大跨度钢结构抗连续倒塌动力分析关键问题研究

对大跨度钢结构抗连续倒塌动力分析中的关键问题进行研究，运用等效荷载瞬时卸载法对结构进行抗连续倒塌的动力分析，并借鉴美国规范对等效荷载提出取值方法建议。分析表明，应用等效荷载瞬时卸载法分析结构抗连续倒塌的精度主要取决于加载的时程曲线。根据动力学知识推导出求解结构关键构件失效前等效荷载最小作用时间的计算式，并与实际工程算例进行比较，其结果吻合较好。同时通过有限元数值分析，提出等效荷载卸载的最长时间为构件失效后模型的第1阶竖向自振周期的1/10。通过实际工程算例介绍抗连续倒塌动力分析的承载力和变形判定准则，分析在关键构件失效瞬间结构的应力比和变形能否满足设计要求。结果表明，应用等效荷载瞬时卸载法模拟大跨度钢结构关键构件失效后的受力和变形情况可行，与静力法相互补充可对大跨度钢结构进行抗连续倒塌分析。

Study on key issues of dynamic analysis for anti-progressive collapse of large span steel structure

The key issues of dynamic analysis for large span steel structure to anti-progressive collapse were studied in this research. The use of equivalent load transient unloading method for anti-progressive collapse of the structure dynamic analysis was introduced. Based on the U.S. codes, the method to determine the values of equivalent loads was proposed. The accuracy of applying equivalent load transient unloading to anti-progressive collapse analysis depends on the load time-history curve. The formula that calculates the minimum action time of equivalent load before the critical component failure was derived based on the dynamics knowledge. The predicted results agreed well with the results obtained from actual engineering example. Through finite element numerical calculation, the maximum unloading time of equivalent load was proposed to be 1/10 of the first order vertical vibration period of component failure model. The paper introduces the load carrying capacity and deformation acceptance criteria of anti-progressive collapse dynamic analysis based on practical engineering example and determines if the load carrying capacity and deformation exceeds limits after the key structural component failure.It is indicated that the equivalent load transient unloading method is applicable to simulate the force and deformation of large span steel structure after the key components failure, and is a complement to the static method for anti-progressive collapse analysis of large-span steel structure.