弱剪型支撑框架的抗震性能研究

Seismic behavior of the weak-shear braced frame

为弥补现行规范中采用人为放大支撑内力设计的强剪型支撑可能存在的缺陷,提出弱剪型支撑设计方法.采用非线性弹塑性时程有限元程序,分析10条地震波作用下的强、弱剪型支撑框架的地震响应.结果表明:强剪型支撑框架在地震波作用下,柱先于支撑屈服发生无侧移失稳,导致结构水平位移和失稳柱竖向位移快速增加;而弱剪型支撑框架在地震波下仅发生侧移变形.同时,强剪型支撑框架的层间剪力-位移曲线和支撑、柱应力应变曲线封闭面积较小,表明结构只发挥一次性的耗能能力,且耗能只依靠柱的无侧移屈曲;而弱剪型支撑框架中,支撑较早屈服使得支撑和梁柱的延性及滞回耗能能力充分发挥作用.因此,建议在设计支撑框架时,增加支撑屈服机构验算,保证支撑屈服后柱子仍基本在弹性阶段工作,使结构成为强柱弱支撑体系.

There may exist deficiencies in current codes for strong-shear braced frame designed by amplifying design force of braces artificially. The weak-shear brace design was thereby developed to ,solve the problem. The nonlinear elastic-plastic timehistory responses of the two types of frames under 10 earthquake records were analyzed by using finite element analysis （FEA） method. Results show that columns in strong-shear braced frames will buckle in a non-sway mode before yielding of the braces, and then horizontal and vertical displacement of frame increases rapidly. But the deformation of weak-shear braced frame is in a sway mode. Curves of inter-story shear force-lateral displacement and the stress-strain response of the brace and the column do not form a hysteretic loop in the strong-shear frame, and energy dissipating capacity is unable to be developed to reduce the earthquake response. In the weak shear frame, the brace yields earlier than the column, therefore the brace and the frame may deform laterally continuously to develop their ductility and the energy-dissipating capacity to reduce the earthquake response. It is suggested that check should be carried out to insure that the brace yields before the column buckle in a nonsway mode, which make the structure to be a strong column weak brace system.