Engineering behaviors of reinforced gabion retaining wall based on laboratory test
Fatigue Behavior of Reinforced Concrete Beams
Fatigue Behavior of Reinforced Concrete Beams Strengthened with Carbon Fiber Reinforced PlasticLaminatesP .J.Heffernan 1and M.A.Erki 2Abstract:Although there has been growing interest and field applications of poststrengthening concrete structures using carbon fiber reinforced plastic ͑CFRP ͒laminates,very little information exists regarding the flexural fatigue behavior of reinforced concrete beams strengthened with CFRP.This paper presents the results of an investigation into the fatigue behavior of reinforced concrete beams poststrengthened with CFRP laminates.The results of twenty 3m and six 5m beams loaded monotonically and cyclically to failure are parisons are made between beams without and with CFRP strengthening.The effect on fatigue life of increasing the amount of CFRP used to strengthen the beams is also examined.DOI:10.1061/͑ASCE ͒1090-0268͑2004͒8:2͑132͒CE Database subject headings:Beams;Concrete,reinforced;Fatigue;Rehabilitation;Fiber reinforced plastics;Reinforcement;Laminates.IntroductionIn the last ten years,engineers have been increasingly post-strengthening reinforced and prestressed concrete members via the bonding of fiber reinforced plastic ͑FRP ͒sheets to their sur-faces.This method,potentially useful for both strengthening weak structures whose capacity is insufficient,or for repairing damaged structures,has many advantages compared to conventional meth-ods.Research to date has shown that the quasi-static flexural strength of reinforced and prestressed concrete members can be increased with FRP sheets applied to the tension face ͑Saadat-manesh and Ehsani 1990;Meier and Kaiser 1991;Triantafillou and Plevris 1992;Meier 1995;Triantafillou 1998͒.However,little is known of the longevity of reinforced concrete beams repaired using these new materials.Specifically,in the area of fatigue loading,tests to date on carbon FRP ͑CFRP ͒strengthened rein-forced concrete beams have been limited to two important stud-ies;one by Meier et al.͑1992͒and the other by Shahawy and Beitelman ͑1999͒.In Meier’s study,beams strengthened with CFRP sheets were cycled at moderate load levels,and observed for damage to the sheet and the sheet to concrete bond.Though the fatigue life of the beams was noted,no comparison was given to conventionally reinforced concrete beams.Failure of the beams was initiated in each instance by fatigue failure of the reinforcing steel bars.It was noted that the softening of the concrete due to fatigue loading could have a detrimental effect on the serviceabil-ity of the member and affect the level of stresses applied to the reinforcing steel over the life of the member.The positive contri-bution of the CFRP strengthening was a probable decrease of the stress concentrations at flexural cracks in the concrete,because the presence of the CFRP results in a greater number of smaller cracks,thereby extending the fatigue life of the steel in the beam.Shahawy and Beitelman tested a six T beam fully wrapped about the entire stem with amounts of CFRP fabric.These beams were cycled to failure.In all samples tested,the stirrups were tack welded to the longitudinal reinforcing bars.The CFRP wraps were shown to extend the fatigue life of the unwrapped beams.Most materials when subjected to cyclic loading over many thousands of repetitions can exhibit lower strengths compared to their static strength,depending on the rate of loading,the stress ratio ͑minimum/maximum cyclic stress ͒,the maximum stress,and the number of cycles.A highway bridge on a Class A route with a design life of 40years can experience a minimum of 58ϫ106loading cycles of varying intensities over its service life ͑CSA 2000͒.Fatigue strengths for concrete beams can be 25%lower if the number of cycles is increased from 5million to 100million cycles ͑Tilly 1979͒.The most common approach to quantify fatigue behavior is the stress-life,S –N ,method.For this method,samples are load cycled at a variety of constant amplitude stress ranges until fail-ure,resulting in the stress-life diagram that plots stress range versus cycles to failure.Certain materials,such as mild steel,have an endurance or fatigue limit,which is the stress level below which the material has an infinite life.However,endurance limits may change or disappear when conditions,such as periodic over-loads,corrosive environments,and high temperatures,are present.Concrete fails at stresses below its ultimate static strength when cyclically loaded to failure and exhibits a strain-softening effect when subject to cyclic uniaxial compression ͑Neville 1975͒.The fatigue properties of concrete are a function of the 1Assistant Professor of Civil and Mechanical Engineering,Royal Military College of Canada,P.O.Box 17000Stn Forces,Kingston ON,Canada K7K 7B4.E-mail:pat.heffernan@rmc.ca 2Professor of Civil Engineering,Royal Military College of Canada,P.O.Box 17000Stn Forces,Kingston ON,Canada K7K 7B4.Note.Discussion open until September 1,2004.Separate discussions must be submitted for individual papers.To extend the closing date by one month,a written request must be filed with the ASCE Managing Editor.The manuscript for this paper was submitted for review and pos-sible publication on July 29,2002;approved on January 2,2003.This D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H u a q i a o U n i v e r s i t y o n 03/10/15. C o p y r i g h t A S C E . F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .Damage in reinforcing steel as a result of cyclic loading mani-fests itself by fatigue cracks.The fatigue strength of reinforcing bars may be affected by such features as corrosion,type of bar,form of manufacture,and mean stress loading pattern.Tilly ͑1979͒concluded that the fatigue strength of mild steel is directly related to its static strength,although the fatigue strength of high strength steel is not proportional to its static strength.The bar geometry greatly effects the fatigue strength of steel,because the deformations on the bars induce stress concentrations that are a principal cause of premature fatigue fracture.Also,corrosion re-duces the strength of steel regardless of the type of loading.While the fatigue properties of CFRP vary with the type of stresses applied,the axial stress fatigue properties of high-modulus CFRP have proven excellent ͑Broutman 1974͒.This paper presents an investigation into the fatigue behavior of reinforced concrete beams,externally strengthened with CFRP sheets.The results of twenty 3m and six 5m beams loaded monotonically and cyclically to failure are pari-sons are made between beams with and without CFRP strength-ening.The effect on fatigue life of increasing the amount of CFRP used to strengthen the beams is also examined.Experimental ProgramReinforced concrete beams,3and 5m long,were tested under monotonic and cyclic loading.The 3m beams were tested to provide a comparison between the fatigue behavior of both con-ventionally reinforced concrete beams and those strengthened with an identical cross-sectional area of CFRP sheets.The same steel reinforcement configuration was used for all the 3m beams which accounts for any changes to fatigue life attributable to the presence of the CFRP sheets.The 5m beam tests were designed to validate the behavior observed in the smaller 3m beams,as well as to investigate the effect on fatigue life of varying the cross-sectional area of the CFRP sheets.Ancillary tests estab-lished the monotonic and cyclic behavior of the concrete in com-pression and the steel reinforcing bars,both ribbed and machined smooth,subjected to the expected stress history of the bars over the life of the beams tested.The monotonic behavior of the CFRP was also examined.The test results summarized in this paper are discussed in detail in Heffernan ͑1997͒.Ancillary TestsFour normal strength concrete batches were required for the test-ing program.The batch for the 3m beams had an 80mm slump,a maximum aggregate size of 10mm,and no air entrainment,while that for the 5m beams had the same slump,but a maximum aggregate size of 20mm and 6%air entrainment.Monotonic and cyclic tests were conducted on concrete cylinders,150mm by 300mm,which had attained a minimum 28day strength.The monotonic uniaxial compression tests were completed in accor-dance with Canadian Standards Association ͑CSA ͒A23.2-9C-M94͑CSA 1994͒.A separate concrete batch,representative of that used for the construction of the beams,was used for the cyclic tests of the concrete cylinders.Control cylinders for the cyclic testing were subjected first to monotonic loading to failure in accordance with CSA A23.2-9C-M94,͑CSA 1994͒,to establish the monotonic concrete strength and the modulus of elasticity.Load ranges were compression–compression cycles,with a low-20%of f c Јto avoid movement of the cylinders during testing.Table 1summarizes the concrete cylinder test types.Three batches of 400Grade steel reinforcing bars were used for various stages of the testing program.The bars tested were No.10͑11.3mm diameter ͒,No.20͑19.5mm diameter ͒,and No.25͑25.2mm diameter ͒.Each batch of reinforcing bars was tested under monotonic load.Tensile coupons were prepared by milling smooth the bars at midlength,and placing two 5mm strain gauges on opposite sides of the bars to monitor tensile straining.The monotonic tests were performed in accordance with Ameri-can Society for Testing and Materials ͑ASTM ͒A370-90A and ASTM A 615M-90͑ASTM 1991͒.The cyclic properties were determined for the machined No.25and nonmachined No.20bars,though these bars were from steel batches other than those used for construction of the beams.The cyclic tests were in ac-cordance with ASTM E606-80͑ASTM 1991͒.The constant am-plitude cyclic stress–strain curve was determined for the material by testing several machined coupons at constant amplitude,fully reversed strain cycles.The intensity of the strain applied was varied for each cycle.The hysteresis behavior of each coupon was recorded.The point of maximum stress and strain for each cou-pon,after stabilization of the hysteresis,was recorded at the half-life of the coupon.The connection of these points forms the con-stant amplitude cyclic stress–strain curve for the coupon.Table 2summarizes the reinforcing bar coupon test types.Two types of carbon fiber sheets were used in the research program.The first type,used for the 3m beam tests,was a carbon fiber unidirectional preimpregnated ͑CFUD-prepreg ͒sheet.The second type,used for the 5m beam tests,was the REPLARK 20carbon fiber sheets.Both types of CFRP sheets are unidirectional carbon fiber laminates impregnated with epoxy resin,partially cured to the B stage.The manufacturer gave the fiber volume as 60%for the CFUD-prepreg and 1.11cm 2per meter width per sheet of REPLARK 20.During application,the CFUD-prepreg and the REPLARK 20were further impregnated with an epoxy resin and allowed to cure in ambient conditions.Carbon fiber coupon specimens were cut from the CFUD-prepreg and REPLARK 20sheets and tested to determine their tensile modulus of elasticity.A test for the ultimate capacity of the Table 1.Concrete Cylinder CyclicRegimeD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H u a q i a o U n i v e r s i t y o n 03/10/15. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .pons,25mm wide by 1000mm long,were cut from the cured sheets.Two 5mm strain gauges were placed on the coupons at midlength to measure the axial strain.The tensile load was ap-plied at a displacement rate of 1.3mm/min,with observations recorded every 3s.Cyclic properties were not determined for the CFRP materials owing to the difficulty of gripping the ends of the coupons.However,carbon fibers are known to be nonsoftening when subjected to tension–tension load cycles ͑Broutman 1974͒.Three Meter Beam TestsTwenty reinforced concrete beams,150ϫ300ϫ3000mm,were constructed with 200mm 2compression reinforcement and 700mm 2tension reinforcement.Shear reinforcement was identical for all beams,and consisted of No.10stirrups spaced at 95mm.Tenof the 3m beams were additionally strengthened each with seven sheets of CFUD-prepreg.The CFRP sheets were cut to 125ϫ2650mm and applied in accordance with the specifications of the manufacturer.The applied sheets corresponded to a total of 89.4mm 2of fiber area for each of the CFRP strengthened beams.The beams were tested under either monotonic or cyclic loading.Fig.1shows the details of the internal reinforcement and the four-point loading setup.Prior to casting the beams,5mm strain gauges were attached to the tensile reinforcement at the midspan of the beam and at 308mm to either side of midspan.The compression bars were instru-mented with 5mm gauges at the midspan.For beams with CFRP sheets,two 5mm strain gauges were placed at the midspan of the beam across the width of CFRP sheets.Deflections in the beams were recorded with three linear variable displacementtransduc-Table 2.400Grade Reinforcing Bar Cyclic TestProgramD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H u a q i a o U n i v e r s i t y o n 03/10/15. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .ers.The first was mounted at the midspan and recorded vertical displacements.The remaining two were mounted to record verti-cal displacements on the top face of the beam above the supports at either end,to account for support settlement of the beams.Two beams,without and with CFRP strengthening,were loaded monotonically to failure at a rate of 1mm/min stroke rate.The remaining beams were loaded cyclically to failure.These beams were loaded by applying a sinusoidal loading pattern at a rate of 3Hz.Stress limits in the tensile steel were chosen to give a mean stress and a stress range that would guarantee fatigue failure of the tensile steel at around 106cycles in the high stress range and 107cycles in the low stress range.From fatigue tests of the tensile steel,and using moment–curvature calculations for the beams,it was determined that a stress range of approximately 60%of the nominal yield stress combined with a lower stress limit of 20%,to represent the ratio of live to dead loads found in most bridges ͑0.2to 0.4͒,would meet these short life require-ments.Also,a stress range of approximately 40%,with the same lower stress limit,would load the beam just above the fatigue limit.A loading plan was chosen that provided a stress range in the tensile steel of between 20%and 80%of the yield strength of the steel for the short-life series and between 20%and 70%,and 20%and 60%,for each of the medium-and long-life series,re-spectively.These stress ranges are given in Table 3.Peak ampli-tude loading was carried out to examine the effect of combining low and high stress range cycles.This is a preliminary step prior to the application of variable amplitude loading,which best rep-resents loading due to traffic loads.Five Meter Beam TestsSix reinforced concrete beams,300by 574by 5000mm,were constructed with 200mm 2compression reinforcement and 1500mm 2tension reinforcement.Shear reinforcement was identical for all beams and consisted of No.10stirrups spaced at 250mm.An extra stirrup was placed at each beam end,halfway between the last two stirrups,to avoid possible shear failures during the cyclic fatigue loading.Five of the beams were additionally strengthened with two,four,or six sheets of REPLARK 20.Fig.2shows the details of the internal reinforcement and the four-point loading setup.The CFRP poststrengthening was designed such that under the applied loading different stresses in the tensile steel would be induced;thereby achieving different fatigue lives for the beams over a wide range.The CFRP sheets were applied in accordance with the specifications of the manufacturer.The applied sheets corresponded to 65.5,131.0,and 196.5mm 2of fiber area for each of the two,four,and six sheet configurations,respectively.Prior to casting the beams,5mm strain gauges were attached to the flexural reinforcement,at the midspan and at 500mm either side of the midspan.The compression bars were gauged with 5mm gauges placed at 500mm either side of the midspan.For beams with CFRP sheets,two 5mm strain gauges were placed at the midspan across the width of the CFRP sheets.Deflections in the beams were recorded as for the 3m beams.One beam of each of the extreme reinforcement configura-tions,namely with zero and six sheets of CFRP reinforcement,was loaded monotonically to failure.The remaining beams were cycled to failure.These beams were loaded at a rate of 1.5Hz.Table 4summarizes these loading regimes.Experimental Results and Discussion Material PropertiesFor the 3m beams,the mean compressive strength of the concrete from four cylinder tests was 37.0MPa,with a standard deviation of 0.56MPa.For the 5m beams,from six cylinder tests,this was 32.9MPa,with a standard deviation of 5.8MPa.CyclicloadingTable 3.Three Meter BeamTestsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H u a q i a o U n i v e r s i t y o n 03/10/15. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .of the cylinders showed softening with an increasing numbers of loading cycles.For clarity,the data were reduced to graphs of elastic and plastic strain ͑Fig.3͒over the life of the cylinders.Each of the cylinders behaved similarly with rapidly increasing elastic and plastic strains at the beginning of the loading period,followed by slowly increasing elastic and plastic strains.For the cylinders cycled between 20and 90%of f c Ј,the elastic and plas-tic strains increased rapidly immediately prior to explosive rup-ture of the cylinders.None of the cylinders loaded between 20and 50or 20and 75%of f c Јexhibited this behavior,nor did they fail under these loading regimes.The uniaxial tensile tests on the steel bars for the 3m beams resulted in mean yield strength for the No.10and No.20bars of 411MPa and 511MPa,respectively.Similarly,for the No.10,No.20,and No.25bars of the 5m beams,this was 407MPa,453MPa,and 479MPa,respectively.As supported by previous work ͑Jhamb and MacGregor 1974͒,the monotonic yield strength of the deformed bars was approximately 7%smaller than that of the machined specimens,namely 420compared to 450MPa.The monotonic stress–strain behavior of all bars was elastic plastic,followed by strain hardening.The cyclic stress–strain behavior was not elastic plastic,but had a smooth curve to failure.The cyclic modulus of elasticity was 5%smaller than the monotonic modulus of elasticity,namely 200GPa compared to 210GPa,indicating the mild steel to be a cyclic softening material.The machined specimens tested at constant strain amplitudes had a rapidly increasing fatigue life as the strain amplitude was lowered.The behavior approached,but did not reach,a limitingvalue at which the specimens would not fail in fatigue;however,the fatigue lives observed at the ranges tested were very large (107)in civil engineering terms.The machined specimens tested with constant stress ampli-tudes showed that for small stress amplitudes there was little change in either the maximum strain or the strain range.For specimens tested with larger stress amplitudes,there was a sig-nificant change in the maximum strain over the life of the speci-men.The rate of increase of maximum strain decreased over the life of the specimen.However,the strain range did not change significantly through the life of the specimen,regardless of the stress range applied.This observation is attributable to cyclic creep.The results of the deformed and machined specimens tested at constant stress amplitudes are depicted in Fig.4as the stress range versus number of cycles to failure ͑log–log ͒.The deformed specimens had a rapidly increasing fatigue life as the stress range was lowered and approached,but did not reach,a limiting value at which the specimens would not fail in fatigue.For the ma-chined specimens tested at constant strain amplitudes,the stress used was that observed at the half-life of the specimen.The de-formed bars had a significantly lower fatigue life than the ma-chined bars.This is attributed to a combination of the stress con-centration resulting from the presence of the circumferential ribs and the surface condition due to rolling.Fatigue data of various other deformed bars are shown in Fig.4for comparison ͑Roper and Hetherington 1982͒.The stress range required to induce fa-tigue failure at 106cycles varied from 670MPa for the machined bars to 230MPa for the deformed bars,a reduction of approxi-mately 66%in the stress range.CFUD-prepreg coupon specimens were tested in uniaxial ten-sion to determine the modulus of elasticity of the fibers.The specimens had linear–elastic behavior to failure.A 10%differ-Fig.3.Elastic and plastic strain history for typical concrete cylinderTable 4.Five Meter BeamTestsD o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H u a q i a o U n i v e r s i t y o n 03/10/15. C o p y r i g h t A S CE .F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .ence was noted between the moduli of elasticity of the CFUD-prepreg specimens cured 1and 2weeks,that is,260GPa after 1week and 233GPa after 2weeks.The elastic modulus of the REPLARK 20sheets was 325GPa,and was independent of cur-ing times ranging from 1to 14days.Three Meter BeamsThe monotonic load versus center span displacement for the two beams tested,without and with seven CFRP sheets,is shown in Fig.5.After the proportional limit,the CFRP strengthened beam continued to resist increasing load as the CFRP sheets carried increasing tensile load,though at a more gradual linear slope of the load versus displacement curve,than that prior to yielding of the steel.This increase in load continued until the failure of the CFRP sheets,when the load dropped until it mirrored the behav-ior of the beam without CFRP strengthening,until failure of the concrete in compression.Failure of the CFRP sheets was by shearing or peeling,as described by Meier ͑1992͒.The moment resistance of the CFRP strengthened beam at the proportional limit of the steel and at maximum capacity was,respectively,21%and 37%higher than that of the beam without CFRP sheets.The center span displacement versus number of cycles for the 3m beams tested at the low stress range is shown in Fig.6.The same are shown in Figs.7and 8for the 3m beams tested at the medium and high stress ranges.The beams without CFRP sheets had a classic pattern of behavior,with rapidly increasing displace-ments at low numbers of cycles.This was followed by a levelingoff of the rate of increase of the center span displacement,which thereafter remained approximately constant until just prior to fail-ure,when the displacements began to increase rapidly,indicating imminent failure.The failure of the beams without CFRP sheets occurred as a result of the brittle fracture of one or more of the tensile steel reinforcing bars.The CFRP strengthened beams failed with brittle fatigue fracture of the tensile reinforcing steel in the beams.No damage to the CFRP sheet or the bond was apparent prior to the sudden rupture following failure of the ten-sile steel.The fatigue lives of the CFRP strengthened beams were significantly increased when compared to the conventionally re-inforced concrete beams,because the CFRP sheets reduced the mean stress in the tensile steel.The fatigue test summary is pre-sented in Table 5.When tested at high,medium,and low load ranges,the addition of the 89.5mm 2of CFUD-prepreg resulted in average increases in fatigue lives of,respectively,155,182,and 537%longer than the conventionally reinforced concrete beams.Fig.9shows the increase in fatigue life of the rehabilitated beams compared to those without CFRP sheets.Fig.10shows the same data displayed as the tensile steel stress range versus number of cycles to failure.When loaded cyclically to failure,the tensile strains at peak loads of the reinforcing steel for both conventionally reinforced and CFRP strengthened beams,were observed to increase over the life of the beam.This occurred in three stages.During early cycling ͑Ͻ50k cycles ͒,a rapid increase in strains was observed.For the remaining life of the beam,a very gradual increaseinFig.5.Reinforced concrete 3m beams tested by monotonic loading tofailureFig.6.3m beams loaded cyclically with a low stress range ͑Table 3͒Fig.7.3m beams loaded cyclically with a medium stress range ͑Table 3͒tofailureFig.8.3m beams loaded cyclically with a high stress range ͑Table D o w n l o a d e d f r o m a s c e l i b r a r y .o r g b y H u a q i a o U n i v e r s i t y o n 03/10/15. C o p y r i g h t A S C E . F o r p e r s o n a l u s e o n l y ; a l l r i g h t s r e s e r v e d .strains was noted.Immediately prior to failure of the beam, strains were noted to increase dramatically as the fatigue cracks propagated through tensile steel reinforcing.Maximum peak in-creases varied at half-life between almost no change to nearly 70%.A noticeable difference,however,was noted between beams without and with CFRP strengthening,especially when beams were loaded at the medium or high stress ranges.For the beams loaded at the medium stress range,the average strain increases in the tensile steel for the CFRP strengthened beams were between 10and20%lower than for those without CFRP strengthening. Similarly,maximum peak strains were observed to be between10 and70%lower for the same beams.This effect is most probably due in large part to the change in crack patterns for the beams reinforced with CFRP sheets.A greater number of smaller cracks form in beams reinforced with CFRP sheets than in beams with-out CFRP strengthening.This tends to mitigate the localized stress effects.Conversely,the strains observed in the CFRP sheets were observed to decrease slightly over the life of a cyclically loaded CFRP strengthened beam,likely due to slippage over time between the layers of CFRP.The decrease in strain varied from approximately10%to35%at the half-life of the specimen.With the given instrumentation,it was not readily discernible how the strains decreased through the thickness of the CFRP sheets.This decrease in CFRP strains,in conjunction with the softening effect of the concrete,could explain some of the increasing strains ob-served in the tensile steel with increasing number of loading cycles.Five Meter BeamsTwo5m beams,without and with six CFRP sheets,were tested under monotonic loading.As for the3m beam tests,the5mTable5.Reinforced Concrete Three Meter Beam Cyclic Fatigue Test SummaryBeam aNumber ofcyclesCenter display͑at cycle1͒͑mm͒Center display͑at half-life͒͑mm͒Center display͑at failure͒͑mm͒Failure mode Low stress range͑Table3͒NFa730,0008.69.159.35Rupture of tensile steelNFb1,063,0007.88.68.6Rupture of tensile steelCFa4,890,000 6.27.67.7Rupture of tensile steel followed by debondingof carbonfiber reinforced plastic CFb6,440,000 5.97.67.95Rupture of tensile steel followed by debondingof carbonfiber reinforced plastic Medium stress range͑Table3͒NFa290,0009.310.611.0Rupture of tensile steelNFb350,00010.111.2511.35Rupture of tensile steelCFa900,0007.99.39.7Rupture of tensile steel followed by debondingof carbonfiber reinforced plastic CFb890,0007.69.09.2Rupture of tensile steel followed by debondingof carbonfiber reinforced plastic High stress range͑Table3͒NFa160,00010.010.810.9Rupture of tensile steelNFb130,00010.3511.611.8Rupture of tensile steelCFa340,0008.810.310.5Rupture of tensile steel followed by debondingof carbonfiber reinforced plastic CFb390,0008.810.110.4Rupture of tensile steel followed by debondingof carbonfiber reinforced plastic NF indicates that no carbonfiber reinforced plastic has been applied and CF indicates that carbonfiber reinforced plastic has been applied.Downloadedfromascelibrary.orgbyHuaqiaoUniversityon3/1/15.CopyrightASCE.Forpersonaluseonly;allrightsreserved.。
矩形钢管混凝土柱的力学性能研究综述岳香华_1
矩形钢管混凝土柱的力学性能研究综述岳香华发布时间：2021-08-05T08:55:33.703Z 来源：《防护工程》2021年11期作者：岳香华[导读] 钢管混凝土柱（简称 CFST）是指在钢管中填充混凝土形成钢管和混凝土共同承受外荷载的结构构件。
钢管混凝土根据截面形式不同，可分为圆钢管混凝土、矩形钢管混凝土和多边形钢管混凝土等[1]。
广东工业大学广东广州 510006摘要：矩形钢管混凝土柱具有承载力高、延性好、施工方便等优势，本文对矩形钢管混凝土柱的静力性能、抗震性能、局部屈曲性能等方面的研究成果进行综述。
关键词：矩形钢管混凝土柱；力学性能钢管混凝土柱（简称 CFST）是指在钢管中填充混凝土形成钢管和混凝土共同承受外荷载的结构构件。
钢管混凝土根据截面形式不同，可分为圆钢管混凝土、矩形钢管混凝土和多边形钢管混凝土等[1]。
矩形钢管混凝土柱具有强度高、刚度大、延性好、耗能大、施工方便、梁柱节点容易处理等优点，在建筑结构中得到了广泛的应用。
近几十年来，国内外学者对矩形钢管混凝土土柱的静力性能、抗震性能、局部屈曲性能等展开深入系统的研究，取得了丰硕的成果。
1. 矩形钢管混凝土柱的静力性能研究1.1 矩形钢管混凝土柱的轴压性能研究Zhang等[2]对24根填充混凝土的矩形钢管混凝土柱进行轴压试验，研究了截面纵横比、约束系数、宽厚比等关键参数对矩形钢管抗轴力性能的影响。
Cai等[3]研究了10个有约束杆试件和5个无约束杆试件的方形钢管混凝土短柱的轴向荷载特性，研究了宽厚比、约束拉杆对钢管混凝土柱极限强度、刚度和延性的影响。
Long等[4]建立了带约束杆的矩形钢管约束混凝土的单轴应力应变关系模型，得到了影响钢管混凝土柱轴压性能的关键参数。
上述研究采用试验和理论分析，表明矩形钢管混凝土柱的轴压性能与截面形式和钢管的性能有关。
钢管不同的初始缺陷或残余应力会导致不同的破坏模式。
可以通过增加约束拉杆和减小宽厚比增加矩形钢管混凝土柱的承载力，通过适当的约束杆纵向间距来延缓甚至避免钢板的弹性局部屈曲，增大极限强度、塑性变形能力和延性。
条带式加筋土挡墙模型试验研究
第38卷第6期西南师范大学学报(自然科学版)2013年6月V o l.38N o.6J o u r n a l o f S o u t h w e s t C h i n aN o r m a lU n i v e r s i t y(N a t u r a l S c i e n c eE d i t i o n)J u n.2013文章编号:10005471(2013)06013605条带式加筋土挡墙模型试验研究①石朗晶1,李贤1,骆龙炳1,王冯哲1,曹烨楠1,21.西南大学工程技术学院土建类大学生创新训练中心,重庆400716;2.D e p a r t m e n t o fC i v i l a n dE n v i r o n m e n t a l E n g i n e e r i n g,C a r n e g i eM e l l o nU n i v e r s i t y,P i t t s b u r g h,P A15213摘要:通过进行加筋挡土墙的模型试验研究,初步探讨了加筋挡土墙结构工作的基本原理.发现加筋土挡墙的作用机理主要是由于筋带对土体的加筋作用改善了挡墙的变形特性,保证了挡土墙的稳定.加筋土挡墙最大位移通常发生在中部偏下处,挡墙工作中处于距底部高度为1/3处面板滑移最大.有限元计算与按规范计算出的滑裂面有明显差异,在挡墙中部及以下,两者的滑裂面形状类似,但是在挡墙上部,有限元法所得与规范推荐破裂面相差很大,规范推荐破裂面有一定的局限性,在设计时应考虑用其他方法补充计算,确保结构安全.关键词:加筋土挡墙;模型试验;内部破裂面;有限元分析中图分类号:T U411文献标志码:A20世纪六十年代法国工程师H e n r iV i d a l提出现代加筋土理论,加筋土技术得到迅速发展.德国‘地下工程“杂志赞誉加筋土为 继钢筋混凝土后又一造福人类的复合材料 [1-2].叶观宝,徐超等通过加筋土挡墙模型试验探究了加筋挡土墙的工作特性[3];周世良等利用台阶式加筋土挡墙模型试验研究了台阶式加筋土挡墙竖直土压力㊁筋带拉力分布及其变形情况[4];莫介臻通过模型试验研究提出加筋土挡墙潜在破裂面的实用计算模式[5];李福林㊁彭芳乐等从试验研究和数值模拟两个角度综合分析了加筋土挡土墙在加载速率变化下的强度特性[6];法国学者A b d e l k a d e rA b d e l o u h a v引入了 使用极限状态 和 最终极限状态 这两种概念来分析挡墙的稳定性[7];宋雅坤㊁郑颖人等运用P L A X I S模拟加筋土挡土墙,得到筋带层数等挡土墙设计参数与破裂面及安全系数的关系,并根据所得出的规律对水富 麻柳湾高速公路的土工格栅加筋土挡墙进行优化设计[8].由于加筋材料的工程性质复杂,加筋土结构的作用机理的特殊性和复杂性,其设计计算理论还不是很成熟,本文通过加筋土结构的模型试验对加筋土挡墙结构工作原理进行探究,对设计方法进行优化研究. 1模型实验材料及其参数试验采用胶合板(厚度为2.0c m)做成的长方体箱形(如图1),内部长73.5c m,宽47c m,高48c m.模型实验箱为四面胶合板围成的开敞式箱体.模型面板由螺丝连接,并由钢带在距顶端2c m处,环绕模型一周,固定模型.实验筋材采用牛皮纸质地纸带,纸带采用抗拉试验测得抗拉强度,参数见表1.采用硬质①收稿日期:20120722基金项目:国家级大学生创新创业训练计划资助(201210635113);国家自然科学基金项目资助(10902091);中央高校基本科研业务费专项资金资助(X D J K2010C014);西南大学科研基金资助项目(S WU208010).Copyright©博看网. All Rights Reserved.作者简介:石朗晶(1990),男,江苏南通人,主要从事土木工程方面的研究.通信作者:李贤,硕士,讲师.牛皮纸做面板,内部尺寸为47.0ˑ48.0c m (如图2),将面板两边和底边向内折5c m ,防止漏沙而影响挡墙建造.回填土材料使用洁净的干砂,试验所用干砂通过环刀法测得重度γ=15.9k N /m 3,三轴试验测量内摩擦角φ=34.2ʎ,干砂通过6次碾压填压密实[1].表1 实验筋材抗拉强度筋带宽度W /mm 102040抗拉强度T a /N19.834.756.2图1试验模型建造图2 筋带初步设计布置方案2 模型初步设计根据‘公路加筋土工程设计规范“(J T J 01591)为依据进行加筋土挡墙模型设计试验采用规范公式:加筋土体第i 层一个节点加筋材料所受力为:T i =K iW i S x S y 其中:T i第i 层一个节点加筋材料所受拉力(K N );K i 至强顶深度为Z i 处的土压力系数;当Z i ɤ6m 时,K i =K o (1-Z i6)+K a Z i 6;当Z i ȡ6m 时,K i =K a =t a n 245ʎ-φ2.w i 第i 层加筋材料所受的法向压力(k P a ),W i =γZ i +q ;其中Z i 为挡土墙顶部至第i 层加筋材料的距离(m );q 为墙顶换算均布荷载(k P a );γ 土的重度(k N /m 3);加筋体填料的内摩擦角φ=34.2ʎ;加筋长度由L i =L 1i +L 2i 确定,其中L i =[K f ]T i2f b (γZ i +q i )=[K f ]K a S x S y 2f b .初步设计方案如表2和图2所示:表2 模型设计计算表筋带层数深度/mm 筋带拉力/N主动区长度/mm 锚固长度/mm筋带总长/mm1603.78144247.8391.8218022.45144247.8391.8330030.0295.3247.8391.8442037.5731.8247.8391.8141第6期 石朗晶,等:条带式加筋土挡墙模型试验研究Copyright ©博看网. All Rights Reserved.3 模型建造与加载试验条带式加筋土挡墙试验内容:在硬质牛皮纸面板上标明筋带位置,将牛皮纸条形筋带用透明胶带粘贴于面板上;固定可移动模型箱面板,将硬质牛皮纸面板紧贴箱面板放入砂箱内;填入干砂,多次压实,分层放下筋带,平铺于砂土面层,再填入细砂,压实,回填至48mm 高处停止;缓慢移除模型箱可移动面板.等待加筋土挡墙模型稳定,之后将装有细砂总重30.0k g 的塑料桶放置于离面板10.0c m 处的模型中央,初步加载完成3m i n 后,若挡墙稳定,则继续加载至挡墙破坏,极限荷载为35k g,试验完毕(图3).4 试验结果分析及有限元模拟4.1 试验结果分析在试验填土压实后,加载之前,挡土墙面板略有变形,中间部分变形稍大,向外鼓胀,上下两边变形较小,距底部1/3处最大.在加载之后,挡土墙变形增长,随荷载大小不同,变形不同,但差异较小,在加载到极限荷载后,挡土墙筋带拉断,主要拉断在筋带与面板连接处(如图4).图3 模型加载试验图4 筋带在粘接处拉断通过本次加筋挡土墙建造与加载模拟实验,分析实验结果发现:1)筋带利用与砂土界面的摩擦力以及筋带拉动填土引起的填土整体滑移而产生的摩擦力,发挥加筋作用.筋带改善了挡墙的变形特性,约束了挡墙的侧向位移,保证了挡土墙的稳定.加筋后的挡土墙整体稳定性有了大幅度的提升.图5 加筋土挡墙试验有限元模型与网格划分2)挡墙变形中间部分稍大,向外鼓胀,上下两边变形较小,距底部1/3处最大.其中距底部高度为1/3处面板滑移最大,应重点改善加筋条件.3)筋带断裂都是在与面板连接处,说明筋带拉力未充分发挥,筋带在连接处出现应力集中,导致筋带多在连接处断裂,在现实设计中应注意.4.2 试验模型破裂面有限元模拟加筋土结构有两个破裂面,一个是整体稳定的外部滑裂面,一个挡墙内部破裂面,挡土241西南师范大学学报(自然科学版) h t t p ://x b b jb .s w u .c n 第38卷Copyright ©博看网. All Rights Reserved.墙的内部潜在破坏面是加筋土结构研究的关键.用岩土工程专业有限元分析软件P L A X I S 按实体模型建立有限元模型(图5),模拟加筋土挡墙内部破裂面,并与模型试验进行对比分析.关于内部潜在破坏面的确定,目前的设计规范广泛采用 0.3H 法.规范推荐破裂面接近朗肯滑裂面,墙上部与墙面平行,与顶部填土交与距面板0.3墙高处.有限元分析中,加筋土挡墙的内部潜在破坏面可认为是筋带的最大拉力点的连线.建立大尺寸有限元模型,将各层筋带的最大拉力值连线起来,可以得出该挡土墙的内部潜在破坏面跟规范推荐破裂面下部较为吻合,上部有一定差距(如图6㊁7).结果表明,有限元滑裂面与规范计算出的滑裂面相差较大.在挡墙中部及以下,两者的滑裂面形状类似;但是在挡墙上部,有限元法所得与规范推荐破裂面相差很大,尤其是第一,二层筋带最大轴力的位置远离面板距离较大,导致滑裂面迅速向墙后延伸,如果完全按照规范设计,挡土墙的安全性无法得到保证.因此,规范推荐破裂面有一定的局限性,在设计时应使用有限元法进行进一步的验证分析.图6 土体加筋时应力分布云图图7 有限元法和规范推荐的破裂面5 结 论本文通过一个小型加筋土挡墙模型试验,分析对比了挡土墙加筋前后的性能,探讨了加筋挡土墙位移,滑裂面的基本性质,具体分析了加筋对于改善土体性质,提高挡墙承载力的作用.得到了与加筋土挡墙设计有关的一些初步规律,取得以下主要结论:1)发现加筋土挡墙的作用机理主要是由于筋带的加筋作用.筋带利用与砂土界面的摩擦力以及筋带拉动填土引起的填土整体滑移而产生的摩擦力发挥作用.加筋后的挡土墙整体稳定性有大幅度的提升.筋带改善了挡墙的变形特性,约束了挡墙的侧向位移,位移的变化更加均匀,保证了挡土墙的稳定.2)加筋土挡墙最大位移通常发生在距底部1/3处.在加筋土挡墙工作中处于距底部高度为1/3处面板滑移最大,应重点改善加筋方式.在中部偏下处挡土墙变形较大,适当地放短上㊁下部的筋带,加长中部的筋带,可以在使用同等筋材量的基础上有效提高挡墙的稳定性,但具体加筋长度与部位有待进一步研究.3)有限元滑裂面与规范计算出的滑裂面有差异,规范推荐破裂面有一定的局限性.在进行加筋土挡墙工程设计时应进行深入的挡墙力学性能分析,保证工程建设的安全性.参考文献:[1]杨广庆.土工格栅加筋土结构理论及工程应用[M ].北京:科学出版社,2010.[2] 何春光.加筋土工程设计与施工[M ].北京:人民交通出版社,2000.[3] 叶观宝,张 振,徐 超,等.加筋土挡墙模型试验研究[J ].勘察科学技术,2010(2):3-5,35.[4] 周世良,何光春,汪承志,等.台阶式加筋土挡墙模型试验研究[J ].岩土工程学报,2007,29(1):152-156.[5] 莫介臻,周世良,何光春,等.加筋土挡墙潜在破裂面模型试验研究[J ].铁道学报,2007,29(6):69-73.341第6期 石朗晶,等:条带式加筋土挡墙模型试验研究Copyright ©博看网. All Rights Reserved.441西南师范大学学报(自然科学版)h t t p://x b b j b.s w u.c n第38卷[6]李福林,彭芳乐,江智森,等.无加筋㊁加筋砂土蠕变特征的有限元分析[J].岩土力学,2011,32(4):1200-1204,1210.[7] A B D E L K A D E R A,D A N I E LD.N u m e r i c a lA n a l y s i so f t h eB e h a v i o r o fM e c h a n i c a l l y S t a b i l i z e dE a r t h W a l l sR e i n f o r c e dw i t hD i f f e r e n tT y p e s o f S t r i p s[J].G e o t e x t i l e s a n dG e o m e m b r a n e s,2011,29(2):116-129.[8]宋雅坤,郑颖人,刘一通,等.土工格栅加筋土挡墙稳定性影响因素敏感性分析[J].后勤工程学院学报,2010,26(3):1-7.O n M o d e l E x p e r i m e n t o fG e o b e l t sR e i n f o r c e dE a r t hR e t a i n i n g W a l lS H IL a n g-j i n g1, L I X i a n1, L U O L o n g-b i n g1,WA N GF e n g-z h e1, C A O Y E-n a n1,21.I n n o v a t i v eE x p e r i m e n t C e n t e r f o r U n d e r g r a d u a t e so f C i v i l E n g i n e e r i n g,C o l l e g eo f E n g i n e e r i n g a n dT e c h n o l o g y,S o u t h w e s t U n i v e r s i t y,C h o n g q i n g400716,C h i n a;2.D e p a r t m e n t o f C i v i l a n dE n v i r o n m e n t a l E n g i n e e r i n g,C a r n e g i eM e l l o nU n i v e r s i t y,P i t t s b u r g h,P A15213A b s t r a c t:A m o d e l e x p e r i m e n to f r e i n f o r c e de a r t hr e t a i n i n g w a l lh a sb e e nc a r r i e do u t t os t u d y t h eb a s i c p r i n c i p l eo f r e t a i n i n g w a l l.B y c o m p a r i s o n o f t h em e c h a n i c a l b e h a v i o r s,w e h a v e f o u n d i n t h em o d e l e x p e r i-m e n t a n dF E Ma n a l y s i s t h a t t h e b a s i cm e c h a n i c a l p r i n c i p l e o f r e i n f o r c e dw a l l s i s s o m e t h i n g t h a t t h e g e o b e-l t s c o u l d i m p r o v e t h e c h a r a c t e r i s t i c o f t h e e a r t h,h e n c e i n c r e a s i n g t h e s a f e t y o f t h ew a l l.T h e l a r g e s t s e t t l e-m e n t o f t h e p a n e l l o c a t e a t t h e1/3p l a c e o f t h ew a l l f r o mt h eb o t t o m.T h e r e s u l t so f t h e e x p e r i m e n t a n d F E Ma n a l y s i sm a t c hw e l l.W e h a v e a l s o f o u n d t h a t t h e s i m u l a t e d s l i pp l a n e i s o f g r e a t d i f f e r e n c ew i t h t h a t r e c o mm e n d e d i n t h eS t a n d a r d J T J01591:T h e l o w e r h a l f p a r t o f t h e s l i pp l a n eb y F E M m e t h o d i s c o n-s i s t e n tw i t h t h e s t a n d a r d c o d e s;h o w e v e r,t h eF E Mr e s u l t s i m p l y l a r g e d i f f e r e n c e f o r t h e u p p e r h a l f p a r t o f t h e s l i pp l a n e.T h i s r e s u l t s h o w s a l i m i t a t i o no f t h e s t a n d a r dc o d e s,a n dw e s h o u l dc o n s i d e r i t i n f u r t h e r s t r u c t u r a l d e s i g n t o e n s u r e t h e s a f e t y o f t h e s t r u c t u r e.K e y w o r d s:r e i n f o r c e d e a r t h r e t a i n i n g w a l l;m o d e l e x p e r i m e n t;i n n e r f r a c t u r e p l a n e;f i n i t e e l e m e n t a n a l y z e责任编辑汤振金Copyright©博看网. 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低周反复荷载下型钢再生混凝土框架中节点抗震性能试验研究_薛建阳
第47卷第10期2014年10月土木工程学报CHINA CIVIL ENGINEEＲING JOUＲNALVol．47Oct．No．102014基金项目：国家自然科学基金（51178384），陕西省留学人员科技活动择优资助项目（陕外专发［2010］26号），住房和城乡建设部科学技术项目（2012-K2-12），陕西省教育厅科研计划项目（12JK0902）和教育部创新团队发展计划（IＲT13089）作者简介：薛建阳，博士，教授收稿日期：2013-08-30低周反复荷载下型钢再生混凝土框架中节点抗震性能试验研究薛建阳鲍雨泽任瑞王刚（西安建筑科技大学，陕西西安710055）摘要：为研究型钢再生混凝土框架中节点的破坏特征和抗震性能，进行4榀粗骨料取代率分别为0%、30%、70%、100%的1ʒ2．5模型试件的低周反复加载试验，观察其破坏形态和受力特点，对框架中节点的荷载-位移滞回曲线、骨架曲线、承载能力、强度退化、刚度退化、层间位移角、延性以及耗能能力等力学性能进行分析研究。
结果表明：型钢再生混凝土框架中节点的典型破坏形态是节点核心区剪切斜压破坏；荷载-位移滞回曲线饱满，位移延性系数介于3．95 4．88；弹塑性极限位移角约为1/19 1/26；破坏时节点的等效黏滞阻尼系数介于0．322 0．335；随着再生粗骨料取代率的增加，型钢再生混凝土框架中节点的抗剪承载力和耗能能力有所降低，延性减小。
但是相对于普通型钢混凝土框架中节点而言抗震性能降低不大。
关键词：型钢混凝土结构；再生混凝土；框架中节点；低周反复加载试验；抗震性能中图分类号：TU398+．9TU317+．1文献标识码：A 文章编号：1000-131X （2014）10-0001-08Experimental study on seismic performance of steel reinforced recycled concreteinner-frame joints under low-cyclic reversed loadingXue JianyangBao YuzeＲen ＲuiWang Gang（Xi ’an University of Architecture and Technology ，Xi ’an 710055，China ）Abstract ：In order to study the failure patterns and seismic performance of steel reinforced recycled concrete （SＲＲC ）inner-frame joints ，low-cyclic reversed loading tests were carried out on four 1ʒ2．5specimens with different coarse aggregate replacement rates．The failure patterns and loading characteristics were observed．The mechanical behaviors ，such as the load-displacement hysteretic curves ，skeleton curves ，load carrying capacity ，degradation of strength and stiffness ，inter-story drift ，ductility and energy dissipation of the inner joints were analyzed．The results show that the main failure patterns of the inner-frame joints are shearing diagonal compression in joint zone．The hysteretic loops of the inner-frame joints are plump and the displacement ductility coefficient is between 3．95and 4．88．The ultimate elastic-plastic drift ratio is about 1/19 1/26，and the equivalent viscous damping coefficient is between 0．322and 0．335when the joints fail．The shear capacity ，energy dissipation capacity and ductility of the steel recycled aggregate concrete inner-frame joint decrease with the increase in the replacement rate of the recycled coarse aggregates．However ，the seismic performances do not degrade obviously compared to the ordinary steel reinforced concrete inner-frame joints．Keywords ：steel reinforced concrete structure ；recycled concrete ；inner-frame joint ；low-cyclic reversed loading test ；seismic performanceE-mail ：jianyang_xue@163．com引言废弃的混凝土是建筑业中排出的最主要废弃物，这些大量的建筑垃圾加剧了自然环境的恶化，为实现可持续发展，解决和处理这些建筑垃圾迫在眉睫，因此混凝土的再生利用显得尤为重要。
英语作文保护犀牛的方法
Protecting rhinoceroses is a critical environmental issue that requires a multifaceted approach.Here are several methods that can be employed to ensure the survival and wellbeing of these magnificent creatures:1.Strict Enforcement of AntiPoaching Laws:Strengthening the legal framework against poaching is essential.This includes harsher penalties for those caught poaching and trafficking in rhino horns.munity Involvement and Education:Engaging local communities in conservation efforts is cating them about the importance of rhinos and the negative impacts of poaching can help change attitudes and behaviors.3.Habitat Preservation:Ensuring that rhinos have ample space to live and breed is crucial. This involves protecting and expanding their natural habitats,which also benefits other species and ecosystems.4.Intensive Surveillance and Monitoring:Using technology such as drones,GPS tracking, and camera traps can help monitor rhino populations and detect poaching activities early.5.International Cooperation:Rhino poaching is often linked to international crime networks.Collaborative efforts between countries to share intelligence and combat the illegal trade in rhino horns are necessary.6.Demand Reduction:Addressing the demand for rhino horns,particularly in countries where they are used in traditional medicine or as status symbols,is key.Public awareness campaigns and efforts to change cultural perceptions can help reduce demand.7.Captive Breeding Programs:In some cases,captive breeding can help increase rhino populations and provide a safety net against poaching.However,its important that these programs are managed responsibly and do not contribute to the illegal trade.8.Financial Support for Conservation Efforts:Adequate funding is necessary to support antipoaching units,research,and habitat preservation.This can come from government budgets,international aid,or private donations.9.Translocation of Rhinos:Moving rhinos to safer areas or creating new populations in different regions can help spread the genetic pool and reduce the risk of local extinction.10.Research and Science:Ongoing research into rhino biology,behavior,and ecology can provide valuable insights that inform conservation strategies and help improve theeffectiveness of protection measures.By implementing these methods in a coordinated and comprehensive manner,we can work towards a future where rhinoceroses thrive in the wild,free from the threats they currently face.。
危岩崩塌防治技术体系及工程选型分析
钻探工程Drilling Engineering第51卷第2期2024年3月Vol. 51 No. 2Mar. 2024：108-118危岩崩塌防治技术体系及工程选型分析周云涛1，2，吴 波*1，3，蔡强1，2，梁炯1，2（1.中国地质科学院探矿工艺研究所，四川 成都 611734； 2.自然资源部地质灾害风险防控工程技术创新中心，四川 成都 611734；3.成都华建地质工程科技有限公司，四川 成都 611734）摘要：危岩崩塌防治技术是保障危岩工程安全稳定的关键。
通过对危岩崩塌防治技术的优缺点、适用条件、工程设置原则以及选型程序的分析，认为危岩崩塌防治技术可分为主动防治技术、被动防治技术和辅助防治技术，各项防治技术设计时应充分考虑其适用条件，按照工程设置原则采纳使用，适时选择多种技术组合方式的治理措施进行危岩崩塌工程防治；危岩崩塌防治技术选型应遵循查清危岩体基本情况→评价危岩体状态→选择危岩防治技术→分析防治技术选型结果的基本程序，确定危岩崩塌防治技术选型程序各环节的关键参数，以确定合适的崩塌防治技术。
研究成果可为危岩崩塌防治工程设计提供理论依据和关键技术支撑。
关键词：危岩崩塌；防治技术体系；选型程序；主动防治技术；被动防治技术；辅助防治技术中图分类号：P642.21；P634 文献标识码：A 文章编号：2096-9686（2024）02-0108-11Analysis of control and prevention technology system andengineering selection for unstable‑rockZHOU Yuntao 1,2，WU Bo *1,3，CAI Qiang 1,2，LIANG Jiong 1,2(1. Institute of Exploration Technology, CAGS, Chengdu Sichuan 611734, China ；2. Technology Innovation Center for Risk Prevention and Mitigation of Geohazard, MNR, Chengdu Sichuan 611734, China;3. Chengdu Huajian Geological Engineering Technology Co., Ltd., Chengdu Sichuan 611734, China )Abstract ： The control and prevention technology for unstable‑rock is the key to guarantee the safety and stability of unstable‑rock. This paper analyzed the merit and demerit ， application condition ， engineering setting principle and selection program of the control and prevention technology ， which is devided into three kinds ， i.e.， active technology ， passive technology and assisted technology. Application conditions of each technology should be considered when these technologies were designed. Each technology should be selected based on the engineering setting principle ， and the treatment measure with multiple technologies to control and prevent unstable‑rock should be duly selected. The selection of technology for unstable‑rock engineering should follow such process of checking the basic information of unstable‑rock → evaluating the state of unstable‑rock → selecting technology → analyzing the result of selected technology ， thus the key parameters of each part of this process were confirmed to select the suitable technology. This research achievement could provide the theoretical foundation and key technology support for unstable‑rock engineering.Key words ： unstable‑rock collapse; control and prevention system; selection process; active technology; passive technology;assisted technology收稿日期：2023-07-22； 修回日期：2023-11-03 DOI ：10.12143/j.ztgc.2024.02.015基金项目：中国地质调查局地质调查项目“高陡碎屑坡生态治理技术应用示范”（编号：DD20230450）；国家重点研发计划专项项目“膨胀土滑坡和工程边坡防护工程健康诊断和快速修复技术”（编号：2019YFC1509904）第一作者：周云涛，男，汉族，1988年生，工程师，地质工程专业，博士，从事岩土与地质工程减灾机理及防控技术研究工作，四川省成都市郫都区港华路139号，**********************。
混凝土中的冷拔钢丝应用原理
混凝土中的冷拔钢丝应用原理混凝土中的冷拔钢丝应用原理1. 引言混凝土是建筑和基础设施建设中最常用的材料之一。
它的强度和耐久性使得其在各个领域都有广泛的应用，包括桥梁、建筑物、道路和水坝等。
为了进一步提高混凝土的性能，冷拔钢丝被广泛地应用于混凝土中。
本文将探讨冷拔钢丝在混凝土中的应用原理及其优势。
2. 冷拔钢丝的特点冷拔钢丝是通过将热轧钢丝在低温下拉拔而成的。
相比于热轧钢丝，冷拔钢丝具有以下特点：- 更高的强度和硬度。
- 更好的抗腐蚀性能。
- 更好的耐久性和稳定性。
3. 冷拔钢丝在混凝土中的应用原理冷拔钢丝在混凝土中的应用原理主要包括以下几个方面：3.1 增强混凝土的强度冷拔钢丝在混凝土中能够增加其抗拉强度和抗压强度。
当混凝土受到外力作用时，冷拔钢丝能够有效地分散和承担应力，从而提高混凝土的整体强度和稳定性。
3.2 提高混凝土的韧性冷拔钢丝的强度和硬度使得其能够有效地增加混凝土的韧性。
韧性是指材料在受力下变形能量吸收的能力。
在冷拔钢丝的作用下，混凝土可以更好地抵抗外力的冲击和震动，减少因突然受力导致的破损和断裂。
3.3 控制混凝土的收缩和开裂混凝土在干燥和固化过程中容易出现收缩和开裂的问题。
冷拔钢丝可以有效地控制混凝土的收缩和开裂。
通过在混凝土中引入冷拔钢丝，可以显著减少混凝土的收缩率，从而减轻开裂的风险，并提高混凝土的耐久性。
3.4 增加混凝土的粘结性能冷拔钢丝在混凝土中分散均匀，并与混凝土胶凝体中的水化产物进行结合，从而增加了混凝土的粘结性能。
这种粘结性能可以有效地提高混凝土的抗渗性、抗水化物侵害和抗冻融性能。
4. 冷拔钢丝在混凝土中的应用案例冷拔钢丝在混凝土中的应用已经得到了广泛的验证和应用。
以下是一些应用案例：4.1 桥梁和建筑结构冷拔钢丝广泛用于桥梁和建筑结构中的预应力混凝土构件。
通过在混凝土中引入冷拔钢丝，可以增加构件的强度和稳定性，减少开裂和变形。
4.2 水坝和隧道工程冷拔钢丝在水坝和隧道工程中也有重要应用。
往复荷载下钢筋混凝土柱受力性能的数值模拟
0
量，均按文献[5]计算。
σ
变； s、s1、s2 为控制参数，按文献[4]计算。其中，
I e 0 = 0.08
Emin
σ c 0 = σ c 0 (1 + 2.4 I e 0 0 1.2 ε c 0 = ε c 0 (1 + 35 I e 0 )
Key words: fiber model; cyclic load; concrete column; hysteretic relation; numerical analysis
钢筋混凝土柱作为混凝土框架结构及桥梁结 构的主要承重构件，在地震作用下受到反复水平地 震力作用，并表现为显著的弹塑性受力特性 。准 确预测地震作用下钢筋混凝土柱的受力性能及其 震后残余变形，对评估结构的震害程度和安全性具 有重要意义。由于材料和结构受力的复杂性，目前 对于反复荷载下钢筋混凝土柱的受力性能和残余 变形的数值模拟还存在欠缺，主要表现在混凝土和 钢筋的滞回本构关系不能全面准确的反映其复杂 的受力行为。 对于长细比较大的杆系结构（例如框架梁柱或 桥柱） ， 可以采用基于杆系结构力学方法 和一维材 料本构的纤维模型进行数值模拟。所谓纤维模型，
0 0
0.7
)
(2)
σf
ft
Emin
式中，σ c 0 、ε c 0 分别为无约束混凝土 （素混凝土） 受压峰值应力和峰值应变； I e 0 为混凝土受压应变 等于峰值应变 ε c 0 时的有效约束指标，是一个与纵
ε c0 ε z ε unε re ε z − ε tz
图 2 混凝土应力-应变曲线 Fig.2 Stress-strain curve of concrete
高强钢绞线网—聚合物砂浆加固偏压柱的试验研究
四川建筑科学研究Sichuan B uilding Sc ience 第33卷 增刊2007年12月收稿日期22作者简介张立峰(8),男,工学硕士,主要从事结构加固研究。
z __f @63高强钢绞线网—聚合物砂浆加固偏压柱的试验研究张立峰,姚秋来,程绍革,王忠海,潘晓峰(中国建筑科学研究院工程抗震研究所,北京 100013)摘 要:高强钢绞线网—聚合物砂浆加固技术是近年发展起来的新型加固技术。
在对9根大偏心和9根小偏心受压混凝土柱的试验研究基础上,通过对试件的破坏形态、裂缝分布、荷载—跨中挠度曲线、钢筋和钢绞线应变以及极限承载力影响因素等的分析,证明了混凝土柱用高强钢绞线网—聚合物砂浆加固后,柱整体工作性能良好,加固效果明显,可在工程中推广应用。
关键词:高强钢绞线网;聚合物砂浆;偏压柱;加固;承载力中图分类号:T U375.3;T U317+.1 文献标识码:A 文章编号:1008-1933(2007)增刊-0146-07Exper i m en ta l i n vestiga ti on on colum n s strengthened with high 2str en gth steel wi r e m es h and poly m er m or tar under eccen tr i c loa d i n gZHAN G L ifeng,Y AO Q iulai,CHENG Shaoge,WAN G Zhonghai,P AN Xiaofeng(I nstit ute of Ea rt hquake Engineering,Ch i na Acade m y of B uilding Re s ea rch,Be iji ng 100013,China )Ab stra ct:Rehabilit a tion of reinforced concrete members with high 2strength steel wire me sh and po l y m er mortar develo p ed in recent years is an excellent and advanced means of re trofitting .Ex peri mentswere conducted t o investigate the behavi ors of 18eccentri c l oaded columns,and the eccentricity va ri e s from la rge to s ma ll .The mode of fa ilure,c racking behavi or,load versusm i d 2pan late ral deflec ti on curve s,stre ss of re i nforced ba rs and stee lwires and ulti ma t e l oad 2carrying capacit y of t he strengthened s peci m ens we re analyzed,and it was p roved tha t the strengthening effec t and working behavi or of strengthened colu mn are ex ce llent .Key wor ds:high 2strength steel wire me sh;poly me r mortar;eccentric l oaded co l umns ;rehab ilitati on;l oad 2carrying capac ity1 概 述高强钢绞线网—聚合物砂浆加固技术是近几年来在国内外发展起来的新型技术。
【工程学科英语(整合第二稿)】 参考答案
Unit OneTask 1⑩④⑧③⑥⑦②⑤①⑨Task 2① be consistent with他说，未来的改革必须符合自由贸易和开放投资的原则。
② specialize in启动成本较低，因为每个企业都可以只专门从事一个很窄的领域。
③ d erive from以上这些能力都源自一种叫机器学习的东西，它在许多现代人工智能应用中都处于核心地位。
④ A range of创业公司和成熟品牌推出的一系列穿戴式产品让人们欢欣鼓舞,跃跃欲试。
⑤ date back to置身硅谷的我们时常淹没在各种"新新"方式之中，我们常常忘记了，我们只是在重新发现一些可追溯至涉及商业根本的朴素教训。
Task 3T F F T FTask 4The most common viewThe principle task of engineering: To take into account the customers ‘ needs and to find the appropriate technical means to accommodate these needs.Commonly accepted claims:Technology tries to find appropriate means for given ends or desires;Technology is applied science;Technology is the aggregate of all technological artifacts;Technology is the total of all actions and institutions required to create artefacts or products and the total of all actions which make use of these artefacts or products.The author’s opinion: it is a viewpoint with flaws.Arguments: It must of course be taken for granted that the given simplified view of engineers with regard to technology has taken a turn within the last few decades. Observable changes: In many technical universities, the inter‐disciplinary courses arealready inherent parts of the curriculum.Task 5① 工程师对于自己的职业行为最常见的观点是：他们是通过应用科学结论来计划、开发、设计和推出技术产品的。
李晓宇完成单位河海大学
项目名称：近海工程混凝土结构性能评估与修复加固关键技术完成人：陈达，侯利军，廖迎娣，江朝华，欧阳峰，庄宁，冯兴国，俞小彤，李晓宇完成单位：河海大学成果类别：应用类项目简介：该项目“近海工程混凝土结构性能评估与修复加固关键技术”，所属水利工程科学技术领域，该成果主要应用于码头、桥梁、水闸、防波堤等近海工程混凝土结构性能评估与修复加固。
近海工程混凝土结构所处环境复杂，不仅遭受海洋环境高盐、高湿、甚至高温和干湿交替等物理化学作用，而且长期处于风、浪、流耦合荷载作用，其耐久性和力学性能退化速度与程度显著高于普通环境，在运行一定年限后常常发生较为严重的钢筋锈蚀、混凝土开裂和剥落等劣化现象，严重影响结构的安全运行。
因此，建立近海环境混凝土结构性能评估方法、开发高效可靠的修复加固技术，是近海工程领域迫切需要解决的关键难题，对结构安全评估与耐久性提升具有重要意义。
该项目依托5项国家自然科学基金、水利部公益性行业科研专项等基金项目，围绕近海工程混凝土性能评估和修复加固进行了深入研究，并开发了集修复加固材料、施工工艺和施工装备于一体的成套修复加固技术。
该项目成果主要分为三部分：（1）研究了海洋干湿交替和硫酸盐侵蚀耦合作用对混凝土物理、力学性能的影响，建立了化学-力学-物理过程多场耦合本构模型，为近海混凝土结构性能评估提供理论模型；研究了荷载与氯盐腐蚀耦合作用下钢筋的锈蚀机理，揭示了荷载对钢筋/混凝土界面破坏、钢筋去钝化以及温度、湿度对钢筋锈蚀的影响效应，构建了钢筋锈蚀剩余寿命预测模型，为混凝土结构运行维护和修复加固设计提供依据。
（2）研发了适用于近海环境混凝土修复的高性能纤维水泥基材料，提出了修复材料配合比定量化优化方案，以及修复材料与既有混凝土的粘结设计方法；提出并试验验证了不锈钢钢筋修复加固锈蚀碳钢钢筋的方案，纠正了通常认为不锈钢钢筋会加速碳钢钢筋锈蚀的观念；开发了锈蚀率定量测定装置和自发电外加电流钢筋锈蚀防护装置，解决了混凝土和钢筋高效修复加固难题。
钢筋混凝土锈蚀损伤研究综述
钢筋混凝土锈蚀损伤研究综述3余王番王景, 曹大富, 李琮琦(扬州大学 建筑科学与工程学院,江苏扬州 225009)摘要:钢筋锈蚀是钢筋混凝土结构耐久性降低的主要因素之一。
简要说明研究钢筋混凝土锈蚀损伤的重要意义,阐述了钢筋混凝土锈蚀件损伤的研究状况。
主要从混凝土中锈蚀钢筋的力学性能、钢筋锈蚀引起的混凝土损伤、锈蚀钢筋与混凝土间粘结性能和锈蚀钢筋混凝土受弯构件、受压构件的受力性能、锈蚀钢筋混凝土构件抗震性能等方面总结归纳了国内外的研究现状与成果,并分析了今后的研究方向。
关键词:钢筋混凝土;锈蚀;损伤;力学性能;承载力中图分类号:T U375 文献标识码:A 文章编号:1006-7329(2007)01-0122-04Rev i ew of Research on Damage of Corroded Re i n forced ConcreteY U Fan-jing,CAO Da-fu,L I Zong-qi(College of A rchitectural Science and Engineering,Yangzhou University,Yangzhou225009,P.R.China)Abstract:The research result shows that the corr osi on of reinforce ment is one of the dom inating fact or f or decreasing the durability of reinf orced concrete structures.I n this paper,the significance of the research of corr oded reinf orced concrete is p resented,and an atte mp t is made t o integrate the latest devel opment with regard t o the mechanical behavi ors of rein2 force ment corr osi on,the da mage of concrete due t o corr oded bars,bond relati onshi p bet w een corr oded bars and concrete, as well as the l oad capacity of corr oded reinf orced concrete flexural me mber and comp ressive me mber and the seis m ic be2 havi or of corr oded reinforced concrete ele ment.And the trend of its devel opment in future is discussed as well. Keywords:reinf orced concrete;corr osi on;da mage;mechanical behavi ors;l oad capacity 钢筋锈蚀是影响混凝土结构耐久性的最主要因素。
工程思维英语
工程思维英语Title: Engineering Thinking in PracticeEngineering thinking is a systematic approach to problem-solving that emphasizes logic, analysis, and practicality. It involves breaking down complex problems into manageable components and applying scientific principles to findeffective solutions. This essay explores the principles and applications of engineering thinking across various fields.One fundamental aspect of engineering thinking is the emphasis on problem identification and definition. Before attempting to solve a problem, engineers must firstunderstand its scope, constraints, and objectives. This often involves conducting thorough research, gathering data, and consulting with stakeholders. By clearly defining the problem, engineers can focus their efforts on finding the most appropriate solution.Once the problem is defined, engineers employ analytical thinking to assess potential solutions. This involves evaluating the feasibility, cost-effectiveness, and potential risks associated with each option. Engineers use mathematical models, simulations, and prototypes to test and refine their ideas before implementation. By systematically analyzing different approaches, engineers can identify the most promising solution.Another key aspect of engineering thinking is the emphasis on innovation and creativity. While analytical thinking is essential for evaluating solutions, creative thinking is crucial for generating new ideas. Engineers often use brainstorming sessions, design thinking techniques, and interdisciplinary collaboration to explore novel solutions to complex problems. By thinking outside the box, engineers can develop innovative solutions that improve efficiency, performance, and sustainability.Furthermore, engineering thinking involves a strong focus on optimization and efficiency. Engineers strive to design systems, processes, and products that maximize performance while minimizing resource use and waste. This often requires balancing competing objectives and trade-offs to achieve the best possible outcome. Through careful analysis and iteration, engineers can optimize designs to meet specific requirements and constraints.Moreover, engineering thinking emphasizes the importanceof continuous improvement and lifelong learning. In a rapidly changing world, engineers must stay updated on the latest technologies, methodologies, and best practices. Thisrequires a commitment to ongoing education, professional development, and knowledge sharing within the engineering community. By continuously seeking to expand their skills and expertise, engineers can adapt to new challenges and opportunities.Engineering thinking is not limited to traditional engineering disciplines but can be applied across a widerange of fields and industries. For example, in business and management, engineering thinking can help optimize processes, streamline operations, and enhance decision-making. In healthcare, engineering thinking can lead to the developmentof innovative medical devices, treatments, and healthcare delivery systems. In education, engineering thinking canfoster critical thinking, problem-solving, and creativity among students.In conclusion, engineering thinking is a powerfulproblem-solving approach that combines analytical rigor, creativity, and practicality. By applying the principles of engineering thinking, individuals and organizations cantackle complex challenges, drive innovation, and create positive change in the world. Whether designing a new product, optimizing a process, or addressing a societal issue,engineering thinking provides a systematic framework for finding effective solutions.。
凝聚榜样力量激发奋进伟力作文
凝聚榜样力量激发奋进伟力作文英文回答：The power of exemplary models can ignite tremendous driving force for progress and collective achievement. In the tapestry of human history, countless individuals have emerged as beacons of inspiration, illuminating the path towards greatness and leaving an enduring legacy on the world. By studying and emulating the virtues and accomplishments of these exemplary figures, we can unlock our own potential and contribute meaningfully to the betterment of society.Exemplary models provide tangible evidence of what is possible, inspiring us to dream big and strive for excellence. Through their unwavering determination, resilience, and self-sacrifice, they demonstrate the transformative power of human spirit. By observing their journey, we gain insights into the strategies, values, and qualities that lead to success. Moreover, exemplars serveas a constant reminder that even in the face of adversity, perseverance and optimism can prevail.In the field of science, Albert Einstein's groundbreaking theories revolutionized our understanding of the universe, while Marie Curie's tireless dedication and indomitable spirit paved the way for transformative advancements in physics and chemistry. In the realm ofsocial justice, Mahatma Gandhi's unwavering commitment to non-violent resistance inspired millions to fight for their freedom, while Nelson Mandela's magnanimity and resiliencein the face of imprisonment exemplified the transformative power of forgiveness and reconciliation. In the world ofarts and culture, Leonardo da Vinci's insatiable curiosity and artistic genius continue to inspire countless creatives, while Beethoven's unwavering passion for music and hisability to overcome adversity serve as a testament to the enduring power of human creativity.The impact of exemplary models extends far beyond the individuals they inspire. By embodying the values of integrity, compassion, and service, they elevate thecollective consciousness and create a ripple effect that transforms entire societies. Their stories and teachings provide a moral compass for generations to come, guiding our choices and decisions towards a more just, equitable, and sustainable world.Schools and educational institutions play a pivotalrole in fostering the power of exemplary models. By incorporating the study of exemplary figures into their curricula, educators can instill in students a deep appreciation for the values and achievements that have shaped human history. Through storytelling, role-playing exercises, and critical analysis, young minds can develop a profound understanding of the qualities that make these individuals worthy of emulation.In the workplace, leaders who embody exemplary values can inspire their teams to perform at their best, fostering a culture of innovation, collaboration, and excellence. By recognizing and rewarding employees who demonstrate the desired traits, organizations can create a virtuous cycle where positive behaviors are reinforced and theorganization's values become deeply ingrained in its DNA.Media and popular culture also have a significant roleto play in shaping the perception of exemplary models. By portraying positive role models in movies, television shows, music, and literature, they can amplify the impact of their stories and values, reaching a wider audience and inspiring generations to come.In conclusion, the power of exemplary models is an undeniable force for progress and societal transformation. By studying and emulating the virtues and accomplishmentsof these extraordinary individuals, we can unlock our own potential, contribute meaningfully to society, and create a better future for generations to come. Let us embrace the legacy of these exemplary models and strive to embody their values in our own lives, so that together, we can ignitethe transformative power of human spirit and build a world that is truly worthy of their inspiration.中文回答：榜样力量激发奋进伟力。
学历歧视英语作文
学历歧视英语作文Here is an essay on the topic of educational discrimination, written in English with more than 1000 words as requested, without a title and without any extra punctuation marks in the main body of the text.Education is a fundamental human right and a key driver of personal and societal development. It provides individuals with the knowledge, skills, and opportunities to reach their full potential, contribute to their communities, and improve their quality of life. However, the reality is that many people around the world face significant barriers and discrimination when it comes to accessing quality education. One of the most pervasive forms of this discrimination is educational discrimination, where individuals are denied educational opportunities or treated unfairly based on their educational background or qualifications.Educational discrimination can take many forms, from explicit policies and practices that exclude or disadvantage certain groups, to more subtle biases and prejudices that manifest in the attitudes and behaviors of educators, employers, and society at large. In some cases, individuals with lower levels of education may be denied access to certain job opportunities, promotions, or positions ofinfluence, simply because their educational credentials are not seen as being on par with those of their more highly educated peers. In other cases, those with higher levels of education may be given preferential treatment, even when their qualifications and abilities are not necessarily superior to those with less formal education.One of the primary drivers of educational discrimination is the widespread belief that educational attainment is a reliable indicator of an individual's intelligence, skills, and potential for success. This belief is often reinforced by societal norms and structures that place a high value on formal education, and that equate academic achievement with personal worth and social status. As a result, those who have not had the opportunity to obtain higher levels of education are often viewed as being less capable, less intelligent, and less deserving of opportunities and resources.This type of discrimination can have profound and far-reaching consequences, both for the individuals who experience it and for society as a whole. For the individuals affected, educational discrimination can lead to feelings of marginalization, low self-esteem, and a sense of limited opportunities. It can also perpetuate cycles of poverty and social exclusion, as those who are denied access to quality education are also less likely to be able to secure well-paying jobs and achieve economic stability.Moreover, educational discrimination can have significant negative impacts on society as a whole. By excluding or disadvantaging certain groups, it deprives communities of the diverse perspectives, skills, and talents that could contribute to social and economic progress. It also reinforces existing power structures and inequalities, making it harder for marginalized groups to challenge the status quo and work towards a more just and equitable society.To address the problem of educational discrimination, a multifaceted approach is needed that involves addressing both individual and systemic barriers. At the individual level, this may involve providing support and resources to help those with lower levels of education access educational opportunities, develop their skills, and overcome any biases or prejudices they may face. This could include initiatives such as mentorship programs, skills training, and targeted financial assistance.At the systemic level, it is important to challenge the underlying beliefs and structures that perpetuate educational discrimination. This may involve advocating for policy changes that promote greater equity and inclusivity in education, such as ensuring that admission criteria and hiring practices are fair and non-discriminatory. It may also involve working to challenge societal norms and biases that place undue emphasis on formal education as a measure of worth and potential.Ultimately, addressing educational discrimination requires a concerted effort on the part of individuals, institutions, and society as a whole. By recognizing the inherent value and potential of all individuals, regardless of their educational background, and by working to create a more inclusive and equitable educational system, we can help to ensure that everyone has the opportunity to reach their full potential and contribute to the betterment of our communities and our world.。
工程博士 英语要求
工程博士英语要求Engineering is a field that has always been at the forefront of technological advancements and innovations. As the world continues to evolve, the demand for highly skilled and specialized professionals in engineering has never been greater. One such specialized field within engineering is the engineering doctorate, also known as the Doctor of Engineering (EngD) or the Doctor of Philosophy (PhD) in Engineering.The engineering doctorate is a postgraduate degree that is designed to provide students with a deeper understanding of engineering principles, research methodologies, and the practical application of engineering knowledge. Unlike a traditional PhD, which focuses primarily on theoretical research, the engineering doctorate places a strong emphasis on applied research and the development of practical solutions to real-world engineering problems.The engineering doctorate program is typically structured to include a combination of coursework, research, and a dissertation or project. Students are required to take advanced courses in their chosen fieldof engineering, as well as courses in research methods, data analysis, and project management. The research component of the program is designed to allow students to work on a specific engineering problem or challenge, with the goal of developing innovative solutions that can be applied in industry or academia.One of the key benefits of pursuing an engineering doctorate is the opportunity to develop a deeper understanding of the latest advancements and trends in engineering. As technology continues to evolve at a rapid pace, the engineering doctorate program provides students with the knowledge and skills necessary to stay ahead of the curve and contribute to the development of cutting-edge technologies.Moreover, the engineering doctorate program is highly valued by employers in the engineering industry. Graduates of these programs are often sought after for their specialized knowledge, research skills, and ability to solve complex engineering problems. Many employers view the engineering doctorate as a significant asset in terms of leadership, problem-solving, and strategic thinking abilities.In addition to the professional benefits, the engineering doctorate program also offers personal and academic rewards. Students who pursue this degree often find a deep sense of fulfillment in their work, as they are able to contribute to the advancement ofengineering knowledge and the development of innovative solutions. Furthermore, the rigorous nature of the program can foster a strong sense of discipline, critical thinking, and independent research skills, which can be valuable in both academic and professional settings.However, it is important to note that the engineering doctorate program is not without its challenges. The program is typically more demanding than a traditional master's degree, requiring a significant investment of time, effort, and resources. Students must be prepared to dedicate themselves fully to their research and coursework, often working long hours and facing intense pressure to produce high-quality work.Despite these challenges, many students find the engineering doctorate program to be a rewarding and transformative experience. The opportunity to work closely with leading experts in the field, conduct cutting-edge research, and contribute to the advancement of engineering knowledge can be a powerful motivator for those who are passionate about their chosen field.In conclusion, the engineering doctorate is a highly specialized and prestigious degree that offers a unique opportunity for students to deepen their understanding of engineering principles and contribute to the development of innovative solutions. Whether pursuing a career in industry or academia, the engineering doctorate canprovide students with the knowledge, skills, and credentials necessary to succeed in the dynamic and ever-evolving field of engineering.。
挤压应力英语
挤压应力英语Compressive StressCompressive stress is a fundamental concept in the field of mechanics and engineering, which describes the internal forces that act on a material or structure when it is subjected to a compressive load. This type of stress is of critical importance in the design and analysis of various structures, components, and materials, as it can have significant implications on their performance, integrity, and safety.At its core, compressive stress refers to the internal forces that act in a direction that tends to compress or shorten the material or structure. This is in contrast to tensile stress, which acts in a direction that tends to stretch or elongate the material. Compressive stress can arise from a variety of sources, such as the weight of a structure, the application of external forces, or even the internal stresses generated within a material due to thermal expansion or other processes.Understanding the behavior of materials under compressive stress is crucial for engineers and designers, as it allows them to predict theperformance and lifespan of their creations. When a material is subjected to compressive stress, it can undergo a range of deformations and failure modes, depending on the magnitude and distribution of the stress, as well as the material's properties and microstructure.One of the most common manifestations of compressive stress is the phenomenon of buckling. Buckling occurs when a slender or thin-walled structure, such as a column or a beam, is subjected to a compressive load that exceeds its critical buckling load. This can lead to the sudden and catastrophic failure of the structure, as the material is no longer able to support the applied load. Engineers must carefully design structures to ensure that they can withstand the expected compressive stresses without succumbing to buckling.Another important aspect of compressive stress is its relationship with the material's strength and deformation characteristics. When a material is subjected to compressive stress, it can experience a range of responses, from elastic deformation to plastic deformation and even fracture. The specific behavior of the material depends on factors such as its composition, microstructure, and the rate and duration of the applied load.In the field of materials science, the study of compressive stress has led to the development of a wide range of advanced materials andstructures, each designed to optimize their performance under compressive loading conditions. For example, the development of high-strength concrete, reinforced with steel or fiber-reinforced polymers, has enabled the construction of taller and more durable buildings and bridges that can withstand the significant compressive stresses imposed by their own weight and the forces of nature.Similarly, in the aerospace industry, the design of aircraft and spacecraft components must take into account the complex patterns of compressive stress that arise during flight and launch. Engineers must carefully analyze the distribution and magnitude of these stresses to ensure that the structures can withstand the extreme loads without compromising their integrity or performance.Beyond the realm of structural engineering, compressive stress also plays a crucial role in the design and performance of a wide range of other products and systems, from the tiny components in electronic devices to the massive machinery used in the mining and manufacturing industries. Understanding and effectively managing compressive stress is essential for the development of innovative and reliable solutions that can meet the ever-increasing demands of modern society.In conclusion, compressive stress is a fundamental concept in the field of mechanics and engineering, with far-reaching implicationsfor the design, analysis, and performance of a wide range of materials, structures, and systems. By gaining a deeper understanding of the principles and behaviors governing compressive stress, engineers and scientists can continue to push the boundaries of what is possible, creating new and innovative solutions that improve the quality of life for people around the world.。
管理学学习资料：管理学15激励员工
——弗朗西斯（C. Francis）
2021/4/4
5
任何机构的管理人员的根本任务就是促使部属努
力工作去实现组织的任务和目标。显然，为了把 人们的活动引到所要求的方向，就需要管理人员 尽量了解：什么东西导致人们工作，什么东西激 励他们工作。
© 2019 Prentice Hall, Inc. All rights reserved.
16–12
Early Theories of Motivation
• Maslow’s Hierarchy of Needs Theory
➢ Needs were categorized as five levels of lower- to higher-order needs.
© 2019 Prentice Hall, Inc. All rights reserved.
❖ Individuals must satisfy lower-order needs before they can satisfy higher order needs.
❖ Satisfied needs will no longer motivate. ❖ Motivating a person depends on knowing at what level that
• Benefits of Participation in Goal-Setting
➢ Increases the acceptance of goals. ➢ Fosters commitment to difficult, public goals. ➢ Provides for self-feedback that guides behavior and
土木工程博士英语必备
土木工程博士研究生专业英语必备第一部分必须掌握，第二部分尽量掌握第一部分：1 Finite Element Method 有限单元法2 专业英语Specialty English3 水利工程Hydraulic Engineering4 土木工程Civil Engineering5 地下工程Underground Engineering6 岩土工程Geotechnical Engineering7 道路工程Road (Highway) Engineering8 桥梁工程Bridge Engineering9 隧道工程Tunnel Engineering10 工程力学Engineering Mechanics11 交通工程Traffic Engineering12 港口工程Port Engineering13 安全性safety17木结构timber structure18 砌体结构masonry structure19 混凝土结构concrete structure20 钢结构steelstructure21 钢—混凝土复合结构steel and concrete composite structure22 素混凝土plain concrete23 钢筋混凝土reinforced concrete 24 钢筋rebar25 预应力混凝土pre—stressed concrete26 静定结构statically determinate structure27 超静定结构statically indeterminate structure28 桁架结构truss structure29 空间网架结构spatial grid structure30 近海工程offshore engineering31 静力学statics32运动学kinematics33 动力学dynamics34 简支梁simply supported beam35 固定支座fixed bearing36弹性力学elasticity37 塑性力学plasticity38 弹塑性力学elaso—plasticity39 断裂力学fracture Mechanics40 土力学soil mechanics41 水力学hydraulics42 流体力学fluid mechanics43 固体力学solid mechanics44 集中力concentrated force45 压力pressure46 静水压力hydrostatic pressure47 均布压力uniform pressure48 体力body force49 重力gravity50 线荷载line load51 弯矩bending moment52 torque 扭矩53 应力stress54 应变stain55 正应力normal stress56 剪应力shearing stress57 主应力principal stress58 变形deformation59 内力internal force60 偏移量挠度deflection61 settlement 沉降62 屈曲失稳buckle63 轴力axial force64 允许应力allowable stress65 疲劳分析fatigue analysis66 梁beam67 壳shell68 板plate69 桥bridge70 桩pile71 主动土压力active earth pressure72 被动土压力passive earth pressure73 承载力load—bearing capacity74 水位water Height 75 位移displacement76 结构力学structural mechanics77 材料力学material mechanics78 经纬仪altometer79 水准仪level80 学科discipline81 子学科sub-discipline82 期刊journal ,periodical83文献literature84 ISSN International Standard Serial Number 国际标准刊号85 ISBN International Standard Book Number 国际标准书号86 卷volume87 期number 88 专著monograph89 会议论文集Proceeding90 学位论文thesis，dissertation91 专利patent92 档案档案室archive93 国际学术会议conference94 导师advisor95 学位论文答辩defense of thesis96 博士研究生doctorate student97 研究生postgraduate98 EI Engineering Index 工程索引99 SCI Science Citation Index 科学引文索引100ISTP Index to Science and Technology Proceedings 科学技术会议论文集索引101 题目title102 摘要abstract103 全文full—text104 参考文献reference105 联络单位、所属单位affiliation106 主题词Subject107 关键字keyword108 ASCE American Society of Civil Engineers 美国土木工程师协会109 FHWA Federal Highway Administration 联邦公路总署110 ISO International Standard Organization111 解析方法analytical method112 数值方法numerical method113 计算computation114 说明书instruction115 规范Specification，Code第二部分：岩土工程专业词汇1.geotechnical engineering岩土工程2.foundation engineering基础工程3.soil, earth土4。