Research On Optimization Design And Damage Identification Of Irregular-shaped Bridge

With the rapid development of China’s economy, the traffic infrastructure constructiondevelops rapidly. As an important part of transportation infrastructure, bridge is prominentin raising transportation efficiency. But bridge structure prone to fatigue damage, under theinfluence of environmental factors such as external load, chloride ion erosion, temperatureand humidity, leading to the bearing performance degradation. It’s profound for protectpeople’s lives and property safety to identify timely and effective damage status of bridgestructure in service and prevent structure destructive injury accidents.In the process of urbanization in our country, in order to enhance effectively theutilization efficiency of urban space, irregular-shaped bridge structure has been widely used.as the connection structure of straight girder bridge and curved girder bridge,irregular-shaped bridge space effect is remarkable, and has a special force way. And becauseof the special geometric structure and design diversity, traditional analysis methods has notable to utilized effectively. Therefore, optimize the design of the bridge type has goodapplication value.In this paper, combining with the project of Jilin province transportation”irregular-shaped priestesses concrete bridge mechanical characteristics analysis and designmethods research”, the corresponding calculation method is put forward and is verified inview of optimization design damage identification research of irregular-shaped bridge. thatcarried out the specific research work in this paper is followed:1. The optimal parameters combination is determine based on the orthogonalexperiment and analytic hierarchy process,in view of optimal design of irregular-shapedbox girder bridge.The method analyze the influence of ramp radius, bifurcate dark beamstiffness, height of box girder cross section and the way of support to irregular-shapedbridge bifurcate dark beam maximum stress, the stress variation coefficient, bridge torsion vibration frequency and degree of curved beam reverse by orthogonal test, and studyprimary and secondary order of the factors that influence on special-shaped bridge overallmechanical characteristics by comprehensive weight analysis, combined with analytichierarchy process. The optimal parameter combination results from comprehensive weightanalysis and balance analysis are compared, the test results from weight analysis parameterscombination are better than the results from balance analysis parameters combination, itverify the accuracy and effectiveness of the comprehensive weight analysis methods infactors influencing sorting of multi-target orthogonal experiment and parameter designoptimization.2. Considering the complex of the irregular-shaped bridge structure, a irregular-shapedbridge damage identification the method of irregular-shaped bridge damage identification isproposed support vector machine, based on Modal flexibility and genetic algorithmoptimization support vector machine (SVM), it verifies the effectiveness of some indicatorssuch as modal flexibility, modal flexibility difference curvature surface curvature, uniformload surface curvature and uniform load surface curvature for the irregular-shaped bridgedamage location identification，and it achieves the irregular-shaped bridge single locationand multi-position damage location and get good recognition effect by choosing the modalflexibility difference curvature index. Three different damage identification parameters, thatis frequency variation, modal ratio and modal flexibility difference curvature, is build inview of the special-shaped bridge damage identification, the effectiveness of the proposedmethod is verified by establishing damage Identification condition of single location andmulti-position, as the input parameters of genetic optimization support vector machine(SVM). The simulation results show that the degree of multi position the damageidentification accuracy based on the methods the modal flexibility difference curvature andgenetic optimization support vector machine (SVM) is superior to the identificationmethods based on frequency variation or vibration mode with Genetic optimization supportvector machine (SVM). The result compared with the optimization neural networkrecognition method based on gen etic algorithm shows that it has better recognition effectand more accurate identification based on gen etic algorithm and supporting vector machine multiple damage.3. Based on PSO fuzzy C-means clustering and combining with the whole structuralmodal frequency variation ratio damage identification index, special-shaped bridge damagelocation identification method of order modal frequency change more than the clusteringanalysis is present. This way gets the clustering center of corresponding to the damageposition by cluster analyzing the damage condition of the modal frequency change ratio. Bycalculating the membership from the model test sample clustering center frequency changesratio to the center of damage location, special-shaped bridge damage location can berealized, and the result verifies the accuracy of this method. On the basis of the damagelocation to determine, using the uniform load surface curvature difference membership forstructural damage level assessment. By measuring the vibration mode of local damage zonenode values, the Uniform load surface curvature difference can be get, calculating themembership of the index to the damage level. Based on the principle of maximummembership degree determine the category, the damage level can be realized. Unit damagerecognition and identification results show that the damage, the method in thespecial-shaped bridge structure damage identification is accurate and feasible.4. Considering the special bridges easily affected by many parameters in the process ofdamage identification, the test that the factors such as damage degree, the modal number,number of sensors, such as impact parameters influence damage identification index iscarried out, and carry out the evaluation work of the damage unit near the fulcrum andspecial-shaped structure damage. And it chooses indicators such as vibration modedifference, the modal flexibility difference, the modal curvature values and modal flexibilitydifference curvature as the research object, according to different damage degree, therecognition effect of all kinds of damage identification index is analyzed, in view of theinfluence of sensors number to damage identification effect, recognition effect of differentdamage identification index is analyzed under51,26,14and8sensors. Two types ofdifferent damage evaluation theory, which are used to evaluate the recognition effect of thetwo kinds of different evaluation indexes, are defined. In view of the influence of modalnumber to damage identification effect, modal data structure identification indexes of different order number are selected, in order to evaluate identification effect of structureindicators, the best identification effect of modal flexibility difference curvature isdetermined, in view of the unit damage near the fulcrum. Vertical and horizontal positioningstrategy based on the modal flexibility difference curvature is proposed, in view of lateralposition damage identification of special-shaped bridge.