考虑剪切效应的RC结构抗倒塌性能评估

Evaluation of Collapse-Resisting Capacity of RC Frames with Shear Effect

讨论剪切效应对结构非线性地震响应的影响及结构抗整体倒塌能力评估中的数值建模、分析方法及倒塌极限状态判定等问题的基础上,按照现行抗震设计规范设计的一榀五层三跨钢筋混凝土框架结构为研究对象,区分和考虑剪切变形和不考虑剪切变形两种情况,利用ETABS、OpenSees有限元分析平台,对其进行了静力推覆分析和增量动力分析,进一步利用多地震动记录输入下的增量动力分析结果,得到了结构的倒塌概率曲线,给出了具有50%倒塌概率的以结构基本自振周期对应的谱加速度Sa(T1,5%)表示的结构抗整体倒塌能力指标。结果表明,结构变形较小时,剪切变形对结构的承载力和变形的影响均不大,考虑剪切变形和不考虑剪切变形的Pushover曲线及IDA曲线基本重合;随着地震动强度的增大,结构变形增大,考虑剪切变形和不考虑剪切变形的Pushover曲线及IDA曲线出现明显差异,考虑剪切后结构变形增大得更快;考虑剪切变形后,在同样的地震动强度下,结构的倒塌概率明显增大。

The influence of shear effect on the nonlinear seismic response of RC frames, the issues of numerical modeling,analytical methods and collapse limit state criteria for global collapse-resisting capacity e- valuation of the structure were discussed. Then,a 5-storey planar RC frame structure with 3 bays designed according to the current seismic design code was modeled by using the software ETABS and OpenSees. The model,with the shear effect considered and without the shear effect considered,was investigated by the pushover analysis（POA） and then by the incremental dynamic analysis（IDA）. Furthermore, collapse probability curves were obtained and the global collapse-resisting capacity indices with 50% collapse probability in terms of the spectral acceleration corresponding to the fundamental period of the structure were derived from the IDA results. The results indicated that the influence of shear effect on its strength and deformation demand was negligible when the deformation level of the structure was low. Pushover curves and IDA curves were almost the same with or without the shear effect considered in this case. With the increase of ground motion intensity, the deformation of the structure developed and the distinct difference existed in the pushover curves and IDA curves with or without the shear effect considered. The deformation of the structure with the shear effect considered developed faster than without the shear effect considered. With the shear effect considered, collapse probability of the structure became significantly larger when the ground motion intensity was the same.