不平衡弯矩作用下板柱节点抗冲切性能非线性分析

Nonlinear analysis of punching shear resistance capacity for slab column connections under unbalanced moment

通过研究不平衡弯矩作用下板柱节点变参数、刚度变化等受力性能的特点和规律,为弥补试验研究的局限性,全面认识板柱节点的受力特征、内力分布规律提供新的研究途径,同时也为工程设计与实践提供理论指导。应用OpenSees(Open System for Earthquake Engineering Simulation)有限元计算平台建立了与试验相同的三维网格梁数值模型,通过数值模拟结果与试验结果的对比分析,验证了有限元分析模型的可行性.对不同的板厚,以不平衡弯矩水平、配筋率及混凝土强度为变参数分别进行了数值模拟.结果表明:数值模拟结果与试验结果吻合较好,不同的不平衡弯矩水平对节点抗冲切性能影响显著,配筋率的变化对构件开裂荷载、极限承载力以及延性影响显著.因此,合理地建立有限元模型可较好地模拟不平衡弯矩作用下板柱节点的受力性能;随着不平衡弯矩水平的增大,极限承载力显著降低,随着配筋率的增大,极限承载力显著增大、延性降低。

The purpose of this paper is to further study the mechanical behavior of slab column connections with dif ferent parameters and stiffness change under unbalanced moment. A new approach can be used to study mechanic characteristics and distribution of internal force completely, and provide a theoretical guidance to design and prac tice. The authors used computing platform named OpenSees to establish the three dimensional grid beam models of slab column components which are tested in the experiment, and to validate the feasibility of finite element analy sis model through the comparison of the simulated results and experimental ones. The numerical simulation analyzed the slab column connections with different slab thicknesses, unbalanced moment levels, reinforcement ratios and concrete strength. The results show that the finite element analysis data are in good agreement with the experimental ones; the different unbalanced moment levels have significant effect on punching shear capacity; the difference of reinforcement ratio in the crosssection affects the cracking load, ultimate bearing capacity and component ductility significantly. Therefore reasonable establishment of finite element model of the slab column connections under un balanced moment could better simulate their mechanical behavior; with the increase of unbalanced moment level in the crosssection, the simulatied slab column connections get lower ultimate strength; with the increase of reinforced ratio in the crosssection, the simulated slab column connections get higher ultimate strength and lower duc tility.