Research On Vehicle-induced Vibration Of Composite Continuous Bridges With Corrugated Steel Webs

In recent years,researchers home and abroad have conducted abundant research on the bending,shearing,torsion,shear buckling,connection and fatigue properties of prestressed composite box girders with corrugated steel webs,prompting the application of large-span corrugated-steel-web continuous bridges with varying cross sections.However,with their application wider and their spans larger,the vibration induced by vehicles,wind and rain will be salient problems,and the dynamic properties of them will begin to affect and even control the design process.Accordingly,it is valuable in both theories and engineering application to conduct research over the dynamic response of large-span continuous bridges with corrugated steel webs.This dissertation is backgrounded by Xinan Bridge,a bridge over Dongbao River in Shenzhen with three spans of 88m+156m+88m.In this dissertation,parametric analyses of the dynamic properties and calculation of the vehicle-bridge coupled vibration of large-span continuous bridges with corrugated steel webs were conducted.The main work includes:(1)conducted an ambient vibration test on Xinan Bridge and extract the experimental modes of it with peak-picking(PP)method and stochastic subspace identification(SSI)method respectively;(2)established an initial 3D finite element model of Xinan Bridge,and updated the model with elliptical base function neural network based on the results of the ambient vibration test,obtaining the baseline finite element model of Xinan Bridge;(3)grounded on the baseline model of Xinan Bridge,compared the differences between the dynamic properties of the hybrid corrugated-steel-web continuous bridge and those of the corrugated-steel-web continuous bridge whose bottom slabs were complete concrete,and then analyzed parametrically the dynamic properties of corrugated-steel-web continuous bridges with varying thicknesses of corrugated steel webs,width-span ratios,etc.so as to summarize the change rules of the dynamic properties of the bridges with the variation of those parameters.(4)conducted research on the vehicle-induced vibration of continuous bridges with corrugated steel webs based on the baseline model of Xinan Bridge to assess the influences of such parameters as road roughness condition,vehicle speed,etc.on the impact factor and the riding comfort of large-span continuous bridges with corrugated steel webs.The main conclusions of this dissertation are:1.The dynamic properties of Xinan Bridge was obtained in the ambient vibration test: the vertical fundamental frequency is 0.884Hz;the transverse fundamental frequency is 1.019Hz;the longitudinal fundamental frequency is 0.929Hz;the torsional fundamental frequency is 4.227 Hz.2.As updated via elliptical base function neural network,the errors of the calculated natural frequencies of the finite element model of Xinan Bridge compared to the measured frequencies are all below 5% and the modal assurance criteria(MAC)are all over 80%,denoting that the updated model could be used as the baseline model of Xinan Bridge in further calculation and analyses.3.There are few differences between the dynamic properties of the hybrid corrugated-steel-web continuous bridge and those of the corrugated-steel-web continuous bridge whose bottom slabs were completely concrete;with the growth of the thickness of the corrugated steel webs all over the bridge,the torsional fundamental frequency rises significantly,while the transverse,longitudinal and vertical frequencies are not influenced much;the thickness of the webs in the girder sections of small heights has a relatively high influence on the dynamic properties of the bridge;with the increase of the bridge width,the transverse frequencies monotonically ascend,whereas the torsional fundamental frequency gradually declines.4.As the road roughness grows,the impact factor of large-span hybrid continuous bridges with corrugated webs became higher;meanwhile when the road roughness remains unchanged,there is no significant correlation between the impact factor and the vehicle speed;for large-span corrugated-steel-web hybrid continuous bridges,the riding comfort declines with the increase of vehicle speed and road roughness,which also connotes that the strength of the bridge vibration grows with the increase of vehicle speed and road roughness during the time when the vehicle passes through the bridge.