Post-fire mechanical performance of modular GFRP multicellular slabs with prefabricated fire resistant panels

Investigation of the post-fire mechanical performance of large-scale glass fibre reinforced polymer (GFRP) structures assembled with prefabricated fire resistant panels is reported in this paper. The GFRP structures were four modular web-flange multicellular sandwich slabs fabricated of face panels and web box sections using adhesive bonding. Three sandwich slabs had fire resistant panels installed, either glass magnesium (GM) board, gypsum plaster (GP) board or calcium silicate (CS) board, at the outer face of the lower face panel using screws. These three specimens were exposed from the underside to an ISO 834 fire curve for up to 70–90 min and then cooled to room temperature. Subsequently they were tested in four-point bending and compared to the fourth specimen without fire exposure. The composite action between face panels and web box sections is discussed and the failure modes of specimens are identified. Importantly, the effects of fire resistant panels on the post-fire mechanical performance of the GFRP multicellular assemblies are highlighted and quantified. Analytical modelling is further developed to estimate post-fire bending stiffness and load-carrying capacity considering the recovery of resin after glass transition but before decomposition and the contribution from the remaining continuous rovings for the decomposed GFRP materials, with satisfactory agreement with the experimental results. It was demonstrated that the specimen with the glass magnesium board showed superior post-fire mechanical performance, with more than half of the post-fire stiffness and capacity remaining after 90 min fire exposure.