五层足尺预应力压接装配框架结构顶层角柱失效试验研究

Experimental study on a five-story full-scale post-tensioned prestressed precast frame with failure of top corner column

为研究预应力压接装配混凝土框架(PPEFF)结构的抗连续倒塌性能,根据国内外现行抗连续倒塌规程中的拆除构件法,设计并建造了一栋2×2跨带楼板的五层足尺PPEFF结构,进行了结构动力特性测试和顶层角柱失效下的抗连续倒塌试验。通过动力特性测试得到了结构的固有频率与阻尼特性,结构实测周期与采用梁柱节点刚接假定的分析结果吻合良好。提出了滑块与双微摩擦面构造及结构柱移除试验方法,能较好地模拟结构柱移除前结构的正常承载状态,操作简便快捷。基于上述方法,开展了移除角柱的抗连续倒塌试验,采用位移计和基于数字图像处理的非接触式位移测量设备,分别获得了顶层角柱失效后的动态响应,两者最大动态位移幅值和残余位移相差不超过3%,吻合良好。试验结果表明,顶层角柱失效后,试验结构在正常使用荷载作用下的抗连续倒塌机制以双向梁悬臂受弯作用为主,楼板作为受拉翼缘提高了梁的悬臂受弯作用,角柱所承担的竖向荷载在剩余结构内进行了重分布,梁内纵向钢筋、楼板钢筋和预应力筋均处于弹性状态,拆柱处悬臂结构最大瞬态转角仅为1/273,PPEFF在顶层角柱失效时具有优异的抗连续倒塌性能。

To study disproportionate collapse resistance performance of the precast prestressed efficiently fabricated frame(PPEFF)system,a five-story full-scale frame with two spans,two bays and precast slabs was designed and constructed according to the alternative-path method from the current domestic and international codes on resisting progressive collapse of buildings.A dynamic structural characteristics test and a top corner column removal test were performed.The natural frequency and damping characteristics of the structure were obtained through the dynamic characteristics test.The measured natural vibration periods are close to the simulation results based on the rigid beam-column connection assumption.A slider double micro-friction surface(SDMFS)detailing and a column removal method were proposed,which are easy to operate and better represent the structural loading states before the column was removed.The top corner column was removed based on the above method.The dynamic response after failure of the top corner column was obtained by LVDTs and the non-contact displacement measurement equipment based on digital image processing,respectively,and the maximum dynamic displacement amplitude difference and residual displacement difference of two methods are all not more the 3%.The disproportionate collapse resistance mechanism of the full-scale test building under service conditions was shown mainly as a bi-directional cantilever beam mechanism after the top corner column was removed,while the slab,as a tension flange,improved the cantilever bending effect of beams.The vertical load borne by the top corner column was redistributed to the remaining structure.The longitudinal bars of the beams,the distribution reinforcements of the slabs and the prestressed tendons were all in the elastic range,and the maximum transient angle of the cantilever structure at the pumping column was only 1/273,showing that the PPEFF system with failure of top corner column possesses excellent progressive collapse resistance performance.