高烈度区连续刚构桥弹塑性地震反应及断层走向影响研究

The elastic-plastic seismic response of continuous rigid frame bridge in high risk earthquake regions and the influence of fault strike

我国西部高烈度区建设了较多的连续刚构桥,部分临近活动断层。建立2座连续刚构桥Midas Civil有限元模型,选取10组脉冲型近断层地震动记录进行弹塑性时程分析,分析了断层走向对刚构桥地震反应的影响。断层走向与桥轴线夹角为75°~125°时,在纵桥向上主墩及主梁地震的反应最大,若不考虑断层走向的影响,则可能会低估20%;而横桥向最大位移则发生在0°~30°或150°~180°夹角范围之间。上述规律几乎未受加速度峰值(PGA)和桥梁墩高、跨度不同的影响。研究还发现,若不考虑断层走向的影响,对近断层地震动下桥墩塑性铰区的发生及位置存在较大的误判可能。

A large number of continuous rigid frame bridges have been built in the high intensity area of the western of China,some of which are near active faults.In this paper,software Midas Civil is used to establish two continuous rigid frame bridge models with different pier heights and spans.Ten groups of near-fault ground motions are selected for elastic-plastic time history analysis.The influence of fault strike on seismic response of rigid frame bridges is mainly studied.The results show that under the horizontal bidirectional near-fault ground motions,when the angle between the strike of the fault and the longitudinal bridge are 75°to 125°,the seismic response of the main pier and the beam in longitudinal bridge of the rigid frame bridge is the largest,which may be underestimated by 20%without regard to the effect of the strike of the fault.The maximum transverse displacement of the bridge occurs between 0°to 30°or 150°to 180°.The above law is almost not influenced by different peak ground accelerations(PGA)and the bridge piers height and span.The study also found that if the influence of fault strike is not considered,there is a great possibility of misjudgment on the occurrence and location of plastic hinge zone of piers under near-fault ground motions.