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箱梁容易在支座、1/4跨及跨中位置出现裂缝,箱梁开裂病害与箱梁过量下挠相互耦合,其作用机理较为复杂,评估箱梁过量下挠的难点在于箱梁裂后的刚度分布特性研究。为了有效评估箱梁裂后刚度,制作了大比例尺预应力混凝土连续箱梁模型,开展了反复荷载作用下的箱梁破坏性试验,分别采用两种方法开展了箱梁裂后刚度分布特性研究。第一种方法,结合试验数据,基于Levenberg-Marquardt优化算法,对已测试得到的不同开裂程度下的挠度进行刚度分布反演;第二种方法,基于模型试验测试的荷载挠度曲线直接建立刚度折减评估参数,对开裂后箱梁的刚度损伤分布进行统计分析。对比分析了两种方法计算得到的箱梁裂后刚度纵向分布特征,验证了评估结果的有效性。研究结果表明:箱梁裂后开裂区域的刚度折减系数以加载位置为参考点,其余部位的刚度损伤沿箱梁纵向呈线性分布。提出了箱梁裂后刚度损伤计算方法。该研究可对开裂后箱梁的服役性能评估提供了理论参考。
The box girder is easy to crack in the support, 1/4 span and mid-span. The cracking of the box girder and the excessive bending of the box girder are mutually coupled, and the mechanism of action is complex. The difficulty in assessing the excess deflection of the box girder lies in the crack of the box girder, Stiffness distribution characteristics of. In order to effectively evaluate the post-box stiffness of the box girder, a large-scale prestressed concrete continuous box girder model was made and the box girder destructive test under repeated load was carried out. The stiffness distribution characteristics of the box girder after cracking were studied by two methods respectively. The first method, combined with the experimental data, is based on the Levenberg-Marquardt optimization algorithm to conduct the stiffness distribution inversion of the deflection under different degrees of cracking that has been tested. The second method, based on the load deflection curve of the model test, By subtracting the evaluation parameters, the stiffness distribution of box girder after cracking was statistically analyzed. The longitudinal distribution characteristics of the box girder stiffness calculated by the two methods are compared and analyzed, which verifies the validity of the evaluation results. The results show that the rigidity reduction coefficient of box girder in cracked area takes the loading position as the reference point, while the stiffness damage in the other parts is linearly distributed along the longitudinal direction of box girder. The calculation method of box girder stiffness after damage is proposed. This research can provide a theoretical reference for service performance evaluation of cracked box girders.