近断层脉冲地震作用下曲线梁桥振动台试验研究

Shaking table test research for curved rigid bridge under near-fault pulse ground motions

为了研究近断层脉冲地震作用下曲线桥结构响应特点,设计了相似比为1∶10的曲线桥试验模型.选取近断层向前方向性效应、滑冲效应和无速度脉冲地震动,进行水平地震激励的振动台试验.结果表明,近断层脉冲地震作用下曲线桥的结构响应明显高于无速度脉冲地震.向前方向性效应地震作用下跨中径向位移和桥墩相对位移响应显著.近断层地震作用下跨中切向位移、梁端位移、支座位移响应与曲线桥和断层的相对位置有关.主梁位移响应具有空间特性,主梁在水平运动的同时兼有转动,近断层脉冲地震双向激励时易激发主梁的转动效应.主梁转动效应使低墩处梁端位移和支座位移更加显著,容易引起落梁和支座脱落.在抗震设计分析中,应考虑近断层脉冲地震作用以及曲线桥与断层相对位置关系对结构响应的影响.

To study the structure response of curved bridges under the action of near-fault pulse ground motion,a test model for a curved bridge with the similar ratio of 1 ∶ 10 was designed. The shaking table tests of horizontal seismic excitation with the forward-directivity effect,the fling-step effect and the non-speed pulse records were carried out, respectively. The results show that the structural response of the curved bridge under the near-fault pulse effect ground motion is significantly higher than that with non-speed pulse ground motion. The radial displacement of the mid-span and the relative displacement of the piers under the forward-directivity effect ground motion are obvious. The tangential displacement of the mid-span, the displacement of the beam end, and the displacement of the bearings under the near-fault ground motion are related to the relative position between the curved bridge and the fault. The displacement response of the main girder has spatial characteristics, and the main girder rotates while moving horizontally. The rotation effect of the main girder is excited easily by the bidirectional excitation of the near-fault pulse ground motion. The rotation effect of the main girder makes the beam end displacement and the bearing displacement more obviously at the low pier, which can cause the girder to fall and the bearing to shed. In seismic design and analysis, the effects of the near-fault pulse ground motion and the relative position relationship between the curved bridge and the fault on the structural response should be considered.