框架-横梁未充分加强型人字撑架的抗侧性能

为了充分了解框架-人字撑架(横梁未充分加强型)的抗侧性能,对50个算例进行静力推覆分析,其中框架分别承担基底总剪力的25％和50％．研究表明:框架分担基底剪力的比例大小和支撑架横梁的强弱是影响这种双重抗侧力体系抗侧性能的最关键因素;框架抗侧承载力占基底剪力的比例越大,支撑架横梁越强,结构体系超强系数就越大．推导了框架-支撑体系中关键点受压支撑屈曲、支撑架横梁和框架形成塑性铰时对应的层侧移角公式．分析表明在这些点中,受压支撑屈曲总是最先发生,此时框架的抗侧承载力发挥很小．此外,由于支撑架横梁没有充分加强,受拉支撑的轴力无法达到其屈服承载力．为了获得较好的抗侧性能,提出了人字撑架横梁需要承担的最小不平衡力．

Lateral resistance of moment resisting-chevron braced frames with weak beams

The elastic-plastic analyses were carried out for 50 moment resisting-chevron braced frames with weak beams for braced frame,in which the brace of out-of-plane slenderness between 30 and 150 and the moment-resisting frames with lateral resistance being respectively 25% and 50% of the total base shear are adopted.The results showed that the relative lateral force resisting capacity of the moment-resisting frames and the strength of beam of braced frame are the two key factors for behaviour of the dual lateral force resisting system.The analyses also indicated that the value of overstrength was larger for a dual system with stronger moment-resisting frame and the beam of braced frame.The solutions for the drift ratio of braced frames corresponding to the buckling of the brace in compression and the formations of plastic hinge in the beams of the braced frame and the moment-resisting frames were also derived.The results of these solutions are verified with those using finite element analyses.The study of this paper also shows that the contribution of the moment-resisting frame to the lateral force resistance of the system is limited when the buckling of the compressive brace always occurs;the tensile brace cannot reach its yielding load in the braced frame with weak beam.