Frequency Identification Of Continuous Bridge Based On Indirect Method Considering The Uneven Deck

The measurement of the bridge dynamic load is an important part of bridge detection,in which the measured bridge frequency is the most intuitive parameter to express the bridge stiffness.By comparing the changes of bridge frequency before and after,the reasonable judgment on the stiffness and bearing capacity of the bridge can be made.The direct measurement method is applying the vibration information of the bridge itself to measure the bridge frequency;the indirect measurement method is applying the sensor installed on vehicle to collect the vibration information of vehicle when crossing bridges,and measuring the bridge frequency through the vibration information of vehicle.This method has advantages such as fast,convenient and economical and so on.The bridge indirect measurement method is evaluated in the present study,which utilize the vehicle vibration response to measure the bridge frequency.The main research contents are as follows:Based on the vehicle-bridge coupling vibration process,the deduction process of vehicle and bridge vibration analysis was introduced,and the relationship between vehicle vibration response and bridge frequency information was established.The vehicle-bridge coupling vibration was simulated by ANSYS software.The APDL command stream of the single axle quarter vehicle and simple supported beam-bridge model was compiled and compared with the references.The results show that the finite element calculation results in this paper agree well with those of references when the bridge deck is smooth and rough.Based on APDL command stream,the two identical dual-axle half-car models were used to drive through continuous bridges with smooth deck and rough deck,respectively.When the bridge deck was smooth,the acceleration curve of the front vehicle body was directly used for spectrum analysis,and the peak point of the acceleration spectrum was utilized to identify the bridge frequency;add the different slope variances to bridge deck,and subtract the acceleration of two vehicles at the same position of the bridge.The obtained acceleration difference curve was used for spectrum analysis,and the peak point of the acceleration difference spectrum was utilized to identify the bridge frequency.The results show that the bridge frequency can be accurately identified when the bridge deck is smooth and rough.The method of subtracting the acceleration of the two vehicles can effectively eliminate the influence of the slope variance on the identification results.The influence of four parameters such as vehicle speed,vehicle weight,traffic stream and environmental noise on frequency identification of continuous bridges with uneven deck was evaluated by the numerical simulation.The results show that lower vehicle speed can improve the accuracy of the identification results;the vehicle weight has less influence on the identification results;the traffic stream has no obvious impact on the identification results;the environmental noise has significant impact on the identification results,which can not be ignored.