Postfire Performance of GFRP Stay-in-Place Formwork for Concrete Bridge Decks

Abstract

This study focuses on the fire performance of glass fiber–reinforced polymer (GFRP) stay-in-place structural formwork used for the rapid construction of reinforced concrete (RC) bridge decks and serves to direct future studies on the matter. Seven beam sections of a concrete deck reinforced using a GFRP stay-in-place form are tested. The beams in this study are subjected to both fire and simulated-fire damage and tested in four-point bending to assess the mechanical contribution of the GFRP stay-in-place formwork. Fire damage was applied to one beam via a 14.5-min heptane pool fire. Experimental results show that the simulated damage was an overly conservative representation of the fire damage sustained. The fire damage was insufficient to reduce the ultimate load or change the failure mode of the specimen when compared to an undamaged control. The embedded T-rib of the GFRP form was protected from fire damage and provided redundancy to the system. Despite a char thickness of about 15% of the base thickness, the GFRP base plate was able to protect the adjacent concrete from temperatures exceeding 100°C. An increased flexural capacity was observed in the fire-damaged specimen hypothesized to be a result of concrete precompression arising from the heating and cooling of the GFRP formwork. A series of direct bond shear tests between GFRP–concrete samples at elevated temperatures found a decrease in bond shear stress and bond stiffness as bond temperatures increased.