Steel-/Carbon Fiber-Reinforced Polymer-Prestressed Concrete Girders in Simulated Hydrocarbon Fire

This paper presents the implications of a hydrocarbon fire on the behavior of bridge girders prestressed with either steel strands or carbon fiber-reinforced polymer (CFRP) tendons. Stemming from a recent bridge fire that occurred in Lakewood, CO, numerical investigations are conducted employing a computational method called agent-based modeling to understand the intricate responses of these girders under thermomechanical loading. As the convection and radiation of surroundings are transformed to conductional thermal energy, the temperature of girder concrete rises, and the internal temperature differentials dwindle over time. Thermally induced damage in the prestressing elements is a function of distance from the surface heat. When loaded without thermal distress, the moment-carrying mechanism of the steel- and CFRP-prestressed girders is analogous; however, with the presence of heat, the development of lever arms and tensile strains of the girders demonstrates palpable differences. The maximum usable strains of the steel and CFRP vary with the degree of thermal exposure, thereby dominating the load-carrying capacity of the girders. From a design perspective, no evidence is noted to distinguish the performance of the steel- and CFRP-prestressed girders under service loadings, and contrary to commonplace notion, their fire ratings are found to be comparable because of sequential heat transfer.