Reseach On The Progressive Collapses Resistance Performance Of Reinforced Concrete Frame Structure

Since the progressive collapse of the Ronan Point apartment building caused by gas explosion in London in 1968, especially after the progressive collapse of WTC buildings caused by terrorist attacks in New York City in the"9.11"event, high attention have been paid by various countries about how to guarantee the ability of the building structures to resist progressive collapse as a result of accidental events.At present, the reinforced concrete frame structure ("RC frame structure"for short) is one of the most extensive structural form in our country. Its safety problem cannot be ignored. In this study, reinforced concrete frame structure is taken as the research object. The factors influencing progressive collapse of a frame structure will be determined through theoretical analysis. Then, the examples are designed. The alternate path method will be used in the numerical simulation of the progressive collapse. The numerical simulation method will take into account of the material and geometrical nonlinear properties. Through the study, determine the factors influencing progressive collapse. Finally, the design recommendations for progressive collapse resistance of frame structures will be proposed.The main content herein is as follows:①Briefly introduced the study background and significance of the progressive collapse of building structure, research status at home and abroad are summarized from the following four aspects: revision of the progressive collapse standards and guidelines, research on performance evaluation of resist progressive collapse, research on design method of resist progressive collapse, collapse simulation and experimental study.②Several key problems concerning the use of the alternate path method are summarized and introduced with reference to the foreign codes, and the notice items is pointed out, providing some references to the study and design staff and providing a basis for subsequent analyses work of this paper.③By using nonlinear static (NS) analysis and nonlinear dynamic (ND) analysis of the alternate path method, the performance of resist progressive collapse of the examples of RC frame structures without support designed by Chinese standard are analysed. The effects of the performance of resist progressive collapse of RC frame structures without support are investigated by setting different storey number, span number, span length and seismic fortification intensity. ④By using nonlinear dynamic (ND) analysis of the alternate path method, taking a RC frame structure of ten layers as research object, the performance of resist progressive collapse of the examples of RC frame structures for different cases for the brace-setting are compared.⑤According to research status resist progressive collapse at home and abroad, combining the related provision of the aseismic measures of the Chinese Seismic Design Code, proposed some measures to enhance the resisting progressive collapses ability.Based on the above research, the main conclusions are as follows:①The structural components which are adjacent to the bay whose column is removed have more contribution to the internal force redistribution when the local damage occurred, so those structural components can improve the ability of the RC frame structures to resist progressive collapse; The structural components which are far away to the bay whose column is removed have little contribution to the internal force redistribution when the local damage occurred, so those structural components have little effect to improve the ability of the RC frame structures to resist progressive collapse.②The increase in span length results in the decrease in resistance to progressive collapse of the RC frames.③The progressive collapse resisting capacity of the RC frames increases as the number of stories increases. This rule is not significant in the low seismic area, but it is more obvious in the highly seismic area.④In the highly seismic area, when the contribution of the seismic load is greater than gravity load, the progressive collapse resistance of the RC frames will increases as the earthquake intensity increases. But this rule is not exist when the contribution of the gravity load is greater than seismic load.⑤For the case that the horizontal brace setting in the bay which the column is removed: The maximum vertical displacement of the top of the removed column and the peak axial force of the columns which are adjacent to the removed column can be reduced effectively when the horizontal brace are setting on the second floor of the RC frame structures relative to the no braced RC frame structures. so it can improve the ability of the RC frame structures to resist progressive collapse. For the case that the horizontal brace setting in the bay which the column is not removed: it has little effect to improve the ability of the RC frame structures to resist progressive collapse when the horizontal brace are setting on the second floor of the RC frame structures.⑥For the case that the horizontal brace setting in the bay which the column is removed: The maximum vertical displacement of the top of the removed column can be reduced effectively when the horizontal brace are setting on the second floor of the RC frame structures relative to the horizontal brace are setting on the top floor. So it can improve the ability of the RC frame structures to resist progressive collapse. The peak axial force of the columns which are adjacent to the removed column can be reduced more effectively when the horizontal brace are setting on the top floor of the RC frame structures relative to the horizontal brace are setting on the second floor. For the case that the horizontal brace setting in the bay which the column is not removed: it has little effect to improve the ability of the RC frame structures to resist progressive collapse when the horizontal brace are setting on the different floor of the RC frame structures.