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.