双柱墩地震反应的轴力-刚度耦合作用
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摘要
地震作用下钢筋混凝土双柱桥墩产生的动轴力不仅会改变桥墩的屈服强度,而且也会相应地改变桥墩的刚度,但目前广泛使用的集中塑性模型一般并未考虑这种轴力-刚度的耦合作用。以自动计入轴力-强度及轴力-刚度耦合作用的纤维模型分析结果为基准,研究了轴力-刚度耦合作用对钢筋混凝土双柱桥墩地震反应的影响。结果表明,轴力-刚度耦合作用对双柱墩弹性阶段的反应有较大影响,但不改变结构的极限承载力;由于拉压桥墩的刚度互为消长,等高双柱墩的地震位移响应在不计轴力-刚度的耦合作用时与实际情况只略有差异,但墩柱弹性内力响应则会被较大地低估;不等高双柱墩的刚度受较矮侧桥墩控制,因此轴力-刚度的耦合作用对结构的地震位移响应和弹性内力响应都有明显影响,桥梁不规则性越大影响越显著,在进行结构分析时不能忽视这一因素的影响。
Earthquake induced dynamic axial force in reinforced concrete(RC) bridge bent columns will not only change the yield strength of the columns but also change their stiffness,which is seldom considered by the common lumped-plasticity line model.Based on the fiber element model results that taking into account the influence of dynamic axial force on strength and stiffness simultaneously,the axial force-stiffness interaction effect on the seismic responses of RC double-column bridges was analyzed.The results show that,axial force-stiffness interaction has a large effect on the seismic responses of the double-column bridge in the elastic range,and it does not alter the ultimate capacity of the columns.Since the stiffness of the columns under compression and tension dynamic axial forces offset each other,the global displacement of bridge bent with equal columns is relatively unaffected by the axial force-stiffness interaction,however,the differences of the column member forces are manifest.For the short column controls the global stiffness,the axial force-stiffness interaction has significant influences on both the global displacement and member force responses.The influences become larger as the irregularity of the bridge bent increases,so the interaction between axial force and member stiffness should be sufficiently considered in seismic analyses.
Earthquake induced dynamic axial force in reinforced concrete(RC) bridge bent columns will not only change the yield strength of the columns but also change their stiffness,which is seldom considered by the common lumped-plasticity line model.Based on the fiber element model results that taking into account the influence of dynamic axial force on strength and stiffness simultaneously,the axial force-stiffness interaction effect on the seismic responses of RC double-column bridges was analyzed.The results show that,axial force-stiffness interaction has a large effect on the seismic responses of the double-column bridge in the elastic range,and it does not alter the ultimate capacity of the columns.Since the stiffness of the columns under compression and tension dynamic axial forces offset each other,the global displacement of bridge bent with equal columns is relatively unaffected by the axial force-stiffness interaction,however,the differences of the column member forces are manifest.For the short column controls the global stiffness,the axial force-stiffness interaction has significant influences on both the global displacement and member force responses.The influences become larger as the irregularity of the bridge bent increases,so the interaction between axial force and member stiffness should be sufficiently considered in seismic analyses.
引文
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[15]Xiao J,Zhang C.Seismic behavior of RC columns withcircular,square and diamond sections[J].Construction and Building Materials,2008,22(5):801-810.
[2]Priestley M,Calvi G,Kowalsky M.Displacement-based seismic design of structures[M].Pavia:IUSSPress,2007.
[3]Computers and Structures Inc.SAP2000v10integratedfinite element analysis and design of structures[M].Berkeley:CSI,2005.
[4]Gregori J,Sosa P,Prada M,et al.A 3Dnumericalmodel for reinforced and prestressed concrete elementssubjected to combined axial,bending,shear andtorsion loading[J].Engineering Structures,2007,29(12):3404-3419.
[5]Ceresa P,Petrini L,Pinho R.Flexure-shear fiberbeam-column elements for modeling frame structuresunder seismic loading-state of the art[J].Journal ofEarthquake Engineering,2007,11(Sup1):46-88.
[6]Berry M,Lehman D,Lowes L.Lumped-plasticitymodels for performance simulation of bridge columns[J].ACI Structural Journal,2008,105(3):270-279.
[7]Mazzoni S,Mckenna F,Scott M H,et al.Openseescommand language manual[R].Berkeley:Universityof California,Pacific Earthquake Engineering Center,2006.
[8]Spacone E,Filippou F C,Taucer F F.Fiber beam-column model for non-linear analysis of R/C frames:part I formulation[J].Earthquake Engng Struct.Dyn.,1996,25(7):711-725.
[9]Kent D C,Park R.Flexural members with confinedconcrete[J].Journal of Structural Division ASCE,1971,97(7):1969-1990.
[10]Scott M,Hamutcuoglu O.Numerically consistentregularization of force-based frame elements[J].Int.J.Numer.Meth.Engng,2008,76:1612-1631.
[11]Scott M,Fenves G.Plastic hinge integration methodsfor force-based beam-column elements[J].Journal ofStructural Engineering,2006,132(2):244-252.
[12]中华人民共和国交通运输部.JTG/T B02-01-2008公路桥梁抗震细则[S].北京:人民交通出版社,2008.
[13]Pacific Earthquake Engineering Research Center.PEERground motion database[DB/OL],http://Peer.Berkeley.Edu/Peer_Ground_Motion_Database,2010.
[14]Adhikari G,Petrini L,Calvi G M.Application of directdisplacement based design to long span bridges[J].Bulletin of Earthquake Engineering,2010,8(4):897-919.
[15]Xiao J,Zhang C.Seismic behavior of RC columns withcircular,square and diamond sections[J].Construction and Building Materials,2008,22(5):801-810.
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