Structural response of liquid-cooled GFRP slabs subjected to fire – Part I: Material and post-fire modeling

Temperature-dependent material properties of glass fiber-reinforced polymer composites were derived from tests performed on the material itself, from references concerned with similar polymer materials and from observations during full-scale fire experiments on load-carrying slabs for building and bridge applications. Effective material properties were determined, which include the effects of evaporation of absorbed moisture, endothermic decomposition of the resin, the shielding effect of delaminated fiber layers, and the loss of glass fiber layers beyond their softening temperature. Two types of post-fire models have been developed: a two-layer model and a three-layer model. Results from the two-layer model showed that the determination of the boundary between the two layers by visual inspection leads to a considerable overestimation of the remaining stiffness of the specimens. However, the stiffness prediction based on a boundary at the depth of the glass transition temperature corresponded well with the results from post-fire measurements. Similar accuracy was obtained for the post-fire behavior prediction using the two-layer model and a more complicated three-layer model with an intermediate partially-degraded layer.