混凝土框架楼梯结构抗震性能拟静力试验研究

Experimental study on seismic performance of concrete frame with staircase under quasi-static loading

为了研究现浇混凝土框架设置楼梯结构的抗震性能,采用1/2缩尺试件,进行框架楼梯间结构单元的拟静力试验。试验得到了试件整体及各部分的具体破坏过程和相互关系,实测了承载力、各部位变形,以及其他抗震性能指标,分析了结构的工作机理。试验结果表明:楼梯与框架采用通常构造方式整体连接时,楼梯部分作为不对称斜撑参与承受侧向荷载,受力后首先开裂,且破损发展迅速,使其难以可靠发挥救援、疏散等功能;楼梯的作用也造成楼梯间框架构件的不均匀受力,导致一侧框架柱发生脆性破坏,引起试件整体失效;试件实测的滞回曲线面积较小,破坏荷载大,峰值荷载后承载力快速下降;半层平台梁与框架柱采用刚接,使该处框架柱成为短柱,且受力状态复杂,致使其突然破坏,其他部位也很快破坏,采用这种整体连接方式的框架楼梯对结构抗震不利。

In order to study the seismic performance of the staircase in the cast-in-place reinforced concrete frame,a1 /2 scaled specimen of the structural unit composed of concrete frame and staircase was tested quasi-statically. The test demonstrated the failure mode and mechanism of the structural unit as a whole and those of its various components,and the load-carrying capacity,displacements and other aspects related to seismic behavior were also measured. The test shows that,when fully connected to the main structure with the conventional manner of construction,the staircase works as asymmetrically inclined bracings in the structure,resulting in its early cracking and fast damaging,and consequently,its functions,such as seismic rescue and evacuation,could not be ensured; meanwhile,it also causes irregular forces of the frame members,leading to the brittle failure of the column in one side of frame and then the complete failure of the specimen. The enclosed area of hysteretic loop of the specimen is relatively small and its peak value of load reaches high but,after that,the capacity decreases fast. The rigid connection between the frame column and the supporting beam of the stair platform on the half story makes some frame columns,which are already in complex state of loading,the short columns,leading to the local collapse of such column and failure in other parts of the frame suddenly. Therefore,the staircase connected to the concrete frame with such a conventional manner as mentioned above is adverse to seismic resistance of the structure.