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对7组横梁未加强的人字支撑框架进行弹塑性分析,支撑几何长细比从43变化至132,支撑又分承担和不承担竖向重力两种。研究表明重力荷载使支撑提前屈曲,降低了支撑抗侧力峰值,抗震设防烈度越低,其影响越大。通过对整体、支撑和框架的侧力-侧移曲线的分析,解释了设计人字撑横梁时不应考虑跨中支撑点作用的原因,对欧美日等将中等长细比的支撑框架列为抗震性能最差的框架支撑体系提供了解释。揭示了支撑与框架的极限抗侧力不同时出现的重要现象,提出了设计对策;提出了塑性破坏机构,推导了横梁跨中挠度和支撑出平面外位移与层侧移角的关系。
The elasto-plastic analysis of the unreinforced herringbone support frame of 7 beams is carried out. The support ratio of the slenderness ratio from 43 to 132 is the same as that of the vertical beam. The research shows that the gravity load causes the support to buckle prematurely and reduces the peak value of supporting lateral force. The lower the seismic fortification intensity is, the greater the impact is. Through the analysis of the whole force, the support and the side-force curve of the frame, the reasons why the mid-span support point should not be considered when designing the cross beam should be considered. The worst case seismic frame support system provides an explanation. The important phenomena that occur when the ultimate bearing capacity of the frame and the frame is not found are revealed. The design countermeasures are put forward. The plastic failure mechanism is proposed and the relationship between the midspan deflection and the out-of-plane displacement of the girder is also derived.