基于截面索温度等效的悬索桥耐火性能分析

Fire resistance analysis of suspension bridge based on temperature equivalence section

为分析悬索桥结构的耐火性能,提出基于分层截面索温度等效的耐火性能分析方法。首先基于传热理论推导平行钢绞线组成的索截面温度计算模型,并通过对比验证进一步建立简化的分层实心截面索的等效温度计算方法;然后建立等效强度的实心索桥梁结构有限元模型,根据等效强度计算方法确定受火部位主缆索的温升曲线,最后通过热力耦合分析实现悬索桥结构的火灾反应过程和耐火性能研究。通过此方法对某悬索桥进行耐火性能实例分析,结果表明:对于此悬索桥主缆4层索截面,在车辆火灾50 min之前存在明显的不均匀温度场。考虑索截面不均匀温度场时的整体桥梁结构反应与不考虑时存在明显区别。基于等效面积和等效强度的分层截面索温度等效方法能考虑索截面温度场的不均匀分布,同时简化索桥结构有限元模型以及避免整体索桥结构的复杂热传导分析,实现索桥结构耐火性能的全过程分析。

In order to analyze the fire resistance of suspension bridge structure,a fire resistance analysis method based on the equivalent temperature section is proposed.The temperature calculation model of cable section composed of parallel steel strands is deduced based on the heat conduction theory,and a simplified equivalent temperature calculation method is further established.Then the finite element model of the cable bridge with equivalent cable area is established,and the temperature rise curve of the main cable at the fire position is determined according to the equivalent temperature calculation method.Finally,the fire response process and fire resistance performance of the suspension bridge structure are studied through thermal coupling analysis.The results show that for the four⁃layer cable of the main cable of the suspension bridge,there is an obvious uneven temperature field before 50 minutes in the vehicle fire.There are obvious differences between the overall bridge structural response when considering the uneven temperature field of cable section and when not considering it.The layered cable temperature equivalent method based on equivalent area and equivalent strength can consider the uneven distribution of cable section,simplify the finite element model of cable bridge and avoid the complex heat conduction analysis of the whole cable bridge.