匝道桥地震响应影响要素分析

Analysis of Factors Influencing Seismic Responses of Ramp Bridges

为探求匝道桥几何非规则性对结构地震响应的影响规律,基于嘉闵线匝道桥,采用SAP 2000软件建立结构有限元分析模型,分析不同跨径组合、纵坡、曲率半径和地震动输入方向下的匝道桥地震响应。结果表明:与简支梁桥相比,多跨连续梁桥顺桥向固定墩、横桥向矮墩和过渡墩的响应均变大;纵坡大小对桥梁纵向地震响应影响轻微,但在横桥向设置大纵坡可减小高墩区墩柱的地震响应;小曲率半径下采用切向或法向输入与地震动最不利输入方向存在角度偏差,会低估结构地震响应,大曲率半径下其地震响应与直线桥基本一致,可简化为直线桥进行分析。

To probe into the laws of influences of the geometry irregularities of ramp bridges on the seismic responses of the bridge structures, a finite element analysis model for the structures was established, using the software SAP2000 based on the example of a ramp bridge on the Jiamin Elevated Road Line and the seismic responses of the ramp bridges under the different span arrangement, longitudinal slopes, curvature radii and ground motion input directions were analyzed. The results of the analysis show that as compared with a simply-supported beam bridge, the multi-span continuous beam bridge can have significant increase of the seismic responses in the fixed piers in the longitudinal direction and in the low piers and transition piers in the transverse direction. The influermes of the longitudinal slope changes on the longitudinal seismic responses of the ramp bridges are slight, however, the arrangement of the heavy slopes in the transverse direction is helpful to the alleviation of the seismic responses of the columns in the high pier area. Under the sharp curvature radii of the ramp bridges, the angle deviations exist between the ground motion input in the tangential and normal directions and the worst ground motion input direction, which may lead to the underestimation of the seismic responses of the structures. Under the gentle curvature radii, the seismic responses of the curved ramp bridges are basically consistent with those of the straight ones and the ramp bridges can be simplified as the straight ones for analysis.