Theoretical And Experimental Study Of Bridge Weigh-in-motion System On Long-span Continuous Bridges

Overloaded vehicles can cause damage to bridges and in some extreme cases they will directly lead to a bridge failure.In recent years,more and more attention has been paid to the accurate and efficient acquisition of vehic le information,especially vehicle weight information.The acquisition of vehicle weight information is of great significance for the management of vehicle overload problems.At the same time,the efficient acquisition of vehicle information will have a si gnificant impact on the establishment of intelligent transportation systems,as well as road and bridge maintenance and management.The Bridge Weigh-in-motion(BWIM)system uses high-precision sensor testing technology to continuously collect the dynamic strain signal from bottom of the bridge,and calibrate the actual influence line of the bridge,and then take the calibrated influence lines of the bridge as a reference to calculate the vehicle weight.The BWIM system transforms the bridge into an automate d device that can measure actual vehicle information continuously.Based on the field test of the main bridge of the Lunzhou Bridge(the rigid-continuous box-girder bridge)and the approach bridge of the Lunzhou Bridge(pre-stressed continuous small box-girder bridge)in Qingyuan,Guangdong,China,this study proposes a new FAD BWIM based on fast Fourier transform method.Thereby,the accuracy of the axle information(axis number,axle spacing and axle weight)detection is greatly improved,and the accuracy of the axle weight identification of the BWIM system is effectively improved.Based on the influence lines of independent calibration of each lane,the i mpact of influence lines on the accuracy of vehicle axle weight identification is studied.The feasibi lity of extending the application of the BWIM system to the long-span concrete girder bridge is discussed,and the data foundation was laid for follow-up research.The main work and conclusions of this thesis include:(1)The fast Fourier transform method is introduced to the BWIM system and used to process the bridge dynamic response signals.The time domain and frequency domain analysis is used to determine the reasonable filtering range,which significantly improves the efficiency and accuracy of axle in formation detection.(2)For the two types of bridges,two optimized BWIM algorithms based on single girder theory and multi-girder theory are proposed,respectively.The BWIM system algorithm consists of three parts,the axle information identification,i nfluence line calibration and vehicle axle weight calculation.Based on the modified algorithm,sufficient accuracy is obtained in the field tests.(3)The rigid-continuous box-girder bridge has the characteristics of large overall stiffness and no obvious local effect under live load.Based on the independent calibration of the influence lines from each lane,the impact of the influence lines to the accuracy of the axle weight identification are analyzed and presented,and a simplified method for influence line calibration is proposed.(4)Due to the obvious transverse load distribution effect of the multi-girder continuous small box-girder bridge,the multi-girder algorithm should be used for axle weight calculation.It is advisable to calibrate the influe nce lines of each lane separately,and calculate the axle weight and gross vehicle weight based on the specific lane.