火灾对钢筋混凝土箱梁桥力学特性影响研究

Study on the Influence of Fire on the Mechanical Properties of Reinforced Concrete Box Girder Bridge

摘要: 对某钢筋混凝土箱梁桥火灾过程进行模拟，研究了火灾高温对钢筋混凝土箱梁桥的力学特性影响。通过查阅现场资料确定模型边界条件以及混凝土本构模型，同时考虑钢筋和混凝土的热工参数因高温影响而变化，在此基础上得出桥梁随时间和空间变化的温度场。将自重与车道荷载作用下火灾前和火灾后该钢筋混凝土箱梁桥力学参数进行比较，研究其力学变化规律，并通过静载试验对其规律进行验证。结果表明，对于小跨径钢筋混凝土箱梁桥受火后的温度场呈单峰状分布，且受火处温度达到峰值；对混凝土而言，由于直接与火源接触，材料受高温影响严重，其强度损失远高于钢筋；并由于各材料力学性能的退化，导致桥梁受火跨整体承载能力降低。

Abstract: The fire process of a reinforced concrete box girder bridge was simulated, and the influence of high temperature on the mechanical properties of reinforced concrete box girder bridge was studied. The boundary conditions of the model and the constitutive model of concrete are determined by consulting the field data, and the thermal parameters of steel and concrete are considered to change due to the influence of high temperature. On this basis, the temperature field of the bridge with time and space is obtained. The mechanical parameters of the reinforced concrete box girder bridge before and after fire under self-weight and lane load are compared to study its mechanical variation law, and the law is verified by static load test. The results show that the temperature field of small span reinforced concrete box girder bridge after fire is a sin-gle peak distribution, and the temperature at the fire reaches the peak value. For concrete, due to direct contact with the fire source, the material is seriously affected by high temperature, and its strength loss is much higher than that of steel bar; due to the degradation of the mechanical properties of each material, the overall bearing capacity of the bridge under fire is reduced.