大位移往复加载下钢框架节点地震损伤试验研究

Experimental study on seismic damage of steel frame joints under large displacement and cyclic loading

结构临近倒塌状态时,构件不可避免发生较大变形。节点区梁柱焊接处是钢框架结构薄弱环节,易发生脆性破坏,本文设计了3个不同的大位移加载制度对钢框架节点构件进行低周往复加载,考察其破坏过程与特征,研究了不同大位移加载方式对钢框架节点的荷载-位移滞回曲线、滞回耗能、损伤演化等力学性能的影响。结果表明:加载制度对构件的破坏形态起控制作用,变幅加载与等幅60 mm循环加载下试件为脆性破坏,等幅90 mm循环加载下试件为延性破坏。钢框架节点梁端作为结构抗震耗能的关键部位,将耗能能力作为评价其抗震性能的指标,建立起简单通用的累积破坏损伤模型,该损伤模型易于评价节点在地震作用下的损伤程度。

When a structure is close to collapse state,its structural members inevitably exhibit large deformation.In a steel frame structure,the welding of beam and column in the joint area is the weak link that is prone to brittle failure.In this study,three different large displacement loading systems are designed for low-cycle reciprocating loading of steel frame joints,and the failure process and characteristics are investigated.The effects of different large displacement loading methods on the load-displacement hysteresis curve,hysteretic energy dissipation,damage evolution,and other mechanical properties of steel frame joints are studied.Results show that the loading system plays a controlling role in the failure modes of the members.The specimen under variable amplitude loading and equal amplitude 60 mm cyclic loading shows brittle failure,while the specimen under equal amplitude 90 mm cyclic loading shows ductile failure.The energy dissipation capacity was taken as the index to evaluate the seismic performance of the joints,the beam end of which was the key part of seismic energy dissipation of the structure.A simple and general cumulative damage model was established,which was easy to evaluate the damage degree of the joints under earthquake.