钢筋混凝土斜拉桥寿命期内整体极限承载力分析

Life-cycle evolution of the ultimate load carrying capacity of RC cable-stayed bridges

提出基于定期检测和健康监测技术的斜拉桥结构服役期内主梁整体失效模式及其极限承载力演化规律的分析方法,为结构的全寿命设计以及结构安全预警的分级提供理论依据。首先,利用结构的检测/监测数据,建立与实际结构状态相符的有限元模型,并分析构件的耐久性损伤,在此基础上计算考虑抗力退化的构件的极限承载力;然后,在有限元模型上施加逐级渐进的车辆荷载,分析各构件的内力状态;最后,将荷载效应超过抗力的主梁截面设置为塑性铰,改变结构体系,继续施加车辆荷载,直至结构承受的车辆荷载达到最大值,对应的变结构体系和车辆荷载分别为最终主梁整体失效模式和极限承载力。利用上述方法对我国北方某座干线斜拉桥在运营期内的4个典型状态进行计算分析,研究该桥在运营期内的失效模式及其极限承载力的演化规律。结果表明,所提出的方法可以获得在车辆荷载作用下斜拉桥主梁整体失效模式和相应的极限承载力;斜拉桥在服役过程中主梁开裂、钢筋锈蚀、边界条件变化等导致桥梁结构损伤、甚至结构体系及其相应的力学模型发生较大的变化,使结构失效模式及其极限承载力发生较大的变化。

The approach for analyzing the evolution of the failure pattern and the corresponding ultimate load carrying capacity （ULC） of reinforced concrete cable-stayed bridges based on inspection and monitoring was proposed. First, a finite element model of the structure was established using periodic inspection and monitoring data. The ultimate bearing capacity of components was calculated with consideration of durability. Then, the vehicle load was applied to the model to obtain the internal force of the girder components. Finally, the location that the load effects exceed the resistance capacity is set as plastic hinge and a variant model was obtained, furthermore, an increased vehicle load was applied to the variant model of the bridge, the load effects are re-calculate and another variant model was obtained. This procedure was continued until the vehicle load reaches the maximum value, which was just the ultimate load carrying capacity, and the corresponding variant model was defined as the failure pattern of the girder. A cable-stayed bridge was employed in the case study. Four representative states of the bridge were selected to demonstrate the evolution of failure pattern and ultimate load carrying capability based on the data of inspection and structural health monitoring using the proposed approach. Evolution of the failure pattern and ultimate load carrying capacity of the bridge during its service period were investigated. The results verified the feasibility of the proposed approach in analyzing the failure pattern and ultimate load carrying capability of the cable-stayed bridge under vehicle loads. The crack of girder, corrosion of steel bar, and change of boundary conditions may result in damage of the bridge and variation in structural analytical model, which have dramatic impact on the failure pattern and ultimate load carrying capacity of the structure.