单调反对称荷载下钢筋砼梁柱中节点数值分析

Nonlinear Analysis of RC Beam-column Interior Joints Under Monotonic Antisymmetric Loads

本文采用ABAQUS对单调反对称荷载作用下的钢筋混凝土梁柱中节点进行了数值模拟。首先分析了损伤因子和模型网格大小对梁端荷载–位移曲线的影响;其次从试件的梁端荷载-位移曲线、破坏模式、邻近节点区梁端受拉纵筋应变3个方面对比分析了有限元计算结果与试验结果,验证了有限元模型的有效性;最后重点研究了不同轴压比和不同核心区配箍率下单调反对称荷载的钢筋混凝土梁柱中节点的钢筋力学行为。研究结果表明:受压损伤因子大小对梁端承载力有明显影响,而受拉损伤因子对梁端承载力的影响可以忽略;邻近节点区梁端纵筋在柱顶轴力施加过程中(梁端未施加荷载)就产生了拉应变;节点核心区箍筋在低轴压比下产生显著应变的时间要早于高轴压比下;处于节点核心区中部区域箍筋应变较其上下箍筋应变大。

In this paper,a finite element（ FE） package ABAQUS is adopted to simulate RC beam-column interior joint specimens under monotonic antisymmetric loads. Firstly,a suitable damage factor and appropriate mesh size are obtained to analyze their influences on load-displacement curves of the beam end. Then,the FE and experimental results for load-displacement curve of beam end,failure mode and the strain of longitudinal reinforcement bars in the beam near joint region are in good agreement,which demonstrate that the FE method is accurate enough. Finally,the verified FE method is used to investigate the influences of different axial compression ratios and stirrup ratios in joint region on mechanical behavior of steels in specimens. The results indicate that the compressive damage factor has a significant influence on the ultimate load at beam end while the influence of tensile damage factor can be ignored. The tensile strain is observed at the longitudinal reinforcement bars in the beam near the joint region during the stage when the axial loading is applied（ prior to the load at beam end）. Moreover,significant values of the strain in stirrups near and inside the joint region are observed earlier in specimens with low column axial loads than that in specimens under high column axial loads. Additionally,the strain of stirrups at the center of joint region is larger than that of the upper and the lower stirrups in the joint region.