Study On Bridge Damage Identification Based On Dynamic Detection

With the development of the transportation, it is of theoretical significance and practicalvalue to make researches on the bridge structure damage identification (SDI). SDI is a keyproblem of bridge structure health monitoring (SHM). In this dissertation, some issues arestudied based on dynamic testing parameters and through theoretical analysis, numericalsimulation and practical application, which are natural frequency and curvature mode rules ofthe damaged beam bridge, and the bridge SDI methods system based on frequency, curvaturemode, flexibility matrix and frequency response functions. The main works are as follows:Through theoretical analysis, the bridge SDI methods applicability of the frequencyvariation, curvature mode, flexibility matrix and frequency response function (FRF) aredefined.Based on Euler-Bernoulli beam and structure dynamics theory, and by means of dynamicfinite element model (FEM) analysis, the natural frequencies are obtained throughcalculations in various kinds of damage states. With the concept of damage factor，frequencychange rate, frequency change rate oscillation amplitude, frequency change rate mid-valueand the ratio of frequency change rate, the thesis researches the rule of beam bridge frequencyresponse from various aspects of natural frequency, frequency change rate and the ratio offrequency change rate characteristics. Through numerical simulation analysis, SDI sensitivityrules with curvature mode and curvature mode difference are obtained.With the fingerprints of frequency ratio of change rate and normalized rate frequencychange ratio, based on the least square objective optimization method and graphical method,the result of damage position identification of simply supported beam bridge with singledamage is effective. According to the theoretical derivation of frequency change square anddamage factor are linear relation, the linear interpolation of the frequency change square anddamage factor numerical simulation line graph can be used to infer the damage degree ofsimply supported beam bridge with single damage.Through numerical simulation analysis, the displacement mode and curvature modedifference of SDI results are comparatively analyzed, the effects of measuring points density on SDI of modal curvature difference are studied, and damage degree is identified using therelative change amount of curvature mode shapes.On the basis of the existing research results of the FRF damage identification, thecurvature difference index of acceleration FRF energy (CEFRF) and the curvature differenceindex of acceleration FRF maximum (CMFRF) are extracted. According to the commonsource of excitation, and taking the pulse excitation signal as the input force, SDI ability withmensuration dots number and noise effects are studied.A flexibility index of modify modal flexibility curvature(MMFC) is presented throughanalyzing these exiting flexibility-matrix-based indexes of flexibility difference, modalflexibility (MF), modal flexibility Index (MFI), modal flexibility curvature (MFC), andchange in uniform load surface curvature (ULSC). These SDI indexes abilities are studiedthrough numerical simulation in the cases of modal testing with incomplete information andtesting error. And the relations of indexes and damage degrees are also studied.The methods system based on the frequency variation, curvature mode, flexibility matrix,and FRF are constructed, and the MATLAB application compositions are programmed.Taking Jinshuigou Bridge as the background, damage location identification capability ofULSC and MMFC methods are comparatively analyzed, CEFRF and CMFRF methods areused for damage location identification, and the method of curvature modal relative variationis used for damage degree identification. These methods are verified to be feasible and correct,which can support for the application of bridge SHM system in theory and methods.