Finite Element Analysis of steel frames subjected to post-earthquake fire

Abstract

Fire and post-earthquake fires pose a major hazard to our built environment. Industrial structures are generally steel structures and are many a times single storey. Risk of fire in an industrial building after an earthquake must be taken into consideration. Cascading combination of multiple hazards is essential to evaluate the real performance of a structure. The paper focused on the response of an unprotected steel frame subjected to post earthquake fire. Initially, the frame was analyzed for Earthquakes and Fire hazards independently. Time History analysis of the steel frame was carried out with the Base of Column subjected to Earthquake Time Histories. Frame damaged due to earthquakes was further subjected to Fire Hazard. Analysis for Gravity load was included in every type of Load case. Finite element tools have the ability to consider sequential loadings of Earthquake and then Fire. Fire analysis was performed considering the strength and stiffness reduction of carbon steel as per the IS800:2007. Bi-Linear stress–strain properties of steel were used considering the effect of temperature over them. The Beam-Column connections were considered rigid and Tie constraints were used to tie the surfaces of Beam to Column. The Joint Panel Zone was observed to suffer damage during the Earthquake Hazard, where the top of column was subjected to stress concentrations. Damage to the frame in a fire hazard was found to be very large compared to the damage due to earthquakes. The impact of these earthquakes on the Fire Ratings were observed considering the Post-Earthquake Fire Hazard.