Cable-supported structures such as bridges and stadia are critical for the surrounding community and the consequences arising from a major fire event can be substantial. Previous computational studies into the thermal response of cables often employed simplistic heat transfer models that assumed lump capacitance or cross-sectional homogeneity without proof of validity. This paper proposes a methodology for calculating the thermal response of a cable cross-section allowing for heat transfer by conduction through each strand contact surface and radiation across inter-strand cavities. The methodology has been validated against two experiments of cables subjected to radiant heating and an input sensitivity analysis has been undertaken for the heat transfer and material parameters. The approach is compared against simple heat transfer lumped methods for a parallel-strand cable where it is shown that these lumped models are not always conservative. The model is then coupled with a two-dimensional generalised plain strain model to study the likely effect of the cross-sectional temperature gradients on the mechanical response. The study considers three qualitatively different hydrocarbon jet fire scenarios, both with and without external insulation for fire protection. It is shown that the proposed methodology can reproduce realistic cross-sectional temperature distributions with up to 50% temperature difference at the cable external surface and can capture the phenomenon of load shedding in a gradually heated cable. It is also shown that assuming a lumped thermal mass neglects the possibility of moment-inducing temperature gradients which are not considered in the ambient design of cables that is driven by tensile capacities. The proposed model and its predictions contribute towards an improved understanding and a more informed structural design of cable-supported structures in fire.

中文翻译：

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结构索在火灾中的热机械响应分析

桥梁和体育场等电缆支撑结构对周围社区至关重要，重大火灾事件造成的后果可能是巨大的。以前对电缆热响应的计算研究通常采用简单的传热模型，这些模型假设集总电容或横截面均匀性，而没有有效性证明。本文提出了一种计算电缆横截面热响应的方法，该方法允许通过每个绞线接触表面的传导和跨绞线间腔的辐射进行热传递。该方法已经针对经受辐射加热的电缆的两个实验进行了验证，并且已经对传热和材料参数进行了输入灵敏度分析。该方法与平行绞线电缆的简单传热集总方法进行了比较，结果表明这些集总模型并不总是保守的。然后将该模型与二维广义平面应变模型相结合，以研究横截面温度梯度对机械响应的可能影响。该研究考虑了三种性质不同的碳氢化合物喷射火灾场景，包括有和没有外部防火隔热材料。结果表明，所提出的方法可以在电缆外表面以高达 50% 的温差重现真实的横截面温度分布，并且可以捕获逐渐加热的电缆中的减载现象。还表明，假设集总热质量忽略了引起力矩的温度梯度的可能性，这在由抗拉能力驱动的电缆的环境设计中没有考虑。所提出的模型及其预测有助于提高对火灾中电缆支撑结构的理解和更明智的结构设计。