Seismic-induced Pounding Analysis And Control Of Highway Bridges

Highway bridge is sensitive to pounding damage due to either the difference of dynamic characteristics between the neighboring segments or the effects of asynchronous earthquake when subjected to strong earthquake excitations. During the structural pounding, highway bridge behaves complex inherent characteristics of material nonlinear, geometric nonlinear and contact nonlinear, which make the impact mechanism very complex. Furthermore, aiming at the seismic-induced pounding of highway bridges, how to prevent the structural pounding using suitable engineering technique is an important issue that should be solved.This dissertation investigates the pounding mechanism and the pounding reduction technique by using the explicit nonlinear finite element approach and the simplified impact model approach. The main contents include:(1) Based on the refining finite element model of a three-span highway bridge, it investigates the pounding mechanism and the effects of the earthquake amplitude, natural frequency of the main span, expansion joint separation and the damping ratio of the base-isolation system on the dynamic responses of the structures.(2) By using rubber cushion material, it investigated the possibility of using the rubber cushion material for the pounding reduction of the highway bridges. The effects of the shear modulus, thickness and the friction coefficient of the material for the performance of the pounding reduction is also investigated by using the explicit nonlinear finite element approach for establishing the parametric selection principle of the rubber cushion material for the pounding reduction of highway bridge.(3) With the theoretical and experimental techniques, the possibility of using MR dampers for preventing the pounding damage of highway bridges is investigated with semi-active control method. During the analysis, it uses the Kelvin and Hertz damp impact model for modeling the structural pounding and develops the semi-active control strategy based on the LQG control algorithm through experiment validation. The analytical results indicate that there are significant difference between the theoretical impact stiffness with structural axial stiffness and the identified impact stiffness. How to determine the parameters of the impact model is an important issue that should be investigated in future. (4) Considering the torsion-induced pounding of highway bridge due to mass eccentricity, it investigates the point-to-surface impact and proposes the corresponding friction-contact impact model for highway bridge with bi-directional earthquake excitations. The analytical model of the highway bridge with point-to-surface pounding is also established. Through the shaking table test with bi-directional earthquake inputs, it validates the accuracy of the proposed friction-contact impact model and the analytical model of the structure with point-to-surface pounding. The experimental results indicate that the torsion-induced pounding of the highway bridges should be paid more attention during the seismic design.