基于纤维单元的钢筋混凝土桥墩地震损伤评价
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摘要
基于纤维模型的梁柱单元特别是柔度法单元有着较高的计算精度,已被较多地用于评价钢筋混凝土桥墩的位移(延性)能力。随着基于性能/位移抗震设计理论的发展,相继提出了残余位移、极限曲率及曲率延性系数、纵筋和混凝土的最大应变、纵筋低周疲劳损伤等桥墩地震损伤量化指标。选用刚度法和柔度法纤维单元,考虑材料非线性、几何非线性和结点锚固钢筋粘结滑移的影响,通过数值分析和试验数据对比研究了利用纤维单元对上述损伤指标进行估计的准确程度及主要影响因素。结果表明,柔度法单元计算的损伤参数均大于刚度法;两种纤维单元计算的滞回曲线及残余位移和试验结果十分接近,刚度法单元计算的截面曲率和纵筋拉应变更接近试验值,当加载位移幅值或剪跨比较大时,两种单元有时会低估桥墩的截面曲率反应;两种单元都会高估桥墩纵筋的最大拉应变,低估核芯混凝土的最大压应变。
For the advantage of high computational accuracy,fiber beam-column elements are widely used in evaluation of displacement ductility capacity of RC bridge columns.With the development of bridge performance/displacement based seismic design,several damage indices have been suggested,such as ultimate curvature and curvature ductility factor of critical section,maximum strain of confined concrete and reinforced steels,low cycle fatigue damage indices of longitudinal reinforcement etc.To study the accuracy degree of damage indices calculated with fiber elements and the main influencing factors,stiffness-based and flexibility-based fiber elements are chosen to compute aforesaid damage indices compared with test data of RC bridge columns,with consideration of material non-linearity,geometrical non-linearity and bond-slip of anchoring steel.The study results show that the damage indices caculated by flexibility-based element are greater than those by stiffness-based element.Force-displacement curves and residual deformation calculated by both elements match the experiment with adequate accuracy.Section curvatures and tensile strain of longitudinal steel by stiffness element are colser to experimental data than those by flexibility element,but both elements underestimate section curvatures if loading displacement amplitude or shear span ratio is large.Both element overestimate tensile strain of longitudinal steel and underestimate compressive strain of concrete.
For the advantage of high computational accuracy,fiber beam-column elements are widely used in evaluation of displacement ductility capacity of RC bridge columns.With the development of bridge performance/displacement based seismic design,several damage indices have been suggested,such as ultimate curvature and curvature ductility factor of critical section,maximum strain of confined concrete and reinforced steels,low cycle fatigue damage indices of longitudinal reinforcement etc.To study the accuracy degree of damage indices calculated with fiber elements and the main influencing factors,stiffness-based and flexibility-based fiber elements are chosen to compute aforesaid damage indices compared with test data of RC bridge columns,with consideration of material non-linearity,geometrical non-linearity and bond-slip of anchoring steel.The study results show that the damage indices caculated by flexibility-based element are greater than those by stiffness-based element.Force-displacement curves and residual deformation calculated by both elements match the experiment with adequate accuracy.Section curvatures and tensile strain of longitudinal steel by stiffness element are colser to experimental data than those by flexibility element,but both elements underestimate section curvatures if loading displacement amplitude or shear span ratio is large.Both element overestimate tensile strain of longitudinal steel and underestimate compressive strain of concrete.
引文
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[2]艾庆华.钢筋混凝土桥墩抗震性态数值评价与试验研究[D].大连理工大学,2008.(AI Qing-hua.Numeri-cal evaluation and experimental study of seismic per-formance for reinforced concrete bridge piers[D].Dalian University of Technology.(in Chinese))
[3]Spacone E,Filippou F C,Taucer F F.Fiber beam-column model for nonlinear analysis of R/C frames:(partⅠ).formulation[J].Earthquake Engineering&Structural Dynamics,1996,25(7):711-725.
[4]陈滔,黄宗明.钢筋混凝土框架非弹性地震反应分析模型研究进展[J].世界地震工程,2002,18(1):91-96.(CHEN Tao,HUANG Zong-ming.A review ofinelastic dynamic analysis models of reinforced con-crete frames under earthquake ground motions[J].World Information on Earthqueake Engineering,2002,18(1):91-96.(in Chinese))
[5]陈滔,黄宗明.基于有限元柔度法的材料与几何双重非线性空间梁柱单元[J].计算力学学报,2006,23(5):524-545.(CHEN Tao,HUANG Zong-ming.Material and geometrically nonlinear spatial beam-col-umn element based on the finite element flexibilitymethod[J].Chinese Journal of Computional Mech-enics,2006,23(5):524-545.(in Chinese))
[6]Lehman D E,Jack P M,et al.Experimental evalua-tion of the seismic performance of reinforced concretebridge columns[J].Journal of Stru.Eng,ASCE,2004,130(6):869-879.
[7]Chang G A,Mander J B.Seismic energy based fatiguedamage analysis of bridge columns(Part 1)[R].Uni-versity at Buffalo,State University of New York,Technical Report NCEER-94-0006.
[8]Zhilong Z,Murray D W.An incremental solutiontechnique for unstable equilibrium paths of shellstructures[J].Computers&Structures,1994,55(5):749-759.
[9]宋振森,沈祖炎,等.求解预定位移水平的改进弧长法[J].计算力学学报,2007,24(4):509-512.(SONGZhen-sen,SHEN Zu-yan,et al.An improved arc-length method for searching pre-defined displacementin nonlinear analysis of structures[J].Chinese Jour-nal of Computional Mechenics,2007,24(4):509-512.(in Chinese))
[10]陈明政,黄音,王正霖,等.基于弧长法的预应力框架结构非线性分析[J].华南理工大学学报(自然科学版),2006,34(7):109-113.(CHEN Ming-zheng,HUANG Yin,WANG Zheng-lin,et al.Nonlinear a-nalysis of prestressed frame based on Arc-Lengthmethod[J].Journal of South China University ofTechnology,2006,34(7):109-113.(in Chinese))
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