不同火灾规模下地下共用结构安全性研究

为探明在不同火灾规模下地下共用结构的整体安全性，进而为类似地下结构防火设计提供参考依据，以义乌商城大道隧道工程为依托，采用有限元软件ANSYS建立火灾下地下共用结构非线性瞬态热-力耦合分析模型，重点研究地下共用结构在不同火灾规模下的位移、应力变化规律以及结构各截面的安全系数。研究结果表明： 1）隧道内火灾规模的扩大会使混凝土力学性能劣化程度愈加严重，在地层荷载作用下受火结构顶板位移急剧增大，而其相邻水平共用结构顶板位移逐渐减小，进而改变共用结构的整体变形形态；且火灾高温作用会使得隧道共用结构发生应力重分布，其应力变化程度随火灾规模的增大而显著增大。2）隧道内大型客车发生火灾时，受火结构对其相邻的水平共用结构应力及安全性有较大影响，而对竖向共用结构影响较小，但可保证共用结构整体安全。

Study on Safety of Underground Combined Structures under Different Fire Scales

In order to clear the holistic safety of the underground combined structure under different fire scales, and provide reference for the fire protection design of tunnel structures, a non linear transient thermal mechanical coupling analysis model for the underground combined structure of Shangcheng Avenue Tunnel in Yiwu under fire is established by using finite element software ANSYS; the variation laws of the displacement and stress of the underground combined structure under different fire scales are studied; and the safety factor of each cross section of the tunnel structure is analyzed as well. The results show that: （1） The increasing fire scale in the tunnel will deteriorate the mechanical properties of the concrete more seriously, and the displacement of the roof of the fire affected structure will increase sharply under loading effect; nonetheless, the displacement of the roof of the adjacent horizontal combined structure decreases gradually, which will change the holistic deformation form of the combined structure; the stress redistribution occurs in the underground combined structure under fire, and the degree of changing stress will increase significantly with the increase of the fire scale. （2） When a megabus in the tunnel is ignited, the fire affected structure has a greater impact on the stress and safety of the adjacent horizontal combined structure, but a smaller impact on the vertical combined structure, which still ensures the holistic safety of the underground combined structure.