支撑长细比及节点板对中心支撑钢框架抗震性能的影响

Effects of Brace Slenderness and Gusset Plate on the Seismic Behavior of Concentrically Braced Steel Frames

支撑作为中心支撑框架主要的抗侧力构件,其性能对整体结构的抗震性能影响较大,其中支撑的长细比是影响支撑性能的关键因素。节点板作为连接支撑与框架常用的连接构件,对体系的刚度也有一定的影响。利用OpenSees建立了考虑节点板作用的3层1跨的中心支撑框架模型,并与试验结果进行对比验证其可靠性。在此模型的基础上对中心支撑框架是否考虑节点板作用及其长细比对整体抗震性能的影响进行了弹塑性时程分析及易损性分析。分析结果表明,在设计过程中考虑节点板的作用,将有利于合理地评估中心支撑框架的抗震性能。我国《建筑抗震设计规范》对长细比的限值过于保守,使得在罕遇地震下支撑仍处于弹性范围内,没有充分发挥其性能。因此,建议适当增大中心支撑框架的支撑长细比,从而保证支撑充分发挥其性能,并减小结构的地震作用。

As the main lateral resistance component in concentrically braced frame(CBF),the performance of braces has significant impact on the seismic performance of system,and the slenderness ratio of brace is the key factor.The gusset plate,as the connecting member between brace and frame,also affects the system behavior.A model is built considering the gusset plate effect using OpenSees and is validated by the test results.Four CBF models are built based on this model,elasto-plastic time-history analysis and fragility analysis are conducted using OpenSees to study the impact of brace slenderness ratio and gusset plate existence to seismic behavior of CBF.The result shows that considering the effect of gusset plate in the design process,the seismic performance of the CBF is more reasonably evaluated.Brace slenderness ratio limit stipulated in Code for Seismic Design of Buildings is too conservative.Brace is still in elastic range and will not make the most advantage of it.And it is recommended to increase the slenderness limit properly to ensure the maximum performance and reduce the seismic effect.