination of available documents, site inspection, materials assessment, and preliminary analysis, (3) Preliminary evaluation, this involves: examination phase, and judgmental phase, and finally (4) the cost-impact study.If the information is insufficient to conduct evaluation to a specific required level, then a detailed evaluation may be conducted following similar steps for the above-mentioned preliminary assessment, but in-depth assessment. Successful analytical evaluation of an existing deteriorated concrete bridge should consider the actual condition of the bridge and level of deterioration of various elements. Factors, e.g. actual concrete strength, level of damage/deterioration, actual size of corroded rebars, loss of bond between steel and concrete, etc. should be modeled into a detailed analysis. If such detailed analysis is difficult to accomplish within a reasonable period of time, thenevaluation by field load testing of the actual bridge in question may be required.5 Bridge Rehabilitation with CFRP CompositesApplication of CFRP composite materials is becoming increasingly attractive to extend the service life of existing concrete bridges. The technology of strengthening existing bridges with externally bonded CFRP composites was developed primarily in Japan (FRP sheets), and Europe (laminates). The use of these materials for strengthening existing concrete bridges started in the 1980s, first as a substitute to bonded steel plates, and then as a substitute for steel jackets for seismic retrofit of bridge columns. CFRP Composite materials are composed of fiber reinforcement bonded together with a resin matrix. The fibers provide the composite with its unique structural properties. The resin matrix supports the fibers, protect them, and transfer the applied load to the fibers through shearing stresses. Most of the commercially available CFRP systems in the construction market consist of uniaxial fibers embedded in a resin matrix, typically epoxy. Carbon fibers have limited ultimate strain, which may limit the deformability of strengthened members. However, under traffic loads, local debonding between FRP sheets and concrete substrate would allow for acceptable level of global deformations before failure.CFRP composites could be used to increase the flexural and shear strength of bridge girders including pier cap beams, as shown in Figure3. In order to increase the ductility of CFRP strengthened concrete girders, the longitudinal CFRP composite sheets used for flexural strengthening should be anchored with transverse/diagonal CFRP anchors to prevent premature delamination of the longitudinal sheets due to localized debonding at the concrete surface-CFRP sheet interface. In order to prevent stress concentration and premature fracture of the CFRP sheets at the corners of concrete members, the corners should be rounded at 50mm (2.0 inch) radius, as shown in Figure3.Deterioration of concrete bridge members due to corrosion of steel bars usually leads in loss of steel section and delamination of concrete cover. As a result, such deterioration may lead to structural deficiency that requires immediate attention. Figure4 shows rehabilitation of structurally deficient concrete bridge pier using CFRP composites.Figure3 Flexural and shear strengthening of concrete bridge pier with FRP compositesFigure4 Rehabilitation of deteriorated concrete bridge pier with CFRP composites6 Summary and ConclusionsEvaluation, non-destructive testing and rehabilitation of deteriorated concrete bridges were presented. Deterioration of concrete bridge components due to corrosion may lead to structural deficiencies, e.g. flexural and/or shear failures. Application of CFRP composite materials is becoming increasingly attractive solution to extend the service life of existing concrete bridges. CFRP composites could be utilized for flexural and shear strengthening, as well as for restoration of deteriorated concrete bridge components. The CFRP composite sheets should be well detailed to prevent stress concentration and premature fracture or delamination. For successful rehabilitation of concrete bridges in corrosive environments, a corrosion protection system should be used along with the CFRP system.第十届东亚太结构工程设计与施工会议2006年8月3-5号，曼谷，泰国碳纤维复合材料修复混凝土桥梁结构的详述及应用Riyad S. ABOUTAHA1, and Nuttawat CHUTARAT2摘要：在各式各样的公路交通网络中，许多现有的古老桥梁，在各种恶劣的环境下，如更重的荷载和更快的车辆等条件下，依然在被使用着。
桥梁工程毕业论文英文
桥梁工程毕业论文英文Title: Analysis and Design of Bridge StructuresAbstract:Bridge engineering is an integral part of civil engineering and plays a crucial role in connecting communities and facilitating transportation. The purpose of this thesis is to analyze and design bridge structures, focusing on key components such as foundations, superstructures, and substructures. The analysis includes evaluating the structural behavior and load carrying capacity through the utilization of various analytical tools. Furthermore, the design phase encompasses selecting suitable materials and designing components to meet safety and durability requirements. The study serves as a comprehensive guide to understanding the principles and processes involved in bridge engineering.1. IntroductionBridges are vital infrastructure that connects people, places, and economies. The study of bridge engineering involves the application of core principles like physics, materials science, and mathematics todesign and construct safe and efficient bridge structures. This thesis aims to provide an overview of the analysis and design principles involved in bridge engineering.2. Structural AnalysisThe analysis of bridge structures is crucial to ensure their safety and functionality. This chapter presents various analytical techniques for evaluating bridge behavior. The use of finite element analysis, structural modeling, and computer-aided design software is discussed in detail. Different load types and load combinations are also considered to determine the resilience and load carrying capacity of the bridge.3. Foundation DesignThe foundation is a critical component of any bridge structure, as it transfers the loads from the superstructure to the underlying ground. This chapter explores various foundation types, such as shallow foundations, deep foundations, and pile foundations. Design considerations, including soil mechanics, bearing capacity, settlement analysis, and groundwater conditions, are discussed. The use ofgeotechnical engineering software to simulate and optimize foundation design is also explored.4. Superstructure DesignThe superstructure refers to the portion of the bridge that supports the traffic loads and transfers them to the substructure. This chapter discusses the different types of superstructures, including beam bridges, truss bridges, and arch bridges. The selection of materials, such as concrete, steel, and composite materials, is analyzed based on their structural properties and cost-effectiveness. The design process incorporates the calculation of load distribution, structural stability, and deflection limits.5. Substructure DesignThe substructure comprises the bridge piers, abutments, and retaining walls, which provide support to the superstructure. This chapter focuses on the design considerations for substructures, including the selection of suitable materials, analysis of load distribution, and evaluation of stability against various forces and environmental conditions. Design principles for reinforced concrete and masonry substructures are explored, along with mitigationstrategies for potential issues such as scour and seismic activity.6. Safety and DurabilityEnsuring safety and durability is of utmost importance in bridge engineering. This chapter discusses the necessary steps for evaluating the safety of bridge structures, including factor of safety calculations, failure mode analysis, and risk assessment procedures. The discussion also includes guidelines for maintenance and inspection to ensure long-term performance and durability.7. ConclusionThis thesis provides an in-depth analysis and design framework for bridge structures. By comprehensively exploring the key components of bridges, including foundations, superstructures, and substructures, it provides valuable insights into the principles and processes involved in bridge engineering. The knowledge gained from this study will contribute to the safe and efficient design and construction of future bridge projects.。
土木工程桥梁方向毕业设计外文及翻译
土木工程桥梁方向毕业设计外文及翻译(总13页)--本页仅作为文档封面，使用时请直接删除即可----内页可以根据需求调整合适字体及大小--学生姓名：学号：班级:专业：土木工程（桥梁方向）指导教师：2010 年 3 月What is traffic engineeringTraffic engineering is still a relatively new discipline within the overall bounds of civil engineering. it has nevertheless already been partially planning. the disciplines are not synonymous though. transportation planning is concerned with the planning, functional design, operation and management of facilities for any mode of transportation in order to provide for the safe, rapid, comfortable, convenient, economical and enviromenally-comparible movement of people and goods. within that broad scope, traffic engineering deals with those functions in respect of roads, road networks, terminal points , about lands and their relationships with other modes of transportation.Those definitions, based on the 1976 ones of the of transportation engineers are complete than, the British instituting of civil engineering which deals with traffic planning and design of roads, of frontage development and of parking facilities and with the control of traffic to provide safe, convenient and economical movement of vehicles and pedestrians.The definitions of the disicipline are becoming clearer: the methodology is developing continuously and becoming increasingly scientific. the early rule-of-thumb techniques are disappearing.Traffic problemThe discipline is young: the problem is large and still growing. in 1920 the total number of motor vehicles, licensed in great Britain was,650, year later the comparable figure was 14,950,000-a growth factor of 23 times. in recent years the rate of growth has slackened somewhat, but it is still considerable: 1955 6,466,0001960 9,439,0001965 12,938,0001970 14,950,0001974 17,247,000In order to see the problem in every day terms ,consider high street. anywhere. assuming that present trends continue, it is expected that within the next fifteen years of so the traffic on this road will increase by around forty to fifty persent. if this increased volume of traffic were to be accommodated at the same standard as today, the road might need to be widened by a similar forty to fifty percent-perhaps extra lane of traffic for the pedestrian to cross. In man cases, to accommodate the foreseeable future demand would destroy the character of the whole urban environment, and is clearly unacceptable.the traffic problem is of world-wide concern, but different countries are obviously at different stages in the traffic escalation-with America in the lead, while a county has few roads and a relatively low problem, as soon as the country is opened up by a road system, the standard of living and the demand for motor transport both rise, gathering momentum rapidly. eventually-and the stage at which this happens is open to considerable debate-the demand for cars, buses and lorries become satiated. the stage is known as saturation level.For comparison ,car ownership figures in different countries in 1970 were:India cars/personIsrael personJapan cars/personIreland cars/personNetherlands cars/personGreat Britain cars/personWest Germany cars/personAustralia cars/personUSA cars/personBut the growth in vehicle ownership is only part of the overall traffic problem. obviously,if a country has unlimited roads of extreme width, the traffic problem would not rise. no country in the world could meet this requirement: apart from anything else, it would not make economic for each vehicle using the roads. This figure is decreasing steadily.Three possible solutionsThe basic problem of traffic is therefore simple-an ever-increasing number of vehicles seeking to use too little roade space. the solution to the problem-is else a not-too-difficult choice from three possiblilities:build, sufficient roads of sufficient size to cope with the demand.Restrict the demand for roads by restricting the numbers of licensed vehicles.A compromise between (a) and (b) build some extra roads, using the and the existing road network to their full potential, and at the same time apply some restraint measures, limiting, the increase in demand as far as possible.With no visible end to the demand yet in sight, and 216 with modern road-making costs ranging around ￡1 million per kilometer cost of building roads in Britain to cope with an unrestricted demand would be far too great. added to this, such clossal use of space in a crowed island cannot be, seriously considered. in Los Angeles, a city built around the parking space for, the automobile. our citie are already largely built-and no one would consider ruining their character by pulling them down and rebuilding around the car, thus the first possible soluting is rule out.Even today,in an age of at least semi-affluence in most of the Western World, the car is still to some extent a status symbol, a symbol of family wants to own one, and takes steps saving or borrowing-to get one. as incomes and standards rise thesecond car becomes the target. any move to restrict the acquisition of the private car would be most unpopular-and politically unlikely.For many purpose the flexibility of the private car-conceptually affording door-to-door personal transport is ideal, and its use can be accommodate. for the mass, movement of people along specific corridors within a limited period of .. particularly the journey to work it may be less easily accommodated. other transport mode may be more efficient. some sort of compromise solution is the inevitable answer to the basic traffic problem .it is in the execution of the compromise solution that, traffic engineering comes into its own. traffic engineering ensures that any new facilities are not over-deigned and are correctly located to meet the demand. it ensures that the existing facilities are fully used, in the most efficient manner. the fulfillment of these duties may entail the selective throttling of demand: making the use of the car less attractive in the peak periods in order that the limited road space can be more efficiently used by public transport.Such restraint measures will often be accompanied by improvements in the public transport services, to accommodate the extra demand for them.Prestressed Concrete BridgesPrestressed concrete has been used extensively in . bridge construction since its first Introduction from Europe in the late 1940s. Literally thousands of highway bridges of both precast, prestressed concrete and cast-in-place post-tensioned concrete has been constructed in the United States. Railroad bridges utilizing prastressed concrete have become common as well. The use and evolution of prastressed concrete bridges is expected to continue in the years ahead.Short-span BridgesShort-span bridges will be assumed to have a maximum of 45 ft .It should be understood that this is an arbitrary figure, and there is no definite line of demarcation between short, moderate, and long spans in highway bridges. Short-span bridges are most efficiently made of precast ,prestressed-concrete hollow slabs, I-beams, solid slabs or cast-place solid slabs. and T-beams of relatively generous proportions.Precast solid slabs are most economical when used on very short spans. The slabs can be made in any convenient width,but widths of 3 or 4 ft to have been frequently are cast in the longitudinal sides of the precast units. After the slabs have been erected and the joints between the slabs have been filled with concrete, the keys transfer live load shear forces between the adjacent slabs.Precast hollow slabs used in short-span bridges may have round or square voids. They too are generally made in units 3 to 4 ft to m) wide with thicknesses from 18 to 27 in to . Precast hollow slabs can be made in any convenient width and depth, and frequently are used in bridges having spans from 20 to 50 ft to . Longitudinal shear keys are used in the joints between adjacent hollow slabs in the same way as with solid slabs. Hollow slabs may or may not be used with a composite, cast-in-place concrete topping an accecptable appearance and levelness.Transverse reinforcement normally is provided in precast concrete bridge superstructures for the purpose of tying the structure together in the transverse direction. Well-designed ties ensure that the individual longitudinal members forming the superstructure will act as a unit under the effects of the live load. In slab bridge construction, transverse ties most frequently consist of threaded steel bars placed through small holes formed transversely through the member during fabrication. Nuts frequently are used as fasteners at each end of the bars. In some instances, the transverse ties consist of post tensionedtendons placed, stressed, and grouted after the slabs have been erected. The transverse tie usually extends from one side of the bridge to the other.The shear forces imposed on the stringers in short-span bridges frequently are too large to be resisted by the concrete alone. Hence, shear reinforcement normally is required. The amount of shear reinforcement required may be relatively large if the webs of the stringers are relatively thin.Concrete diaphragms, reinforced with post-tensioned reinforcement or nonprestressed reinforcement, normally are provided transversely at the ends and at intermediate locations along the span in stringer-type bridges. The disaphragms ensure the lateral-distribution of the live load to the various stringers and prevent individual stringers from displacing or rotating significantly with respect to the adjacent stringers.No generalities will be made here about the relative cost of each of the above types of construction; construction costs are a function of many variables which prohibit meaningful generalizations. However, it should be noted that the stringer type of construction requires a considerably greater construction depth that is required for solid, hollow, or channel slab bridge superstructures. Stringer construction does not require a separate wearing surface, as do the precast slab types of construction, unless precast slabs are used to span between the stringers in lieu of the more commonly used cast-in-place reinforced concrete deck. Stringer construction frequently requires smaller quantities of superstructure materials than do slab bridges (unless the spans are very short). The construction time needed to complete a bridge after the precast members have been erected is greater with stringer framing than with the slab type of framing.Bridges Of Moderate SpanAgain for the purpose of this discussion only, moderate spans for bridges of prestressed concrete are defined as beingfrom 45 to 80 ft to . Prestressed concrete bridges in this span range generally can be divided into two types: stringer-type bridges and slab-type bridges. The majority of the precast prestressed concrete bridges constructed in the United States have been stringer bridges using I-shaped stringers, but a large number of precast prestressed concrete bridges have been constructed with precast hollow-box girders (sometimes also called stringers). Cast-in-place post-tensioned concrete has been used extensively in the construction of hollow-box girder bridges-a form of construction that can be considered to be a slab bridge.Stringer bridges, which employ a composite, cast-in-place deck slab, have been used in virtually all parts of the United States. These stringers normally are used at spacing s of about 5 to 6 ft to . The cast-in-place deck is generally from to in to in thickness. This type of framing is very much the same as that used on composite-stringer construction for short-span bridges.Diaphram details in moderate-span bridges are generally similar to those of the short spans, with the exception that two or three interior diaphragms sometime are used, rather than just one at midspan as in the short-span bridge.As in the case of short-span bridges, the minimum depth of construction in bridges of moderate span is obtained by using slab construction, which may be either solid – or hollow – box in cross section. Average construction depths are requires when stringers with large flanges are used in composite construction, and large construction depths are required when stringers with small bottom flanges are used. Composite construction may be developed through the use of cast-in-place concrete decks or with precast concrete decks. Lower quantities of materials normally are required with composite construction , and the dead weight of the superstructure normally is less for stringer construction than for slab construction.Long-Span BridgesPrestressed concrete bridges having spans of the order of 100ft are of the same general types of construction as structures having moderate span lengths, with the single exception that solid slabs are not used for long spans. The stringer spacings are frequently greater (with stringers at 7 to 9 ft) as the span lengths of bridges increase. Because of dead weight considerations, precast hollow-box construction generally is employed for spans of this length only when the depth of construction must be minimized. Cast-in-place post-tensioned hollow-box bridges with simple and continuous spans frequently are used for spans on the order of 100 ft and longer.Simple, precast, prestressed stringer construction would be economical in the United States in the spans up to 300 ft under some conditions. However, only limited use has been made of this type of construction on spans greater than 100 ft. For very long simple spans, the advantage of precasting frequently is nullified by the difficulties involved in handling, transporting, and erecing the girders, which may have depths as great as 10 ft and weigh over 200 tons. The exceptions to this occur on large projects where all of the spans are over water of sufficient depth and character that precast beams can be handled with floating equipment, when custom girder launchers can be used, and when segmental construction techniques can be used.The use of cast-in-place , post-tensioned, box-girder bridges has been extensive. Although structures of these types occasionally are used for spans less than 100ft, they more often are used for spans in excess of 100 ft and have been used in structuresHaving spans in excess of 300 ft. Structurally efficient in flexure, especially for continuous bridges, the box girder is torsionally stiff and hence an excellent type of structure for use on bridges that have horizontal curvature. Some governmental agencies use this form of construction almost exclusively in urban areas where appearance from underneath the superstructure,as well as from the side, is considered important.交通工程介绍什么是交通工程交通工程仍然是在土木工程的总的界限内的一种相对新的训练。
道桥专业毕业设计外文翻译---
专业外文翻译原文road surface of pitch1 Debulk1.1 SummaryGood pitch road surface quality is it reflect , appear any quality defect will all that has been achieved has come to nothing in rolling through rolling to want. The durable performance of meeting pitch road surface of the structure demand is affected by two indexes mainly, namely the mixture and debulk designed. In these two indexes , lack any durable performance that can't ensure the pitch road surface , if insufficient debulk, optimum mixture that design will reduce serviceability , pitch of road surface, and good debulk can improve the result of a kind of nonstandard mixture effectively . So, debulk is considered to influence one of the most important factors of durable performance of road surface of pitch .Debulk course to reduce pitch course , air vent of content in the mixture, for solid particle stemming and orientating among one viscoplasticity medium course this, in the form of forming a kind of closely more knit and more effective particle to arrange. This course only takes place under the construction state in theory, but not under the traffic condition.1.2 Impact on debulk of composition material on the pitch road surface1.2.1collects material performancein order to reach the ideal solidity of pressing, it is very important to collect material and detailed some nature of collecting material thickly: Such as the particle form, raised angle , the absorbing water rate and surface are constructed, grade mix mixture most heavy to collect material size , thick to collect material proportion , consumption and type ,etc. , consumption of sand and powder of ore pigeonhole to pitch mixture solidity have direct influence.Under the same situation as other indexes , collect material one grade of mixture or disconnected grade mixed and mix mixture than exchanging debulk more than the single size from thick to the detailed even grade of mixture mixed , thick to collectmaterial proportion heavy pitch mixture, must increase the strength of keeping notably , could obtain the necessary space rate . On the other hand, many sand, ordetailed grade buy bituminous concrete to be very much easy to be plastic, this kindof mixture is still difficult to reach proper closely knit degree. The pitch mixture ofmuch sand tends towards pushes and shoves and difficult with debulking underdebulk function . The different kinds of packing has remarkable influence on debulkof the pitch mixture, according to survey, in a situation that other conditions are the same, ordinary silicate packing than lime stone ore powder pitch mixture and cement stone pitch mixture easy debulk bituminous concrete, pitch mixture total hole rate too very heavy difference have behind the shaping, 8% , 9.1% , 12% respectively.1.2.2pitch viscidity influencepitch viscidity influence pitch mixture strength degree, and can debulk nature have something to do with mixture. At the mixture, high viscidity can pin down particle move often as debulk pitch, if pitch viscidity too low, is it collect material to be particle easy to move and push and shove in real time to press. When pitch mixture temperature is higher, pitch is it is it collect material particle rub lubricant of obstruction to overcome to make, when the mixture has already been cooled, the pitch makes and combines the combinationmaterial which is collected the material particle. Generally speaking, in fixed 135 pitch being viscidity high,resistance, mixture of person who reduces space the heavier. So use high viscidity at the pitch , adopt higher debulk temperature to reduce viscidity promote pitch road surface but debulk essential means. Show according to materials data give temperature definitely , low drip of viscidity educate than high closely knit high degree that pitch reach of viscidity, through rise debulk temperature, high viscidity drip is it can reach high solidity of pigeonholing as low viscidity pitch to educate. Therefore understand debulk state , pitch of viscidity under the temperature to promote pitch road surface good debulk there are important meanings.1.2.3 performance of mixture influencein fact, performance , pitch of mixture, influence degree, road surface of debulk the heaviest to pitch, the influence than simple to collect material or drip breedobvious even. When pitch consumption is lower in the pitch mixture easy to is it do astringent , coarse mixture to form, often difficult debulk; When pitch consumption istoo great, can form and lubricate the mixture excessivly , make the mixture under thefunction of the road roller, form unstable and can fracture ing , mixture suffused withthe oil after the traffic is open; For lower than best pitch mixture of consumption, canthrough increase efficiency , debulk of course reduce the space rate, reach a kind ofsatisfaction; But if pitch consumption at the optimum value of higher thanning , press real-time , can't prevent out of shape limit , pitch of mixture from almost; Secondly , collect material water content meet the requirement of norm minimum while drying, such wet pitch mixture, present the inclination moved in the course of debulk, it is very difficult for the result to press worker.1.3 Temperature impact on pitch roadsurface debulk pitch debulk performance , mixture of road surface receive matchratio design, influence of factor, variety of pitch and temperature ,etc. of debulk, it isthe most influential but with debulk temperature. As everyone knows, the propertiesof pitch and pitch mixture are very sensitive to temperature, is it can know(125C1130 ) in the same grade is it under the mixture , roll rising of temperature atthe same time to mix to test. Mixture try on pieces of density increase , air rate reduce , until a certain temperature (145 1150 ) , mixture try on a density up to most heavy, at the same time the air rate is dropped to minimumly . If is it rise to continue under temperature this, can make density reduce, atmosphere rate increases. It is obvious temperature of mixture on the low side on the high side , will influence density and air rate , pitch of mixture (pigeonhole the solidity). The temperature of the pitch mixture is very important too in debulk of the construction site mixture. The temperature of the mixture has already become one of the two major factors influencing the solidityof high pressure of construction site and low air rate. Dark- Kui expressway layers of grains of type in being thick for 4cm the pitch. Construct location windy (4-5), organize the pitch but layer construct in with high temperatures period only, keep temperature bring 80 one 90 up to , make layer receive further debulk the pitch after all.1.4 mechanical impact on pitch roadBecause pitch road surface quality should reflect the mechanical impact on pitch road surface debulk of debulk through rolling finally, so, the selecting type and disposing of debulk machinery seems particularly important. Dark- expressway two bid section (13.4km ) pitch concrete road surface project Kui, construct by Xinjiang the north new construction of road and brige Limited Company, the layers of structure for 6cm thick grains of type grains of grains of type bituminous concrete of the typeten 4cm in the +5cm, the lower floor is the cement stability gravel storey. Each constructed to begin since April of 2000 by the end of September of the same age. Pitch by day work N eight P-1600 for dose rein in 1800 types mix and stir , paver of mixing and stir etc. mixture. According to the regional climate situation of known construction , and mix and stir the productivity of the equipment , paver, transporting the distance and transportation situation, the characteristic of the mixture, pave the thickness, pave layers of location ,etc. , select and make up to the mechanical pattern. Namely use two CC2l a pair of steel and a round of vibration road roller while pressing for the first time , press quietly twice at the speed of 3-5km; When is it press to replying, adopt two CC21 pairs of steel rounds of vibration road roller still, vibration at the speed of 4-5km/11 roll four, dispose the tire road roller of a Model YL16 at the same time, roll twice at the speed of 4-5km/h; After all when pressing, adopt one 2Y8/10 pairs of steel rounds of vibration road roller, at the speed of 3-4km/h quiet to press and accept mere twice. Make from the machinery of the above up and analyse that can be drawn , the having direct relations all over the speed that is counted , rolling with rolling of debulk on the road surface . As thickness , environmental temperature , effective debulk time of paving being when constructing within the person who allow, the ones that rolled would play a decisive role to the debulk of the road surface all over the speed that is counted with rolling.Can know according to experience. The rolls and only fix through testing section all over countinging of pitch road surface, and should also be in the type of the road roller, solidity of pressing, shake frequently under the situation confirmed of valid debulk time of the amplitude , mixture, could get . Can select through conclusion totest section to debulk speed at the same time. By result of the test analyse can know , while rolling all over counting the samly , roll slow than roll speed get high solidity ofpigeonholing soon, but it is only higher to press the solidity 0.4-0.8, there is no actualuse value, while replying and press and press after all, should try one' s best to choosethe high speed of rolling , in order to improve and press the mechanical homeworkefficiency of the way, reduce its quantity allocated1.5 pitch concrete glueand form analysis and research VFA (pitch consumption) of strength and pitch kind to solve pitch concrete glued and marries the strength problem. Because Marshall's test method has not already accorded with the actual conditions(because the concrete road surface of pitch has been pressed gently by the automobile tire on the real highway, Marshall test hit real number of times whether two sides each hit 75 times, if increase and hit the real number of times at the same time, aggregate break up and break to pieces, but gentle to press and increase aggregate have broken situation take place even quiet year again), so we must solve with other theory pitch concrete oilstone of as with glueing reason of envelope come and explain pitch concrete oil film thickness of as problem we (oilstone than) problem, we spread certain paste to paste while glueing envelopes, with the increase of the pressure, the surplus paste is crowded out, the tighter the envelope mouth is glued, there is the relation between certain pressure and thickness of the paste, the bigger the pressure is, the thinner the thickness of the paste is, it is the bigger to glue the strength of forming. The thickness of oil film of concrete of pitch is the same too, the greater the pressure of rolling the equipment (the tire) adopted when we construct is, keep high temperature for the first time, oil film thickness thin, pitch concrete that form it glues to be heavy to marry strength, this is that the American engineer JOHN.L.MCRAE gentleman's GTM machine rotates the gentle theory of pressing, this GTM testing machine has well solved the equipment (the pressure of the tire) of rolling, rolls the relation that temperature compares with oilstone (the thickness of the oil film). Seeing that of our country large-scale car amount tire pressure up to 1.0 Mpa more than already, propose and use GTM testing machine go on and rotate with 1.0 pressure of Mpa gentle to pigeonhole, temperature130 ∽ 135 when testing, after being steady in order to design the amount of oil used with the oil amount. The on-the-spot construction technological requirement is repliedand pigeonholes the temperature after finishing to control above 130 degrees, pressand adopt the large tonnage tire road roller for the first time (pressure of tires is morethan of 1.0 Mpas).The kind of the pitch and ore material glue the strength of forming influencingthe pitch concrete to the seizing of the pitch directly in addition, so the good modified pitch with good resisting splitting at the time of the low temperature at the same time of high-temperature stability has appeared at home, and should deal with the acid and neutral hard quality ore material , improve the seizing, generally adopt and catch the lime wash and is washed or mixed and adds the quick lime powder or low grade cement.2 Pitch preventative maintenance and machinery of concrete road surface2.1 The characteristic of concrete road surface of original sin and type ofdamagingPitch because concrete road surface use and glue and form strength better pitchmaterial made and combine the material , therefore gluing the strength of formingwhile strengthening the ore material greatly , has improved the intensity and stabilityof the mixture, make to use the quality and durability raise road surface . Pitchconcrete road surface have surface level, infiltrate, drive a vehicle advantage comfortable, with low noises, therefore find more and more extensive application. But it is often influenced by respects, such as weather, temperature, driving a vehicle and material, and such reasons of the respect as the road surface structure is designed, will present various disease unavoidably, and the disease has brought harmful influence on driving speed, road surface service life, passenger's comfortableness and traffic safety.Pitch damage of concrete road surface overall to can be divided into two bigclasses, one is structural damage , including the destruction of a certain part whole or among them of structure of road surface , the ones that made road surface unable tosupport and is scheduled loaded; Another functional damage, it might follow and structural damage take place, but because roughness and resisting the decline inslippery performance,etc. make it not have a function booked again, thus influencedquality of driving a vehicle.Pitch early disease of concrete road surface show as early rut and decay ofroughness, suffused with oil and resist slippery decline of performance often atexpressway, show as early small crack at ordinary arterial highway, detailed material lose cause undisguised, polishes, , the host is lost, surface disease that the road surface infiltrates. That the pitch wears out. If disease the can deal with but develop as one pleases in early days, must lead to the fact surface to be loose further, or cause serious deformation disease, such as peeling off and rut of depth of lower floor. Because of infiltrating, then cause structural damage, such as whole trough, thus must adopt the repairing method to carry on road surface maintenance. So seek one swift helping, cost rational settlement pitch concrete road surface early applicable technology of disease to maintain to be solved problem urgently in the work2.2 Important meaning of preventative maintenanceAround the relation that is built and maintaining, maintaining and preventing,with the constant perfection of the road network, only keep good road surface serviceability for a long time, the huge investment of road construction could give full play to its investment benefit , keep road surface good technological state must have one maintaining and support system come guarantee powerful for a long time, come from this meaning and say , maintain a kind of continuation that is road construction in fact. In the road surface maintains the relation with maintenance, People always get used to it after the road surface begins to be damaged for a long time , just remembers that will carry on maintenance to it, Carry on preventative meaning of maintenanceknow enough often under being also in good state to road surface. Preventative maintenance is a kind of periodic pressure maintenance measure in fact, it does not consider whether there is a certain damage on the road surface, Preventative maintenance best to implement opportunity should to in good state still in road surface, or go on only at the time of some disease omen .Though preventative maintenance needs to invest some expenses, it is a kind of expenses- benefit than very good maintenance measure. American departmentmentions in the road surface solution , what the American road industry was oncepassed to different grades of hundreds of thousands kilometers is followed, find thatthe serviceability and life-span of these roads have a common change characteristic :A road with qualified quality, performance drops by 40% within service life 75%,called preventative maintenance stage this stage. Such as be unable to in time maintenance, in 12% service life in the time, performance drops by 40% again afterwards, cause and maintain cost increase by a large margin , call that and correct maintenance stage this stages. Count and draw and invest through investigation 1 preventative maintenance fund can economize 3- l0 yuan correct maintenance conclusion of fund each time. U.S.A. SHRP plan one important achievement point out preventative maintenance delay road surface serviceability worsen the speed, lengthen its service life and economize the important meaning of expenses of life cycle.Correct serviceability that implement preventative maintenance and can keep theroad surface good , lengthen life cycle of road surface , reduce life cycle expenses andeconomize and maintain the fund. Plan and estimate according to SHRP , go onpreventative maintenance of 3-4 can lengthen 10- 1 years such as service life within life cycle of whole road surface, economize and maintain 45-50% of expenses, these foreign experience of benefitting is worth we drew lessons from . Need emphasize , implement to one- two road preventative maintenance can not give full play to his potential benefit and function only, put it preventative maintenance in network of highways support height of the system pay only, could fully embody its important strategic meaning and function .2.3 Choose suitable preventative maintenance machineryCarry on maintenance promptly when the road surface presents disease omen , make it not happen or continue developing, expanding , influence the stability of the basic unit, should carry on preventative maintenance. Preventative maintenance capital equipment have and irritate and sew machinery, road surface part mend homework machinery, heavy area surface punish machinery, usually.The pressure type irritates the sewing machine: Adopt artificial way to irritate and sew the homework, though can prevent the infiltration of the sub-surface ofrainwater , alleviate the development with further crack, but because the sealedmaterial is not irritated deeply enough, it is very difficult to reach the lasting result.Adopt pressure type irritate person who sew can irritate deep layer to reach the cracksealed material, irritate and sew better result , can lengthen service life of roadsurface , raise and go the security and comfortableness of the vehicle.Irritate and sew homework want and carry on clear to go on and irritate and sew after sewing first generally, greater than 3 crack of mm need and slot the homework generally. Irritate the heating that the sewing machine should be furnished with the control device of pressure, sealed material mainly or keep the device warm, for prevent spray gun hose from stop up and should take corresponding heating, keep measure warm also. The main characteristic of the pulling type is: Heat storehouse volume 470L, relatively more complete function havesuitable for irritating and sewing the homework by a large scale. Pair set up yuans of hand person who push away hot to irritate heating storehouse of person who sew volume 40 L, small easy to operate using flexible, low fabrication cost company, can look at according to work load feeling worthy of and heat cauldron again separately, suitable for hot to caulk the irritating and sewing the homework of material mainly; Have function cold to irritate person who sew without heating, use polymer modify water quality caulk the material mainly. If department pitch cold to irritate and sew material to modify emulsification, as emulsification after the solidification pitch, the modified pitch and crack of high polymer are glued and formed closely, can guarantee that there is good strength of seizing to irritate and sew the material and crack . Because cold to irritate and sew simple, easy to use craft, road surface give person who defend maintenance have wide prospects in pitch.Mend the hole machine in spraying type: Person who spray pitch road surfacemend technology one high-efficient mending road surface hole maintenancetechnology of pool fast, cardinal principle to utilize way of spaying with high presure , mix emulsification pitch that heat already through nozzle with conveyer belt dept. oforthopedics come to convey, spray the mixture to the hole pool of road surface evenly through the compressed air at a high speed, because passing through function reachesand glues the result formed closely knitly. Because craft simple, need and go on androll again, mend hole short activity duration, can open traffic quickly.Hope that you remember my result every day. Car chassis (or pulling type); Pitchpot of emulsification and heating and keep the device warm, sending the pipeline; Theaggregate stores the storehouse and conveyer belt; The cleaner stores the pot; Liquor pressure drive; Air compressor machine and nozzlemake up . In pool go on and clear up, after repairing, attenbant need and know one nozzle (operate button at nozzle handle) can finish the hole pool of road surface mend the homework only to hole. Should pay attention to controlling the quality of the good aggregate and grading in using; Choose the broken milk tempo of the good emulsification pitch ; Grasp the spraying amount and so as to ensure roughness of road surface after mending, Mend machinery in hot regeneration of road surface : For economize valuable way spend material, reduce and mill old material pollution of the environment these come down to plane, many place popularize old way spend regeneration of material, pitch hot recycled craft because with cold to mill- factory mix recycled craft compare on the spot among them in a more cost-effective manner, reduce old material freight and factory mix regeneration need use continuous type to mix and stir the reasons, such as equipment. Generally, the maintenance of the expressway is widely used with maintaining in JiangsuProvince. Reach materials that company offer according to Great Britain, " repair the roads king " its mend method compare with traditional method, it can save 5/6 to mend time, personnel save 1/2 for homework, the old way totally utilizes with the material, new pitch mixture consumption can save 1/2 .Hot recycled key part of equipment to heat board mainly on the spot, it wantoffer high-efficient heat energy of radiating, heat and should short time to old road surface have, and reach certain depth; Can't be overheated, make the pitch wear out , lose the recycled meaning. Great Britain reach company repair the roads king heat board take interval heating way, can one is penetrated to the road surface deep layer, and road surface top layer pitch wear out again and hotly, well solve this problem . Inaddition according to mend area of uniform size, heat board it's better to have the sub-zone function.The rare thick liquid seals one layer of pitch rare thick liquid of emulsificationwith modifying and seals one layer of pavers: Rare thick liquid seal layers oftechnology to new, old wear out, crack, smooth loose of road surface, hole trough.Disease can play prevent and function of maintenance, make road surface waterproof,resist slippery, levels, wear-resisting performance is raised rapidly. In recent years, because rare thick liquid seal layers of standardization that construct, standardize, construction quality raise and reducing of cost, rare thick liquid seal layer apply common road and expressway maintained and had in early days extensively already.Modify emulsification pitch rare thick liquid seal layer modify emulsification pitch with roll and break to pieces by water quality high polymer intensive material, mineral packing, water and surface that additive make up punish layer one, can pave the thin layer , solidify fast, can open traffic in an hour after constructing in characteristic, because modify the pitch rare thick liquid of emulsification seal one layer of solidification time faster than the ordinary rare thick liquid, modify emulsification pitch rare thick liquid seal layer can seal than traditional rare thick liquid layer thick. Used in the punishment of constructing disease, such as repairing, chap, rut, etc. of road surface mainly, can be used for sealing and improving resisting slippery punishment of road surface. But modify the pitch rare thick liquid of emulsification is the same as other thin layers are punished, only have highway section with steady structure now suitably, must construct after mending strongly when curved sinking value is not enough. Guarantee modify emulsification pitch there aren't the thick liquid not rares. Modify emulsification pitch rare thick liquid material viscidity heavy, pave layer relatively thick, generally speaking, modify emulsification pitch raise than the emulsification pitch viscidity not modifying by 30-50%, result in and make obstruction heavy thick liquid, the speed slows down. Demand and modify emulsification pitch rare thick liquid seal layers of equipment device corresponding to strengthen power store to make thick liquid, cloth fast, mobility fine, cloth speed pave range that the thickness regulate heavy, in order to meet modifying the constructionrequest for sealing layer of rare thick liquid of pitch of emulsification.The pitch road surface maintains machinery and cares the car synthetically, cares the car etc. multi-functionally, have given play to one's own characteristics in the maintenance of the superhighway. As the constant increase,, especially the expressway of the superhighway increase, and the constant innovation on maintenance work craft and material , the mechanical manufacturer to maintaining , including the respects, such as designing, making, after-sale service. Put forwardhigher and higher request. Too should maintain mechanical applying unit from maintenance, quality of attenbant of equipment, maintenance exertion of material,etc. pays enough attention, it is in many aspects to accomplish, multi-disciplinary close cooperation, could promote the preventative maintenance mechanized development of the highway to the maximum extent .3 pitch concrete road surface in constructing1.one of precautions infiltrate, design and grade kind pitch concrete match ratiovery in theory in constructing, in not butting if can't construct it guarantee by pitch concrete homogeneity(include and grade and last homogeneity that shut pitch , homogeneity that pave, roll homogeneity of shaping), pitch concrete road surface equally will produce infiltrate, purt thick liquid, rut, suffused with oil,etc. destroy the phenomenon in early days. Stone fit expressway pitch concrete finish adopt many broken stone pitch concrete (SAC) make finish structure, SAC structure does not infiltrate theoretically, and have good resisting the slipping and temperature stability, can meet and construct TD of depth > request for 0.7mm, why is it very good in some paragraphs on the line of Ann of stone, some paragraph very serious to destroy phenomenon in early days, main reason to guarantee pitch concrete homogeneity of road surface and pigeonhole solidity, pursue the roughness to cause excessivly. Guarantee pitch homogeneity of concrete and pigeonhole solidity key problem very in constructing. Sand celebrate academician Lin in " expressway pitch road surface destroy phenomenon with predict " book chapter ten describe to pitch concrete importance of homogeneity specially " in early days. Only brief here to sum up the。
桥梁设计外文翻译
中文4840字附录 2 外文资料翻译原文11.7.4 Deflection11.7.4.1 Dead Load and Creep DeflectionGlobal vertical deflections of segmental box-girder bridges due to the effects of dead load and post-tensioning as well as the long-term effect of creep are normally predicted during the design process by the use of a computer analysis program. The deflections are dependent, to a large extent, on the method of construction of the structure, the age of the segments when post-tensioned, and the age of the structure when other loads are applied. It can be expected, therefore, that the actual deflections of the structure would be different from that predicted during design due to changed assumptions.The deflections are usually recalculated by the contractor’s engineer, based on the actual construction sequence.11.7.4.2 Camber RequirementsThe permanent deflection of the structure after all creep deflections have occurred, normally 10 to 15 years after construction, may be objectionable from the perspective of riding comf ort for the users or for the confidence of the general public. Even if there is no structural problem with a span with noticeable sag, it will not inspire public confidence. For these reasons, a camber will normally be cast into the structure so that the p ermanent deflection of the bridge is nearly zero. It may be preferable to ignore the camber, if it is otherwise necessary to cast a sag in the structure during onstruction.11.7.4.3 Global Deflection Due to Live LoadMost design codes have a lim it on the allowable global deflection of a bridge span due to the effects of live load. The purpose of this limit is to avoid the noticeable vibration for the user and minimize the effects of moving load iMPact. When structures are used by pedestrians as well as motorists,the limits are further tightened.11.7.4.4 Local Deflection Due to Live LoadSimilar to the limits of global deflection of bridge spans, there are also limitations on the deflection of the local elements of the box-girder cross section. For example, the AASHTO Specifications limit the deflection of cantilever arms due to service live load plus iMPact to ¹⁄₃of the cantilever length,except where there is pedestrian use [1].11.7.5 Post-Tensioning Layout11.7.5.1 Exter nal Post-TensioningWhile most concrete bridges cast on falsework or precast beam bridges have utilized post-tensioning in ducts which are fully encased in the concrete section, other innovations have been made in precast segmental construction.Especially prevalent in structures constructed using the span-by-span method, post-tensioning has been placed inside the hollow cell of the box girder but not encased in concrete along its length. This is know as external post-tensioning. External post-tensioning is easily inspected at any time during the life of the structure, eliminates the problems associated with internal tendons, and eliminates the need for using expensive epoxy adhesive between precastsegments. The problems associated with internal tendons are (1) misalignment of the tendons at segment joints, which causes spalling; (2) lack of sheathing at segment joints; and (3) tendon pull-through on spans with tight curvature (see Figure 11.39). External prestressing has been used on many projects in Europe, the United States, and Asia and has performed well.11.7.5The provision for the addition of post-tensioning in the future in order to correct unacceptable creep deflections or to strengthen the structure for additional dead load, i.e., future wearing surface, is now required by many codes. Of the positive and negative moment post-tensioning, 10% is reasonable. Provisions should be made for access, anchorage attachment, and deviation of these additional tendons. External, unbonded tendons are used so that ungrouted ducts in the concrete are not left open. 11.8 Seismic Considerations11.8.1 Design Aspects and Design CodesDue to typical vibration characteristics of bridges, it is generally accepted that under seismic loads,some portion of the structure will be allowed to yield, to dissipate energy, and to increase the period of vibration of the system. This yielding is usually achieved by either allowing the columns to yield plastically (monolithic deck/superstructure connection), or by providing a yielding or a soft bearing system [6].The same principles also apply to segmental structures, i.e., the segmental superstructureneeds to resist the demands imposed by the substructure. Very few implementations of segmental struc-tures are found in seismically active California, where most of the research on earthquake-resistant bridges is conducted in the United States. The Pine Valley Creek Bridge, Parrots Ferry Bridge, and Norwalk/El Segundo Line Overcrossing, all of them being in California, are examples of segmental structures; however, these bridges are all segmentally cast in place, with mild reinforcement crossing the segment joints.Some guidance for the seismic design of segmental structures is provided in the latest edition of the AASHTO Guide Specifications for Design and Construction of Segmental Concrete Bridges [2], which now contains a chapter dedicated to seismic design. The guide allows precast-segmental construction without reinforcement across the joint, but specifies the following additional require-ments for these structures:•For Seismic Zones C and D [1], either cast-in-place or epoxied joints are required.•At least 50% of the prestress force should be provided by internal tendons.•The internal tendons alone should be able to carry 130% of the dead load.For other seismic design and detailing issues, the reader is referred to the design literature providedby the California Department of Transportation, Caltrans, for cast-in-place structures [5-8].11.8.2 Deck/Superstructure ConnectionRegardless of the design approach adopted (ductility through plastic hinging of the column or through bearings), the deck/superstructure connection is a critical element in the seismic resistant system. A brief description of the different possibilities follows.11.8.2.1 Monolithic Deck/Superstructure ConnectionFor the longitudinal direction, plastic hinging will form at the top and bottom of the columns. Since most of the testing has been conducted on cast-in-place joints, this continues to be the preferred option for these cases. For short columns and for solid columns, the detailing in this area can be readily adapted from standard Caltrans practice for cast-in-place structures, as shown on Figure 11.40. The joint area is then essentially detailed so it is no different from that of a fully cast-in-place bridge. In particular, a Caltrans requirement for positive moment reinforcement over the pier can be detailed with prestressing strand, as shown below. For large spans and tall columns, hollow column sections would be more appropriate. In these cases, care should be taken to confine the main column bars with closely spaced ties, and joint shear reinforcement should be provided according to Reference [3 or 7]. The use of fully precast pier segments in segmental superstructures would probably require special approval of the regulating government agency, since such a solution has not yet been tested for bridges and is not codified. Nevertheless, based upon first principles, and with the help of strut–tiemodels, it is possible to design systems that would work in practice [6]. The segmental superstructure should be designed to resist at least 130%of the column nominal moment using the strength reduction factors prescribed in Ref. [2]. Of further interest may be a combination of precast and cast-in-place joint as shown in Figure 11.41, which was adapted from Ref.[8]. Here, the precast segment serves as a form for the cast-in-place portion that fills up the remainder of the solid pier cap. Other ideas can also be derived from the building industry where some model testing has been performed. Of particular interest for bridges could be a system that works by leaving dowels in the columns and supplying the precast segment with matching formed holes, which are grouted after the segment is slipped over the reinforcement [9]11.8.2.2Deck/Superstructure Connection via BearingsTypically, for spans up to 45 m erected with the span-by-span method, the superstructure will be supported on bearings. For action in the longitudinal direction, elastomeric or isolation bearings are preferred to a fixed-end/expansion-end arrangement, since these better distribute the load between the bearings. Furthermore, these bearings will increase the period of the structure, which results in an overall lower induced force level (beneficial for higher-frequency structures), and isolation bearings will provide some structural damping as well.In the transverse direction, the bearings may be able to transfer load between super- and sub-structure by shear deformation; however, for the cases where this is not possible, shear keys can be provided as is shown in Figure 11.42. It should be noted that in regions of high seismicity,for structures with tall piers or soft substructures, the bearing demands may become excessive and a monolithic deck–superstructure connection may become necessary.For the structure-on-bearings approach, the force level for the superstructure can be readily，determined, since once the bearing demands are obtained from the analysis, they can be applied to the superstructure and substructure. The superstructure should resist the resulting forces at ultimate (using the applicable code force-reduction factors), whereas the substructure can be allowed to yield plastically if necessary.11.8.2.3 Expansion HingesFrom the seismic point of view, it is desirable to reduce the number of expansion hinges (EH)to a minimum. If EHs are needed, the most beneficial location from the seismic point of view is at midspan. This can be explained by observing Figure 11.43, where the superstructure bending midspan and for an EH at quarterspan. For the latter, it can be seen that the moment at the face The location of expansion hinges within a span, and its characteristics, depends also on the stiffness of the substructure and the type of connection of the superstructure to the piers. presents general guidelines intended to assist in the selection of location of expansion hinges.11.8.2.4 Precast Segmental PiersPrecast segmental piers are usually hollow cross section to save weight. From research inother areas it can be extrapolated that the precast segments of the pier would be joined by means of unbonded prestressing tendons anchored in the footing. The advantage of unbonded over bonded tendons is that for the former, the prestress force would not increase signi ficantly under high column displace-ment demands, and would therefore not cause inelastic yielding of the strand, which would other-wise lead to a loss of prestress.The detail of the connection to the superstructure and foundation would require some insight into the dynamic characteristics of such a connection, which entails joint opening and closing providing that dry joints are used between segments. This effect is similar to footing rocking, which is well known to be bene ficial to the response of a structure in an earthquake. This is due to the period shift and the damping of the soil. The latter effect is clearly not available to the precast columns, but the period shift is. Details need to be developed for the bearing areas at the end of the columns, as well as the provision for clearance of the tendons to move relative to the pier during the event.If the upper column segment is designed to be connected monolithically to the superstructure, yielding of the reinforcement should be expected. In this case, the expected plastic hinge length should be detailed ductile, using closely spaced ties [3,5].11.9 Casting and Erection11.9.1 CastingThere are obvious major differences in casting and erection when working with cast-in-placecantilever in travelers or in handling precast segments. There are also common features, which must be kept in mind in the design stages to keep the projects simple and thereby economic and ef ficient,such as• Keeping the length of segments equal and segments straight, even in curved bridges; • Maintaining constant cross section dimensions as much as possible;• Minimizing the number of diaphragms and stiffeners, and avoiding dowels through form- work.11.9.1.1 Cast-in-Place CantileversThe conventional form traveler supports the weight of the fresh concrete of the new segment by means of longitudinal beams or frames extending out in cantilever from the last segment. These beams are tied down to the previous segment. A counterweight is used when launching the traveler forward. The main beams are subjected to some de flections, which may produce cracks in the joint between the old and new segments. Jacking of the form during casting is sometimes needed to avoid these cracks. The weight of a traveler is about 60% of the weight of the segment.The rate of construction is typically one segment per traveler per week. Precast concrete anchor blocks are used to speed up post-tensioning operations. In cold climates, Conventional Travelers Construction Camber Controlcuring can be accelerated by various heating processes.The most critical practical problem of cast-in-place construction is deflection control. There are five categories of deflections during and after construction:•Deflection of traveler frame under the weight of the concrete segment;•Deflection of the concrete cantilever arm during construction under the weight of segment plus post-tensioning;•Deflection of cantilever arms after construction and before continuity;•Short- and long-term deflections of the continuous structure;•Short- and long-term pier shortenings and foundation settlements.The sum of the various deflection values for the successive sections of the deck allows the construc-tion of a camber diagram to be added to the theoretical profile of the bridge. A construction camber for setting the elevation of the traveler at each joint must also be developed.11.9.1.2 Precast SegmentsOpposite to the precast girder concept where the bridge is cut longitudinally in the precast segmental methods, the bridge is cut transversally, each slice being a segment. Segments are cast in a casting yard one at a time. Furthermore, the new segment is cast against the previously cast segment so that the faces in contact match perfectly. This is the match-cast principle. When the segments are reassembled at the bridge site, they will take the same relative position with regard to the adjacent segments that they had when they were cast. Accuracy of segment geometry is an absolute priority, and adequate surveying methods must be used to ensure follow-up of the geometry.Match casting of the segments is a prerequisite for the application of glued joints, achieved by covering the end face of one or both of the meeting segments with epoxy at the erection. The epoxy serves as a lubricant during the assembly of the segments, and it ensures a watertight joint in thefinished structure. Full watertightness is needed for corrosion protection of internal tendons (ten-dons inside the concrete). The tensile strength of the epoxy material is higher than that of the concrete, but, even so, the strength of the epoxy is not considered in the structural behavior of the joint. The required shear capacity is generally provided by shear keys, single or multiple, in com-bination with longitudinal post-tensioning.With the introduction of external post-tensioning, where the tendons are installed in PE ducts,outside the concrete but inside the box girder, the joints are relieved of the traditional requirement of watertightness and are left dry. The introduction of external tendons in connection with dry joints greatly enhanced the efficiency of precasting.11.9.1.3 Casting MethodsThere are two methods for casting segments. The first one is the long-line method, where all the segments are cast in their correct position on a casting bed that reproduces the span. The second method, used most of the time, is the short-line method, where all segments are cast in the same place in a stationary form, and against the previously cast segment. After casting and initial curing, the previously cast segment isremoved for storage, and the freshly cast segment is moved into place.11.9.1.4 Geometry ControlA pure translation of each segment between cast and match-cast position results in a straight bridge(Figure 11.45). To obtain a bridge with a vertical curve, the match-cast segment must first be translated and given a rotation in the vertical plane (Figure 11.46). Practically, the bulkhead is left fixed and the mold bottom under the conjugate unit adjusted. To obtain a horizontal curvature, the conjugate unit is given a rotation in the horizontal plane (see Figure 11.47). To obtain a variable superelevation, the conjugate unit is rotated around a horizontal axis located in the middle of the top slab (Figure 11.48).All these adjustments of the conjugate unit can be combined to obtain the desired geometry of the bridge.11.9.2 ErectionThe type of erection equipment depends upon the erection scheme contemplated during the design process; the local conditions, either over water or land; the speed of erection and overall construction schedule. It falls into three categories, independent lifting equipment such as cranes,deck-mounted lifting equipment such as beam and winch or swivel crane, and launching girder equipment.The principle of the method is to erect or cast the pier segment first, then to place typical segments one by one from each side of the pier, or in pairs simultaneously from both sides. Each newly placed precast segment is fixed to the previous one with temporary PT bars, until the cantilever tendons are installed and stressed. The closure joint between cantilever tips is poured in place and continuity tendons installed and stressed.In order to carry out this erection scheme, segments must be lifted and installed at the proper location. The simplest way is to use a crane, either on land or barge mounted. Many bridges have Bridge with superelevation.been erected with cranes as they do not require an investment in special lifting equipment. This method is slow. Typically, two to four segments per day are placed. It is used on relatively short bridges. An alternative is to have a winch on the last segment erected. The winch is mounted on a beam fixed to the segment. It picks up segments from below, directly from truck or barge. After placing the segment, the beam and winch system is moved forward to pick up the next segment and so on. Usually, a beam-and-winch system is placed on each cantilever tip. This method is also slow; however, it does not require a heavy crane on the site, which is always very expensive, especially if the segments are heavy.When bridges are long and the erection schedule short, the best method is the use of launching girders, which then take full advantage of the precast segmental concept for speed of erection.There are two essential types of self-launching gantries developed for this erection method. The first type is a gantry with a length slightly longer than the typical span (see Figure 11.49). During erection of the cantilever, the center leg rests on the pier while the rear leg rests on the cantilever tip of the previously erected span, which must resist the corresponding reaction. Prior to launching,the back spans must be made continuous. Then, the center leg is moved to the forward cantilever tip, which must resist the weight of the gantry plus the weight of the pier segment.This stage controls the design of the gantry, which must be made as light as possible, and of the cantilever.The second type of gantry has a length that is twice that of the typical span (see Figure 11.50).The reaction from the legs during the erection and launching of the next span is always applied on the piers, so there is no concentrated erection load on the cantilever tip. Each erection cycle consists of the erection of all typical segments of the cantilever and then the placement of the pier segment for the next cantilever, without changing the position of the truss.The gantries can be categorized by their cross section: single truss, with portal-type legs, and two launching trusses with a gantry across. The twin box girders of the bridge in Hawaii were built with two parallel, but independent trusses (see Figure 11.51), with a typical span of 100.0 m, segmentweights of 70 tons; the two bridge structures are 27.5 m apart with different elevations and longi-tudinal slopes. This system is a refinement of the first type of gantry applied to twin decks with variable geometry.Normally, the balanced cantilever method is used for spans from 60 to 110 m, with a launching girder. One full, typical cycle of erection is placing segments, installing and stressing post-tensioning tendons, and launching the truss to its next position. It takes about 7 to 10 days, but may vary greatly according to the specifics of a project and the sophistication of the launching girder. With proper equipment and planning, erection of 16 segments per day has been achieved.译文11.7.4 挠度11.7.4.1 恒载和徐变部分箱梁的整体变形是由恒载和后加张力造成的，也包括在设计过程中用电脑分析软件正常算出的徐变的长期影响。
桥梁毕业设计外文原文及翻译
外文文献翻译BRIDGE ENGINEERING AND AESTHETICSEvolvement of bridge Engineering,brief reviewAmong the early documented reviews of construction materials and structure types are the books of Marcus Vitruvios Pollio in the first century B.C.The basic principles of statics were developed by the Greeks , and were exemplified in works and applications by Leonardo da Vinci,Cardeno,and Galileo.In the fifteenth and sixteenth century, engineers seemed to be unaware of this record , and relied solely on experience and tradition for building bridges and aqueducts .The state of the art changed rapidly toward the end of the seventeenth century when Leibnitz, Newton, and Bernoulli introduced mathematical formulations. Published works by Lahire (1695)and Belidor (1792) about the theoretical analysis of structures provided the basis in the field of mechanics of materials .Kuzmanovic(1977) focuses on stone and wood as the first bridge-building materials. Iron was introduced during the transitional period from wood to steel .According to recent records , concrete was used in France as early as 1840 for a bridge 39 feet (12 m) long to span the Garoyne Canal at Grisoles, but reinforced concrete was not introduced in bridge construction until the beginning of this century . Prestressed concrete was first used in 1927.Stone bridges of the arch type (integrated superstructure and substructure) were constructed in Rome and other European cities in the middle ages . These arches were half-circular , with flat arches beginning to dominate bridge work during the Renaissance period. This concept was markedly improved at the end of the eighteenth century and found structurally adequate to accommodate future railroad loads . In terms of analysis and use of materials , stone bridges have not changed much ,but the theoretical treatment was improved by introducing the pressure-line concept in the early 1670s(Lahire, 1695) . The arch theory was documented in model tests where typical failure modes were considered (Frezier,1739).Culmann(1851) introduced the elastic center method for fixed-end arches, and showed that three redundant parameters can be found by the use of three equations of coMPatibility.Wooden trusses were used in bridges during the sixteenth century when Palladio built triangular frames for bridge spans 10 feet long . This effort also focused on the three basic principles og bridge design : convenience(serviceability) ,appearance , and endurance(strength) . several timber truss bridges were constructed in western Europe beginning in the 1750s with spans up to 200 feet (61m) supported on stone substructures .Significant progress was possible in the United States and Russia during the nineteenth century ,prompted by the need to cross major rivers and by an abundance of suitable timber . Favorable economic considerations included initial low cost and fast construction .The transition from wooden bridges to steel types probably did not begin until about 1840 ,although the first documented use of iron in bridges was the chain bridge built in 1734 across the Oder River in Prussia . The first truss completely made of iron was in 1840 in the United States , followed by England in 1845 , Germany in 1853 , and Russia in 1857 . In 1840 , the first iron arch truss bridge was built across the Erie Canal at Utica .The Impetus of AnalysisThe theory of structuresThe theory of structures ,developed mainly in the ninetheenth century,focused on truss analysis, with the first book on bridges written in 1811. The Warren triangular truss was introduced in 1846 ,supplemented by a method for calculating the correcet forces .I-beams fabricated from plates became popular in England and were used in short-span bridges.In 1866, Culmann explained the principles of cantilever truss bridges, and one year later the first cantilever bridge was built across the Main River in Hassfurt, Germany, with a center span of 425 feet (130m) . The first cantilever bridge in the United States was built in 1875 across the Kentucky River.A most impressive railway cantilever bridge in the nineteenth century was the First of Forth bridge , built between 1883 and 1893 , with span magnitudes of 1711 feet (521.5m). At about the same time , structural steel was introduced as a prime material in bridge work , although its quality was often poor . Several early examples are the Eads bridge in St.Louis ; the Brooklyn bridge in New York ; and the Glasgow bridge in Missouri , all completed between 1874 and 1883.Among the analytical and design progress to be mentioned are the contributions of Maxwell , particularly for certain statically indeterminate trusses ; the books by Cremona (1872) on graphical statics; the force method redefined by Mohr; and the works by Clapeyron who introduced the three-moment equations.The Impetus of New MaterialsSince the beginning of the twentieth century , concrete has taken its place as one of the most useful and important structural materials . Because of the coMParative ease with which it can be molded into any desired shape , its structural uses are almost unlimited . Wherever Portland cement and suitable aggregates are available , it can replace other materials for certain types of structures, such as bridge substructure and foundation elements .In addition , the introduction of reinforced concrete in multispan frames at the beginning of this century imposed new analytical requirements . Structures of a high order of redundancy could not be analyzed with the classical methods of the nineteenth century .The importance of joint rotation was already demonstrated by Manderla (1880) and Bendixen (1914) , who developed relationships between joint moments and angular rotations from which the unknown moments can be obtained ,the so called slope-deflection method .More simplifications in frame analysis were made possible by the work of Calisev (1923) , who used successive approximations to reduce the system of equations to one simple expression for each iteration step . This approach was further refined and integrated by Cross (1930) in what is known as the method of moment distribution .One of the most import important recent developments in the area of analytical procedures is the extension of design to cover the elastic-plastic range , also known as load factor or ultimate design. Plastic analysis was introduced with some practical observations by Tresca (1846) ; and was formulated by Saint-Venant (1870) , The concept of plasticity attracted researchers and engineers after World War Ⅰ, mainly in Germany , with the center of activity shifting to England and the United States after World War Ⅱ.The probabilistic approach is a new design concept that is expected to replace the classical deterministic methodology.A main step forward was the 1969 addition of the Federal Highway Adiministration (FHWA)”Criteria for Reinforced Concrete Bridge Members “ that covers strength and serviceability at ultimate design . This was prepared for use in conjunction with the 1969 American Association of State Highway Offficials (AASHO) Standard Specification, and was presented in a format that is readily adaptable to the development of ultimate design specifications .According to this document , the proportioning of reinforced concrete members ( including columns ) may be limited by various stages of behavior : elastic , cracked , andultimate . Design axial loads , or design shears . Structural capacity is the reaction phase , and all calculated modified strength values derived from theoretical strengths are the capacity values , such as moment capacity ,axial load capacity ,or shear capacity .At serviceability states , investigations may also be necessary for deflections , maximum crack width , and fatigue . Bridge TypesA notable bridge type is the suspension bridge , with the first example built in the United States in 1796. Problems of dynamic stability were investigated after the Tacoma bridge collapse , and this work led to significant theoretical contributions Steinman ( 1929 ) summarizes about 250 suspension bridges built throughout the world between 1741 and 1928 .With the introduction of the interstate system and the need to provide structures at grade separations , certain bridge types have taken a strong place in bridge practice. These include concrete superstructures (slab ,T-beams,concrete box girders ), steel beam and plate girders , steel box girders , composite construction , orthotropic plates , segmental construction , curved girders ,and cable-stayed bridges . Prefabricated members are given serious consideration , while interest in box sections remains strong .Bridge Appearance and AestheticsGrimm ( 1975 ) documents the first recorded legislative effort to control the appearance of the built environment . This occurred in 1647 when the Council of New Amsterdam appointed three officials . In 1954 , the Supreme Court of the United States held that it is within the power of the legislature to determine that communities should be attractive as well as healthy , spacious as well as clean , and balanced as well as patrolled . The Environmental Policy Act of 1969 directs all agencies of the federal government to identify and develop methods and procedures to ensure that presently unquantified environmental amentities and values are given appropriate consideration in decision making along with economic and technical aspects .Although in many civil engineering works aesthetics has been practiced almost intuitively , particularly in the past , bridge engineers have not ignored or neglected the aesthetic disciplines .Recent research on the subject appears to lead to a rationalized aesthetic design methodology (Grimm and Preiser , 1976 ) .Work has been done on the aesthetics of color ,light ,texture , shape , and proportions , as well as other perceptual modalities , and this direction is both theoretically and empirically oriented .Aesthetic control mechanisms are commonly integrated into the land-use regulations and design standards . In addition to concern for aesthetics at the state level , federal concern focuses also on the effects of man-constructed environment on human life , with guidelines and criteria directed toward improving quality and appearance in the design process . Good potential for the upgrading of aesthetic quality in bridge superstructures and substructures can be seen in the evaluation structure types aimed at improving overall appearance .LOADS AND LOADING GROUPSThe loads to be considered in the design of substructures and bridge foundations include loads and forces transmitted from the superstructure, and those acting directly on the substructure and foundation .AASHTO loads . Section 3 of AASHTO specifications summarizes the loads and forces to be considered in the design of bridges (superstructure and substructure ) . Briefly , these are dead load ,live load , iMPact or dynamic effect of live load , wind load , and other forces such as longitudinal forces , centrifugal force ,thermal forces , earth pressure , buoyancy , shrinkage andlong term creep , rib shortening , erection stresses , ice and current pressure , collision force , and earthquake stresses .Besides these conventional loads that are generally quantified , AASHTO also recognizes indirect load effects such as friction at expansion bearings and stresses associated with differential settlement of bridge components .The LRFD specifications divide loads into two distinct categories : permanent and transient .Permanent loadsDead Load : this includes the weight DC of all bridge components , appurtenances and utilities, wearing surface DW and future overlays , and earth fill EV. Both AASHTO and LRFD specifications give tables summarizing the unit weights of materials commonly used in bridge work .Transient LoadsVehicular Live Load (LL)Vehicle loading for short-span bridges :considerable effort has been made in the United States and Canada to develop a live load model that can represent the highway loading more realistically than the H or the HS AASHTO models . The current AASHTO model is still the applicable loading.桥梁工程和桥梁美学桥梁工程的发展概况早在公元前1世纪，Marcus Vitrucios Pollio 的著作中就有关于建筑材料和结构类型的记载和评述。
道路与桥梁专业外文翻译中英对照
本科毕业设计论文专业外文翻译专业名称：土木工程专业道路与桥梁年级班级：道桥08-5班学生姓名：指导教师：二○一二年五月十八日Geometric Design of HighwaysThe road is one kind of linear construction used for travel. It is made of the roadbed, the road surface, the bridge, the culvert and the tunnel. In addition, it also has the crossing of lines, the protective project and the traffic engineering and the route facility.The roadbed is the base of road surface, road shoulder, side slope, side ditch foundations. It is stone material structure, which is designed according to route's plane position .The roadbed, as the base of travel, must guarantee that it has the enough intensity and the stability that can prevent the water and other natural disaster from corroding.The road surface is the surface of road. It is single or complex structure built with mixture. The road surface require being smooth, having enough intensity, good stability and anti-slippery function. The quality of road surface directly affects the safe, comfort and the traffic.Highway geometry designs to consider Highway Horizontal Alignment, Vertical Alignment two kinds of linear and cross-sectional composition of coordination, but also pay attention to the smooth flow of the line of sight, etc. Determine the road geometry, consider the topography, surface features, rational use of land and environmental protection factors, to make full use of the highway geometric components of reasonable size and the linear combination.DesignThe alignment of a road is shown on the plane view and is a series of straight lines called tangents connected by circular. In modern practice it is common to interpose transition or spiral curves between tangents and circular curves.Alignment must be consistent. Sudden changes from flat to sharp curves and long tangents followed by sharp curves must be avoided; otherwise, accident hazards will be created. Likewise, placing circular curves of different radii end to end compound curves or having a short tangent between two curves is poor practice unless suitable transitions between them are provided. Long, flat curves are preferable at all times, as they are pleasing in appearance and decrease possibility of future obsolescence. However, alignment without tangents is undesirable on two-lane roads because some drivers hesitate to pass on curves. Long, flat curves should be used for small changes in direction, as short curves appear as “kink”. Also horizontal and vertical alignment must be considered together, not separately. For example, a sharp horizontal curve beginning near a crest can create a serious accident hazard.A vehicle traveling in a curved path is subject to centrifugal force. This is balanced by an equal and opposite force developed through cannot exceed certain maximums, and these controls place limits on the sharpness of curves that can be used with a design speed. Usually the sharpness of a given circular curve is indicated by its radius. However, for alignment design, sharpness is commonly expressed in terms of degree of curve, which is the central angle subtended by a 100-ft length of curve. Degree of curve is inversely proportional to the radius.Tangent sections of highways carry normal cross slope; curved sections are super elevated. Provision must be made for gradual change from one to the other. This usually involves maintaining the center line of each individual roadway at profile grade while raising the outer edge and lowering the inner edge to produce the desired super elevation is attained some distance beyond the point of curve.If a vehicle travels at high speed on a carefully restricted path made up of tangents connected by sharp circular curve, riding is extremely uncomfortable. As the car approaches a curve, super elevation begins and the vehicle is tilted inward, but the passenger must remain vertical since there is on centrifugal force requiring compensation. When the vehicle reaches the curve, full centrifugal force develops at once, and pulls the rider outward from his vertical position. To achieve a position of equilibrium he must force his body far inward. As the remaining super elevation takes effect, further adjustment in position is required. This process is repeated in reverse order as the vehicle leaves the curve. When easement curves are introduced, the change in radius from infinity on the tangent to that of the circular curve is effected gradually so that centrifugal force also develops gradually. By careful application of super elevation along the spiral, a smooth and gradual application of centrifugal force can be had and the roughness avoided.Easement curves have been used by the railroads for many years, but their adoption by highway agencies has come only recently. This is understandable. Railroad trains must follow the precise alignment of the tracks, and the discomfort described here can be avoided only by adopting easement curves. On the other hand, the motor-vehicle operator is free to alter his lateral position on the road and can provide his own easement curves by steering into circular curves gradually. However, this weaving within a traffic lane but sometimes into other lanes is dangerous. Properly designed easement curves make weaving unnecessary. It is largely for safety reasons, then, that easement curves have been widely adopted by highway agencies.For the same radius circular curve, the addition of easement curves at the ends changes the location of the curve with relationto its tangents; hence the decision regarding their use should be made before the final location survey. They point of beginning of an ordinary circular curve is usually labeled the PC point of curve or BC beginning of curve. Its end is marked the PT point of tangent or EC end of curve. For curves that include easements, the common notation is, as stationing increases: TS tangent to spiral, SC spiral to circular curve, CS circular curve to spiral, and ST spiral go tangent.On two-lane pavements provision of a wilder roadway is advisable on sharp curves. This will allow for such factors as 1 the tendency for drivers to shy away from the pavement edge, 2 increased effective transverse vehicle width because the front and rear wheels do not track, and 3 added width because of the slanted position of the front of the vehicle to the roadway centerline. For 24-ft roadways, the added width is so small that it can be neglected. Only for 30mph design speeds and curves sharper than 22°does the added width reach 2 ft. For narrower pavements, however, widening assumes importance even on fairly flat curves. Recommended amounts of and procedures for curve widening are given in Geometric Design for Highways.2. GradesThe vertical alignment of the roadway and its effect on the safe and economical operation of the motor vehicle constitute one of the most important features of road design. The vertical alignment, which consists of a series of straight lines connected by vertical parabolic or circular curves, is known as the “grade line.” When the grade line is increasing from the horizontal it is known as a “plus grade,” and when it is decreasing from the horizontal it is known as a “minus grade.” In analyzing grade and grade controls, the designer usually studies the effect of change in grade on the centerline profile.In the establishment of a grade, an ideal situation is one inwhich the cut is balanced against the fill without a great deal of borrow or an excess of cut to be wasted. All hauls should be downhill if possible and not too long. The grade should follow the general terrain and rise and fall in the direction of the existing drainage. In mountainous country the grade may be set to balance excavation against embankment as a clue toward least overall cost. In flat or prairie country it will be approximately parallel to the ground surface but sufficiently above it to allow surface drainage and, where necessary, to permit the wind to clear drifting snow. Where the road approaches or follows along streams, the height of the grade line may be dictated by the expected level of flood water. Under all conditions, smooth, flowing grade lines are preferable to choppy ones of many short straight sections connected with short vertical curves.Changes of grade from plus to minus should be placed in cuts, and changes from a minus grade to a plus grade should be placed in fills. This will generally give a good design, and many times it will avoid the appearance of building hills and producing depressions contrary to the general existing contours of the land. Other considerations for determining the grade line may be of more importance than the balancing of cuts and fills.Urban projects usually require a more detailed study of the controls and finer adjustment of elevations than do rural projects. It is often best to adjust the grade to meet existing conditions because of the additional expense of doing otherwise.In the analysis of grade and grade control, one of the most important considerations is the effect of grades on the operating costs of the motor vehicle. An increase in gasoline consumption and a reduction in speed are apparent when grades are increase in gasoline consumption and a reduction in speed is apparent when grades are increased. An economical approach would be to balancethe added annual cost of grade reduction against the added annual cost of vehicle operation without grade reduction. An accurate solution to the problem depends on the knowledge of traffic volume and type, which can be obtained only by means of a traffic survey.While maximum grades vary a great deal in various states, AASHTO recommendations make maximum grades dependent on design speed and topography. Present practice limits grades to 5 percent of a design speed of 70 mph. For a design speed of 30 mph, maximum grades typically range from 7 to 12 percent, depending on topography. Wherever long sustained grades are used, the designer should not substantially exceed the critical length of grade without the provision of climbing lanes for slow-moving vehicles. Critical grade lengths vary from 1700 ft for a 3 percent grade to 500 ft for an 8 percent grade.Long sustained grades should be less than the maximum grade on any particular section of a highway. It is often preferred to break the long sustained uniform grade by placing steeper grades at the bottom and lightening the grade near the top of the ascent. Dips in the profile grade in which vehicles may be hidden from view should also be avoided. Maximum grade for highway is 9 percent. Standards setting minimum grades are of importance only when surface drainage is a problem as when water must be carried away in a gutter or roadside ditch. In such instances the AASHTO suggests a minimum of %.3. Sight DistanceFor safe vehicle operation, highway must be designed to give drivers a sufficient distance or clear version ahead so that they can avoid unexpected obstacles and can pass slower vehicles without danger. Sight distance is the length of highway visible ahead to the driver of a vehicle. The concept of safe sight distance has two facets: “stopping” or “no passing” and “passing”.At times large objects may drop into a roadway and will do seriousdamage to a motor vehicle that strikes them. Again a car or truck may be forced to stop in the traffic lane in the path of following vehicles. In dither instance, proper design requires that such hazards become visible at distances great enough that drivers can stop before hitting them. Further more, it is unsafe to assume that one oncoming vehicle may avoid trouble by leaving the lane in which it is traveling, for this might result in loss of control or collision with another vehicle.Stopping sight distance is made up of two elements. The first is the distance traveled after the obstruction comes into view but before the driver applies his brakes. During this period of perception and reaction, the vehicle travels at its initial velocity. The second distance is consumed while the driver brakes the vehicle to a stop. The first of these two distances is dependent on the speed of the vehicle and the perception time and brake-reaction time of the operator. The second distance depends on the speed of the vehicle; the condition of brakes, times, and roadway surface; and the alignment and grade of the highway.On two-lane highways, opportunity to pass slow-moving vehicles must be provided at intervals. Otherwise capacity decreases and accidents increase as impatient drivers risk head-on collisions by passing when it is unsafe to do so. The minimum distance ahead that must be clear to permit safe passing is called the passing sight distance. In deciding whether or not to pass another vehicle, the driver must weigh the clear distance available to him against the distance required to carry out the sequence of events that make up the passing maneuver. Among the factors that will influence his decision are the degree of caution that he exercises and the accelerating ability of his vehicle. Because humans differ markedly, passing practices, which depend largely on human judgment and behavior rather than on the laws of mechanics, vary considerablyamong drivers.The geometric design is to ensure highway traffic safety foundation, the highway construction projects around the other highway on geometric design, therefore, in the geometry of the highway design process, if appear any unsafe potential factors, or low levels of combination of design, will affect the whole highway geometric design quality, and the safety of the traffic to bring adverse impact. So, on the geometry of the highway design must be focus on.公路几何设计公路是供汽车或其他车辆行驶的一种线形带状结构体.它是由路基、路面、桥梁、涵洞和隧道组成.此外,它还有路线交叉、工程和交通工程及沿线设施.路基是路面、路肩、边坡、等部分的基础.它是按照路线的平面位置在地面上开挖和成的土物.路基作为行车部分的基础,必须保证它有足够的强度和稳定性,可以防止水及其他自然灾害的侵蚀.路面是公路表面的部分.它是用混合料铺筑的单层或多层结构物.路面要求光滑,具有足够的强度,稳定性好和抗湿滑功能.路面质量的好环,直接影响到行车的安全性、舒适性和通行.公路几何线形设计要考虑公路平面线形、纵断面线形两种线形以及横断面的组成相协调,还要注意视距的畅通等等.确定公路几何线形时,在考虑地形、地物、土地的合理利用及环境保护因素时,要充分利用公路几何组成部分的合理尺寸和线形组合.1、线形设计道路的线形反映在平面图上是由一系列的直线和与直线相连的圆曲线构成的.现代设计时常在直线与圆曲线之间插入缓和曲线.线形应是连续的,应避免平缓线形到小半径曲线的突变或者长直线末端与小半径曲线相连接的突然变化,否则会发生交通事故.同样,不同半径的圆弧首尾相接曲线或在两半径不同的圆弧之间插入短直线都是不良的线形,除非在圆弧之间插入缓和曲线.长而平缓的曲线在任何时候都是可取的,因为这种曲线线形优美,将来也不会废弃.然而,双向道路线形全由曲线构成也是不理想的,因为一些驾驶员通过曲线路段时总是犹豫.长而缓的曲线应用在拐角较小的地方.如果采用短曲线,则会出现“扭结”.另外,线路的平、纵断面设计应综合考虑,而不应只顾其一,不顾其二,例如,当平曲线的起点位于竖曲线的顶点附近时将会产生严重的交通事故.行驶在曲线路段上的车辆受到离心力的作用,就需要一个大小相同方向相反的由超高和侧向磨擦提供的力抵消它,这些控制值对于某一规定设计车速可能采用曲线的曲率作了限制.通常情况下,某一圆曲线的曲率是由其半径来体现的.而对于线形设计而言,曲率常常通过曲线的程度来描述,即100英尺长的曲线所对应的中心角,曲线的程度与曲线的半径成反比.公路的直线地段设置正常的路拱,而曲线地段则设置超高,在正常断面与超高断面之间必须设置过渡渐变路段.通常的做法是维持道路每一条中线设计标高不变,通过抬高外侧边缘,降低内侧边缘以形成所需的超高,对于直线与圆曲线直接相连的线形,超高应从未到达曲线之前的直线上开始,在曲线顶点另一端一定距离以外达到全部超高.如果车辆以高速度行驶在直线与小半径的圆曲线相连的路段,行车是极不舒服.汽车驶近曲线路段时,超高开始,车辆向内侧倾斜,但乘客须维持身体的垂直状态,因为此时未受到离心力的作用.当汽车到达曲线路段时,离心力突然产生,迫使乘客向外倾斜,为了维持平衡,乘客必须迫使自己的身体向内侧倾斜.由于剩余超高发挥作用,乘客须作进一步的姿势的调整.当汽车离开曲线时,上述过程刚好相反.插入缓和曲线后,半径从无穷大逐渐过渡到圆曲线上的某一固定值,离心力逐渐增大,沿缓和曲线心设置超高,离心力平稳逐渐增加,避免了行车颠簸.缓和曲线在铁路上已经使用多年,但在公路上最近才得以应用,这是可以理解的.火车必须遵循精确的运行轨道,采用缓和曲线后,上述那种不舒服的感觉才能消除.然而,汽车司机在公路上可以随意改变侧向位置,通过迂回进入圆曲线来为自己提供缓和曲线.但是在一个车道上有时在其他车道上做这种迂回行驶是非常危险的.设计合理的缓和曲线使得上述迂回没有必要.主要是出于安全原因,公路部门广泛采用了缓和曲线.对于半径相同的圆曲线来说,在未端加上缓和曲线就会改变曲线与直线的相关位置,因此应在最终定线勘测之前应决定是否采用缓和曲线.一般曲线的起点标为PC或BC,终点标为PT或EC.对含有缓和曲线的曲线,通常的标记配置增为：TC、SC、CS和ST.对于双向道路,急弯处应增加路面宽度,这主要基于以下因素：1驾驶员害怕驶出路面边缘；2由于车辆前轮和后轮的行驶轨迹不同,车辆有效横向宽度加大；3车辆前方相对于公路中线倾斜而增加的宽度.对于宽度为24英尺的道路,增加的宽度很小,可以忽略.只有当设计车速为30mile/h,且曲度大于22℃时,加宽可达2英尺.然而,对于较窄的路面,即使是在较平缓的曲线路段上,加宽也是很重要推荐加宽值及加宽设计见公路线形设计2、纵坡线公路的竖向线形及其对车辆运行的安全性和经济性的影响构成了公路设计中最重要的要素之一.竖向线形由直线和竖向抛物线或圆曲线组成,称为纵坡线.纵坡线从水平线逐渐上升时称为坡度变化的影响.在确定坡度时最理想的情况是挖方与填方平衡,没有大量的借方或弃方.所有运土都尽可能下坡运并且距离不长,坡度应随地形而变,并且与既有排水系统的升、降方向一致.在山区,坡度要使得挖填平衡以使总成本最低.在平原或草原地区,坡度与地表近似平行,介是高于地表足够的高度,以利于路面排水,苦有必要,可利用风力来清除表面积雪.如公路接近或沿河流走行,纵坡线的高度由预期洪水位来决定.无论在何种情况下,平缓连续的坡度线要比由短直线段连接短竖曲线构成的不断变向的坡度线好得多.由上坡向下坡变化的路段应设在挖方路段,而由下坡向上坡变化的路段应设在填方路段,这样的线形设计较好,往往可以避免形成与现状地貌相反的圭堆或是凹地.与挖填方平衡相比,在确定纵坡线时,其他考虑则重要得多.城市项目通常比农村项目要求对控制要素进行更详尽的研究,对高程进行更细致地调整.一般来说,设计与现有条件相符的坡度较好,这样可避免一些不必要的花费.在坡度的分析和控制中,坡度对机动车运行费用的影响是最重要的考虑因素之一.坡度增大油耗显然增大,车速就要减慢.一个较为经济的方案则可使坡度减小而增加的年度成本与坡度不减而增加的车辆运行年度成本之间相平衡.这个问题的准确方法取决于对交通流量和交通类型的了解,这只有通过交通调查才能获知.在不同的州,最大纵坡也相差悬殊,AASHTO标准建议由设计车速和地形来选择最大纵坡.现行设计以设计车速为70mile/h时最大纵坡为5%,设计车速30mile/h时,根据地形不同,最大纵坡一般为7％－12％.当采用较长的待续爬坡时,在没有为慢行车辆提供爬坡道时,坡长不能够超过临界坡长.临界坡长可从3％纵坡的1700英尺变化至8%纵坡的500英尺.持续长坡的坡度必须小于公路任何一个断面的最大坡度,通常将长的持续单一纵坡断开,设计成底部为一陡坡,而接近坡顶则让坡度减小.同时还要避免由于断面倾斜而造成的视野受阻.调整公路的最大纵坡为9%只有当路面排水成问题时,如水必须排至边沟或排水沟,最小坡度标准才显示其重要性.这种情况下,AASHTO标准建议最小坡度为%.3、视距为保证行车安全,公路设计必须使得驾驶员视线前方有足够的一段距离,使他们能够避让意外的障碍物,或者安全地超车.视距就是车辆驾驶员前方可见的公路长度.安全视距具有两方面含义：“停车视距”或“不超车视距”或“超车视距”.有时,大件物体也许会掉到路上,会对撞上去的车辆造成严重的危害.同样,轿车或卡车也可能会被一溜车辆阻在车道上.无论是哪种情况发生,合理设计要求驾驶员在一段距离以外就能看见这种险情,并在撞上去之前把车刹住.此外,认为车辆通过离开所行驶的车道就可以躲避危险的想法是不安全的,因为这会导致车辆失控或与另一辆车相撞.停车视距由两部分组成：第一部分是当驾驶员发现障碍物面作出制动之前驶过的一段距离,在这一察觉与反应阶段,车辆以其初始速度行驶；第二部分是驾驶员刹车后车辆所驶过的一段距离.第一部分停车视距取决于车速及驾驶员的察觉时间和制动时间.第二部分停车视距取决于车速、刹车、轮胎、路面的条件以及公路的线形的坡度.在双车道公路上,每间隔一定距离,就应该提供超越慢行车辆的机会.否则,公路容量将降低,事故将增多,因为急燥的驾驶员在不能安全超车时冒着撞车危险强行超车,能被看清的允许安全超车的前方最小距离叫做超车视距.驾驶员在做出是否超车的决定时,必须将前方的能见距离与完成超车动作所需的距离对比考虑.影响他做出决定的因素是开车的小心程度和车辆加速性能.由于人与人的显着差别,主要是人的判断和动作而不是力学定理决定的超车行为随着驾驶员的不同而大不相同.公路是确保交通安全的基础,建设的其他项目都围绕的而展开,因此,在的过程中,如果出现任意的不安全潜在因素,或者低水平的组合,都会影响到整个的质量,并对交通的安全带来不利影响.因此对于的必须予以重点关注.。
桥梁毕业设计外文翻译---混凝土桥的结构处理工具
第二部分英文翻译Reliability analysis :a structures management tool for concrete bridgesReinforced concrete structures are susceptible to a variety of deterioration mechanisms, including alkali-thaw action and chloride ingress. Substantial research has been undertaken in relation to these mechanisms and other problems. This has particularly been the case over the last 20 years or so, where the objective has been to identify causes, consequences and develop remediation strategies. This has improved understanding of long-term behaviour of reinforced concrete and resulted in the development of techniques to increase deterioration resistance.At present, the most common approach is to act after a problem has been identified, known as re-active maintenance. This may not be the most economic solution since, in many cases, maintenance is more costly than preventative treatments. However, owners are often reluctant to pay for preventative treatments before deterioration is apparent. Early application of treatments may not be the optimal solution in the long run. Integrated deterioration and performance prediction modeling is essential to pro-actively plan and prioritise inspection, testing and maintenance. This becomes increasingly important as infrastructure ages and justification for maintenance funding becomes increasingly critical.Performance assessment can be achieved through surveys, testing and formal calculations, ideally based on site data that represent, as accurately as possible, the state of the structure. By integrating predictive deterioration models with assessment tools and performance criteria (at element, structure or group level) it becomes possible to base the maintenance regime on time-dependent performance profiles. This is particularly relevant in the context of whole-wife costing procedures.Substantial research has been undertaken in relation to these mechanisms and other problems. This has particularly been the case overthe last 20 years or so, where the objective has been to identify causes, consequences and develop remediation strategies. This has improved understanding of long-term behaviour of reinforced concrete and resulted in the development of techniques to increase deterioration resistance.At present, the most common approach is to act after a problem has been identified, known as re-active maintenance. This may not be the most economic solution since, in many cases, maintenance is more costly than preventative treatments. However, owners are often reluctant to pay for preventative treatments before deterioration is apparent. Early application of treatments may not be the optimal solution in the long run. Integrated deterioration and performance prediction modeling is essential to pro-actively plan and prioritise inspection, testing and maintenance. This becomes increasingly important as infrastructure ages and justification for maintenance funding becomes increasingly critical.Reliability analysis has emerged as an important tool in this multi-objective management process, which must take into account safety, functionality and sustainability criteria. In simple terms, the reliability of a structure or a system is the probability of achieving a particular performance level. Probability or likelihood is the appropriate measure, since all engineering systems are susceptible to uncertainties, arising from random phenomena and incomplete knowledge. Reliability analysis in structural engineering enables quantification of uncertainties associated with loading, materials, deterioration, modeling and other factors. These are integrated into a method that estimates the probability of reaching the specified performance level during the service life of a structure. The method is increasingly being used in bridge engineering, both for calibration of safety levels in codes and standards and improving and refining assessment methodologies. The purpose of this article is to outline its application in managing bridges susceptible to deterioration.Although data for many deterioration variables can be derived from laboratory studies, there is an absence of similar data real structures. Animportant feature of the model is the facility to modify initial predictions, based on published (known as ‘prior’) data, using information and data obtained directly from the actual structures. Reliability analysis is appropriate for this pursose as if it can readily incorporate additional data, updating the probability of reaching a performance target. The concept is analogous to updating the probability of arriving on time whilst on a train, having just obtain some extra information regarding the operating conditions ahead.Typical results produced by the probabilistic deterioration model for a crossbeam chloride exposure zone, similar to the delaminated area shown in Figure 3,are shown in Figure 4.Assuming a threshold of 40% initiation is specified for the first inspection, the model suggests that it should be undertaken after eight years .Assuming that inspection indicates significantly less corrosion initiation (e.g.only about 10%) and attributed, through site investigations, to concrete cover being higher than expected, a revised prediction of the performance profile may be generated .The bridge management actions may then be altered accordingly.Figure 5 illustrates how a limit state profile for this zone changes with assumed conditions. The deterioration model has been integrated with bond limit state equations .Thus, assuming that the component has a target nominal probability of failure of 1×10-5 per year, profile 1 suggests a lifetime of only 17 to 18 years, whereas Profile 2 suggests 30 to 31 years. Both are short lifetimes when compared with the normal life expectancy of bridges. However, initial conditions relating to these results assume that the deck joint has failed from the outset .Alternatively ,the expressions for modelling bond strength may be over-conservative ,as they were developed for intact structures.Substantial research has been undertaken in relation to these mechanisms and other problems. This has particularly been the case over the last 20 years or so, where the objective has been to identify causes, consequences and develop remediation strategies. This has improvedunderstanding of long-term behaviour of reinforced concrete and resulted in the development of techniques to increase deterioration resistance.At present, the most common approach is to act after a problem has been identified, known as re-active maintenance. This may not be the most economic solution since, in many cases, maintenance is more costly than preventative treatments. However, owners are often reluctant to pay for preventative treatments before deterioration is apparent. Early application of treatments may not be the optimal solution in the long run. Integrated deterioration and performance prediction modeling is essential to pro-actively plan and prioritise inspection, testing and maintenance. This becomes increasingly important as infrastructure ages and justification for maintenance funding becomes increasingly critical.Bridge performance criteriaCurrent UKassessment codes are concerned with ultimate limit states (ULS) and do not explicitly require checking of serviceability limit states (ULS). It is assumed that an existing structure has experienced SLS loads during its life. However, the widely accepted SLS criteria of deflection and cracking do not fully take into account the problems posed by deterioration. Deterioration-based criteria such as rust staining, delamination and spalling need to be considered because they clearly influence bridge performance, both functional and financial. These often prove the dominant factor with regard to bridge management strategy.By explicitly considering and specifying performance levels, the engineer is aware of the important deterioration indicators in order to establish the inspection and maintenance regime for the particular structure/member. These performance levels may change over time, due to changes in function, loading, structure importance etc. for example, the relationship between actual and required performance is conceptualized by the diagram shown in Figure 1. Thus, reliability analysis may be used to formulate the probability that performance will exceed that required, thereby estimating the reliability of the structure. The performancemeasure can be related to safety, functionality or any other appropriate criterion.Modeling chloride-induced deteriorationThis particular project concentrated on one specific area of reinforced concrete deterioration, specifically arising from chloride ingress. Chlorides are present in de-icing salts used in the UK during winter. Chloride ions migrate though the concrete, e.g. by absorption and diffusion. Under suitable conditions, they initiate reinforcement bar corrosion. The corrosion mechanism produces rust. The increased volume of the metal, due to the rust, leads to cracking, delamination and spalling of the concrete cover. This results in more rapid and extensive reinforcement corrosion.Reinforced concrete bridge elements located below expansion joints are particularly susceptible to chloride attack if the joint fails. Highway viaducts in the UK typically consist of a reinforced concrete crossbeam directly located below the expansion joint,(see Figure 2).Many crossbeams have suffered severe reinforcement corrosion, delamination and spalling. A typical example is shown in Figure 3, where the reinforcement cover over the crossbeam has delaminated.A probabilistic deterioration model for reinforced concrete bridge components was developed, taking into account the characteristics of these structures and their environment. It assumes that both diffusion and absorption play a part in chlotide migration through the concrete, the variability in the quantity of de-icing salts reaching the crossbeam surface and how these quantities vary annually. Typical chloride exposure zones considered for the crossbeams include the:●Horizontal surface below a failedexpansion joint where water ponding can occur●vertical surface below a failed expansion jointsurfaces below an intact expansion joint, but exposed to traffic spray etc.Although data for many deterioration variables can be derived from laboratory studies, there is an absence of similar data real structures. An important feature of the model is the facility to modify initial predictions, based on published (known as ‘prior’) data, using information and data obtained directly from the actual structures. Reliability analysis is appropriate for this pursose as if it can readily incorporate additional data, updating the probability of reaching a performance target. The concept is analogous to updating the probability of arriving on time whilst on a train, having just obtain some extra information regarding the operating conditions ahead.Typical results produced by the probabilistic deterioration model for a crossbeam chloride exposure zone, similar to the delaminated area shown in Figure 3,are shown in Figure 4.Assuming a threshold of 40% initiation is specified for the first inspection, the model suggests that it should be undertaken after eight years .Assuming that inspection indicates significantly less corrosion initiation (e.g.only about 10%) and attributed, through site investigations, to concrete cover being higher than expected, a revised prediction of the performance profile may be generated .The bridge management actions may then be altered accordingly.Laboratory and site data are essential for improved deterioration modeling and reliability .Much data collection and test interpretations made in the deterioration models. Given the costs associated with maintaining safe, reliable infrastructure systems, this is an area where a concreted effort by industry and organizations could yield substantial benefits.Figure 5 illustrates how a limit state profile for this zone changes with assumed conditions. The deterioration model has been integrated with bond limit state equations .Thus, assuming that the component has a target nominal probability of failure of 1×10-5 per year, profile 1 suggests a lifetime of only 17 to 18 years, whereas Profile 2 suggests 30 to 31 years. Both are short lifetimes when compared with the normal lifeexpectancy of bridges. However, initial conditions relating to these results assume that the deck joint has failed from the outset .Alternatively ,the expressions for modelling bond strength may be over-conservative ,as they were developed for intact structures.Concluding remarksReliability analysis provides a rational and consistent framework for treating uncertainties .It can be a useful management tool with which similar structures can be compared through performance profiles which change over time. The results must be interpreted with care, and stand up to common sense and engineering judgement . Sensitivity analysis is strongly recommended, and can be readily performed.Laboratory and site data are essential for improved deterioration modeling and reliability .Much data collection and test interpretations made in the deterioration models. Given the costs associated with maintaining safe, reliable infrastructure systems, this is an area where a concreted effort by industry and organizations could yield substantial benefits.AcknowledgementsThis work was performed with the support of the Highways Agency. The views expressed are those of the authors and are not necessarily shared by the Highways Agency.可靠性分析——混凝土桥的结构处理工具钢筋混凝土桥结构对多种恶化机制敏感，包括碱趋于和缓行动和氯化物进入。
桥梁工程毕业设计外文翻译
Review of assessment and repair of fire-damaged RChighway bridgesAbstract：This paper presents a review of the progress of the research and engineering practice of assessment and repair of fire-damaged RC highway bridges，based on which existing and pressing problems of the evaluation method are pointed out．At last，Prospect for the development of assessment and repair of fire-damaged highway bridges is also proposed．Key words：fire damage；assessment；repair techniques；RC structure；bridge 1 PrefaceFires can cause great structural damage to bridges and major disruption to highway operations．These incidents stem primarily from vehicle accident (often oil tanker) fires，bridges might also be damaged by fires in adjacent facilities and from other causes．Quite a few of them，though rarely happened，lead to severe structural damage or collapse and casualty．On June 2，2008，fire disaster broke out under the 18th span of Nanjing Yangtze River Bridge and lasted for approximate 75min．During the fire’s development and extinguishment，the structure experienced the sharp rise and fall in temperature causing severe damage to fire- stricken segments．On April 29，2007，a gasoline tanker overturned on the connector from Interstate 8O to Interstate 880 in California．The intense heat from the subsequent fuel spill and fire weakened the stee1 underbelly of the elevated roadway ,collapsing approximately 165 feet of this elevated roadway onto a section of I—880below．On March 25，2004，Connecticut，United States，a tanker truck carrying fuel swerved to avoid a car and overturned，dumping 8000 gallons of home heating oil onto the Howard Avenue overpass．The consequent towering inferno melted the bridge structure and caused the southbound lanes to sag several feetUndocumented number of bridge fires occurring throughout the world each year cause varying degrees of disruption，repair actions，and maintenance cost．Althoughfires caused damage to the bridge structures ,some bridges continue to function after proper repair and retrofit．Still in some situations they have to be repaired for the cause of traffic pressure even though supposed to be dismantled and reconstructed．However ,in other cases，structures are severely damaged in the fire disaster and fail to function even after repair，or the costs of repair and retrofit overweigh their reconstruction costs overwhelmingly even if they are repairable，under which situation reconstruction serves as a preferable option．Therefore in—situ investigation and necessary tests and analyses should be conducted to make comprehensive assessment of the residual mechanical properties and working statuses after fire and to evaluate the degrees of damage of members and structures , in reference to which decisions are made to determine whether Fire damaged structures should be repaired or dismantled and reconstructed．Urgent need from engineering practice highlighted the necessity to understand the susceptibility and severity of these incidents as wel1 as to review available information on mitigation strategies，damage assessments，and repair techniques.2 Progress in Research and Engineering Practice2.1 Processes of Assessment and Repair of Fire damaged BridgeStructureIn China and most countries in the world，most highway bridges are built in RC structure．And the practice of the assessment and repair techniques of bridge structure after fire directly refer to that of RC structure，which，to date，domestic and foreign scholars have made great amount of research on，with their theories and practices being increasingly mature .As for the assessment and repair of fire-damaged reinforced concrete structures，there are two mainstream assessment processes in world．Countries including United States，United Kingdom and Japan adopt the assessment process stipulated by The British Concrete Society .This process grates the severity of fire damage of concrete structure into four degrees according to thedeflection，damage depth，cracking width, color，and loading capacity variation of fire-damaged structures and adopt four corresponding strategies (including demolish，strengthen after safety measures，strengthen. and strengthen in damaged segments) to deal with them accordingly．In general，this process is a qualitative method and considered，however，not quantity enough.In Chinese Mainland and Taiwan ，the prevailing as assessment and repair process of fire damaged incorporates following steps：In comparison this process is more detailed．(1)Conduct In-situ inspections，measurements，and tests including color observation，concrete observation，degree of rebar exposure observation，cracking measurement，deflection measurement，various destructive and nondestructive test methods as grounds for assessment of fire—damaged structures．In assessment of the post -fire mechanical properties of fire—damaged structures，historical highest temperature and temperature distribution of structure during the fire serve as decisive factors．The common methods to determine them incorporate petrographic analysis，ultrasonic method，Rebound method，Ignition Loss method，core test，and color observation method(2)calculate to determine whether the fire-damaged structure can meet the demand of strength and deflection under working loads after fire using mechanical properties of rebar and concrete before and after fire based on the historical highest and temperature distribution of structures obtained from step one．There are two main methods to evaluate the post -fire performance of fire-damaged structures：FEM method and Revised Classic Method．(3)On the basis of test and calculation results obtained from step two，take corresponding repair strategies and particular methods to strengthen the fire-damaged structures.2．2 Repair TechniquesFor the repair of fire—damaged bridge，proper repair methods should be taken according to the degree and range of the structure’s damage．Meanwhile the safetyand economy of the repair methods should be concerned with by avoiding destructing the original structure，preserving the valuable structural members，and minimizing unnecessary demolishment and reconstruction。
桥梁论文中英译文
毕业设计(论文)外文资料翻译系别：专业：班级：姓名：学号：外文出处：土木工程网附件： A.英文文献； B. 译文附录A英文文献BridgesBridges are great symbols of mankind’s conquest of space.The sight of the crimson tracery of the Golden Gate Bridge against a setting sun in the Pacific Ocean, or the atch of the Garabit Biaduct soaring triumphantly above the deep gorge. Fills one’s heart with wonder and admiration for the art of their builders[11]. They are the enduring expressions of mankind’s determination to remove all barriers in its pursuit of a better and freer world. Their design and building schemes are conceived in dream-like bisions. But vision and determination are not enough. All the physical forces of nature and gravity must be understood with mathematical precision and such forces have to be resisted by manipulating the right materials in the right pattern. This requires both the inspiration of an artist and the skill of an artisan.Scientific knowledge about materials and structural behavior has expanded tremendously, and computing techniques are now widely available to manipulate complex theories in innumerable ways very quickly. Engineers have virtually revolutionized bridge design and construction methods in the past decade. The advances apply to short-medium and long-span bridges.For permanent bridge，the most commonly used materials are steel and concrete. Bridge of many different type are built with these materials, used singly or in combination. Timber may be used for temporary above-water construction, for the elements of a structure that lie below the waterline (particularly timber pile s), or for short-span bridges located on secondary roads. A few short-span aluminum bridges have been built in the United States on an experimental basis.The principal portions of a bridge may be said to be the “substructure” and the “superstructure.” This division is used here simply for convenience, since in many bridges there is no clear dividing lint between the two.Common elements of the substructure are abutments (usually at the bridge ends) and piers (between the abutments).Piers and abutments often rest on separately constructed foundations such as concrete spread footings or groups of bearing piles;these foundations are part of the substructure. Occasionally a bridge substructure comprises a series of pile bents in which the piles extend above the waterline and are topped by a pile cap that, in turn, supports the major structural elements of the superstructure. Such bents often are used in arepetitive fashion as part of along, low, over-water crossing.In recent years, the dividing lines between short-medium and long-span bridge have blurred somewhat. Currently, spans of 20 to 100 ft (6.1 to 30.5m) are regarded as short by many designers, who have developed many standardized designs to handle these spans economically. Medium spans range up to, per-haps, 400ft (121.9m) in modern bridge practice, depending on the organization involved and the materials used. Long spans range up to 4000ft (1219.2m) or more, but a clear span above 1000ft (304.8m)is comparatively rare.In the United States, highway bridges generally must meet loading, design, and construction requirements of the AASHTO Specification. The design and construction of railway bridges are governed by provisions of the AREA Manual for Railway Engineering. Design requirements for pedestrian crossings and bridges serving other purposes may be established by local or regional codes and specifications. ACI Code provisions are often incorporated by reference, and in most cases serve as model provisions for other governing documents.Bridge spans to about 100 ft often consist of pre-cast integral-deck units. These units offer low initial cost, minimum maintenance, and fast easy constrction, with traffic interruption. Such girders are generally pretensioned, the units are placed side by side, and are often post-tensioned laterally at intermediate diaphragm lacations, After which shear keys between adjacent units are filled with non-shrinking mortar. For highway spans, an asphalt wearing surface may be applied directly to the top of the pre-cast concrete. In some cases, a cast-in-place slab is placed to provide composite action.For medium-span highway bridges, to about 120 ft, AASHTO standard I beams are generally used. he are intended for use with a composite cast-in-place roadway slab. Such girders often combine pre-tensioning of the pre-cast member withpost-tensioning of the composite beam after the deck is placed.Pre-cast girders may not be used for spans much in excess of 120 ft because of the problems of transporting and erecting large, heavy units. On the other hand, there is a clear trend toward the use of longer spans for bridges. Highway safety is improved by eliminating central piers and moving outer piers away from the edge of divided highways. For elevated urban expressways, long spans facilitate access and minimize obstruction to activities below. Concern for environmental damage has led to the choice of long spans for continuous viaducts. For river crossing, intermediate piers may be impossible because of requirements of navigational clearance.Such requirements have led to the development in Europe, and more recently in the western hemisphere, of long span segmental pre-stressed concrete box girder bridges. In typical construction of this type, piers are cast-in-place, often using the slip-forming technique. A “hammerhead” section of box girder is then cast at the top of the pier, and construction proceeds in each direction by the balanced cantilever method. The construction is advanced using either cast-in-place or pre-cast segments, each post-tensioned to the previously completed construction. Finally, after the closing cast-in-place joint is made at mid-span, the structure is further post-tensioned for full continuity.Bridge may also be classed as “deck” or “through” types. In the deck type of bridge, the roadway is above the supporting structure; that is, the load-carrying elements of the superstructure are below the roadway. In the through type of bridge, the roadway passes between the elements of the super-structure, as in a through steel-truss bridge. Deck structures predominate: they have a clean appearance, provide the motorist with a better view of the surrounding area, and are easier to widen if future traffic requires it.Examples of short-span concrete bridges include cast-in-lace, reinforced concrete beam (and slab);simple-span, pre-stressed (this type incorporates pre-cast, pre-stressed I-girders or box girders topped by a cast-in-place deck);and cast-in place box girder.The designer of each medium-and long-span bridge tries to devise a structurethat is best suited to the conditions encountered at that particular location. The result is an almost bewildering variety of structures that differ either in basic design principles or in design details.General categories of steel bridge are briefly described in the following paragraphs.Girder bridges come in two basic varieties-plate and box girders.Plate girders are used in the United States for medium spans. They generally are continuous structures with maximum depth of girder over the piers and minimum depth at mid-span. The plate girders generally have an I cross section; they are arranged in lines that support stringers, floor-beams, and, generally, a cast-in-lace concrete deck. The girders are shop-fabricated by welding; field connections generally are by high-strength bolts.Welded-steel box girder structures are generally similar to plate girder spans except for the configuration of the bridge cross section.Rigid frames are used occasionally, most often for spans in the range of 75 to 100 ft (22.9 to 30.5 m) and for grade0separation structures.Arch bridges are used for longer spans at locations where intermediate piers cannot be used and where good rock is available to withstand the thrusts at the arch abutments.Variations in the arch bridge are specially suited in the span range of 200 to 500m and thus provide a transition between the continuous box girder bridge and the stiffened suspension cable. The cables provided above the deck and connected to the towers would permit elimination of intermediate piers facilitating a larger width for purposes of navigation. Because of the damping effect of inclined cables, the cable-stayed decks are less prone to wind-induced oscillations than suspension bridges.Suspension bridges are used for very long spans or for shorter spans where intermediate piers cannot be built. An example is the Verrazano Narrows Bridge which was completed in 1964.The $305 million,4260ft(1298.5m)structure spans the entrance to New York Harbor to join Staten Island and Brooklyn.Concrete bridges come in nearly as great a variety as do steel bridges.The bridge construction in France benefits by a strong growth in rail and highway infrastructures. For the time being the competition with other material turns to the advantage of composite bridge solutions. Before presenting any features concerning the recent trends in composite bridge design it is important to clarify, the bridge market, through the analysis of some statistical data.In France, there is a very limited market for long span bridges. In the recent construction, the demand for bridges of span length higher than 200m is rather exceptional. The main market is for bridges of span length (or multi span length) less than 100m.In France 800 to 1200 bridges are built every year, which represent about 300,000m to 500,000m of deck surface. However the majority of bridges being erected each year are of small span length. Less than 10% of the bridge patrimony have span. Length greater than 30m and deck surface greater than 1000 m2. Now that the market has been identified lets have an idea, in term of competitiveness, of the French market situation between several bridge types. In 1977 less than 2.5%.Of bridges were steel or composite bridges. The steel-concrete composite construction has continued to grow steadily over the last 15 years. This trend is mainly attributable to the gain in competitiveness of composite bridges against reinforcedand prestressed concrete bridges.For short span length the majority of steel bridges is of concrete type. Bridges composed of steel beams encased in concrete are very often used for railway bridges of small span length in order to meet stiffness requirements.The recent statistical evaluation, performed by SETRA [1] on the bridges recently built in France between 1990 to 1993 by various owners (State, Highway concession companies, Departments and Communities, SNCF) shows that the competitive span length range for steel and concrete composite bridges is between 30 and 110 m with a very distinctive peak for the interval 60 to 80 m. In that range of spans length it is noticed that 85% of bridges being built belong to the composite category (Fig. 4).The statistical analysis of the deck cost per square metre of surface confirms that the average price for a composite bridge is less than the price for a concrete bridge for spans length within intervals of 40 to 60 m and 60 to 80 m. The difference being of 1 500 FF/m2 over a total cost of 8 200 FF/m2 (VAT excluded) in favour of the composite bridge. It means that an 18% cost difference represents a great shift in terms of competition.The last 15 years have seen a great simplification of composite bridges for both roadway and railway bridges, which have made them, as previously indicated, very competitive compared to prestressed and reinforced bridges. These composite bridges, that we will name them as classical, have however several features which are described hereafter. Then, from these classical features, improvements have been constantly brought to the design and execution of composite bridges, which will be depicted later on.The traditional composite roadway bridge is composed of two longitudinal girders which are connected to the concrete slab by shear connectors (usually welded stud are mostly met; however steel angle connectors are still used). A limited number of transverse cross beams joining the two longitudinal girders, usually not connected to the slab — see half cross section (a) are welded to the vertical stiffeners. The main girders have a few numbers of horizontal stiffeners, if any which are mostly needed to resist the stress state in the girder webs occurring at the launching phase.Plain concrete is formed form a hardened mixture of cement, water, fine aggregate, coarse aggregate (crushed stone or gravel), air, and often other admixtures. The plastic mix is placed and consolidated in the formwork, then cured to facilitate the acceleration of the chemical hydration reaction of the cement/water mix, resulting in hardened concrete. The finished product has high compressive strength, and low resistance to tension, such that its tensile strength is approximately one-tenth of its compressive strength. Consequently, tensile and shear reinforcement in the tensile regions of sections has to be provided to compensate for the weak-tension regions in the reinforced concrete element.It is this deviation in the composition of a reinforced concrete section from thehomogeneity of standard wood or steel sections that requires a modified approach to the basic principles of structural design. The two components f the heterogeneous reinforced concrete section are to be so arranged and proportioned that optimal use is made of the materials involved. That is possible because concrete can easily be given any desired shape by placing and compacting the wet mixture of the constituent ingredients into suitable forms in which the plastic mass hardens. If the various ingredients are properly proportioned, the finished product becomes strong, durable, and, in combination with the reinforcing bars, adaptable for use as main members of any structural system.The techniques necessary for placing concrete depend on the type of member to be cast: that is, whether it is a column, a beam, a wall, a slab, a foundation, amass concrete dam, or an extension of previously placed and hardened concrete. For beams, columns, and walls, the forms should be well oiled after cleaning them, and the reinforcement earth should be compacted and thoroughly moistened to about 6 in. in depth to avoid absorption of the moisture present in the wet concrete. Concrete should always be placed in horizontal layers which are compacted by means of high-prequency power-driven vibrators of either the immersion or external type, as the case requires, unless it is placed by pumping. It must be kept in mind, however, that over vibration can be harmful since it could cause segregation of the aggregate and bleeding of the concrete.Hydration of the cement takes place in the presence of moisture at temperatures above F50. It is necessary to maintain such a condition in order that the chemical hydration reaction can take place. If drying is too rapid, surface cracking takes place. This would result in reduction of concrete strength due to cracking as well as the failure to attain full chemical hydration.It is clear that a large number of parameters have to be dealt with in proportioning a reinforced concrete element, such as geometrical width, depth, area of reinforcement, steel strain, concrete strain, steel strees, and so on. Consequently, trial and adjustment is necessary in the choice of concrete sections, with assumptionsbased on conditions at site, availability of the constituent materials, particular demands of the owners, architectural and headroom requirements, the applicable codes, and environmental conditions. Such an array of parameters has to be considered because of the fact that reinforced concrete is often a site-constructed composite, in contrast to the standard mill-fabricate beam and column sections in steel structures.A trial section has to be chosen for each critical location in a structural system. The trial section has to be analyzed to determine if its nominal resisting strength is adequate to carry the applied factored load. Since more than one trial is often necessary to arrive at the required section, the first design input step generates into a series of trial-and-adjustment analyses.The trial-and-adjustment procedures for the choice of a concrete section lead to the convergence of analysis and design. Hence every design is an analysis once a trial section is chosen. The availability of approach as a more efficient, compact, and speedy instructional method compared with the traditional approach of treating the analysis of reinforced concrete separately from pure design.The rapid growth from 1945 onwards in the prestressing of concrete shows that there was a real need for this high-quality material. The quality must be high because the worst conditions of loading normally occur at the beginning of the life of the member, at the transfer of stress later, when the concrete has become stronger and the stress in the steel has decreased because of creep in the steel and the concrete, and shrinkage of the concrete. Faulty members are therefore observed and thrown out early, before they enter the structure, or at least before it becomes inconvenient and expensive to remove them.The main advantages of prestressed concrete in comparison with reinforced concrete are:(a) The whole concrete cross-section resists load. In reinforced concrete about half the section, the cracked area below the neutral axis, does no useful work. Working deflections are smaller.(b) High working stresses are possible. In reinforced concrete they are notusually possible because hey result in severe cracking which is always ugly and may be dangerous if it causes rusting of the steel.(c) Cracking is almost completely avoided in prestressed concrete.The main disadvantage of prestressed concrete is that much more care is needed to make it than reinforced concrete and it is therefore more expensive, but because it is of higher quality less of it needs to be used.It can therefore happen that a solution of a structural problem may be cheaper in prestressed concrete than in reinforced concrete, and it does often happen that a solution is possible with prestressing but impossible without it.Prestressing of the concrete means that it is placed under compression before it carries any working load. This means that the section can be designed so that it takes no tension or very little under the full design load. It therefore has theoretically no cracks and in practice the concrete in which it is embedded has hardened. After the concrete has hardened enough to take the stress from the steel, some of the stress is transferred from the steel to the concrete. In a bridge with abutments able to resist thrust, the prestress can be applied without steel in the concrete. It is applied by jacks forcing the bridge inwards from the abutments. This method has the advantage that the jacking force, or prestress, can be varied during the life of the structure as required.In the ten years from 1950 to 1960 prestressed concrete ceased to be an experimental material and engineers won confidence in its use. With this confidence came an increase in the use of precast prestressed concrete particularly for long-span floors or the decks of motorways. Wherever the 500 m long, provided that most of the spans could be made the same and not much longer than 18 m, it became economical to use factory-precast prestressed beams, at least in industrial areas near a precasting factory. Most of these beams are heat-cured so as to free the forms quickly or reuse.In this period also, in the United States, precast prestressed roof beams and floor beams were used in many school buildings, occasionally 32 m long or more. Such long beams over a single span could not possibly be successful in reinforced concrete unless they were cast on site because they would have to be much deeper and muchheavier than prestressed concrete beams. They would certainly be less pleasing to the eye and often more expensive than the prestressed concrete beams. These school buidings have a strong, simple architectural appeal and will be a pleasure to look at for many years.The most important parts of a precast prestressed concrete beam are the tendons and the concrete. The tendons, as the name implies, are the cables, rods or wires of steel which are under tension in the concrete. Before the concrete has hardened (before transfer of stress), the tendons are either unstressed (post-tensioned prestressing) or are stressed and held by abutments outside the concrete (pre-tensioned prestressing). While the concrete is hardening it grips each tendon more and more tightly by bond along its full length. End anchorages consisting of plates or blocks are placed on the ends of the tendons of post-tensioned prestressed units, and such tendons are stressed up at the time of transfer, when the concrete has hardened sufficiently. In the other type of presstressing, with pre-tensioned tondons, the tendons are released from external abutments at the moment of transfer, and act on the concrete through bond or anchorage or both, shortening it by compression, and themselves also shortening and losing some tension.Further shortening of the concrete (and therefore of the steel) takes place with time. The concrete is said to creep. This means that it shortens permanently under load and spreads the stresses more uniformly and thus more safely across its section. Steel also creeps, but rather less. The result of these two effects (and of the concrete shrinking when it dries) is that prestressed concrete beams are never more highly stressed than at the moment of transfer.The factory precasting of long prestressed concrete beams is likely to become more and more popular in the future, but one difficulty will be road transport. As the length of the beam increases, the lorry becomes less and less manoeuvrable until eventually the only suitable time for it to travel is in the middle of the night when traffic is at a minimum. The limit of length for road transport varies tith the traffic in the district and the route, whether the roads are straight or curved. Precasting at the site avoids these difficulties; it may be expensive, but it has often been used for largebridge beams.Materials for building must have certain physical properties to be structurally useful. Primarily, they must be able to carry a load, or weight, without changing shape per- manently. When a load is applied to a structure member, it will deform; that is, a wire will stretch or a beam will bend. However, when the load is removed, the wire and the beam come back to the original positions. This material property is called elasticity. If a material were not elastic and a deformation were present in the structure after removal of the load, repeated loading and unloading eventually would increase the deformation to the point where the structure would become useless .All materials used in architect- tural structures, such as stone and brick, wood, steel, aluminum, reinforced concrete, and plastics, behave elastically within a certain defined range of loading. If the loading is increased above the range, two types of behavior can occur: brittle and plastic. In the former, the material will break suddenly. In the latter, the material begins to flow at a certain load (yield strength), ultimately leading to fracture. As examples, steel exhibits plastic behavior, and stone is brittle. The ultimate strength of a material is measured by the stress at which failure (fracture) occurs.A second important property of a building material is its stiffness. This property is defined by the elastic modulus, which is the ratio of the stress (force per unit area), to the strain (deformation per unit length). The elastic modulus, therefore, is a measure of the resistance of a material to deformation under load. For two materials of equal area under the same load, the one with the higher elastic modulus has the smaller deforma- tion. Structural steel, which has an elastic modulus of 30 million pounds per square in- ch (psi), or 2 100 000 kilograms per square centimeter, is 3 time as stiff as aluminum, 10 times as stiff as concrete, and 15 times as stiff as wood.Masonry consists of natural materials, such as stone, or manufactured products, such as brick and concrete blocks. Masonry has been used since ancient times; mud bricks were used in the city of Babylon for secular buildings, and stone was used for the great temples of the Nile Valley. The Great Pyramid in Egypt, standing 481 feet (147 meters) high, is the most spectacular masonry construction. Masonry units origin- nally were stacked without using any bonding agent, but all modern masonryconstruc- tion uses a cement mortar as a bonding material. Modern structural materials include stone, brick of burnt clay or slate, and concrete blocks.Masonry is essentially a compressive material; it cannot withstand a tensile force, that is, a pull. The ultimate compressive strength of bonded masonry depends on the strength of the masonry unit and the mortar. The ultimate strength will vary from 1 000 to 4 000 psi (70 to 280 kg/sq cm), depending on the particular combination of masonry unit and mortar used.Timber is one of the earliest construction materials and one of the few natural ma- terials with good tensile properties. Hundreds of different species of wood are found throughout the world, and each species exhibits different physical characteristics. Only a few species are used structurally as framing members in building construction. In the United States, for instance, out of more than 600 species of wood, only 20 species are used structurally. These are generally the conifers, or softwoods, both because of their abundance and because of the ease with which their wood can be shaped. The species of timber more commonly used in the United States for construction are Douglas fir, Southern pine, sqruce, and redwood. The ultimate tensile strength of these species varies from 5 000 to 8 000 psi (350 to 560 kg/sq cm). Hardwoods are used primarily for cabinetwork and for interior finishes such as floors.Because of the cellular nature of wood, it is stronger along the grain than across the grain. Wood is particularly strong in tension and compression parallel to the grain. And it has great bending strength. These properties make it ideally suited for columns and beams in structures. Wood is not effectively used as a tensile member in a truss, however, because the tensile strength of a truss member depends upon connections between members. It is difficult to devise connections which do not depend on the shear or tearing strength along the grain, although numerous metal connectors have been produced to utilize the tensile strength of timbers.Steel is an outstanding structural material. It has a high strength on a pound-for- pound basis when compared to other materials, even though its volume-for-volume weight is more than ten times that of wood. It has a high elastic modulus, which results in small deformations under load. It can be formed by rolling into variousstructural shapes such as I-beams, plates, and sheets; it also can be cast into complex shapes; and it is also produced in the form of wire strands and ropes for use as cables in suspension bridges and suspended roofs, as elevator ropes, and as wires for prestressing concrete. Steel elements can be joined together by various means, such as bolting, riveting, or welding. Carbon steels are subject to corrosion through oxidation and must be protected from contact with the atmosphere by painting them or embedding them in concrete. Above temperatures of about 700F (3710C), steel rapidly loses its strength, and there- fore it must be covered in a jacket of a fireproof material (usually concrete) to increase its fire resistance.The addition of alloying elements, such as silicon or manganese, results in higher strength steels with tensile strengths up to 250 000 psi (17 500 kg/sq cm). These steels are used where the size of a structural member becomes critical, as in the case of co- lumns in a skyscraper.Aluminum is especially useful as a building material when lightweight, strength, and corrosion resistance are all important factors. Because pure aluminum is extremely soft and ductile, alloying elements, such as magnesium, silicon, zinc, and copper, must be added to it to impart the strength required for structural use. Structural aluminum alloys behave elastically. They have an elastic modulus one third as great as steel and therefore deform three times as much as steel under the same load. The unit weight of an aluminum alloy is one third that of steel, and therefore an aluminum member will be lighter than a steel member of comparable strength. The ultimate tensile strength of aluminum alloys ranges from 20 000 to 60 000 psi (1 400 to 4 200 kg/sq cm).Aluminum can be formed into a variety of shapes; it can be extruded to form I- beams, drawn to form wire and rods, and rolled to form foil and plates. Aluminum members can be put together in the same way as steel by riveting, bolting, and (to a lesser extent) by welding. Apart from its use for framing members in buildings and prefabricated housing, aluminum also finds extensive use for window frames and for the skin of the building in curtain-wall construction.Concrete is a mixture of water, sand and gravel, and portland cement. Crushed。
毕设必备道路桥梁专业毕业设计英文翻译(英文原文+中文翻译)
Accident Analysis and PreventionThis paper describes a project undertaken to establish a self-explaining roads (SER) design programmeon existing streets in an urban area. The methodology focussed on developing a process to identifyfunctional road categories and designs based on endemic road characteristics taken from functionalexemplars in the study area. The study area was divided into two sections, one to receive SER treatments designed to maximise visual differences between road categories, and a matched control area to remainuntreated for purposes of comparison. The SER design for local roads included increased landscaping andcommunity islands to limit forward visibility, and removal of road markings to create a visually distinctroad environment. In comparison, roads categorised as collectors received increased delineation, additionof cycle lanes, and improved amenity for pedestrians. Speed data collected 3 months after implementationshowed a significant reduction in vehicle speeds on local roads and increased homogeneity of speeds onboth local and collector roads. The objective speed data, combined with r esidents’ speed choice ratings,indicated that the project was successful in creating two discriminably different road categories.2010 Elsevier Ltd. All rights reserved.1. Introduction1.1. BackgroundChanging the visual characteristics of roads to influencedriver behaviour has come to be called the self-explaining roads(SER) approach (Theeuwes, 1998; Theeuwes and Godthelp, 1995;Rothengatter, 1999). Sometimes referred to as sustainable safety,as applied in the Netherlands, the logic behind the approach isthe use of road designs that evoke correct expectations and drivingbehaviours from road users (Wegman et al., 2005; Weller etal., 2008). The SER approach focuses on the three key principlesof functionality, homogeneity, and predictability (van Vliet andSchermers, 2000). In practice, functionality requires the creation ofa few well-defined road categories (e.g., through roads, distributorroads, and access roads) and ensuring that the use of a particularroad matches its intended function. Multifunctional roadslead to contradictory design requirements, confusion in the mindsof drivers, and incorrect expectations and inappropriate drivingbehaviour. Clearly defined road categories promote homogeneity intheir use and prevent large differences in vehicle speed, direction,and mass. Finally, predictability, or recognisability, means keepingthe road design and layout within each category as uniform as possibleand clearly differentiated from other categories so that thefunction of a road is easily recognised and will elicit the correctbehaviour from road users. The SER approach has been pursued tothe largest extent in the Netherlands and the United Kingdom but ithas also been of some interest inNewZealand. In 2004, the NationalRoad Safety Committee and the Ministry of Transport articulateda new National Speed Management Initiative which stated “Theemphas is is not just on speed limit enforcement, it includes perceptualmeasures that influence the speed that a driver feels is appropriatefor the section of road upon which they are driving–in effect the ‘selfexplainingroad”’ (New Zealand Ministry of Transport, 2004).In cognitive psychological terms, the SER approach attempts toimprove road safety via two complementary avenues. The first is toidentify and use road designs that afford desirable driver behaviour.Perceptual properties such as road markings, delineated lane width,and roadside objects can function as affordances that serve as builtininstructions and guide driver behaviour, either implicitly orexplicitly (Charlton, 2007a; Elliott et al., 2003; Weller et al., 2008).This work is more or less a direct development of work on perceptualcountermeasures, perceptual cues in the roading environmentthat imply or suggest a particular speed or lane position, eitherattentionally or perceptually (Charlton, 2004, 2007b; Godley et al.,1999).A second aspect of the SER approach is to establish mentalschemata and scripts, memory representations that will allowroad users to easily categorise the type of road on which they are.1.2. Localised speed managementThe traditional approaches to improving speed management,traffic calming and local area traffic management (LATM) havefocussed on treating specific problem locations or “black spots”in response to crash occurrences or complaints from the public(Ewing, 1999). A potential disadvantage of these approaches is thataddressing the problem with localised treatments can lead to are-emergence of the problem at another location nearby. Further,when applied inappropriately, localised approaches may addressthe problem from only one perspective, without considering theimpact on other types of road users or residents. When traffic calmingtreatments rely on physical obstacles such as speed humpsthey can be very unpopular with bothresidents and road users andcan create new problems associated with noise, maintenance, andvandalism (Martens et al., 1997).From an SER perspective, treatments that are highly localizedor idiosyncratic may do more harm than good by adding to themultiplicity of road categories and driver uncertainty, rather thanbuilding driver expectations around a few uniform road types.Instead of considering a single location in isolation, SER roaddesigns are considered within a hierarchy of road functions; e.g.,access roads, collector roads, and arterial roads. Although SERschemes may employ physical design elements used in trafficcalming schemes (e.g., road narrowing with chicanes and accesscontrols) they also employ a range of more visually oriented featuressuch as median and edge line treatments, road markings,pavement surfaces, and roadside furniture. For an effective SERscheme it is important to select the combination of features that will afford the desired driver speeds and to ensure their consistentuse to form distinct categories of road types (van der Horst andKaptein, 1998; Wegman et al., 2005).road category that would meet the three SER principles of functional use, homogeneous use, and predictable use. Herrstedt (2006)reported on the use of a standardised catalogue of treatments compiledfrom researcher and practitioner advice. Goldenbeld and vanSchagen (2007) used a survey technique to determine road characteristicsthat minimise the difference between drivers’ ratingsof preferred speed and perceived safe speed and select road featuresthat make posted speeds “credible”. Aarts and Davidse (2007)used a driving simulator to verify whether the “essential recognisabilitycharacteristics” of different road classes conformed to theexpectations of road users. Weller et al. (2008) employed a range of statistical techniques, including factor analysis and categoricalclustering to establish the road characteristics that drivers use tocategorise different road types.The practical difficulties of implementing an SER system thusbecome a matter of finding answers to a series of questions. Howdoes one create a discriminable road hierarchy for an existingroad network? What road characteristics should be manipulatedto establish category-defining road features? How can SER roadfeatures and selection methods be made relevant and appropriatefor a local context? (Roaddesigns appropriate for The Netherlandswould not be suitable in New Zealand, in spite of its name.) A surveyof national and international expert opinion in order establishcategory-defining road features for New Zealand roads revealedthat the regional character and local topography of roads oftenundercut the usefulness of any standardised catalogue of designcharacteristics (Charlton and Baas, 2006).1.4. Goals of the present projectThe project described in this paper sought to develop anddemonstrate an SER process based on retrofitting existing roadsto establish a clear multi-level road hierarchy with appropriatedesign speeds, ensuring that each level in the hierarchy possesseda different “look and feel”. Rather than transferring SER designs already in use internationally, the project attempted to develop amethod that would build on the features of roads in the local area;extending road characteristics with desirable affordances to otherroads lacking them and creating discriminable road categories inthe process. Of interest was whether such a process could producecost-effective designs and whether those designs would be effectivein creating different road user expectations and distinct speedprofiles for roads of different categories.2. MethodsThe research methodology/SER design process developed forthis project progressed through a series of five stages: (1) selectionof study area; (2) identification of the road hierarchy; (3) analysisof the road features; (4) development of a design template; and (5)implementation and evaluation of the SER treatments. Each of thestages is described in the sections that follow.2.1. Selection of study areaThe study area for this project (Pt England/Glen Innes in Auckland)was selected in consultation with a project steering groupcomprised of representatives from the Ministry of Transport, NewZealand Transport Agency, New Zealand Police, and other localtransport and urban agencies. The study area was an establishedneighbourhood contained amix of private residences, small shops,schools, and churches, and was selected, in part, because of its historyof cyclist, pedestrian and loss of controlcrashes, almost twicethe number。
桥梁设计外文翻译文献
桥梁设计外文翻译文献(文档含中英文对照即英文原文和中文翻译) 原文：A Bridge For All CenturiesAn extremely long-and record setting-main span was designed for the second bridge to across the Panama Canal in order to meet the owner’s requirement that no piers be placed in the water.Because no disruption of canal traffic was permitted at any time,the cable-stayed bridge of cast-in-place cancrete was carefully constructed using the balanced-cantilever method.In 1962 ,the Bridge of Americas(Puente de las America) opened to traffic,serving as the only fixed link across the Panama Canal .The bridge was designed to carry 60,000 vehicles per day on four lanes, but it has beenoperating above its capacity for many years.Toalleviate bottlenecks on the route that the bridge carries over the canal-the Pan-AmericanHighway(Inter-American Highway)-and promotegrowth on the western side of Panama,the country’s Ministry of Public Works(Ministerio de Obras Publicas,or MOP )decided to build a new highway systerm linking the northern part of Panama City,on the eastern side of the canal, to the town of Arraijan,located on the western side of the canal.The Centennial Bridge –named to commemorate 100 years of Panamanian independence-has noe been constructed and, when opend, will carry six lanes of traffic. This cable-stayed bridge of cast-in-place cancrete features a main span of 420m,the longest such span for this type of bridge in the Western Hemisphere.In 200 the MOP invited international bridge design firms to compete for the design of the crossing, requesting a two-package proposal:one techinical, the other financial. A total of eight proposals were received by December 2000 from established bridge design firms all over the world. After short-listing three firms on the basis of the technical merits of their proposals, the MOP selected T.Y.Lin International, of San Francisco, to prepare the bridge design and provide field construction support based on the firm’s financial package.The Centennial Bridge desige process was unique and aggressive,incorporating concepts from the traditional design/build/bid method, the design/build method , and the sa-called fast-track design process.To complete the construction on time-that is ,within just 27 months-the design of the bridge was carried out to a level of 30 percent before construction bidding began, in December 2001.The selected contractor-the Wiesbaden,Germany,office of Bilfinger Berger,AG-was brought on board immediately after being selected by the MOP ,just as would be the case in a fast-track approach. The desige of the bridge was then completed in conjunction with construction , a process that id similan to desige/build.The design selected by the client features two single-mast towers,each supporting two sets of stay cables that align in one vertical plane.Concrete was used to construct both the towers and the box girder deck,as well as the approach structures.The MOP , in conjunction with the Panama Canal Authority,established the following requirements for the bridge design :A 420m,the minimum length for the main span to accommodate the recently widened Gaillard Cut,a narrow portion of the canal crossing the Continental Divide that was straightened and widened to 275m in 2002;A navigational envelope consisting of 80m of vertical clearance and 70mof horizontal clearance to accommodate the safe passage of a crane of World War 11 vintage-a gift from the ernment that is used by the Panama Canal Authority to maintain the canal gates and facilities;A roadway wide enough to carry six lanes of traffic, three in each direction;A deck able to accommodate a 1.5m wide pedestrian walkway;A design that would adhere to the American Association of State Highway and Transportation Official standard for a 100-year service life and offer HS-25 truck loading;A structure that could carry two 0.6m dianeter water lines;A construction method that would not cross the canal at any time or interrupt canal operationa in any way.Because of the bridge’s long main span and the potential for strong seismic activity in the area,no single building code covered all aspects of the project.Therefore the team from T.Y. Lin International determinded which portions of several standard bridge specifications were applicable and which were not.The following design codes were used in developing the design criteria for the bridge，it is standard specifications for highway bridge ,16th ed,1996It was paramount that the towers of the cable-stayed structucture be erected on land to avoid potential ship collision and the need to construct expensive deep foundation in water. However, geological maps and boring logs produced during the preliminary design phrase revealed that the east and west banks of the canal, where the towers were to be located, featured vastly different geologicaland soil conditions. On the east side of the canal, beneath shallow layers of overburden that rangs in consistency from soft to hard, lies a block of basalt ranging from medium hard to hard with very closely spaced joint.The engineers determined that the basalt would provide a competent platform for the construction of shallow foundation for tower, piers, and approach structures on this side of bridge.The west side, however,featured the infamous Cucaracha Formation, which is a heterogeneous conglomerate of clay shale with inclusions of sandstone, basalt,and ash that is prone to landslide. As a sudsurface stratum the Cucaracha Formation is quite stable,but it quickly erodes when exposed to the elements. The engineers determined that deep foundations would therefore be needed for the western approach structure,the west tower,and the western piers.Before a detailed design of the foundationa could be developed,a thorough analysis of the seismic hazards at the site was required,The design seismic load for the project was developed on the basis of a probabilistic seismic hazard assessment that considered the conditions at the site.Such an assessment establishes the return period for a given earthquake and the corresponding intensity of ground shaking in the horizontal directtion in terms of an acceleration response spectrum.The PSHA determined two dominant seismic sources: a subduction source zone associated with the North Panama Deformed Belt capable of producing a seimic event as strong as 7.7MW,and the Rio Gatun Fault, capable of producing an event as strong as 6.5MW.The 7.7MW NPDB event was used as the safety evluation earthquake,that is,the maximum earthquake that could strike without putting the bridge out of service.The damage to the bridge would be minor but would require some closures of the bridge.The 6.5MWRio Gatun Fault event was used as the foundational evaluation earthquake,a lower-level temblor that would cause minimal damage to the bridge and would not require closures.For the FEE load case,the SEE loading was scaled back by two-thirds.The FEE is assumed to have a peak acceleration of 0.21g and a return period of 500 years; the probability that it will be exceeded within 50 years is 10 pencent and within 100 years,18 persent.The SEE is assumed to have a peak acceleration of 1.33g and a return period of 2,500 years;the probability that it will be exceeded within 50 years is 2 pencent and within 100 years,4 persent.Because of uncertainty about the direction from which the seismic waves would approach the site, a single response spectrum-a curve showing the mathematically computed maximum response of a set of simple damped harmonic oscillators of different natural frequencies to a particular earthquake ground acceleration-was used to characterize mitions in two mutually orthogonal directions in the horizontal plane.To conduct a time-history analysis of the bridge’s multiple supports,a set of synthetic motions with three components-longitudinal,transverse,and vertical-was developd using an iterative technique.Recorded ground motions from an earthquake in Chile in 1985 were used as “seed”motions for the sythesis process.A time delay estimate-that is,an estimate of the time it would take for the motions generated by the SEEand FEE earthquakes to travel from one point to the next-was create using the assumed seismic wave velocity and the distance between the piers of the ing an assumed was velocity of approximately 2.5km/s,a delay on the order of half a second to a secondis appropriate for a bridge 1 to 2km long.Soil-foundation interaction studies were performed to determine the stiffness of the soil and foundation as well as the seismic excitation measurement that would be used in the dynamic analyses.The studieswere conducted by means of soil-pile models using linear and nonlinear soil layera of varying depths.The equivalent pile lengths in the studies-that is, the lengths representing the portions of a given pile that would actually be affected by a given earthquake-induced ground motion-ranged from2to10m.In such a three-dimensional model,there are six ways in which the soil can resist the movement of the lpile because of its stiffness:throngh axial force in the three directions and through bending moments in three directions.Because the bridge site contains so many layers of varying soil types,each layer had to be represented by a different stiffness matrix and then analyzed.Once the above analyses were completed,the T.Y.Lin International engineers-taking into consideration the project requirements developedby the owener-evaluated several different concrete cable-stayed designs.A number of structural systems were investigated,the main variables,superstructure cross sections,and the varying support conditions described above.The requirement that the evevation of the deck be quite high strongly influenced the tower configuration.For the proposed deck elevation of more than 80m,the most economical tower shapes included single-and dual-mast towers as well as “goal post”towers-that is,a design in which the two masts would be linked to each other by crossbeams.Ultimately the engineers designd the bridge to be 34.3m wide with a 420mlong cable-stayd main span,two 200mlong side spans-one on each side of the main span-and approach structures at the ends of the side spans.On the east side there is one 46m long concrete approach structure,while on the west side there are three,measuring 60,60,and 66m,for a total bridge length of 1,052m.The side spans are supported by four piers,referred to,from west to east,as P1.P2,P3,and P4.The bridge deck is a continuous single-cell box girder from abutment to abutment; the expansion joints are located at the abutments only. Deck movements on the order of 400 mm are expected at these modular expansion joints Multidirectional pot bearings are used at the piers and at the abutments to accommodate these movements.The deck was fixed to the two towers to facilitate the balanced-cantilevermethod of construction and to provide torsional rigidity and lateral restraint to the deck.. Transverse live loads, seismic loads, and wind loads are proportionally distributed to the towers and the piers by the fixity of the deck to the towers and by reinforced-concrete shear keys located at the top of P1, P3, and P4. The deck is allowed to move longitudinally over the abutments and piers. The longitudinal, seismic, live, and temperature loads are absorbed by what is known as portal frame structural behavior, whereby the towers and the deck form a portal-much like the frame of a door in a building-that acts in proportion to the relative stiffness of the two towers.As previously mentioned, the presence of competent basalt on the east side of the site meant that shallow foundations could be used there; in particular, spread footings were designed for the east tower, the east approach structure, and the east abutment. The west tower, the west approach structure, and the western piers (P2 and P3), however, had to be founded deep within the Cucaracha Formation. A total of 48 cast-in-drilled-hole (CIDH) shafts with 2 m outer diameters and lengths ranging from 25 to 35 m were required. A moment curvature analysis was performed to determine the capacity of the shafts with different amounts of longitudinal steel rebar. The results were plotted against the demands, and on the basis of the results the amount of required longitudinal reinforcing steel was determined to be 1 percent of the amount of concrete used in the shafts. The distribution of the longitudinal reinforcing steel was established by following code requirements, with consideration also given to the limitations of constructing CIDH piles with the contractor’s preferred method, which is the water or slurry displacement method.A minimum amount of transverse steel had to be determined for use in the plastic regions of the shaft-that is, those at the top one-eighth of eighth of each shaft and within the shaft caps, which would absorb the highest seismic demands. Once this amount was determined, it was used as the minimum for areas of the shafts above their points of fixity where large lateral displacements were expected to occur. The locations of the transverse steel were then established by following code requirements and by considering the construction limitations of CIDH piles. The transverse steel was spiral shaped.Even though thief foundation designs differed, the towers themselves were designed to be identical. Each measures 185.5 m from the top of its pile cap and is designed as a hollow reinforced-concrete shaft with a truncated elliptical cross section (see figure opposite). Each tower’s width in plan varies along its height, narrowing uniformly from 9.5 m at the base of the tower to 6 m at the top. In the longitudinal direction, each pylon tapers from 9.5 m at the base to about 8 m right below the deck level,which is about 87 m above the tower base. Above the deck level the tower’s sections vary from 4.6 m just above the deck to 4.5 m at the top. Each tower was designed with a 2 by 4 m opening for pedestrian passage along the deck, a design challenge requiring careful detailing.The towers were designed in a accordance with the latest provisions of the ATC earthquake design manual mentioned previously (ATC-32). Owing to the portal frame action along the bridge’s longitudinal axis, special seismic detailing was implemented in regions with the potential to develop plastic hinges in the event of seismic activity-specifically, just below the deck and above the footing. Special confining forces and alternating open stirrups-with 90 and 135 degree hooks-within the perimeter of the tower shaft.In the transverse direction, the tower behaves like a cantilever, requiring concrete-confining steel at its base. Special attention was needed at the joint between the tower and the deck because of the central-plane stay-cable arrangement, it was necessary to provide sufficient torsional stiffness and special detailing at the pier-to-deck intersection. This intersection is highly congested with vertical reinforcing steel, the closely spaced confining stirrups of the tower shaft, and the deck prestressing and reinforcement.The approach structures on either side of the main span are supported on hollow reinforced-concrete piers that measure 8.28 by 5 m in plan. The design and detailing of the piers are consistent with the latest versions of the ATC and AASHTO specifications for seismic design. Capacity design concepts were applied to the design of the piers. This approach required the use of seismic modeling with moment curvature elements to capture the inelastic behavior of elements during seismic excitation. Pushover analyses of the piers were performed to calculate the displacement capacity of the piers and to compare them with the deformations computed in the seismic time-history analyses. To ensure an adequate ductility of the piers-an essential feature of the capacity design approach-it was necessary to provide adequate concrete-confining steel at those locations within the pier bases where plastic hinges are expected to form.The deck of the cable-stayed main span is composed of single-cell box girders of cast-in-place concrete with internal, inclined steel struts and transverse posttensioned ribs, or stiffening beams, toward the tops. Each box girder segment is 4.5 m deep and 6 m long. To facilitate construction and enhance the bridge’s elegant design, similar sizes were used for the other bridge spans. An integral concrete overlay with a thickness of 350 mm was installed instead of an applied concrete overlayon the deck. In contrast to an applied overlay, the integral overlay was cast along with each segment during the deck erection. Diamond grinding equipment was used to obtain the desired surface profile and required smoothness. The minimum grinding depth was 5 mm.A total of 128 stay cables were used, the largest comprising 83 monostrands. All cables with a length of more than 80 m were equipped at their lower ends with internal hydraulic dampers. Corrosion protection for the monostrands involved galvanization of the wires through hot dipping, a tight high-density polyethylene (HDPE) sheath extruded onto each strand, and a special type of petroleum wax that fills all of the voids between the wires.The stays are spaecd every 6 m and are arranged in a fan pattern.They are designed to be stressed from the tower only and are anchored in line with a continuous stiffening beam at the centerline of the deck.The deck anchorage system is actually a composite steel frame that encapsulates two continous steel plates that anchor the stays and transfer the stay forces in a continuous and repetitive system-via shear studs-throuthout the extent of the cable-supported deck (see figure above).A steel frame was designed to transfer the stays’horizontal forces to the box girders through concrete-embedded longitudinal steel plates and to transfer the boxes’ vertical forces directly through the internal steel struts.This innovative and elegant load transfer system made rapid construction of the concrete deck segments-in cycles of three to five days-possible.In addition to the geotechnical and seismic analyses,several structural analyses were performed to accurately capture the behavior of this complex bridge.For the service-load analysis,which includes live,temperature,and wind loads,the engineers used SAP2000, a computer program created and maintained by Computers &Structrures,Inc.(CSI), of Berkeley, California.This program was selected for its ability to easily model the service loads and to account for tridimensional effects.For correct SAP2000 modeling, it was necessary to define a set of initial stresses on the cables, deck, and tower elements to capture the state of the structure at the end of construction.For the calculation of those initial stresses, a series of iterations on the basic model were performed to obtain the stay forces in the structure that balance both the bridges’s self-weight and the superimposed dead loads. Once the correct cable stiffness and stress distribution were obtained, all subsequent service-load analyses were performed to account for the geometric stiffness and P-deltaeffects, which consider the magnitude of an applied load (P) versus the displacement(delta).The seismic analysis of the structure was conducted using the SADSAP structural analysis program, also a CSI product, based on the differences in seismic motions that will be experienced at the different piers based on their distance from one another.This sophisticated program has the capability to model inelastic behavior in that flexural plastic hinges can readily be simulated.Plastic hinge elements were modeled at varous locations along the structure where the results from a preliminary response spectrum analysis in SAP2000 indicated that inelastic behavior might be expected.The time-history records pertaining to the site were used in conjunction with the SADSAP model to botain a performace-based design of the piers and towers and to verifh the design of several deck stctions.As previously mentioned,the construction contractor was brought on board early in the process;the company’s bid of $93 million was accepted and the project was awarded in March 2002.To guarantee unimpeded canal traffic,the bridge had to be constructed without the use of the canal waters.To accomplish this, the cast-in-place main-pain superstructure was erected using the balanced-cantilever method.Form travelers were used to accomplish this, and they were designed in such a way that they could be used as an integral part of the pier tables’falsework.After assembly on the ground, two 380 Mg form travelers were raised independently into the pier table casting position and connected to each other.After an initial learning period, the contractor was able to achieve a four-day cycle for the casting of the cantilevered deck segments, an achievement that greatly enhanced the ability of the team to construct the project on time.Once the side-span and mai-span closures were cast, the travelers had to be removed from locations adjacent to the towers rather than over water so as to avoid any influence on canal traffic.To save time, the towers approach structure, and piers were built simultaneously.The approach viaducts were designed and built using the span-by-span erection method by means of an underslung suupport truss.The east viaduct span was built first and the support truss was then removed and transferred to the west side so that it could be used to build the three spans of the west viaduct, one span at a time.The bridge construction was completeed in Auguse 2004 at a cost of approximately $2,780 per square meter.Its opening awaits the completion of the rest of the highway it serves.跨越世纪之桥1962年，横跨巴拿马运河的美国大桥作为仅有的固定连接开放交通车。
毕业设计外文原文加译文
Basic Concepts PrimerTOPIC P.1: Bridge MechanicsBasic Equations of Bridge Mechanicswhere: A =area; cross-sectional areaA w = areaof web c = distance from neutral axisto extreme fiber (or surface) of beamE = modulus of elasticityF = force; axial force f a= axial stress f b= bending stress f v = shear stress I = moment of inertia L = original length M = applied moment S = stressV = vertical shear force due toexternal loadsD L = change in length e = strainBasic Concepts Primer Topic P.1 Bridge MechanicsP.1.1Introduction Mechanics is the branch of physical science that deals with energy and forces andtheir relation to the equilibrium, deformation, or motion of bodies. The bridgeinspector will primarily be concerned with statics, or the branch of mechanicsdealing with solid bodies at rest and with forces in equilibrium.The two most important reasons for a bridge inspector to study bridge mechanicsare:Ø To understand how bridge members functionØ To recognize the impact a defect may have on the load-carrying capacityof a bridge component or elementWhile this section presents the basic principles of bridge mechanics, the referenceslisted in the bibliography should be referred to for a more complete presentation ofthis subject.P.1.2Bridge Design Loadings Bridge design loadings are loads that a bridge is designed to carry or resist and which determine the size and configuration of its members. Bridge members are designed to withstand the loads acting on them in a safe and economical manner. Loads may be concentrated or distributed depending on the way in which they are applied to the structure.A concentrated load, or point load, is applied at a single location or over a very small area. Vehicle loads are considered concentrated loads.A distributed load is applied to all or part of the member, and the amount of load per unit of length is generally constant. The weight of superstructures, bridge decks, wearing surfaces, and bridge parapets produce distributed loads. Secondary loads, such as wind, stream flow, earth cover and ice, are also usually distributed loads.Highway bridge design loads are established by the American Association of State Highway and Transportation Officials (AASHTO). For many decades, the primary bridge design code in the United States was the AASHTO Standard Specifications for Highway Bridges (Specifications), as supplemented by agency criteria as applicable.During the 1990’s AASHTO developed and approved a new bridge design code, entitled AASHTO LRFD Bridge Design Specifications. It is based upon the principles of Load and Resistance Factor Design (LRFD), as described in Topic P.1.7.P.1.1SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.2Bridge design loadings can be divided into three principal categories:Ø Dead loadsØ Primary live loads Ø Secondary loadsDead LoadsDead loads do not change as a function of time and are considered full-time, permanent loads acting on the structure. They consist of the weight of the materials used to build the bridge (see Figure P.1.1). Dead load includes both the self-weight of structural members and other permanent external loads. They can be broken down into two groups, initial and superimposed.Initial dead loads are loads which are applied before the concrete deck is hardened, including the beam itself and the concrete deck. Initial deck loads must be resisted by the non-composite action of the beam alone. Superimposed dead loads are loads which are applied after the concrete deck has hardened (on a composite bridge), including parapets and any anticipated future deck pavement. Superimposed dead loads are resisted by the beam and the concrete deck acting compositely. Non-composite and composite action are described in Topic P.1.10.Dead load includes both the self-weight of the structural members and other permanent external loads.Example of self-weight: A 6.1 m (20-foot) long beam weighs 0.73 kN per m (50 pounds per linear foot). The total weight of the beam is 4.45 kN (1000 pounds). This weight is called the self-weight of the beam.Example of an external dead load: If a utility such as a water line is permanently attached to the beam in the previous example, then the weight of the water line is an external dead load. The weight of the water line plus the self weight of the beam comprises the total dead load.Total dead load on a structure may change during the life of the bridge due to additions such as deck overlays, parapets, utility lines, and inspection catwalks.Figure P.1.1 Dead Load on a BridgePrimary Live LoadsLive loads are considered part-time or temporary loads, mostly of short-term duration, acting on the structure. In bridge applications, the primary live loads are moving vehicular loads (see Figure P.1.2).To account for the affects of speed, vibration, and momentum, highway live loads are typically increased for impact. Impact is expressed as a fraction of the liveSECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.3load, and its value is a function of the span length.Standard vehicle live loads have been established by AASHTO for use in bridge design and rating. It is important to note that these standard vehicles do not represent actual vehicles. Rather, they were developed to allow a relatively simple method of analysis based on an approximation of the actual live load.Figure P.1.2 Vehicle Live Load on a BridgeAASHTO Truck LoadingsThere are two basic types of standard truck loadings described in the current AASHTO Specifications . The first type is a single unit vehicle with two axles spaced at 14 feet (4.3 m) and designated as a highway truck or "H" truck (see Figure P.1.3). The weight of the front axle is 20% of the gross vehicle weight, while the weight of the rear axle is 80% of the gross vehicle weight. The "H" designation is followed by the gross tonnage of the particular design vehicle.Example of an H truck loading: H20-35 indicates a 20 ton vehicle with a front axle weighing 4 tons, a rear axle weighing 16 tons, and the two axles spaced 14 feet apart. This standard truck loading was first published in 1935.The second type of standard truck loading is a two unit, three axle vehicle comprised of a highway tractor with a semi-trailer. It is designated as a highway semi-trailer truck or "HS" truck (see Figure P.1.4).The tractor weight and wheel spacing is identical to the H truck loading. The semi-trailer axle weight is equal to the weight of the rear tractor axle, and its spacing from the rear tractor axle can vary from 4.3 to 9.1 m (14 to 30 feet). The "HS" designation is followed by a number indicating the gross weight in tons of the tractor only.SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.414’-0”(4.3 m)8,000 lbs (35 kN) 32,000 lbs (145 kN)(3.0 m)10’-0”CLEARANCE AND LOAD LANE WIDTH6’-0” (1.8 m)2’-0” (0.6 m)Figure P.1.3 AASHTO H20 Truck14’-0”(4.3 m)8,000 lbs (35 kN) 32,000 lbs (145 kN)(3.0 m)10’-0”CLEARANCE AND LOAD LANE WIDTH6’-0”(1.8 m)2’-0” (0.6 m)32,000 lbs (145 kN)VFigure P.1.4 AASHTO HS20 TruckExample of an HS truck loading: HS20-44 indicates a vehicle with a front tractor axle weighing 4 tons, a rear tractor axle weighing 16 tons, and a semi-trailer axle weighing 16 tons. The tractor portion alone weighs 20 tons, but the gross vehicle weight is 36 tons. This standard truck loading was first published in 1944.In specifications prior to 1944, a standard loading of H15 was used. In 1944, theSECTION P: Basic Concepts Primer Topic P.1: Bridge MechanicsP.1.5H20-44 Loading HS20-44 Loadingpolicy of affixing the publication year of design loadings was adopted. In specifications prior to 1965, the HS20-44 loading was designated as H20-S16-44, with the S16 identifying the gross axle weight of the semi-trailer in tons.The H and HS vehicles do not represent actual vehicles, but can be considered as "umbrella" loads. The wheel spacings, weight distributions, and clearance of the Standard Design Vehicles were developed to give a simpler method of analysis, based on a good approximation of actual live loads.The H and HS vehicle loads are the most common loadings for design, analysis, and rating, but other loading types are used in special cases.AASHTO Lane LoadingsIn addition to the standard truck loadings, a system of equivalent lane loadings was developed in order to provide a simple method of calculating bridge response to a series, or “train”, of trucks. Lane loading consists of a uniform load per linear foot of traffic lane combined with a concentrated load located on the span to produce the most critical situation (see Figure P.1.5).For design and load capacity rating analysis, an investigation of both a truck loading and a lane loading must be made to determine which produces the greatest stress for each particular member. Lane loading will generally govern over truck loading for longer spans. Both the H and HS loadings have corresponding lane loads.* Use two concentrated loads for negative moment in continuous spans (Refer to AASHTO Page 23)Figure P.1.5 AASHTO Lane Loadings.Alternate Military LoadingThe Alternate Military Loading is a single unit vehicle with two axles spaced at 1.2 m (4 feet) and weighing 110 kN (12 tons)each. It has been part of the AASHTO Specifications since 1977. Bridges on interstate highways or other highways which are potential defense routes are designed for either an HS20 loading or an Alternate Military Loading (see Figure P.1.6).SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.6110 kN (24 k)110 kN (24 k)Figure P.1.6 Alternate Military LoadingLRFD Live LoadsThe AASHTO LRFD design vehicular live load, designated HL-93, is a modified version of the HS-20 highway loadings from the AASHTO StandardSpecifications. Under HS-20 loading as described earlier, the truck or lane load is applied to each loaded lane. Under HL-93 loading, the design truck or tandem, in combination with the lane load, is applied to each loaded lane.The LRFD design truck is exactly the same as the AASHTO HS-20 design truck. The LRFD design tandem, on the other hand, consists of a pair of 110 kN axials spread at 1.2 m (25 kip axles spaced 4 feet) apart. The transverse wheel spacing of all of the trucks is 6 feet.The magnitude of the HL-93 lane load is equal to that of the HS-20 lane load. The lane load is 9 kN per meter (0.64 kips per linear foot) longitudinally and it is distributed uniformly over a 3 m (10 foot) width in the transverse direction. The difference between the HL-93 lane load and the HS-20 lane load is that the HL-93 lane load does not include a point load.Finally, for LRFD live loading, the dynamic load allowance, or impact, is applied to the design truck or tandem but is not applied to the design lane load. It is typically 33 percent of the design vehicle.Permit VehiclesPermit vehicles are overweight vehicles which, in order to travel a state’s highways, must apply for a permit from that state. They are usually heavy trucks (e.g., combination trucks, construction vehicles,or cranes) that have varying axle spacings depending upon the design of the individual truck. To ensure that these vehicles can safely operate on existing highways and bridges, most states require that bridges be designed for a permit vehicle or that the bridge be checked to determine if it can carry a specific type of vehicle. For safe and legal operation, agencies issue permits upon request that identify the required gross weight, number of axles, axle spacing, and maximum axle weights for a designated route (see Figure P.1.7).SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.7Figure P.1.7 910 kN (204 kip) Permit Vehicle (for Pennsylvania)Secondary LoadsIn addition to dead loads and primary live loads, bridge components are designed to resist secondary loads, which include the following:Ø Earth pressure - a horizontal force acting on earth-retaining substructureunits, such as abutments and retaining wallsØ Buoyancy -the force created due to the tendency of an object to rise whensubmerged in waterØ Wind load on structure - wind pressure on the exposed area of a bridge Ø Wind load on live load -wind effects transferred through the live loadvehicles crossing the bridgeØ Longitudinal force -a force in the direction of the bridge caused bybraking and accelerating of live load vehiclesØ Centrifugal force -an outward force that a live load vehicle exerts on acurved bridgeØ Rib shortening -a force in arches and frames created by a change in thegeometrical configuration due to dead loadØ Shrinkage - applied primarily to concrete structures, this is a multi-directional force due to dimensional changes resulting from the curing processØ Temperature -since materials expand as temperature increases andcontract as temperature decreases, the force caused by these dimensional changes must be consideredØ Earthquake -bridge structures must be built so that motion during anearthquake will not cause a collapseØ Stream flow pressure -a horizontal force acting on bridge componentsconstructed in flowing waterØ Ice pressure - a horizontal force created by static or floating ice jammedagainst bridge componentsØ Impact loading - the dynamic effect of suddenly receiving a live load;this additional force can be up to 30% of the applied primary live load forceØ Sidewalk loading - sidewalk floors and their immediate supports aredesigned for a pedestrian live load not exceeding 4.1 kN per square meter (85 pounds per square foot)Ø Curb loading -curbs are designed to resist a lateral force of not less than7.3 kN per linear meter (500 pounds per linear foot)Ø Railing loading -railings are provided along the edges of structures forprotection of traffic and pedestrians; the maximum transverse load appliedto any one element need not exceed 44.5 kN (10 kips)SECTION P: Basic Concepts PrimerTopic P.1: Bridge MechanicsP.1.8A bridge may be subjected to several of these loads simultaneously. The AASHTO Specifications have established a table of loading groups. For each group, a set of loads is considered with a coefficient to be applied for each particular load. The coefficients used were developed based on the probability of various loads acting simultaneously.P.1.3Material Response to LoadingsEach member of a bridge has a unique purpose and function, which directly affects the selection of material, shape, and size for that member. Certain terms are used to describe the response of a bridge material to loads. A working knowledge of these terms is essential for the bridge inspector.ForceA force is the action that one body exerts on another body. Force has two components: magnitude and direction (see Figure P.1.8). The basic English unit of force is called pound (abbreviated as lb.). The basic metric unit of force is called Newton (N). A common unit of force used among engineers is a kip (K), which is 1000 pounds. In the metric system, the kilonewton (kN), which is 1000 Newtons, is used. Note: 1 kip = 4.4 kilonewton.FyFigure P.1.8 Basic Force ComponentsStressStress is a basic unit of measure used to denote the intensity of an internal force. When a force is applied to a material, an internal stress is developed. Stress is defined as a force per unit of cross-sectional area.The basic English unit of stress is pounds per square inch (abbreviated as psi). However, stress can also be expressed in kips per square inch (ksi) or in any other units of force per unit area. The basic metric unit of stress is Newton per square meter, or Pascal (Pa). An allowable unit stress is generally established for a given material. Note: 1 ksi = 6.9 Pa.)A (Area )F (Force )S (Stress =毕业设计外文译文桥梁力学基本概论《美国桥梁检测手册》译文：桥梁结构的基础方程S=F/A(见1.8节)fa=P/A(见1.14节)ε=△L/L(见1.9节)fb=Mc/I(见1.16节)E=S/ε(见1.11节)fv=V/Aw（见1.18节）桥梁额定承载率=（允许荷载–固定荷载）*车辆总重量/车辆活荷载冲击力式中：A=面积；横截面面积Aw=腹板面积c=中性轴与横梁边缘纤维或外表面之间的距离E=弹性模量F=轴心力；轴向力fa=轴向应力fb=弯曲应力fv=剪切应力I=惯性距L=原长M=作用力距S=应力V=由外荷载引起的垂直剪应力△L=长度变量ε=应变1桥梁主要的基本概论第一章桥梁力学1.1引言结构力学是研究物体的能量、力、能量和力的平衡关系、变形及运动的物理科学的分支。
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外文资料The Tenth East Asia-Pacific Conference on Structural Engineering and ConstructionAugust 3-5, 2006, Bangkok, ThailandStructural Rehabilitation of Concrete Bridges with CFRPComposites-Practical Details and ApplicationsRiyad S. ABOUTAHA1, and Nuttawat CHUTARAT2 ABSTRACT: Many old existing bridges are still active in the various highway transportation networks, carrying heavier and faster trucks, in all kinds of environments. Water, salt, and wind have caused damage to these old bridges, and scarcity of maintenance funds has aggravated their conditions. One attempt to restore the original condition; and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP) composites. There appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. In this paper, guidelines for nondestructive evaluation (NDE), nondestructive testing (NDT), and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges are also discussed and presented.KEYWORDS: Concrete deterioration, corrosion of steel, bridge rehabilitation, CFRP composites.1 IntroductionThere are several destructive external environmental factors that limit the service life of bridges. These factors include but not limited to chemical attacks, corrosion of reinforcing steel bars, carbonation of concrete, and chemical reaction of aggregate. If bridges were not well maintained, these factors may lead to a structural deficiency, which reduces the margin of safety, and may result in structural failure. In order to rehabilitate and/or strengthen deteriorated existing bridges, thorough evaluation should be conducted. The purpose of the evaluation is to assess the actual condition of any existing bridge, and generally to examine the remaining strength and load carry capacity of the bridge.1 Associate Professor, Syracuse University, U.S.A.2 Lecturer, Sripatum University, Thailand.One attempt to restore the original condition, and to extend the service life of concrete bridges is by the use of carbon fiber reinforced polymer (CFRP) composites.In North America, Europe and Japan, CFRP has been extensively investigated and applied. Several design guides have been developed for strengthening of concrete bridges with CFRP composites. However, there appear to be very limited guides on repair of deteriorated concrete bridges with CFRP composites. This paper presents guidelines for repair of deteriorated concrete bridges, along with proper detailing. Evaluation, nondestructive testing, and rehabilitation of deteriorated concrete bridges with CFRP composites are presented. Successful application of CFRP composites requires good detailing as the forces developed in the CFRP sheets are transferred by bond at the concrete-CFRP interface. The effect of detailing on ductility and behavior of CFRP strengthened concrete bridges will also be discussed and presented.2 Deteriorated Concrete BridgesDurability of bridges is of major concern. Increasing number of bridges are experiencing significant amounts of deterioration prior to reaching their design service life. This premature deterioration considered a problem in terms of the structural integrity and safety of the bridge. In addition, deterioration of a bridge has a considerable magnitude of costs associated with it. In many cases, the root of a deterioration problem is caused by corrosion of steel reinforcement in concrete structures. Concrete normally acts to provide a high degree of protection against corrosion of the embedded reinforcement. However, corrosion will result in those cases that typically experience poor concrete quality, inadequate design or construction, and harsh environmental conditions. If not treated a durability problem, e.g. corrosion, may turn into a strength problem leading to a structural deficiency, as shown in Figure1.Figure1 Corrosion of the steel bars is leading to a structural deficiency3 Non-destructive Testing of Deteriorated Concrete Bridge PiersIn order to design a successful retrofit system, the condition of the existing bridge should be thoroughly evaluated. Evaluation of existing bridge elements or systems involves review of the asbuilt drawings, as well as accurate estimate of the condition of the existing bridge, as shown in Figure2. Depending on the purpose of evaluation, non-destructive tests may involve estimation of strength, salt contents, corrosion rates, alkalinity in concrete, etc.Figure2 Visible concrete distress marked on an elevation of a concrete bridge pier Although most of the non-destructive tests do not cause any damage to existing bridges, some NDT may cause minor local damage (e.g. drilled holes & coring) that should be repaired right after the NDT. These tests are also referred to as partial destructive tests but fall under non-destructive testing.In order to select the most appropriate non-destructive test for a particular case, thepurpose of the test should be identified. In general, there are three types of NDT to investigate: (1) strength, (2) other structural properties, and (3) quality and durability. The strength methods may include; compressive test (e.g. core test/rebound hammer/ ultrasonic pulse velocity), surface hardness test (e.g. rebound hammer), penetration test (e.g. Windsor probe), and pullout test (anchor test).Other structural test methods may include; concrete cover thickness (cover-meter), locating rebars (rebar locator), rebar size (some rebar locators/rebar data scan), concrete moisture (acquameter/moisture meter), cracking (visual test/impact echo/ultrasonic pulse velocity), delamination (hammer test/ ultrasonic pulse velocity/impact echo), flaws and internal cracking (ultrasonic pulse velocity/impact echo), dynamic modulus of elasticity (ultrasonic pulse velocity), Possion’s ratio (ultrasonic pulse velocity), thickness of concrete slab or wall (ultrasonic pulse velocity), CFRP debonding (hammer test/infrared thermographic technique), and stain on concrete surface (visual inspection).Quality and durability test methods may include; rebar corrosion rate –field test, chloride profile field test, rebar corrosion analysis, rebar resistivity test, alkali-silica reactivity field test, concrete alkalinity test (carbonation field test), concrete permeability (field test for permeability).4 Non-destructive Evaluation of Deteriorated Concrete Bridge PiersThe process of evaluating the structural condition of an existing concrete bridge consists of collecting information, e.g. drawings and construction & inspection records, analyzing NDT data, and structural analysis of the bridge. The evaluation process can be summarized as follows: (1) Planning for the assessment, (2) Preliminary assessment, which involves examination of available documents, site inspection, materials assessment, and preliminary analysis, (3) Preliminary evaluation, this involves: examination phase, and judgmental phase, and finally (4) the cost-impact study.If the information is insufficient to conduct evaluation to a specific required level, then a detailed evaluation may be conducted following similar steps for the above-mentioned preliminary assessment, but in-depth assessment. Successful analytical evaluation of an existing deteriorated concrete bridge should consider the actual condition of the bridge and level of deterioration of various elements. Factors, e.g. actual concrete strength, level of damage/deterioration, actual size of corroded rebars, loss of bond between steel and concrete, etc. should be modeled into a detailed analysis. If such detailed analysis is difficult to accomplish within a reasonable period of time, thenevaluation by field load testing of the actual bridge in question may be required.5 Bridge Rehabilitation with CFRP CompositesApplication of CFRP composite materials is becoming increasingly attractive to extend the service life of existing concrete bridges. The technology of strengthening existing bridges with externally bonded CFRP composites was developed primarily in Japan (FRP sheets), and Europe (laminates). The use of these materials for strengthening existing concrete bridges started in the 1980s, first as a substitute to bonded steel plates, and then as a substitute for steel jackets for seismic retrofit of bridge columns. CFRP Composite materials are composed of fiber reinforcement bonded together with a resin matrix. The fibers provide the composite with its unique structural properties. The resin matrix supports the fibers, protect them, and transfer the applied load to the fibers through shearing stresses. Most of the commercially available CFRP systems in the construction market consist of uniaxial fibers embedded in a resin matrix, typically epoxy. Carbon fibers have limited ultimate strain, which may limit the deformability of strengthened members. However, under traffic loads, local debonding between FRP sheets and concrete substrate would allow for acceptable level of global deformations before failure.CFRP composites could be used to increase the flexural and shear strength of bridge girders including pier cap beams, as shown in Figure3. In order to increase the ductility of CFRP strengthened concrete girders, the longitudinal CFRP composite sheets used for flexural strengthening should be anchored with transverse/diagonal CFRP anchors to prevent premature delamination of the longitudinal sheets due to localized debonding at the concrete surface-CFRP sheet interface. In order to prevent stress concentration and premature fracture of the CFRP sheets at the corners of concrete members, the corners should be rounded at 50mm (2.0 inch) radius, as shown in Figure3.Deterioration of concrete bridge members due to corrosion of steel bars usually leads in loss of steel section and delamination of concrete cover. As a result, such deterioration may lead to structural deficiency that requires immediate attention. Figure4 shows rehabilitation of structurally deficient concrete bridge pier using CFRP composites.Figure3 Flexural and shear strengthening of concrete bridge pier with FRP compositesFigure4 Rehabilitation of deteriorated concrete bridge pier with CFRP composites6 Summary and ConclusionsEvaluation, non-destructive testing and rehabilitation of deteriorated concrete bridges were presented. Deterioration of concrete bridge components due to corrosion may lead to structural deficiencies, e.g. flexural and/or shear failures. Application of CFRP composite materials is becoming increasingly attractive solution to extend the service life of existing concrete bridges. CFRP composites could be utilized for flexural and shear strengthening, as well as for restoration of deteriorated concrete bridge components. The CFRP composite sheets should be well detailed to prevent stress concentration and premature fracture or delamination. For successful rehabilitation of concrete bridges in corrosive environments, a corrosion protection system should be used along with the CFRP system.第十届东亚太结构工程设计与施工会议2006年8月3-5号，曼谷，泰国碳纤维复合材料修复混凝土桥梁结构的详述及应用Riyad S. ABOUTAHA1, and Nuttawat CHUTARAT2摘要：在各式各样的公路交通网络中，许多现有的古老桥梁，在各种恶劣的环境下，如更重的荷载和更快的车辆等条件下，依然在被使用着。