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针对受火后混凝土箱梁悬臂板的挠变与塌裂耦合灾害,利用热-力耦合方法对局部火灾模式下混凝土箱梁高温场、悬臂板变形及有效分布宽度进行了分析,研究了混凝土箱梁单侧局部火灾高温强热模式,计算了此模式下混凝土箱梁横桥向和纵桥向温度场的分布状态,分析了迎火面和背火面悬臂板变形和有效分布宽度随延火时间与荷载比的变化规律。研究结果表明:箱梁单侧腹板和翼缘板下侧受火,迎火面温度相对其他部位较高,背火区温度无变化,火温从箱形截面外侧到内侧呈明显的半渗层状梯度分布;顺桥向温度梯度线以强热区为中心沿跨径呈层流状分布,火灾的局部效应显著;迎火面悬臂板挠度随延火时间的增加逐渐增大,背火面悬臂板挠度随延火时间的增加直线下降,迎火面悬臂板挠度变化趋势明显大于背火面悬臂板挠度的变化趋势,并且挠度随荷载比的增加呈非线性增长关系;迎火面悬臂板有效分布宽度随延火时间的增加而减小,背火面悬臂板有效分布宽度随延火时间的增加而增大。研究可为桥梁的抗火设计实用方法的提出与火灾后桥梁加固提供依据。
In the light of the coupled deformation of the cantilever plate and the collapse and collapse of the concrete box girder subjected to fire, the high temperature field, the deformation of the cantilever plate and the effective distribution width of the concrete box girder in the partial fire mode are analyzed by means of the thermo-mechanical coupling method. The temperature distribution of the concrete box girder in both transverse and longitudinal directions was calculated and the deformation and effective distribution width of the cantilever facing the fire and the backfire were analyzed. Time and load ratio changes. The results show that the single side of the box girder and the flange on the lower side of the fire, the fire face temperature relative to other parts of high temperature, backfire zone temperature did not change, the fire temperature from the box cross-section to the inside of the obvious semi-permeability Stratified gradient distribution; along the bridge to the temperature gradient line to the strong hot zone as the center along the span is laminar flow distribution, the local effect of fire significant; fire cantilever deflection increases with increasing delay time, backfire The deflection of the cantilever plate decreases linearly with the increase of the delay time, and the deflection of the cantilever plate at the reheating surface is obviously larger than the deflection of the cantilever plate at the backfire surface. The deflection increases nonlinearly with the increase of the load ratio. The effective distribution width of the plate decreases with the increase of the extension time, and the effective distribution width of the cantilever plate increases with the increase of the extension time. The research can provide the basis for the practical method of fire-resistant design of bridges and the reinforcement of post-fire bridges.