Study of Temperature Field Inhomogeneities in Parallel Wire Strand Sections under ISO834 Fire

An accurate prediction of temperatures of parallel wire strands is essential to determine the fire-induced mechanical responses of cable-supported bridges. In this paper, the theoretical formula applicable to the temperature field calculation of parallel wire strand sections is established based on the basic theory of heat transfer, and its accuracy is verified. An equivalent steel round bar numerical model of the parallel wire strand is established, and the temperature history of the parallel wire strand section under ISO834 fire is analyzed using the theoretical formula and the equivalent steel round bar numerical model. The results show that the heating law of each layer steel wires of the parallel wire strand section is basically the same and all have a tendency to approach the fire source temperature with the increase of fire time. Due to the existence of thermal resistance, large temperature gradients occur in the parallel wire strand sections. The temperature field of the parallel wire strand section shows more significant inhomogeneous distribution than that of its equivalent steel round bar section due to the influence of the cavities. It indicates that the traditional equivalent steel round bar model does not genuinely reflect the inhomogeneous temperature rising characteristics of the parallel wire strand section. The temperature of the surface layer steel wires of the parallel wire strand section and its equivalent steel round bar section is very close. In contrast, the temperature difference of the inner steel wires is significant, i.e., the parallel wire strand section has a larger temperature gradient than its equivalent steel round bar section.