Research On Anti-progressive-collapse Performance Of Steel Frame By Considering The Influences Of Composite Floor Based On GSA2013

With the continuous improvement of China's construction level,lightweight and high-strength steel structure building system is widely applied.However,accidental loading and other events impose great risks to the safety of buildings.How to enhance the building's anti-progressive-collapse ability has become a hot issue.America,UK and other countries have made in-depth research on the anti-progressive-collapse performance of structures and relevant codes have been produced.However,most of the researches focus on steel frame and reinforced concrete frame.Insufficient researches are about the influences of composite floor in the combined structure on the anti-progressive-collapse performance,and on the internal force redistribution in the process of structural collapse.Based on these facts,the main contents in this paper are listed as follows:(1)AP method in new American anti-progressive-collapse design code GSA2013 was introduced and compared with China's anti-progressive collapse code.(2)With a steel frame designed by Chinese design code as the engineering background,finite element analysis based on SAP2000 was established.Taking the middle column working condition as an example,three kinds of analysis methods in GSA2013 were introduced in details.Three analysis results are compared.by the analysis results,SAP2000 can better apply these three analysis methods from the code.Progressive collapse will occur in structure under the middle column fail conditions.The eventual distribution of plastic hinge and the vertical displacement of fail points can be used as the indices of rational non-linear evaluation.(3)The theory for composite floor was simplified,and the composite floor was simulated by the layered shell element.The finite element model was established with regards to the composite floor.The anti-progressive-collapse performance was compared between considering RC floor or not considering floor.According to the evaluation on the anti-progressive-collapse performance under three demolishing conditions through the non-linear evaluation indices,it's shown that the composite floor can significantly improve the anti-progressive-collapse performance of the structure,while no progressive collapse occurs under three demolishing conditions.Structure considering the RC floor is close to collapse under the corner post condition.It's irrational to consider composite floor as the safety stock of structure while it's rational for RC floor.(4)The anti-progressive-collapse performance of steel frame with or without composite floor was compared and the redistribution of internal force was researched.In this paper,the influence coefficient was applied to quantify the influence of components on the redistribution of structural internal force.The analysis results show that the composite floor can effectively strengthen the spatial connection ability of the components,balance the difference in the internal force between the vertical and horizontal frame components,improve the structure's ability in redistributing the internal force and increase the number of force transfer paths.