考虑土-结相互作用的黏滞阻尼器减震结构振动台试验研究

Shaking table tests for structures with viscous dampers considering SSI effect

通过对黏滞阻尼器消能减震钢框架结构模型在刚性地基和群桩地基条件下进行对比振动台试验,研究土-结动力相互作用(SSI)对阻尼器减震效果的影响。根据量纲分析法确定了试验模型与原型的相似关系。采用粉质黏土作为试验用土,采用叠层剪切型土箱以减轻边界的影响。上部结构为5层钢框架,消能元件为黏滞阻尼器。通过振动台试验获取了不同地震输入下减震结构及非减震结构在不同基础条件下的动力特性、楼层加速度及位移的地震反应数据。对于桩基础模型,测量了桩身应变及桩土接触面的压力值。试验结果表明:对于非减震结构,SSI效应使结构体系的阻尼比有较大的提高,而对于减震结构,SSI效应对结构体系的阻尼比影响则不大;SSI效应对结构楼层加速度反应具有显著的影响,其对上部结构地震反应的主要影响体现为减震效应,且随着地震输入量级的增大,减震效应愈大,群桩基础上阻尼器的减震效率与刚性地基相比具有较大程度的下降;对于桩基础结构,阻尼器在降低上部结构反应的同时,减小了桩基础的地震反应,上部结构和基础两个方面的安全性都得到了提高。

In order to investigate influences of soil-structure interaction （SSI） on aseismic effect of viscous dampers in structures, shaking table tests for a steel frame energy-dissipating structure model with viscous dampers on rigid and pile group foundations were conducted. The similarity relationship between the original structure and the tested model was determined according to the dimensional analysis. The soil used in tests was silty clay and a laminar shear type soil box was adopted to reduce the boundary effect. The super-structure of the model was a 5-storey steel frame structure, its energy-dissipating elements were viscous dampers. The data of structural dynamic characteristics, floor accelerations and displacements of the model with and without viscous dampers under different seismic excitations and different base conditions were obtained with shaking table tests. For the pile group supported model, strains of plies and contact pressures of soil-pile interfaces were measured. The results indicated that for structures without viscous dampers, the damping ratio of the structure system has a considerable increase due to SSI effect; however, for structures with viscous dampers, SSI effect has little influence on the damping ratio of the structure system; SSI effect has a significant influenceon floor acceleration responses, SSI effect reduces the seismic responses of the super-structure of the model, the larger the seismic inputs, the greater the SSI effect, the aseismic efficiency of dampers for pile group foundations has a bigger decline compared with that for rigid foundations; for structures on a pile group base, the viscous dampers can not only reduce seismic responses of the super structure, but also reduce those of the base, the safety of both the super structure and the base is improved.