城市综合管廊火灾温度场分布及结构损伤数值模拟

Numerical Simulation of the Fire Temperature Distribution Field and Structural Damages in an Urban Utility Tunnel

为了对火灾下城市综合管廊的消防及其结构设计提供一定参考依据,文章以义乌商城大道地下综合管廊工程为依托,采用三维火灾动力学模拟软件FDS5.0建立高压电力舱火灾模型,针对电缆火灾对其舱室内部火灾发展过程及温度分布进行模拟研究。并将300℃作为混凝土结构高温损伤的临界条件,通过ANSYS有限元软件对舱室结构进行热分析,得到火灾下管廊结构温度场分布以及结构高温损伤深度。研究结果表明,若电缆舱室内下层电缆发生火灾时,其同侧上部电缆和另一侧电缆将先后被引燃,火势迅速扩大,其火灾最大热释放速率为11.5MW;且电缆燃烧范围相比于整个防火分区较小,可采用密闭自熄方式并辅以自动灭火系统进行火灾处理,属通风控制型火灾;在短期电缆火灾作用下,舱室内电缆燃烧使管廊结构形成了温度梯度较大的非线性温度场,且仅在一定范围内对结构造成高温损伤。

In order to provide certain reference for the fire protection and structural design of the urban utility tunnel under the fire scenario, based on the Shangcheng Avenue urban utility tunnel project, a three-dimensional fire dynamics simulation software FDS5.0 was used to establish the fire model of high voltage power cabin, and simulated the fire development process and temperature distribution in the cabin under the cable fire. Meanwhile, taking 300% as the critical temperature of concrete damages, and carrying out the thermal analysis of the cabin structure by using the finite element software ANSYS, the temperature distribution of the structure and the structural damage degree at elevated temperature were obtained, providing a certain basis for the design of structure and fire protection of urban utility tunnel. The research results show that： if the bottom cables were in fire in the cable cabin, the cables on the same side and the other side would be ignited successively, and the scale of fire would expand rapidly. The maximum heat release rate of the cable cabin under a fire is 11.5 MW. Moreover, the cable burning range is smaller than the entire fire compartment. It was reasonable to use the closed self-extinguishing mode and automatic fire extinguishing system for fire suppression, and the fire is of the ventilation controllable type. Under the action of short-term cable fire, a non-linear temperature field with a large temperature gradient in the cabin structure is formed, only causing heat damage to the structure within a certain range.