Structural Optimization And Shock Absorption Analysis Of Rigid Frame Bridge With High Pier Under Random Excitation

High pier rigid bridges are widely concerned about their seismic safety due to their high flexible piers and large superstructure masses,which form an adverse seismic system.The installation of damping devices and optimization of seismic system are considered as effective ways to improve the seismic performance of the structure.Therefore,it is important to investigate the structural optimization of high pier rigid bridges under random excitation and the optimization of damper parameters.The paper firstly explores the random response law of high pier and high pier stiffened bridges considering the hysteresis characteristics of piers,and then investigates the optimization of pier stiffness distribution of high pier stiffened bridges considering the plasticity of piers under nonstationary random excitation and the optimal design of tuned inertia dampers(TID)for damping.The main research contents and conclusions are as follows:(1)Based on Euler beam theory,a Bouc-Wen numerical model with stiffness and strength degradation effects is derived for simulating the moment-curvature evolution relationship of beam units.The effect of low-frequency strong earthquakes significantly increases the curvature of the pier bottom section and excites the effect of higher-order formations,resulting in plastic hinges at both the pier bottom and the middle of the pier.(2)In order to consider the influence of superstructure and adjacent pier constraints,a numerical model for random response analysis of high pier rigid bridges was established to investigate the effects of site type and peak seismic acceleration on the random response of the whole bridge;it was shown that the effect of low-frequency strong earthquakes would significantly increase the curvature of the control section of the bridge pier and the relative displacement of the pier and beam,resulting in serious damage to the bridge;the influence of the stiffness ratio,stiffness and strength degradation rate of the bridge pier before and after yielding on the random response of the structure was investigated.The influence of the stiffness ratio,stiffness and strength degradation rate on the random response of the structure was investigated.(3)Based on the stochastic response analysis model of the whole bridge,the optimization of pier stiffness distribution under moderate and strong earthquakes was achieved with the objective of minimizing the root mean square peak of pier curvature,analyzing the law of stiffness distribution and its influence on the seismic performance of the structure,exploring the influence of site characteristic frequency and damping ratio on the optimization effect of the structure,and elucidating its robust performance.(4)The state space equations of the rigid bridge and the TID damping system under random excitation are derived,and the peak root mean square of pier curvature is used as the performance function to optimize the TID parameters under moderate and strong earthquakes,respectively,to improve the seismic performance of the structure,and to investigate the effect of TID damping and the influence of site characteristic frequency and the effects of the TID damping effect and the site characteristic frequency and damping ratio on the damping effect were investigated,and the robustness performance was elucidated.