带板钢筋混凝土框架连续倒塌理论分析

THEORETICAL ANALYSIS ON THE PROGRESSIVE COLLAPSE OF RC FRAME STRUCTURES WITH SLABS

采用拆除构件法对一榀两层2×1跨带板钢筋混凝土框架结构进行拟静力倒塌试验,分析了框架结构底层边柱失效后,剩余结构竖向倒塌的变形破坏模式以及受力机制。试验结果表明:带板混凝土结构连续倒塌抗力先后由梁拱-板压膜机制、梁拱-板拉膜机制、梁悬索-板拉膜机制、板拉膜机制提供;结构变形先后经历外推、内收、倒塌三个阶段,结构最大抗力出现在框架柱内收-外推转换点(梁悬索-板拉膜机制)。框架梁破坏后,结构转化为板柱模型,现浇板仍能将抗力维持在较高水平。理论分析了结构竖向连续倒塌关键变形处的临界位移和抗力值,提出了结构极限承载力计算方法,并建议同时考虑极限承载力和梁端转角对混凝土结构进行倒塌判定。

A quasi-static test was carried out to experimentally study the progressive collapse of a two-story 2×1 bay spatial frame structure with slabs.The progressive collapse mechanism and deformation failure mode of the residual structure due to a side column loss were analyzed.The results indicate that the whole collapse resistance of RC frame structure is successively provided by beam arch-slab pressure membrane mechanism,beam arch-slab tensional membrane mechanism,beam catenary-slab tensional membrane mechanism and slab tensional membrane mechanism.The structural deformation process experiences three stages including the extrapolative stage,adductive stage and collapsed stage.The maximum resistance appears at a breaking point,which lies between stringing inward section and pushing outward section of the frame column(beam catenary-slab tensional membrane mechanism).The structure changes into a slab-column model when the beam is damaged,and the slab can maintain the resistance at a high level.The resistance and critical displacement at the key points of structural collapse are theoretically analyzed.A calculation method of structural ultimate load-bearing capacity is proposed.The ultimate load-bearing capacity and beam’s rotation angle should be taken into consideration in the criteria for structural collapse.