考虑氯离子侵蚀与冲刷作用的桥梁抗震韧性分析

Seismic Toughness Analysis of Bridge Considering Chloride Ion Erosion and Scouring Effect

为分析氯离子侵蚀与冲刷作用下的桥梁抗震韧性,根据氯离子侵蚀机理,得到了氯离子侵蚀下的材料性能退化规律,构建了桥墩冲刷深度的计算模型,基于地震易损性理论提出了桥梁抗震韧性分析方法。以国内某跨河梁桥为工程实例,分别分析了该桥在氯离子侵蚀下、冲刷作用下及氯离子侵蚀与冲刷共同作用下的桥墩地震易损性与抗震韧性,研究表明:随着服役年限的增加,桥墩冲刷深度不断增加,氯离子侵蚀桥墩程度不断加重,桥墩在各损伤状态下的超越概率也不断增加;冲刷作用较氯离子侵蚀作用对桥墩地震易损性的影响更严重,考虑氯离子与冲刷共同作用下的桥墩超越概率要略小于仅考虑冲刷作用的桥墩超越概率;随着地震强度(PGA)的增大,桥墩的抗震韧性不断减小,并且当PGA较小时,抗震韧性下降较快,PGA较大时,抗震韧性趋于平缓,减速为先快后慢,表明大震作用下,桥墩抗震韧性已达到极限;随着桥梁服役时间的增加,仅考虑冲刷作用、仅氯离子侵蚀及两者共同作用下的桥墩抗震韧性均有不同程度下降,其中冲刷作用较氯离子侵蚀作用对桥墩抗震韧性影响更为明显,两者共同作用下的桥墩抗震韧性小于仅考虑冲刷作用或仅考虑氯离子侵蚀作用下的抗震韧性。

In order to analyze the seismic toughness of bridge under chloride ion erosion and scouring effect,the degradation law of material properties under chloride ion erosion was obtained according to the chloride ion erosion mechanism,and the calculation model of pier scouring depth was constructed.Based on the seismic vulnerability theory,the seismic toughness analysis method of bridge was proposed.Taking a river-crossing girder bridge in China as an engineering example,the seismic vulnerability and seismic toughness of the bridge piers under chloride ion erosion,scouring effect and combined action of chloride ion erosion and scouring effect are analyzed respectively.The research shows that:with the increase of service life,the scouring depth of pier increases,the degree of chloride ion erosion of pier increases,and the overrunning probability of pier under different damage conditions increases.The impact of scouring effect on seismic vulnerability of pier is more serious than that of chloride ion erosion.The overtaking probability of pier considering chloride ion erosion and scouring effect is slightly lower than that considering only scouring effect.With the increase of earthquake intensity(PGA),the seismic toughness of pier decreases continuously,and when PGA is small,the seismic toughness decreases rapidly,and when PGA is large,the seismic toughness tends to be flat,and the deceleration is first fast and then slow,which indicates that the seismic toughness of pier has reached the limit under the action of large earthquake.With the increase of bridge service time,the seismic toughness of piers only under the consideration of scouring effect,chloride ion erosion and their combined action decreases to varying degrees.The seismic toughness of piers under the scouring effect is greater than that under the consideration of chloride ion erosion,and the seismic toughness of piers under the combined action is smaller than that under the consideration of scouring effect or chloride ion erosion.