考虑粘结滑移效应的墩柱低周往复加载模拟方法

SIMULATION METHOD OF LOW CYCLE RECIPROCATING LOADING OF PIER COLUMN CONSIDERING BOND-SLIP EFFECT

针对桥梁墩柱和承台内的粘结滑移现象,基于fib混凝土规范(fib Model Code)推荐的混凝土粘结滑移模型,推导了纵筋滑移量的计算公式,并通过对墩柱塑性区域受拉纵筋的应力-应变本构进行修正,以引入墩柱塑性区域和承台内的纵筋滑移量,作为一种等效方法,以考虑粘结滑移对墩柱地震响应的影响,并用试验结果验证了该方法的合理性。此外,还对所提等效方法和零长度截面单元法的计算结果进行了对比。结果表明:未考虑粘结滑移会高估墩柱的侧向刚度、累计滞回耗能和残余位移,且无法客观反映滑移导致的墩柱强度退化问题;零长度截面单元法和所提等效方法均能考虑强度退化问题,但前者对粘结滑移的模拟效果受纵筋直径影响显著,后者则能合理捕捉滑移影响下的墩柱往复加载过程。

Based on the stress-slip model of concrete proposed by fib Model Code,the slip of rebar was derived and formulated to consider the bond-slip phenomenon occurring both in the column and in the footing.Furthermore,the stress-strain constitutive model of the tensile rebars located within the plastic zone of the column was modified to incorporate the rebar slips in the column and in the footing.In this way,the effect of bond-slip on the seismic responses of the column can be equivalently considered.The feasibility of this method was verified by experimental results.Besides,the comparison was made of the results between the proposed method and the ZeroLength Section Element(ZLSE)method.It can be concluded that the lateral stiffness,the cumulative hysteretic energy,and the residual displacement are all overestimated without considering the bond-slip phenomenon.Apart from that,the strength degradation of the column is unable to reflect objectively.Both the ZLSE method and the proposed equivalent method have the capability to resolve the issue of strength degradation.However,the former method yields the numerical results prominently susceptible to the rebar diameter,while the latter one can efficaciously capture the reciprocating loading process of the column affected by the bond-slip phenomenon.