地震作用下掉层钢框架结构抗倒塌能力分析

Analysis on collapse resistance of steel frame structures with dropped floors under earthquake action

采用PERFORM-3D程序对掉层钢框架结构进行了抗震倒塌能力研究。考虑不同的掉层情况和结构措施,设计了2个普通钢框架结构模型和4个掉层钢框架结构模型(其中2个模型带拉梁加强),利用增量动力分析方法对上述钢框架模型进行了易损性分析和抗震倒塌能力评估。结果表明,掉层钢框架结构的抗震倒塌能力与掉层数关系不大;采用拉梁加强的掉层钢框架,上接地侧的抗震倒塌能力和抗震倒塌安全储备性能有所提高,但掉层侧的抗震倒塌能力和抗地震倒塌安全储备降低;增加拉梁的数量对该类结构影响不大,但会改变其破坏模式;上接地侧倒塌模式下,上接地一层是上接地侧最薄弱的楼层;掉层侧倒塌模式下,上接地二层是掉层侧最薄弱的楼层。

PERFORM⁃3D was used to study the seismic collapse capacity of steel frame structures with dropped floors.Considering different floor dropping conditions and structural measures,two models of ordinary steel frame structures and four models of steel frame structures with dropped floors(two of which are strengthened with tie beams)were designed,and the fragility analysis and seismic collapse resistance assessment of the above steel frame models were carried out by using incremental dynamic analysis methods.Results show that the number of dropped stories has little influence on the seismic collapse capacity of steel frame structures with dropped floors.For the dropped floor steel frame reinforced with tie beams,the seismic collapse resistance and seismic collapse safety reserve of upper grounding side are improved,but they are reduced for the dropped floor side.Increasing the number of tie beams does not have a significant effect on this type of structure,but it does change its damage pattern.In the upper grounding side collapse mode,the ground floor of the upper grounding is the weakest floor on the upper grounding side;in the drop side collapse mode,the secondt floor of the upper grounding is the weakest floor on the drop side.