| With the continuous enhancement of China’s overall national strength,the process of urbanization is gradually accelerating,and the country’s transportation infrastructure construction has also achieved significant development.As an important part of transportation infrastructure,bridges have attracted extensive attention from Chinese and foreign scholars.Because the traditional direct measurement method requires expensive costs and cumbersome operations,it is difficult to meet the requirement of bridge inspection.Therefore,the indirect measurement method with the advantages of convenience,economy and high efficiency appears in the view of scholars.This method only needs to install sensors on the moving vehicle,and then analyze the response signal of the vehicle to obtain the dynamic information of the beam bridge.This thesis takes simple supported beam bridge as the research object,establishes a three-vehicle-bridge coupling model through VBI element,and carries out theoretical derivation,numerical simulation and field test research related to bridge frequency identification,damping identification,modal shape identification and element stiffness identification.The main research contents completed are summarized as follows:(1)Theoretical derivation: A three-vehicle-bridge coupling model considering the effects of vehicle and bridge damping and road roughness is established;and the approximate analytical solution of the vibration response of the two test vehicles in the three-vehicle-bridge coupling model is solved through theoretical derivation.Theoretically,it explained that the two test vehicles first performed position synchronization in the time domain,and then subtracted the acceleration signal to eliminate the effect of road roughness.Then,the fusion improved direct stiffness method is introduced,including the theory of the bridge damping ratio identification,the theory of improved direct stiffness method and data extension.All mentioned above leads to the three-vehicle technology proposed in this thesis.Finally,an example is given to verify the effectiveness of eliminating bridge road roughness and bridge damping ratio,and identifying bridge element stiffness.(2)Numerical simulation: Using control variable method,the effects of parameters such as vehicle frequency,vehicle spacing,vehicle speed,bridge deck roughness,bridge damping ratio,and environmental noise on the three-vehicle technology are studied.Then,based on numerical simulation,the appropriate test vehicle parameters can be chosen.And the feasibility of identifying the stiffness of the bridge bearings based on the threevehicle technology is studied.(3)Filed test: The indirect measurement method test of Liziwan Bridge is conducted to study the practical application of identifying the bridge modal shape and element stiffness based on the three-vehicle technology.First,through a series of preparation tests,including the test vehicle forced vibration test,test vehicle power test,bridge microvibration test,bridge and test vehicle transmission test,the basic characteristics of test vehicles and bridge can be studied.Then,based on the three-vehicle technology,identifying the bridge frequency,eliminating the effect of bridge deck roughness and bridge damping ratio,extracting the bridge mode and calculating the bridge element stiffness can be done.Finally,the comparison of bridge strength and deflection is used to verify the accuracy of the method for identifying the elements stiffness of bridge based on the three-vehicle technology. |
