Investigation of Progressive Collapse of Knee Braced Frame in Steel Structures under Fire Loading

Document Type : Original Article


1 Department of Civil Eng, Yasouj University,Yasouj,Iran

2 Department of Civil Engineering,Yasouj University, Yasouj, Iran.

3 Department of Civil Engineering, Faculty of Engineering, Mazandaran University of Science and Technology, Mazandaran, Iran.


In this research, the progressive collapse of braced frames with knee braces in steel structures under fire load was investigated based on the software modeling method. In order to carry out the research 3, 6 and 9-story steel frames with coaxial and off-axis knee bracing systems were considered in the shape of inverted-V and were analyzed and analyzed using the software method and ABAQUS and SAP software. In this regard, at first, the frames were analyzed and designed by modeling the frames in SAP software, and the sections of the frames were determined. In the following, the frame was analyzed in ABAQUS software under the fire load. the frame without and with the removal of the critical elements was analyzed successively under the fire load in the SAP software to check and compare the energy of the frame samples in each case based on the results obtained from the analysis. Based on the study conducted on the frame with off-axis and coaxial knee bracing, it was determined that the bracing type of off-axis had a significant effect on reducing the energy of the frame compared to the coaxial bracing system. The 3,6 and 9-storyframes with off-axis knee bracing had 35%, 50% and 65% less energy than the frames with coaxial knee braces during the fire and in the entire time period.


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