毗邻边坡连续刚构梁桥地震位移和加速度分析

Seismic Displacement and Acceleration Analyses of a Continuous Rigid Frame Bridge Adjacent to Slope

建立毗邻边坡的连续刚构梁桥三维有限元动力计算模型,分析结构体系自振特性,计算刚构连续梁桥结构体系主要特征点的地震位移和加速度反应,并与桥梁实际地震破坏性状和特征比较,证实计算方法的合理性。计算分析表明,桩体横向地震位移最大值为11.9 cm,出现在边坡上侧的边桩桩顶位置;纵梁以横向位移反应为主,最大位移10.7 cm出现在边跨纵梁跨中位置,在边坡中位置不同的3根同跨纵梁横向位移差别不大。横梁最大横向位移11.8 cm出现在边坡下侧边跨横梁跨中位置,比相应位置的纵梁高1 cm左右,但中间跨不明显。桩体最大加速度为边坡上侧边桩桩顶横向加速度9.949 m/s^(2),竖向和纵向加速度最大值在边坡中部边桩桩顶位置,分别为9.81、8.54 m/s^(2);边坡上侧边跨纵梁竖向加速度11.1 m/s^(2)为纵梁最大加速度值;中间跨纵梁各位置的横向加速度与边跨纵梁相差3.31 m/s^(2)以上;边坡上、下侧次边跨横梁横向加速度10.55、10.84 m/s^(2)为横梁加速度中较大者,边坡上侧3根横梁的竖向加速度相差不大,但次边跨横梁与边跨和中间跨横梁的纵向加速度相差较大,分别达到3.43、1.42 m/s^(2)。这些位置为该类体系地震作用下的薄弱点。

A 3D finite element dynamic model of a continuous rigid frame bridge adjacent to a slope was established to investigate its natural vibration characteristics,and the seismic displacements and accelerations of the main positions at piles,piers and girders were also calculated in detail.The rationality of the calculation method was verified by the comparisons between the actual seismic damage performances of the bridge and the calculation results in the paper.The calculations showed that the maximum lateral seismic displacement of the pile was 11.9 cm,which appeared at the top of the side-pile in upside slope;the lateral seismic displacements were the main responses of longitudinal beam on earthquake,and the maximum was 10.7 cm,which occurred at the middle of the beam in side-span;the quantitative difference of the lateral displacements was not distinct among three longitudinal beams with different locations in the same span.For the cross beam,the maximum lateral displacement was 11.8 cm,which appeared at the middle of side-span beam in downside slope,and was about 1 cm higher than that of the longitudinal beam,but no significant difference between cross and longitudinal beam was founded in the mid-span.The maximum seismic acceleration of the pile was 9.949 m/s 2 at the top of the side-pile in upside slope,the maximum vertical and longitudinal accelerations of the pile were 9.81 and 8.54 m/s^(2)at the top of the side-piles in midslope,respectively.The vertical acceleration of 11.1 m/s^(2)of the side-span girder in upside slope was the largest one among the main beams,and the lateral accelerations of the mid-span girders were smaller than those of the side-span by more than 3.31 m/s^(2).The lateral accelerations of crossbeams of sub-side span in upside and downside slope were relatively larger,to 10.55 and 10.84 m/s^(2),respectively.The vertical accelerations of the three crossbeams in upside slope were not significantly different,but the longitudinal accelerations of crossbeams in subside span differed greatly from those in side and middle spans,reaching 3.43 and 1.42 m/s^(2),respectively.These locations were the most vulnerable subjected to earthquake in similar structure systems.