GFRP reinforced concrete slabs in fire: Finite element modelling

Abstract

In a fire incident, service loads are present when the structure is engulfed by the fire. This sequence of structural loading followed by the heat exposure is employed in the finite element (FE) modelling of GFRP reinforced concrete (RC) slabs. The FE model is validated against two sets of full-scale fire tests of GFRP RC slabs and one set of steel RC slabs. The FE model successfully predicts temperature distribution within the elements as well as the rapid thermal bowing deflections due to the temperature gradient within the depth of the slabs. The heat transfer analysis parameters were modified to achieve a realistic heat distribution in the unexposed zones. The paper discusses the various parameters in modelling of reinforced concrete in a fire and identifies the coefficient of thermal expansion (CTE) of the concrete and reinforcing bars as the most significant parameter in predicting the deflection behaviour in a fire. The FE modelling showed that stress in the GFRP reinforcing bars increases rapidly at the beginning of the fire (first 30 min) and becomes steady after that. The model is an effective tool to predict the required concrete cover and the unexposed anchor zones to achieve the desired fire resistance.