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为分析青藏铁路多年冻土区多跨简支梁桥地震响应情况,建立了一座10×32m箱形多跨简支梁桥三维全桥模型,以等效基础弹簧考虑桩-土相互作用;以具有初始间隙的并联弹簧-阻尼单元模拟伸缩缝两端结构的碰撞,研究了冻土融化深度、行波效应及碰撞效应对多跨简支桥梁结构地震响应的影响。结果表明:随着融土下限加深,等效基础弹簧刚度明显减小,在强地震动作用下,桥梁结构易发生落梁、桥墩倾覆等震害;当相邻碰撞体的相向位移超过伸缩缝宽度时两者发生碰撞,碰撞次数及碰撞力随地震动视波速及行进距离不同而不同,在行波波速较低且行进距离较小时碰撞效果明显,对桥梁地震响应影响较大,极易导致落梁;此外桥台对结构地震响应亦有显著影响。在对多年冻土区多跨简支梁桥抗震性能进行评估时,应特别重视夏季地震动低速行波时可能发生的震害。
In order to analyze the seismic responses of multi-span simply supported girder bridges in permafrost regions along the Qinghai-Tibet Railway, a three-dimensional full-bridge model of 10 × 32m box-shaped multi-span simply supported girder bridges is established and the pile-soil interaction is considered with equivalent base springs. The parallel spring-damper unit with initial clearance simulates the impact of the structure at both ends of the expansion joint. The influence of the thawing depth of frozen soil, the traveling wave effect and the collision effect on the seismic response of simply supported simply supported bridges is studied. The results show that with the lower limit of soil melting, the equivalent base spring stiffness decreases obviously. Under the action of strong ground motions, the bridge structure prone to earthquakes such as falling beams and bridge pier capsize. When the relative displacements of adjacent collision bodies exceed the expansion joints The width of the collision between the two, the number of collisions and impact force with the ground motion velocity and travel distance is different, low traveling wave velocity and the distance is small, the collision effect is obvious, a greater impact on the bridge seismic response, can easily lead to fall In addition, the abutment has a significant effect on the seismic response of the structure. In the assessment of the seismic performance of multi-span simply-supported bridges in permafrost regions, special attention should be paid to the possible damage caused by moving earthquakes at low speeds during summer earthquakes.