A Comparative Study On Progressive Collapse Analysis Methods For RC Frame Structures Under Blast Loads

The damage of the key structural components which eventually lead to theprogressive collapse of buildings, caused by terrorist attack and accidental explosion,has induced serious casualties and huge economic losses. On September the eleventh2001, the twin towers of the New York’s world trade center collapsed completelybecause of terrorist attack, which has drown great attention of the world to structuralprogressive collapse. Many research works have been done on analysis of structuralprogressive collapse.To universalize the research results, the United States Department of Defenseissued Unified Facilities Criteria (UFC) documents of ‘Design of Buildings to ResistProgressive Collapse’ in2005, and updated it in2009. The alternate path method isused in the UFC to design buildings. In this method, the linear static analysis,nonlinear static analysis and nonlinear dynamic analysis are employed to analyze thestructure after the key component removed. However, the cause of the key structuralcomponents failure is unconsidered in this method.In this paper, the progressive collapse of structure caused by the key structuralcomponents failure due to blast loads has been studied by numerical simulation. Theanalysis results have been compared with the results using the UFC code. The primaryworks are as follows:(1) The numerical model of a typical four-storey two-spanreinforced concrete frame structure has been established using the explicit dynamicfinite element analysis software LS-DYNA. The collapse responses of the structurecaused by the damage of center or corner column on the ground floor due to blastloads of different scaled distances have been analyzed.(2) Linear static analysis andnonlinear dynamic analysis of the same four-storey structure have been done usingalternate path method of the UFC.(3) The direct simulated results of the structureunder blast loads have been compared with the results calculated by using alternatepath method of the UFC. The deficiency of The alternate path method has beenfigured out. The proposal of the improved design method of buildings to resistprogressive collapse due to blast has been made.