预压装配式预应力混凝土框架边柱拆除时抗连续倒塌性能试验研究与理论分析

对一榀二层二跨预压装配式预应力混凝土(PC)平面框架进行了静力拆除底层边柱的试验及理论分析,探究了裂缝发展、变形能力、破坏模式及连续倒塌机理。根据试验框架达到极限承载力时的状态,提出了边柱失效时简化的结构抗力分析模型,并推导出结构抗倒塌极限承载力的计算方法; 基于能量法建立近似的动力响应评估模型,根据试验框架静力加载荷载-位移曲线近似得到其在边柱瞬时失效时的动力响应曲线。结果表明:框架的受力过程可分为弹性、弹塑性、塑性铰以及倒塌4个阶段; 加载时试件的混凝土裂缝开展及破坏集中在失效边柱相邻区域框架梁两侧梁端结合部,除失效边柱外,其余框架柱以及失效柱远离区域框架梁端基本完好; 框架在小变形阶段按梁机制受力,存在压拱效应及空腹效应; 在大变形阶段不能按悬链线机制受力,由梁的受弯机制和空腹机制共同抵抗不平衡荷载; 边柱失效时预压装配式预应力混凝土框架最大抗力达到60.9 kN,最终倒塌位移为430 mm,梁端转角为10.0°～15.3°,具有较好的抗连续倒塌能力。

Experimental Research and Theoretical Analysis on Progressive Collapse Resistance of Prestressed Fabricated PC Frame with Removal of Side Columns

The experiment and theoretical analysis of static removal of bottom side columns of a two-story and two-span prestressed fabricated prestressed concrete(PC)plane frame were carried out, and the crack development, deformation capacity, failure mode and progressive collapse mechanism were explored. According to the state when the test frame reached the ultimate bearing capacity, a simplified structural resistance analysis model when the side column failed was proposed, and the calculation method of the ultimate bearing capacity of the structure against collapse was deduced. An approximate dynamic response evaluation model was established based on the energy method, and the dynamic response curve of the test frame under transient failure of the side column was approximately obtained according to the static load-displacement curve of the test frame. The results show that the stress process of the frame can be divided into four stages of elasticity, elastoplasticity, plastic hinge and collapse. During loading process, the concrete crack development and failure of the specimen are concentrated in the joint of the beam ends on both sides of the frame beam in the adjacent area of the failed side column. Except for the failed side columns, the other frame columns and the frame beam ends far away from the failed columns are basically intact. In the small deformation stage, the frame is stressed according to the beam mechanism, and there are compression arch action and vierendeel frame action. In the stage of large deformation, it can not be stressed according to the catenary mechanism, the unbalanced load is resisted by the bending mechanism and vierendeel frame action of the beam.When the side column fails, the maximum resistance of the prestressed fabricated PC frame reaches 60.9 kN, the final collapse displacement is 430 mm, and the beam end angle is 10.0°～15.3°, which has good resistance to progressive collapse.