钢管混凝土拱桥台阵试验研究:场地条件的影响

SHAKING TABLE RESEARCH ON A CFST ARCH BRIDGE MODEL:EFFECT OF SITE CONDITION

为了研究不同场地条件对钢管混凝土拱桥地震响应的影响规律,以某钢管混凝土拱桥为原型,设计制作1/16缩尺比例模型,依据NEHRP场地分类标准,选取符合不同场地条件的ChiChi地震波,利用多子台积木式振动台台阵系统,完成了纵向、横向、竖向、横向＋纵向和横向＋竖向一致地震动输入的对比试验。研究结果表明：场地条件对此类钢管混凝土拱桥响应的影响较为显著,结构响应由A类至E类场地逐类递增,结构在E类场地下的响应为A类场地的1.6倍~4.1倍;相对于水平向加速度响应,拱顶竖向加速度响应对场地条件更为敏感,场地条件对竖向加速度的放大作用要高于水平向加速度,在确定设计加速度反应谱时,如果竖向设计加速度反应谱与水平设计加速度反应谱采用相同的场地系数会使竖向加速度反应谱最大值偏小。

To study the effects induced by varying sites on seismic responses of a CFST arch bridge, an actual CFST based scaled （1 ： 16） model has been employed to conduct the shaking table test. Based on the local sites classification of NEHRP, several real recorded ground motions at different site conditions from the ChiChi Earthquake are selected as the ground motion input, and then a comparative test on the multi-shaking table array system was carried out. During this experiment, the structure subjected to the uniform excitation are investigated, by considering the cases of longitudinal, transverse and vertical ground motion input, as well as the combination of transverse and longitudinal input and transverse and vertical input. This study reveals that local site condition has a significant influence on the seismic response of the CFST arch bridge. The seismic response increases with the site classification from A to E, and the seismic response in the E-class site is around 1.6~4.1 times high than that in the A-class. The vertical acceleration response of a vault is much more sensitive to site condition than the horizontal. As a result, the peak value of vertical design spectrum will be smaller if the same site coefficient is used with the horizontal one.