考虑节点非弹性变形的RC框架地震反应分析

钢筋混凝土梁柱组合体试验结果表明节点内纵筋滑移和节点剪切变形对组合体的抗震性能有明显影响,但框架的非弹性地震反应分析一般忽略了节点非弹性变形的影响.为了模拟节点区非弹性变形的影响,在纤维模型基础上采用在梁端附加零长度截面单元的方法,并通过σ-s本构模型考虑节点内梁纵筋粘结滑移,以及通过σ-sslip-shear本构模型同时考虑节点内纵筋滑移和节点剪切变形.考察了典型平面框架在罕遇地震下的非线性反应,对比分析了节点非弹性变形对框架整体和局部反应的影响.结果表明,考虑节点非弹性变形之后结构的最大顶点位移、最大层间位移角将增大或仅略有变化,梁端、柱端塑性铰数量将减少,梁、柱的转角延性需求总体而言将减小;地震作用下框架节点距离剪切失效尚有一定安全储备.框架地震反应大时忽略节点非弹性变形将导致明显误差,地震反应较小时可采用不考虑节点非弹性变形的常规有限元分析模型.

Seismic Response Analysis of RC Frame Considering Inelastic Deformations of Beam-column Joints

Experiment results of RC beam-column subassemblage show that the slippage of the longitudinal bar within joint and shear deformation of joint have significant influence on the seismic behavior of the subassemblage, but this kind of joint inelastic deformations has always been ignored in the seismic response analysis of RC frames.In order to simulate the effect of the inelastic deformations of beam-column joints, a zero-length section element was combined to the ends of the beam based on the fiber model.Longitudinal bar slippage was modeled with stress-slippage constitutive model, while stress-equivalent slippage constitutive model was adopted to simulate longitudinal bar slippage and joint shear deformation simultaneously.Nonlinear responses of a typical RC planar frame under rare earthquake excitations were investigated, and the effect of joint inelastic deformations on the global and local responses of the frame was analyzed contrastively.The results show that the maximum top displacements and maximum inter-story drift ratios increase or change slightly, the quantities of the plastic hinge of the beam and the column ends decrease, and the rotation ductility demand of the beam and the column decreases as a whole when joint inelastic deformations are considered.There is a certain safety margin for the joints of the frame to avoid shear failure.Ignoring joint inelastic deformations will result in significant errors if the seismic response of RC frame is large, and the ordinary finite element model of ignoring joint inelastic deformations can be adopted if the seismic response of the structure is relatively small.