交叉支撑内力取值方法对结构抗震性能的影响

Influence of value assigning of inner forces in cross-braced frame on its anti-seismic behavior

针对现行规范中人为放大支撑内力设计交叉支撑存在的缺陷,提出弱剪型支撑设计方法.采用弹塑性时程有限元程序,对地震波作用下的强剪型和弱剪型支撑框架进行地震分析,结果表明:强剪型支撑框架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下仅发生有侧移变形;强剪型支撑框架的支撑与柱应力应变曲线封闭面积小,表明耗能能力差,而弱剪型支撑框架中,支撑能够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.建议设计支撑框架时,增加支撑屈服机构验算,保证支撑屈服后柱仍在弹性阶段工作.

Aimed at the defect in designing cross-braced frame with enhanced inner force in it, which is stipulated by current norm, a design method of weak-shear cross-braced frames was proposed. The strong- shear and weak-shear cross-braced frames subjected to the action of seismic wave were analyzed by using finite element program of elastic-plastic time-history responses. It was found that columns in SSBF would buckle in a non-sway mode before yielding of the braces, so that the horizontal and vertical displacement of the frame rapidly increased. But the deformation of a WSBF was in a sway mode. Curves of the stressstrain response of the brace and the column in the SSBF did not form a hysteretic loop, meaning its bad ability of energy dissipation. In the WSBF, the brace yielded earlier than the column, therefore the brace and the frame might deform laterally and continuously to develop their ductility and energy-dissipating capacity due to the hysteresis, so that its function was fully brought into play. It was suggested that the checking of the frame yielding be carried out to make sure that the brace yielded before the column buckled in a non-sway mode, so that it did still work in elastic mode.