地震体验装置 外文翻译

外文原文：Damage as a measure for earthquake-resistant design ofmasonry structuresauthor：Miha TomazˇevicAbstract:The results of lateral resistance tests of masonry walls and shaking table tests of a number of models of ma-sonry buildings of various structural configurations, built with various materials in different construction systems, havebeen analyzed to find a correlation between the occurrence of different grades of damage to structural elements, character-istic limit states, and lateral displacement capacity. On the basis of correlation between acceptable level of damage and displacement capacity, it has been shown that the range of elastic force reduction factor values used to determine the de-sign seismic loads for different masonry construction systems proposed by the recently adopted European standard Euro-code 8 EN-1998-1 for earthquake resistant design are adequate. By using the recommended design values, satisfactory performance of the masonry buildings that have been analyzed may be expected when subjected to design intensity earth-quakes with respect to both the no-collapse and damage-limitation requirements.Key words: masonry structures, seismic-resistant design, seismic performance, damage, limit states, behavior factor.1. IntroductionEarthquake-resistant design of masonry structures is a combination of tradition, experience, and modern engineer-ing principles based on experimental research. Usually, it is a two-step procedure: ( i ) the structure is conceived accord-ing to traditional requirements regarding structural configu-ration and ( ii ) the seismic resistance is verified by calculations and the dimensions and distribution of structural elements are modified, if necessary.Since no-collapse and damage-limitation requirements should be fulfilled, the ultimate state (associated with collap-se) and the serviceability limit state (associated with the oc-currence of minimum damage) also need to be verified in the case of masonrystructures. According to the recently adopted Eurocode 8 standard,Design of structures for earth-quake resistance (CEN 2004), the structure should be de-signed to withstand the design seismic action, i.e., earthquake, with a return period of 475 years and a 10% probability of exceedance in 50 years, and the no-collapse requirement defined in Eurocode 8 as ……without local or global collapse, thus retaining its structural integrity and a residual load bearing capacity after the seismic events.‟‟However, the structure should also be designed to withstand an earthquake having a larger probability of occurrence than the design earthquake, i.e., earthquake with return period of 95 years with 10% probability of exceedance in 10 years, as well as the damage-limitation requirement defined in Euro-code 8 as ……without the occurrence of damage and limita-tion of use, the costs of which would be disproportionately high in comparison with the costs of the structure itself.‟‟According to Eurocode 8, for all structural members and for the structure as a whole, the design resistance capacity Rd shall be greater than the design load Ed , which includes seismic actions if the structure is exposed to seismic haz-ard. The form in which the seismic action is used in seis-mic resistance verification depends on the importance and complexity of the structure under consideration. In the case of structures with regular structural configuration,where the response is not significantly affected by the con-tribution of higher modes of vibration, such as masonry structures, response spectra methods provide adequate re-sults. The calculations for these regular structures are fur-ther simplified by taking into account only one horizontal component of the seismic ground motion and analyzing the structure in each orthogonal direction separately. Non-linear dynamic response analysis is replaced by equivalent elastic static analysis, where the design seismic loads are evaluated on the basis of the design response spectra, con-sidering the structure as an equivalent single-degree-of-freedom system.The ordinates of the elastic response spectra are reduced by the structural behavior factor (elastic force reduction factor), q, defined by Eurocode 8 as a ……factor used for de-sign purposes to reduce the forces obtained from a linear analysis, in order to account for thenonlinear response of a structure‟‟ and it takes into account the energy dissipation and displacement capacity of the structure under considera-tion. According to Eurocode 8, ……the behavior factor q is an appr oximation of the ratio of the seismic forces that the structure would experience if its response was completely elastic with 5% viscous damping, to the minimum seismic forces that may be used in the design —with a conventional elastic analysis model —still ensuring a satisfactory re-sponse of the structure.‟‟ A ……satisfactory response,‟‟ in this case, means a ductile response; however, a response with a limited amount of damage to structural elements. Therefore,to prevent excessive damage to structural walls, the dam-age-limitation requirement should be the leading parameter when deciding upon the design ductility capacity of the structural type under consideration and, consequently, deter-mining the value of behavior factorq to be considered in the design.The amou A limited number of seismic vulnerability and other stud-ies already provide basic information regarding the damage-limitation requirements (Alcocer et al. 2004; Calvi 1999;D‟Ayala 1998) to be considered in the design and seismic esistance verification of masonry structures of different ypologies and construction systems.As a contribution to ex-isting information, experimental results obtained in the past by testing different walls and models of masonry buildings at the Slovenian National Building and Civil Engineering In-stitute (ZAG) in Ljubljana, Slovenia, have been analyzed.The results of this analysis indicate that structural damage is correlated with storey drift in anuniform way, not depending on the type of masonry under consideration. Consequently, adequate seismic performance of masonry structures may be expected if, besides ductility and energy dissipation capacity of the structure, damage-limitation requirements in terms of.maximum acceptable storey drift are taken into account when determining the design seismic loads and respective values of the elastic force reduction factor q2. Seismic resistance and limit statesBasic information regarding the seismic behaviour of structures or structural elements is obtained on the basis of known relationships between lateral resistance and displace-ments. By knowing the so-called resistance curve and of damage that is associated with typical limit states defined on the curve, the seismic performance of the structure for the case of the expected seismic loads can be assessed. In the case of unreinforced and confined masonry struc-tures, the resistance curve is adequately represented by the relationship between the resistance R of the critical storey, usually the first storey of the building, and storey drift d (relative storey displacement) of the same storey (Fig. 1). Usually, the curve is presented in a nondimensional form. The resistance is given in terms of the seismic resistance co-efficient (SRC), i.e., the ratio between the resistance, R , and weight of the building, W, above the critical section (SRC = R/W ). The displacements, however, are expressed in terms of storey rotation F , which is the ratio between the storey drift, d, and storey height, h ( F = d/h). The following four main limit states, which are used in seismic resistance verification and determine the usability of buildings, are defined on the resistance curve (Fig. 1):(1) Crack (damage) limit state, where the first cracks occur in the walls causing evident changes in stiffness of the structural system. Crack limit on the resistance curve is sometimes associated with the serviceability limit state of the structure.(2) Maximum resistance.(3) Design ultimate limit state, where the resistance of the system degrades below the acceptable level. Convention-ally, 20% of degradation of the maximum resistance is acceptable. Consequently, part of the resistance curve, where the resistance degrades below 80% of the maxi-mum, is no longer considered for design purposes. Itonly provides information about additional ductility and energy dissipation capacity, i.e., additional safety of the structure. (4) Limit of collapse, defined by partial or total collapse of the structure.3. Correlation between damage, limit states and usabilityUsability of earthquake-damaged buildings is assessed on the basis of the observed damage. Different categories of damage such as light, moderate, heavy, and very heavy (severe) are attributed to different categories of usability. Fig. 2 provides examples of post-earthquake damage obser-vations of a number of typical central European masonry buildings, showing moderate, heavy, and severe damage (near collapse). A number of unreinforced and confined masonry walls have been tested in the laboratory, by subjecting them to cyclic lateral loading, and a series of models of the same types of masonry construction systems have been tested on a shaking table. An attempt has been made to correlate the resulting physical damage to the tested walls and model buildings with the limit states and, consequently, use this information for the assessment of usability of earthquake-damaged buildings. Complete (true replica) models have also been tested on the shaking table and correlation tests, carried out on prototype and model masonry walls, showed very good agreement between the model and prototype masonry with respect to the similarity of resistance curves as well as damage patterns at the characteristic limit states. Therefore, although the information was obtained on the models, it can also be considered reliable for the case of the prototype structures. As the first step of analysis, typical damage categories (grades) have been defined. Although the types of damage to masonry walls and buildings vary depending on masonry materials and construction systems, damage to structural walls can be classified and damage grades can be defined in a uniform way. The classification of damage and damage grades proposed by the European macroseismic scale (EMS-98) (Gru¨ nthal 1998) for masonry buildings has been used as a basis for the description of structural damage to masonry walls. In the case of prevailing shear behavior, typical for all masonry construction systems when subjected to seismic loads, the following characteristic damage patterns can be attributed to damage grades as defined by the EMS-98 scale:Grade 1 — no structural damage.Grade 2 —slight structural damage, cracks in many walls: formation of the first hardly visible diagonally oriented cracks in the middle part of the wall, light damage. Grade 3 — moderate structural damage, cracks in many walls: increased number of cracks with limited width (less than 0.2 mm wide), oriented diagonally in both diag-onal directions; moderate, repairable damage which maybe defined as acceptable damage at the serviceability limitstate.Grade 4 —heavy structural damage, serious failure of walls: increased number of diagonally oriented cracks that are more than 1 mm but less than 10 mm wide; crushing of individual masonry units; heavy damage, which is in most cases repairable, but sometimes repair is not economical.Grade 5 —total or near total collapse: increased crack width (more than 10 mm); crushing of units along both wall diagonals; severe strength degradation and final col-lapse.Typical damage patterns at characteristic damage grades for the case of plain masonry walls tested in the laboratory are presented in Fig. 3.Similar correlation between the observed damage, attrib-uted damage grades, andlimit states has been made for the case of the tested model buildings:Grade 2 —first structural damage, which may cause noticeable decay of the first natural vibration frequency of the building.Grade 3 — increased number of cracks, typical for the governing behavior mechanism of the structural system (diagonal cracks in the case of shear, horizontal tension cracks in the case of a flexural mechanism). As in the case of individual walls, this type of crack pattern is typi-cally observed at, or very soon after, the attained maxi-mum lateral resistance of the building. Moderate, repairable damage.Grade 4 —heavy damage to the walls, defined by crush-ing at the corners of the building, falling out of parts of the walls, and (or) crushing of individual masonry units.Damage is in most cases repairable, but sometimes the re-pair is not economical. Grade 5 — increased damage to the walls. Damage to horizontal structural elements, such as slabs and bond beams; crushing of concrete; and rupture or buckling of reinforcing bars (if reinforced). Final collapse.It is obvious that damage grades 2 and 5 define the crack limit and limit of collapse, respectively. As indicated by the analysis of experimentally obtained resistance curves, the displacement levels at which the crack limit and maximum resistance are attained are relatively close together (see Table 1). It has also been found that grade 3 damage can develop sometime after the attained maximum resistance. The analysis of the experiments has shown that such damage may generally occur at storey drift, equal to approximately three times the storey drift (rotation) at the occurrence of the first cracks in the walls.Grade 4 damage is observed near the point that is defined as the design ultimate limit state, where the actual resistance of the structure degrades to 80% of the maximum. However, as grade 4 damage is often not economical torepair, it is proposed that, in addition to the criterion of 20% degradation of resistance, the damage-limitation requirement should also be considered when deciding on the level of design ultimate limit state. As indicated by this analysis, the occurrence of grade 3 damage seems to be an adequate measure. It is, therefore, recommended that in their design, displacement and ductility capacity of masonry structures should not be usedbeyond the storey drift, which is equal to three times the displacement (rotation) at the occurrence of the first cracks in structural walls. Therefore, the design ultimate state on the idealized resistance curve may be defined by either the displacement (rotation) value, where the resistance degrades to 80% of the maximum (no-collapse requirement), or the displacement (rotation) value, which attains three times the value of the displacement (rotation) at the occurrence of cracks (damage-limitation requirement), whichever is less:Fire following an earthquake is an important factor causing damage to buildings and life-line structures. There-fore, besides satisfying structural design requirements for normal loads, such as dead and live loads including the seismichazard, buildings should also be designed to withstand the fire following earthquakes for a certain minimum duration as required for a desired level of performance. This period of time will allow occupants to evacuate the building safely and the emergency crews to cope with the fire. Also, it is essential to reduce the post-earthquake fire (PEF) ignitions and mini-mize the damage to active fire protection systems as much as possible to prevent the spread of fire. This paper presents a state-of-the-art review on the PEF hazard and discusses the causes, mitigation measures, and performance of building structures under this hazard. Mitigation measures that could be developed based on the experience from the structural engi-neering field are identified. Both local and global approaches that should be taken to mitigate the PEF hazard, including structural and nonstructural design, various urban planning aspects, and their interactive combinations, are discussed.Based on the review, it is concluded that that there is a strong need for the development of guidelines for structural firesafety design for PEF scenarios. In addition, appropriate analysis and numerical simulation techniques for the evaluationof the structural performance under earthquake-induced fire conditions need to be developed. It is also necessary to con-duct experimental studies to validate such numerical models and refine them.文献来源：Miha Tomazˇevic 《Damage as a measure for earthquake-resistantdesign of masonry structures》损害为砌体结构的抗震设计措施作者：Miha Tomazˇevic摘要：对砌体墙抗侧力测试和振动的砌体建筑模型的各种结构配置表测试的结果，在不同的建筑系统各种材料建成的，进行了分析，发现不同档次的损坏的结构元素的发生之间的相关性特征，极限状态，和侧位移量。