Author : Chiranjivee Hadole 1
Date of Publication :7th March 2017
Abstract: The occurrence of fire inside a building is an unexpected phenomenon and can break out at any time due to various reasons. Conflagrations following the 1906 San Francisco and 1923 Tokyo earthquakes lead to serious discussions among engineers about simultaneous safety of buildings against earthquake and fire. The correlative study of fire and earthquake can be done in two ways viz. structure subjected to fire following earthquake (post-earthquake fire) and fire affected structure subjected to an earthquake (Pre-earthquake fire). The present study focuses on seismic behaviour of building subjected to pre-earthquake fire. Often, buildings which are subjected to fire are made usable by performing non-structural and cosmetic repairs without proper seismic evaluation and retrofitting. In reality, the fire leads to material strength deterioration; however, the extent of reduction in strength depends on exposure time and temperature. Moreover, the reduction in overall strength of building is uncertain and therefore, the assessment of seismic performance of such fire affected structure becomes important. In this paper results of an analytical study on a five storey RC public building subjected to one hour standard fire is presented. The propagation of fire is considered in vertical direction (i.e. upward as well as downward direction) inside building. Seismic performance assessment of the fire affected models is performed by using non-linear static pushover (NSP) analysis. The lumped plasticity models of fire affected cross-sections are developed for various exposure durations for the standard fire as per Euro code (EC-2). Capacity curve results obtained from NSP shows that fire in bottom storey is more critical and capacity of structure reduces drastically with increase in exposure time. If building does not collapse during fire event, its post fire seismic performance assessment shall be made mandatory.
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