底层楼板大开洞对高层框筒结构抗震性能的影响

Seismic Effect of Bottom-layer Floor-openings on High-rise Frame-tube Buildings

对典型高层框筒结构进行了分析,考察了底层大开洞对抗震性能的具体影响.通过分析和讨论得出如下结论:对于底层开洞高层框筒结构的抗震分析,一般意义上的刚性板楼层假定,以及与实际受力行为相符的弹性板假定,二者相比存在一定差距.开空层楼板平面内传递的水平力要小于开空上一层楼板,需要增加板厚来降低板应力.楼板配筋可采用小震时主拉应力小于混凝土开裂应力、中震时不超过钢筋抗拉强度的原则控制楼板的厚度和配筋量;同时,开空上一层的框架梁有必要考虑其受轴向力的影响.可以采用弹性板模型指导设计,并使用合并模型(即开洞层与上一层合并的模型)的计算结果,对开空层及其上一层的水平和竖向抗侧力构件内力进行复核.

This paper analyzes the typical high-rise frame-tube structure, and examines the specific impact ofbottom-layer floor-openings on the seismic performance. Some conclusions are drawn after analysis and dis-cussion. For seismic analysis of high-rise frame-tube buildings with bottom-layer floor-openings, there arecertain differences between the two analysis models： one is based on rigid-floor assumption and the other isfrom elastic-floor assumption, with the latter being more consistent with actual situation. The seismic forceon the floor-opening layer is less than that on the above layer, so the increase in floor-thickness is a goodchoice for the reduction of the floor stress. The principle can be used to control the floor thickness and steelamount, when at small earthquakes the floor stress should be less than floor-cracking stress, and at mediumearthquakes the stress does not exceed the tensile strength of reinforcement. Furthermore, it is necessary toconsider the axial-force impact on the frame beams above the openings layer. It is suitable to use the elastic-floor model for guiding the design and supplying the combination model （ i. e. combination between the o-pening layer and the above layer） for rechecking.