考虑退化、捏拢和双向耦合效应的等强度延性需求谱

摘要

传统的等强度延性需求谱通常难以有效地考虑强度退化、刚度退化、捏拢效应以及双向恢复力耦合效应的影响.鉴于此,基于双轴Bouc-Wen-Baber-Noori模型,建立了双向地震激励作用下单质点双自由度体系非弹性地震反应谱的基本方程,并定量分析了强度退化、刚度退化、捏拢效应和双向恢复力耦合效应对结构地震延性需求的影响,进而分别建立了等强度延性需求的均值谱和标准差谱的预测方程.分析结果表明:强度退化、刚度退化和捏拢效应会增大结构的地震延性需求;双向恢复力的耦合效应对地震延性需求的影响,取决于结构沿两个主轴方向地震耗能能力的相互竞争;退化、捏拢和耦合效应会明显增大结构地震延性需求的标准差,且非线性程度越高,随机性表现越明显;随着结构沿两个主轴方向自振周期的增加,等强度地震延性需求的均值和标准差均逐渐减小.%Traditional constant-strength ductility demand spectrum is difficult to consider the influence of strength degradation,stiffness degradation,pinching effect and coupling effect of bi-directional restoring forces effectively.Here,the fundamental equations of inelastic seismic response spectra for a single mass 2-DOF (SM-2DOF) system under bidirectional seismic excitations were established based on the biaxial Bouc-Wen-Baber-Noori (BWBN) model.Then the influences of strength degradation,stiffness deterioration,pinching effect and coupling effect of bi-directional restoring forces on the seismic ductility demand of the SM-2DOF system were investigated quantitatively.Furthermore,the prediction equations for the mean value spectrum and standard deviation one of the constant-strength ductility demand were derived,respectively.The results showed that strength degradation,stiffness deterioration and pinching effect can increase the seismic ductility demand of the SM-2DOF system significantly;the influence of coupling effect of bi-directional restoring forces on the seismic ductility demand is dependent on mutual competition between the system's seismic energydissipating capacities along two principal axial directions of the SM-2DOF system;degradation,pinching and coupling effect can increase the standard deviation of the seismic ductility demand,especially,for the SM-2DOF system with higher nonlinearity;the mean value and standard deviation of the constant-strength seismic ductility demand decrease with increase in natural vibration periods of two principal axial directions of the SM-2DOF system.