不同场地条件地震作用下曲线桥振动台试验

Shaking table test of curved bridge under ground motion under different site conditions

摘要:

为研究不同场地条件地震对曲线桥结构响应的影响,以一座5%纵坡的曲线桥为研究对象,设计了缩尺比例为1∶10 的曲线桥缩尺模型,选取不同场地条件的地震波进行了振动台试验.研究结果表明:场地条件对曲线桥结构响应的影响显著,从Ⅰ类到Ⅳ类场地,曲线桥结构响应逐渐增大,双向地震激励下结构响应较单向激励显著；主梁结构响应具有空间性,顺桥向地震激励时,主梁平动的同时沿固定墩产生转动,横桥向地震激励时,主梁则以平动为主；曲线桥结构响应与曲线桥和主震方向的相对位置有关,平行于主震方向时,切向位移显著,垂直于主震方向时,径向位移更加敏感；桥墩位移方向与地震激励方向夹角越小,相应的位移响应越大.墩高越高,桥墩位移的放大作用越显著,固定墩切向位移对地震响应比较敏感；当曲线桥平行于主震方向单向激励时,低墩处支座容易脱落,双向激励和垂直主震方向时,高墩处支座容易脱落,在曲线桥抗震设计分析中应予以重视.

Abstract:

To study the effects of different site ground motions on curved bridges, a scale model of a curved bridge with the scale ratio of 1∶10 was designed by taking a curved bridge with 5% longitudinal slopes as the research object. Ground motions in different site conditions were selected for shaking table test. The results show that the influence of site conditions on the response of the curved bridge was significant. The structural response increased gradually with the site classification changing from I to IV. Compared to unidirectional input, the structural response under bidirectional input was obviously large. The structural response of the main girder was affected the directions of the excitation. When the bridge was excited by the ground motion in the longitudinal direction, the main girder moved horizontally androtated along the fixed pier simultaneously. When the bridge was excited by the ground motion in the transverse direction, the movement of main girder was mainly translational. The structural response of the curved bridge was related to the bridge arrangement and the direction of the principal seismic. When the curved bridge was parallel to the direction of the principal seismic, the tangential displacement response was remarkable. The radial displacement was more significant when it was perpendicular to the direction of the principal seismic. The smaller the angle between the displacement direction of the pier and the direction of the ground motion excitation was, the greater the displacement response of the pier became. The higher the pier height was, the more obvious the magnification of the displacement of the pier was, and the more sensitive the tangential displacement of the fixed pier was to the seismic response. When the curved bridge was parallel to the direction of the principal seismic in unidirectional input, the bearing of the low pier was easy to fall off. When bidirectional input and the curved bridge were perpendicular to the direction of the principal seismic, the high pier was easy to fall off. Therefore, much attention should be paid to the seismic design and analysis of curved bridges.