Numerical simulation of shaking table tests on dynamic response of a bridge model with scoured piled foundation

The simplified analysis process of soil structure interaction is proposed in this re-search, which studies on the response of the bridge with scoured piled foundation under earthquakes. The simplified analysis applies soil springs to simulate soil structure interac-tion behavior. The real measurement of soil shear wave and dynamic shear modulus used to estimate initial value of linear soil spring is the special point in this research. The study supposes the soil in the near field effected zone and the pile occur the same shear de-formation and modify the shear modulus of soil according to the relationship between effective shear strain and maximum shear modulus under earthquakes, then obtain the final soil spring parameters after few amount of iterations. Furthermore, this research suggests simplifing soil according to significant frequency of transfer function between layers under seismic signal. Base on the method mentioned ahead, the study establishes equivalent linear numerical model to simulate behavior of soil-pile interaction, and com-pares to the previous results of shaking table tests of bridge model with scoured piled foundation. Conducting dynamic system identification to the previous shaking table model to realize dynamic characteristics and verifies the numerical model. In the dry soil, the ex-perimental identification results show that the period of the structure increase and the damping ratio of system decrease as exposure length of foundation increase. In the saturated soil, the experimental identification results show that the period and damping ratio of system will be larger than the results of the dry soil experiments. Before soil liquefaction occurs, the saturated soil will reduce the stiffness more easily due to the disturbances. When soil liquefaction phenomenon takes place, the damping ratio and the period of system will increase dramatically. The numerical analysis results show that whether in full cover or explosion of pile foundation in the dry soil experiment, the structure period of numerical mode will con-sistent with experiment result. It could simulate the responses of the acceleration and the relative displacement in the superstructure, and the strain responses of top pile and the maximum strain of pile effectively. In the prediction results, double layers model is more accurate than single layer model under several earthquake experiments. In saturated soil experiment under scoured piled foundation, the structure period of numerical model ap-proximate to the experiment result, and also can simulate the acceleration and relative displacement responses of superstructure, the strain response of top pile and the maxi-mum strain of pile under El Centro 100gal, and prediction results of double layers model is more exact than single one.