独塔宽幅斜拉桥基于能力需求比的抗震性能评估

Seismic Performance Assessment of Cable-Stayed Bridge with Single Pylon and Wide Deck Based on Capacity Demand Ratio Method

为研究独塔宽幅斜拉桥在设计地震下的抗震安全及其地震易损性,基于能力需求比提出了一种新的抗震评估流程,建立了与桥梁整体抗震性能关联的3个水平性能目标,根据纤维有限元法和Priestley等效原则提出了混凝土构件的3个水平抗震能力计算方法,并构建了典型构件的能力需求比计算公式,最后采用该流程对某独塔宽幅斜拉桥进行两水准抗震评估及地震易损性评估。结果表明:该桥在现行规范两水准地震下的安全储备较低,横桥向会形成多个抗震薄弱环节;随着地震动的增大,2号墩分别在0.20g、0.25g、0.30g时出现纵筋屈服、塑性变形和局部破坏机制,是全桥最易损伤的构件。评估结果说明基于能力需求比的评估流程既可结合规范进行抗震复核,又能捕捉不同水准地震下桥梁的损伤位置及程度。

To study the seismic safety and seismic vulnerability of the cable-stayed bridge with a single pylon and wide deck under the designed earthquake, a new flow chart of seismic performance assessment of the bridge was proposed based on the capacity demand ratio method. 3 levels of the performance targets associated with the global seismic performance of the bridge were established and according to the fiber finite element method and the Priestley equivalent rules, the calculation methods for the 3 levels of the seismic capacity of the concrete components of the bridge were provided, the formulas of the capacity demand ratios for the typical components were derived and finally, the new flow chart was used to assess the 2 levels of the seismic performance and seismic vulnerability of an example cablestayed bridge with a single pylon and wide deck. The results of the assessment suggest that according to the 2 levels of the ground motion in the current code, the safety margin of the bridge is low and the bridge may have a number of the seismic vulnerability in its transverse direction. With the increase of the ground motion, the longitudinal reinforcement yield , plastic deformation and local damage mechanism of the pier No. 2 of the bridge will take place respectively at 0. 20g , 0. 25g and 0. 30g and the pier is the most vulnerable component of the whole bridge. The results of the assessment also show that the flow chart of the seismic performance assessment based on the capacity demand ratio method can be not only used to check the seismic resistance of the bridge, but also can capture the damage locations and degrees of the bridge under the different levels of ground motion.