考虑材料性能劣化的桥墩地震易损性分析

Seismic Vulnerability Analysis of Bridge Pier Considering Material Deterioration

为分析材料性能劣化对桥墩抗震性能的影响,基于氯离子侵蚀机理以及钢筋锈蚀原理,得到了混凝土以及钢筋的力学性能退化规律,根据地震易损性原理,通过位移延性比确定了桥墩的损伤指标,以此构建了考虑材料性能劣化的桥墩地震易损性模型,以百崎湖大桥为工程实例,选取了36条符合场地条件的地震波,对考虑材料性能退化的桥墩地震进行了分析,基于此建立了桥墩在不同服役年限下的地震易损性曲线。研究表明:桥墩服役时间越长,其达到各损伤状态的超越概率显著增加;桥墩在轻微损伤、中度损伤、严重损伤之间的超越概率差明显小于严重损伤与完全破坏之间的超越概率差,表明桥墩在轻微损伤、中度损伤、严重损伤之间的延性能力要小于其在严重损伤与完全破坏之间的延性能力;桥墩在服役51~75年之间的地震易损性曲线间隔明显大于服役0~25年、26~50年以及76~100年之间的间隔,即桥墩在51~75年间的超越概率增加明显,表明此阶段锈蚀导致钢筋以及混凝土的力学性能显著降低,导致其抗震性能下降明显。

In order to analyze the influence of material deterioration on the seismic performance of bridge piers,based on the chloride ion erosion mechanism and the steel bar corrosion principle,the mechanical property degradation law of concrete and steel bars is obtained.According to the seismic vulnerability principle,the damage index of bridge piers is determined through the displacement ductility ratio,and the seismic vulnerability model of bridge piers is constructed considering material deterioration.Taking Baiqihu Bridge as an engineering example,36 seismic waves conforming to site conditions are selected to analyze the seismic response requirements of piers considering material property degradation.Based on this,the seismic vulnerability curves of piers under different service life are established.The results show that the exceedance probability of the pier reaching each damage state increases significantly with longer service time.The exceedance probability difference between minor damage,moderate damage and severe damage is significantly smaller than that between severe damage and complete damage,indicating that the ductility of piers between minor damage,moderate damage and severe damage is smaller than that between severe damage and complete damage.The interval of seismic vulnerability curves between 51 and 75 years of service is significantly greater than that between 0 to 25 years of service,26 to 50 years and 76 to 100 years of service,that is,the exceedance probability of bridge piers during 51 to 75 years of service increases significantly,indicating that corrosion at this stage leads to a significant decrease in the mechanical properties of steel bars and concrete,resulting in a significant decline in seismic performance.