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通过地震现场调查,对汶川地震中大量倒塌的外廊式钢筋混凝土框架结构的破坏特点、倒塌方向及堆积情况进行了总结。设计相似比为1/4的两层外廊式框架结构模型,并进行了振动台框架倒塌试验。试验再现了典型外廊式框架的倒塌过程。根据框架倒塌模式及试验结果分析,研究了各层加速度反应随结构破坏程度加深的关系及层间位移角变化规律。总结出框架结构破坏不同阶段所对应的层间位移角限值,计算了不同输入下各柱的动轴压力大小,分析了外廊式框架的破坏机理及倒塌原因。研究结果表明:在倾覆弯矩引起的动轴压力作用下,外廊式框架单柱侧的总轴压比升高,延性显著降低,柱端塑性铰区出现压剪破坏是引起外廊式框架倒塌的主要原因。
Through the earthquake site investigation, the destruction characteristics, collapse direction and accumulation of a large number of collapsed veranda type reinforced concrete frame structures in the Wenchuan earthquake are summarized. A two-story verandah frame structure model with a similarity ratio of 1/4 was designed, and a shaking table frame collapse test was conducted. The test reproduces the collapse of a typical veranda frame. Based on the analysis of the collapse model and the experimental results, the relationship between the acceleration response of each layer and the deepening of structural damage and the law of the displacement angle between layers are studied. The displacement angles corresponding to different stages of frame structure failure are summed up, the dynamic axis pressures of different columns under different input are calculated, and the failure mechanism and collapse reason of the corridor-type frame are analyzed. The results show that under the action of the dynamic axis pressure caused by the overturning bending moment, the total axial pressure ratio on the side of the single-column frame of the corridor increases, the ductility decreases significantly, and the shear deformation of the plastic hinge area at the column end causes the corridor-type frame. The main reason for the collapse.