等强度折减下延性结构的位移放大系数

为方便地由弹性位移计算最大弹塑性位移反应,对等强度折减的双折线弹塑性滞回模型的单自由度(SDOF)体系在地震作用下的弹塑性位移响应进行分析,得到不同标准化周期、场地类型、强度折减系数、阻尼比、后期刚度和二阶效应等不同参数组合的位移放大系数Cd2谱.结果表明,Cd2在固定周期处各强度折减系数所对应的数据点均服从对数正态分布;Cd2随着阻尼比(除短周期)的减小而减小,随着后期刚度的增大而减小;二阶效应的存在将导致Cd2显著增加.为分析不同滞回模型对Cd2的影响,又计算反向加载时刚度退化的修正克拉夫(MC)滞回模型、剪切滑移(SSP)和无任何耗能能力的双线性弹性(BIL)模型下的Cd2谱,与理想弹塑性(EPP)下的Cd2进行对比,发现EPP的Cd2在4类模型中是最小的.

Inelastic displacement amplification factor for ductile structures with the same strength reduction factor

In order to estimate the maximum inelastic displacement response induced by the designed seismic action from the elastic displacement response,elastic-plastic time-history earthquake analysis of single degree of freedom (SDOF) system was performed. The inelastic displacement amplification factor Cd2 of the bilinear elastic-plastic hysteretic model with the same yield strength was investigated at different normalized periods,site types,strength reduction factors,damping ratios,post yield stiffness ratios and second-order effect. It is found that the probability distribution of Cd2satisfies the lognormal distribution. The factor Cd2decreases with the increasing post yield stiffness and the decreasing damping ratios in the range of medium and long periods. The existence of P-Δ effect will increase the Cd2significantly. The modified-Clough model (MC),shear-slipped model (SSP) and bilinear elastic model (BIL) were analyzed to check the effect of hysteretic models on Cd2,and results were compared to those of EPP model. It is found that the value of Cd2 for EPP model is the smallest among these four hysteretic models.