桩-土-结构相互作用对超大跨度斜拉桥动力特性的影响

Influence of Pile-soil-structure Interaction on Dynamic Characteristics of Super-long-span Cable-stayed Bridge

对于运用钻孔灌注群桩基础的超大跨度桥梁来说,桩-土-结构相互作用效应(PSSI)是影响桥梁结构动力性能的重要因素,其模拟的精度直接影响动力性能分析的准确性。采用改进的集中质量模型中应用最为广泛的Penzien模型,即在每根桩相应节点施加集中质量-弹簧粘滞阻尼器体系模拟桩-土-结构相互作用效应,并考虑结构的几何非线性与恒载刚度的影响,研究桩-土-结构相互作用对超大跨度斜拉桥动力特性的影响。研究结果表明:桩-土-结构相互作用使得结构变柔,刚度降低,自振周期变长,在动力分析时须予以考虑,尤其针对斜拉桥自振频率较低,模态振型较为集中且高度耦合,且由于桥塔在主梁以上未设置横梁使其具有自身独特的动力特性,更需引起注意。

Pile - soil - structure interaction （PSSI） played an important role in dynamic characteristics of thebridge which used bored pile group foundation. The simulation accuracy of foundation directly affected the analysis resultsof super - long - span cable - stayed bridge. Firstly, the Penzien model, which was widely used in lumped mass model,was modified to simulate PSSI by applying the mass - spring viscous damper system at corresponding nodes of each pile,then, geometric nonlinearity and dead load stiffness of the bridge were considered to study the influence of PSSI on dynamiccharacteristics of super - long span cable - stayed bridge. The results shown that the PSSI made the bridge becomesoft, the rigidity was reduced, the vibration period became longer, and it was necessary to take PSSI into considerationwhen dynamic analysis, meanwhile, the natural frequencies of the bridge were lower, the modal shapes were intensiveand highly coupled, besides, the bridge tower didn^t set upper beam so it had its own unique dynamic characteristics,which need pay more attention.