Research On Sheet Cracks Identiifcation Of Birdge Structure Based On Wavelet Analysis

When bridge structures have been long used, they inevitably occur allkinds of damage, When these damages accumulate to some extent, thestiffness and bearing capability of the structures will decrease a lot，whichaffect the service performance and durability of the whole structure, even maylead to catastrophic failures causing great loss of money and human lives.Thereby, it would be very important to study on the method which can succeed indetecting the damages efficiently and conveniently, and they are essential inboth theory aspect and practical aspect.By use of the structural dynamics theory and modern damageidentification technology to identify the structural damage has been gettinghigh attention. In recent years, using wavelet analysis to identify structuraldamage has become a hotspot of the research. Based on the wavelet theory,damage identification of the bridge structure with sheet cracks is researched.Cracks can performance the bridge structural aging characteristics, itsposition and direction can accurately reflect the position of the aging bridgesand characteristics. The existing research will usually be simplified to cracksthrough the thickness of the direction in structural damage diagnosis, so itsimplified complex structural damage identification problem, at the same timeit inevitably lead to the deviation of the calculation results, the accuracy ofdamage identification is also influenced. Based on the wavelet analysis theoryin this paper, by building the bridge structural finite element model, we studythe influence of the flake cracks for bridge structure modal parameter, andgive the principle of bridge structure damage identification with the flakecracks. Take Gauss1 wavelet for mother wavelet, through to bridge structuralmodal parameters with the flake cracks for continuous wavelet transform, thewavelet is great value to identify model with flake cracks bridge damageposition, developed a method based on wavelet analysis theory to identify thebridge structural damage with flake cracks.The paper chose a three-span continuous steel box girder bridge withhorizontal semicircular surface cracks as research object, and the cracks arenon-through and unsymmetrical. Solving modal parameters of beams with cracks by means of the three-dimensional finite element theory, and applyingcontinuous wavelet transform (CWT) to analyze the displacement mode、strain mode and curvature mode by Gauss1 wavelet, then the position of thecracks could be identified by the maximum of wavelet coefficients. Thevalidity of the method has been proved by numerical calculation and analysis.Based on the study of the continuous steel box girder bridge as thefoundation, the paper proposes to using the beam element and entity elementsimulation to simulate the steel box stiffening girder suspension bridge cracks,establishing three dimension finite element model of the whole bridge withsheet cracks, taking Gauss1 wavelet as mother wavelet, Through steel box ofstiffening girder suspension bridge finite element method (FEM), by use ofdisplacement, strain and curvature mode of wavelet transform method, singlespan steel box stiffening girder suspension bridge were studied and spancontinuous steel box stiffening girder suspension bridge sheet cracks ofdamage identification, and we obtained satisfied effect, verified the validity ofthe proposed method. This method may be useful in damage identificationbridge structure with sheet cracks.