中文摘要：

为研究钢-混组合箱梁受火时的挠度变化、破坏模式和耐火时间,以某钢-混组合简支箱梁为背景,采用ANSYS软件建立有限元模型,计算不同受火工况和火灾场景下梁跨中截面的温度场,分析梁的挠变规律和破坏模式,研究其耐火极限。结果表明：钢箱底板受火时,梁的跨中挠度呈线性增加趋势;腹板受火时,挠度很快进入大幅增长阶段;钢箱底板受火时,梁随受火时间逐渐下挠而破坏;腹板受火时,梁发生翘曲,受火侧腹板屈曲,两侧和一侧腹板受火时,梁分别发生对称变形和单侧翘曲;同一火灾场景下,腹板受火时梁的耐火时间比钢箱底板受火时大幅减小;受火位置相同时,HC火灾下梁的耐火时间比ISO834火灾下的耐火时间明显缩短;在设定的延火时间内,External和Design火灾下梁未破坏。

英文摘要：

To study the deflection changes, failure modes and fire resistance time of the sim-ply-supported steel and concrete composite box girder exposed to the fire, a composite box girder of the same kind was selected as an example and the software ANSYS was used to build up the fi-nite element model for the girder. The temperature fields of the midspan section of the girder un-der the different fire cases and fire scenarios were calculated, the laws of the deflection changes and the failure modes of the girder were analyzed and the fire resistance limit was studied. The results of the study show that when the bottom plate of the steel box the girder is exposed to the fire, the midspan deflection of the girder exhibits the tendency of linear increment and when the web of the girder is exposed to the fire, the deflection rapidly comes to the stage of substantial increase. When the bottom plate is exposed to the fire, the girder deflects gradually and fails with the pass-ing of the time that the bottom plate has been exposed to the fire and when the web is exposed to the fire, the girder warps and the side of the web that is directly exposed to the fire buckles. Whenthe webs on the two sides and the web on the one side are exposed to the fire, the girder respec-tively deforms symmetrically and warps on the one side. In the same fire scenario, the fire resist-ance time of the girder when its web is exposed to the fire is greatly shortened as compared to that of the girder when its bottom plate is exposed to the fire. In the same position of the fire, the fire resistance time of the girder under the HC fire is obviously shorter than that of the girder under IS0834 fire. In the set fire duration, the girder under the External and Design fire does not fail.