混凝土空间板柱结构震致落层倒塌的试验研究

EXPERIMENTAL STUDY ON PANCAKE COLLAPSE OF RC SPACIAL SLAB-COLUMN STRUCTURES UNDER EARTHQUAKE

开展了2个具有薄弱层的3层混凝土空间板柱结构模型的地震模拟振动台试验,采用加速度峰值逐级加大的El-Centro(NS)波作为输入激励,直至薄弱层发生落层倒塌。量测了倒塌前、倒塌后模型各层的水平加速度响应,以及倒塌碰撞引发的薄弱层及其下层楼板的竖向加速度响应。模型M-2相比于模型M-1额外施加了附加配重。试验结果表明:1)随着地震损伤程度的增加,模型的扭转效应有所增大;2)倒塌前模型M-1和模型M-2的基本频率仅比初始值分别降低8.9%和4.7%,采用频率改变幅度进行结构倒塌预警可能是不现实的;3)倒塌碰撞导致模型各层的水平加速度出现短时剧烈波动,波动期间模型M-1和模型M-2各层的绝对加速度最大值介于5g^10g之间,分别为倒塌前各层绝对加速度最大值的5倍~20倍和10倍~50倍;4)倒塌碰撞引发的楼板竖向加速度高达30g^40g。

Shaking table tests were conducted for two three-story spacial slab-column structure models with weak stories. The EI-Centro （NS） earthquake record was used to produce the excitation and its peak acceleration increased gradually until the pancake collapse of the weak story occurred. Horizontal accelerations were recorded for all stories before and after the occurring of pancake collapse. The vertical accelerations induced by the pancake collapse were also recorded for the floor slabs of the weak story and the story just below. Model M-2 had more weight than Model M-1. Test results show that： 1） with the increasing of the seismic damage degree, the models＇ torsional responses increased; 2） the fundamental frequencies of Models M-1 and M-2 prior to the occurring of pancake collapse were only 8.9% and 4.7% lower than their initial values respectively, indicating that it may be impractical to use the change of frequency to predict structural collapses; 3） intensive fluctuation occurred in a very short time period for the horizontal acceleration of each story due to the pancake collapse; and the maximum absolute accelerations of Models M-1 and M-2 during the fluctuating period were in a range of 5g-10g, 5-20 times larger of M-1＇s and 10-50 times larger of M-2＇s maximum absolute accelerations respectively; 4） the vertical accelerations of the weak story floor slab and the floor slab just below the weak story induced by the pancake collapse were in a range of 30～40g.