Post‐earthquake fire resistance of CFRP strengthened reinforced concrete structures

Abstract

SUMMARYPost‐earthquake fire (PEF) presents a high risk to buildings that have been partially damaged in a prior earthquake, particularly in urban areas. As most standards and criteria ignore the possibility of fire after earthquake, buildings are not adequately designed for that possibility, and thus, PEF is a high‐risk load needed to be scrutinized further, codified and become part of a routine design. An investigation based on sequential analysis inspired by FEMA356 is performed here on two RC frames, of three and five stories, at the Life Safety performance level and designed to the ACI 318‐08 code, after they have been subjected to a spectral peak ground acceleration of 0.35 g. A fire analysis of the weakened structures follows, from which the time it takes for the damaged structures to collapse is determined. As a point of reference, the fire resistance is also determined for undamaged structures and before the occurrence of earthquake. The results show that structures previously damaged by the earthquake and exposed to PEF are considerably more vulnerable than those that have not been damaged previously. A method using carbon fiber‐reinforced polymer as a means of relocation of plastic hinges away from the column faces towards the beams is introduced as a function of the time required for fire extinguishment or evacuation. This is carried out to increase the structural load‐carrying capacity, thus reducing the potential damage for the anticipated earthquake and thereby improve the PEF resistance. The results show a considerable improvement in the PEF resistance of the frames. While the investigation and the proposition relate to a certain class of structures (ordinary buildings, intermediate RC structures, three and five stories) and the results can therefore be applied only to the cases investigated, it is hoped that this study paves the way for further research into this very important phenomenon and leads to an eventual revision of codes. Copyright © 2013 John Wiley & Sons, Ltd.