油罐车火灾下钢？不熳楹狭？续箱梁-性能及失效机理
Performance failure of steel？？concrete composite continuous？？box girder exposed to tanker fire

针对钢？不熳楹狭？续箱梁在油罐车火灾下性能退化过程，以两跨钢？不熳楹狭？续箱梁为研究对象，采用热？擦？耦合计算方法，基于ANSYS软件建立有限元模型，在温度场中提取研究截面的控制点温度值，分析油罐车火灾下钢？不熳楹狭？续箱梁的温度场分布特点，得到其火灾下的竖向温度梯度，获得热？擦？耦合作用下所研究关键截面的荷载？参灰魄？线，揭示油罐车火灾下两跨钢？不熳楹狭？续箱梁极限承载力的衰减规律，并分析不同桥梁火灾场景下两跨钢？不熳楹狭？续箱梁的破坏过程。研究结果表明：桥下火灾时，钢？不熳楹狭？续箱梁的钢箱梁部位整体升温剧烈，根据距火源远近，钢梁温度从高到低依次为底板、腹板、翼板，混凝土整体升温幅度较小；桥面火灾时，混凝土板整体升温较桥下火灾时大，钢梁部位升温较桥下火灾时小，不同桥梁火灾场景下受火断面沿梁高方向均呈现较大的温度梯度；桥下火灾时极限承载力丧失较桥面火灾时更为严重，受火25 min中支点附近受火极限承载力丧失95%以上，跨中受火时丧失约68%，边支点受火时丧失约64%，中支点附近受火发生屈曲破坏，跨中受火及边支点受火发生弯曲破坏；桥面受火25 min极限承载力丧失较少，仅为29%，由于混凝土隔热作用显著，钢梁性能退化较少，最终在跨中位置形成塑性铰。
To investigate the performance failure of steel？？concrete composite continuous box girders when exposed to tanker fire, ANSYS finite element model of a two？？span steel？？concrete continuous composite box girder bridge was built using the thermo？？structural coupling analysis method. For a scenario that assumed the box girder was exposed to tanker fire, the model simulated the temperature at important points on the test section and the vertical temperature gradient of the box girder. In addition, the distribution of the temperature field of the girder was analyzed, and the load displacement of the test section and attenuation of the ultimate bearing capacity of the girder were obtained. Furthermore, the failure process of the box girder was analyzed under two different fire scenario The result shows that, when the fire occurs beneath the bridge, the entire steel girder heats up quickly, the base plate attains the highest temperature because its proximity to the fire, followed by the web plate, and then the flange plate. The temperature of the concrete changes minimally. When the fire occurs above the bridge, the concrete attains a higher temperature than that of the case where the fire occurs beneath the bridge, and the temperature of steel girder is lower. The cross section of the box girder indicates a large vertical temperature gradient. The reduction in the ultimate bearing capacity of the bridge is more substantial when the fire occurs beneath the bridge than when it occurs above the bridge. In addition, after the fire burns for 25 min, the ultimate bearing capacity decreases by more than 95% at the middle fulcrum, by about 68% at mid？？span, and by about 64% at the side fulcrum. Furthermore, buckling failure occurs at the middle fulcrum, bending failure occurs at mid？？span and at the side fulcrum. When the fire occurs above the bridge, the ultimate bearing capacity at mid？？span reduces by only 29% due to thermal insulation by the concrete and less heat impact on the steel girder. In addition, a plastic hinge occurs at