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为揭示多梁式混凝土T型梁桥的整体抗火性能,利用热-力耦合方法对5片混凝土T型梁桥火灾场形变和主拉应力进行了分析,研究了变区域桥面受火模式,分析了相对应各片梁跨中和两侧四分点断面横桥向挠度在延火前后期自重荷载作用下的空间变化规律及主拉应力分布规律。研究结果表明:桥面整跨火灾下多梁式混凝土T型梁桥梁肋反拱值较其他区域火灾下梁肋反拱值大,延火后期跨中边中肋挠差为四分点边中肋挠差的1.5倍,中肋呈余弦状波浪形;部分区域火灾下,近火源区域关键截面的边中肋挠差较远火源区域的边中肋挠差大,其最大比值可达4.0倍;不同火源区域模式下,延火后期跨中挠度始终保持挠度最大值;随延火时间的增加,混凝土T型梁桥在火荷载作用下顶板主拉应力由点条状分布状态逐渐交替发展,最终主拉应力区出现在梁肋下缘。
In order to reveal the overall fire resistance of multi-girder concrete T-Beam Bridges, the deformation and the main tensile stress of five concrete T-Beam Bridges were analyzed by using thermo-mechanical coupling method. The effects of fire mode , The spatial variation of transverse bridge deflection and the distribution of principal tensile stress under the self-supporting load before and after preheating were analyzed. The results show that the inverse arching of multi-girder concrete T-Beam bridge ribs under full span fire is larger than that of the other regions under fire across the bridge deck, and the mid- 1.5 times of the difference of the rib deflection, and the mid-rib has the shape of a cosine wavy. Under some regional fires, the deflection of the central rib in the critical section near the source region is larger than that in the far-source region, 4.0 times. Under different ignition source area modes, the mid-span deflexion of the late stage of post-fire maintains the maximum deflection all the time. With the increase of the delay time, the main tensile stress of the roof T-beam under the fire load gradually increases from point-like distribution Alternating development, the ultimate tensile stress zone appears in the lower edge of the beam rib.