考虑氯离子侵蚀的近海桥梁结构地震易损性分析

Seismic Fragility Analysis of Offshore Bridge Structure Considering Chloride Erosion

分析氯离子侵蚀作用对近海桥梁结构抗震性能的影响,提出了近海桥梁时变地震易损性分析方法.以一座近海简支梁桥为例,基于概率方法得到氯离子侵蚀作用引起的纵筋直径和屈服强度、箍筋直径、保护层混凝土抗压强度随时间的退化规律,研究发现随着钢筋腐蚀程度增加,小剪跨比的桥墩会由弯曲破坏转变为弯剪或剪切破坏.基于OpenSees软件建立桥墩在不同服役时间考虑弯曲、粘结和剪切变形的有限元模型并进行Pushover分析和增量动力分析以评估腐蚀桥墩的抗震性能.定义腐蚀桥墩的损伤状态,评估各级损伤状态能力,通过易损性分析方法得到桥梁时变地震易损性曲线.研究结果表明,在氯离子侵蚀作用下,桥墩的材料性能不断退化,导致近海桥梁地震易损性随服役时间逐渐增长.

In order to analyze the effect of chloride ion corrosion on seismic performance of offshore bridge structures,a time-varying seismic fragility analysis method for offshore bridges was proposed.An offshore bridge of simply supported beam was taken as an example,the degradation law of longitudinal reinforcement diameter and yield strength,stirrups diameter and cover concrete compressive strength were obtained based on the probabilistic method,and the results show that the pier with small shear-span ratio changes from flexural failure to flexural shear or shear failure with the steel corrosion degree increasement.The finite element model of piers considering bending,bond-slip and shear deformation at different service time were established by OpenSees software,and pushover analysis and incremental dynamic analysis were carried out to evaluate the seismic performance of corroded pier.The damage states of corroded pier were defined and the damage states capacity was evaluated,then the time-varying seismic fragility curves of the bridge were obtained by the fragility analysis method.The results show that under the influence of chloride ion erosion,the material performance of the pier is degraded continuously,and the seismic fragility of the offshore bridge increases with its service time.