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.

准确预测平行线股的温度对于确定索支撑桥梁的火灾引起的机械响应至关重要。本文基于传热基本理论建立了适用于平行线股截面温度场计算的理论公式，并验证了其准确性。建立了平行线股等效圆钢数值模型，利用理论公式和等效圆钢数值模型分析了ISO834火灾下平行线股截面的温度历程。结果表明，平行丝股段各层钢丝的加热规律基本相同，并且随着着火时间的增加都有接近火源温度的趋势。由于热阻的存在，平行线股段出现较大的温度梯度。由于空腔的影响，平行线股截面的温度场比其等效钢圆棒截面表现出更显着的不均匀分布。表明传统等效钢圆棒模型不能真实反映平行线股截面的不均匀温升特性。平行线股截面与其等效钢圆棒截面的表层钢丝温度非常接近。相比之下，内部钢丝的温差显着，即平行钢丝股段的温度梯度大于其等效钢圆棒段的温度梯度。