翼缘削弱的型钢混凝土框架抗震性能研究

为了研究翼缘削弱的型钢混凝土框架的抗震性能,对一榀两跨三层型钢混凝土框架模型进行了低周反复荷载试验。框架模型按"强柱弱梁"原则设计,且对节点核心区附近梁端工字形型钢的上、下翼缘采取狗骨式削弱,并适当增加最大削弱部位纵向钢筋的配筋率。通过对框架模型顶层施加低周反复水平荷载,观察了框架模型的破坏过程,测得框架模型的荷载-位移滞回曲线和骨架曲线以及各阶段的荷载和位移值,并分析了框架模型的延性、耗能、强度降低、刚度退化以及破坏机制。试验结果表明:框架模型的承载能力、变形能力和耗能能力高,延性大(延性系数大于7),满足延性框架的抗震要求。进一步分析了翼缘削弱在型钢混凝土框架中的具体作用。分析结果表明:翼缘削弱不仅能将塑性铰从梁端根部转移到翼缘削弱部位,从而降低节点核心区所受的剪力以及梁柱连接焊缝的应力,而且有利于框架形成梁铰耗能机构,从而提高框架的整体耗能能力。翼缘削弱能有效提高型钢混凝土框架的抗震性能,可在型钢混凝土

Seismic behavior of steel reinforced concrete frames with reduced beam sections

The seismic behavior of steel reinforced concrete(SRC) frames with reduced beam sections is investigated through a cyclic loading experiment and its analysis for a model of 2-bay,3-story SRC frame.The frame model is designed according to the principle of "strong column and weak beam",in which the upper and lower flanges of the H-type steel at the beam ends near the joint cores are treated with the dog-bone style reduction and the ratio of longitudinal reinforcements at the location of the maximum section reduction is properly increased.Through the cyclic lateral loading at the top floor of the frame model,the damage process is observed,the load-displacement hysteresis loops and its skeleton curves and the load and displacement values are tested,and the ductility,energy dissipation,strength reducing,rigidity degenerating,and failure mechanism are investigated.The tested results show that the load bearing,deformation and energy dissipation capacities are high,and the ductility is larger than 7,which meets the requirements for seismic design of ductile frames.The specific functions of the reduced beam section in the SRC frame are further analyzed.The analyzed results show that the reduced beam section may not only transfer a plastic hinge from the root of beam end to the reduced beam section so as to reduce the shear applied to the core zone of joint and the stress of the welded joint between beam and column,but also help the frame form the energy dissipation mechanism with plastic hinges at beam ends so as to increase the integral energy dissipation capability of frame.A conclusion is given that the reduced beam section is capable to improve the seismic behavior of SRC frames effectively,and may be widely applied to the seismic design of SRC frames.