Study On Fine Recognition Method Of The Bridge Dynamic Parameters Based On Vehicle-bridge Coupling Analysis

Currently, the most effective and direct way on the assessment of the bridge carrying capacity can be regard as loading test, but long closed to traffic load, static load instrument complex installation, long test time and other defects were required by the traditional loading test, so how quickly and accurately judge the service bridge whether they have adequate safety margin has been got more and more attention.Now for the rapid assessment of the carrying capacity of the bridge is mostly based on exploring the dynamic loading test and on dynamic loading test evaluation system is not yet mature. Dynamic loading test is regard as an important part of vehicle dynamic response test, which can be evaluated the dynamic magnification effect of the vehicle on the bridge, and the impact factor is obtained. However a dynamic magnification effect of a certain section or bridge was only representd by the impact factor, and the dynamic characteristics of the whole structure could not be represented. How to make a deep analysis on the dynamic deflection time history curve of the vehicle dynamic response test is focused by this paper, and the related impact factor, crack parameters and signal analysis which involved in the dynamic time-history curve is studied. The main contents and results are summarized as follows:(1) Some classical theories of forced vibration is simply dicussed, and by using the ANSYS APDL language compiled calculation command, some classic examples is used to verify the accuracy of the calculation results, and some problems and methods of the calculation of ANSYS about vehicle-bridge coupling action are discussed.(2) Some common calculation methods of the bridge impact factor is dicussed, which focuses on digital filtering method, the order of the filter for the separation of static and dynamic response is researched comparatively. A brief introduction is made about the use of empirical mode decomposition(EMD) low-pass filtering effect for static and dynamic response. The road surface roughness is simulated, and the different speed and different road surface roughness of the deflection curve are studied.(3) When the beam weight were considered, the effects of different forms and parameters of crack on the dynamic deflection of the vehicle’s dynamic response is studied, and the absolute dynamic magnification effect of open fracture effect and relative dynamic magnification effect of breathing crack are put forward. By a three span continuous box beam is used as example, this bridge was rated as the third type of bridge, three axle load carrying vehicle model is made by using ANSYS, crack occurred during the test are input in ANSYS, the measured data is compared with the calculated data.(4) The dynamic response of the damaged and undamaged bridge is analyzed by the Hilbert-Huang Transform(HHT), and vibrational frequency and instantaneous frequency of vehicle-bridge coupling system are obtained, and the feasibility of the Hilbert-Huang Transform is explored in dynamic analysis of bridges.