Seismic Response Analysis And MR Damper Control For Long-span Bridges Under Multi-support Excitations

How to improve the seismic safety of long-span bridges, as an important part of the traffic key projects and the lifeline engineering, is always the focus problem to be paid more attention in the engineering field, in which two aspects are included, one is the methods of seismic response analysis and another is the measures for seismic absorption and control.In this dissertation, the seismic responses analysis and Magnetorheological (MR) damper control for the long-span bridges under multi-support excitations are systematically studied, and the following creativity work and achievements are included,(1) The equations of motion of long-span bridges, subjected to seismic multi-support excitation, are deduced, and two seismic response analysis methods, including the mode superposition method and the state space method, for the long-span bridges under definite traveling wave excitations are proposed.(2) A power spectral model of the stochastic earthquake ground motion suitable for the long-span bridges is proposed, and its parameters are determined. Based on the proposed model, the stochastic seismic response analysis method for the long-span bridges is presented, and a method used to quantitatively estimate the seismic responses of the long-span bridges is established based on the random vibration theory. (3) The state space equations to analyze the seismic absorption and control for the long-span bridges under multi-support excitations are built, and a control algorithm suitable for long-span bridges is proposed based on the mode superposition method. The hysteresis behavior of the MR damper and its application technology in the seismic absorption and control for the long-span bridges is explored.(4) Taking a four-span continuous rigid-framed prestressed concrete bridge in Tianjin Light Railway project and a long-span cable-stayed bridge under construction in Hong Kong and with the main span of 1018m as the examples, the seismic responses of the continuous rigid-framed bridge and the long-span cable-stayed bridge, under the uniform excitation and traveling wave excitation of the definite earthquake ground motion and the multi-support excitation of the stochastic earthquake ground motion, and the seismic absorption and control, based on MR damper and under different control strategies, are numerically simulated, and the influence of the traveling wave effect on the control effect is investigated, which provides an important theoretical reference for improving the seismic safety of the continuous rigid-framed bridge and the long-span cable-stayed bridge and for the engineering application of the MR damper in the seismic absorption and control of the long-span bridges.