| For the problems of low efficiency,long period and lack of quantitative scientific basis of bridge safety inspection,it has the prominent advantages of holography,convenience and economy to monitor the structure with digital image,which is in line with the development trend of digital information in the future.Supported by the National Natural Science Foundation of China(NSFC)project "exploration of bridge holographic deformation and structural state deduction method based on image contour superposition analysis(51778094)" and "cross scale analysis method of bridge structural damage evolution and failure process based on surface shape spatiotemporal data(51708068)",and the damage identification method of holographic deformation of bridge structure obtained from Digital Orthophoto Image is explored.The main research contents are as follows:1.The method of reconstructing digital 3D model based on sequence image is studied,the factors influencing the accuracy of digital 3D model are discussed,the distortion causes of original bridge image are analyzed,the image correction formula considering radial distortion and tangential distortion is deduced,and the original image distortion correction is carried out;the algorithm based on multi view image joint adjustment and stereo matching is proposed The experiment of Digital Orthophoto Image Generation Based on three-dimensional model of structure is carried out,and the Digital Orthophoto Image Extraction of test beam is realized.2.The multi condition damage load test of steel truss concrete composite beam specimen is carried out;the multi view sequence images of the test beam under each condition are obtained,and the high-precision digital three-dimensional model is established;the Digital Orthophoto Image of the test beam is obtained through the generation theory of three-dimensional model Digital Orthophoto Image,and the quality evaluation of the test beam structure Orthophoto Image is carried out,and The ability of Digital Orthophoto Image to characterize the structure of the test beam was verified.3.The edge detection results of different edge detection operators are compared and analyzed,and the Sobel edge detection operator is used to carry out the edge extraction of Digital Orthophoto Image of test beam;the method of obtaining the real edge line of structure is studied,and the mechanism of image noise on the abnormal edge of structure is revealed.The holographic deformation curve of test beam under various working conditions is obtained by unifying the smoothing constraint of algorithm A method of extracting the continuous curve of edge holographic deformation with noise in structure image is proposed;the mapping of edge continuous curve from pixel scale to actual measurement scale is completed by pixel calibration;the verification experiment of structure edge holographic deformation is carried out,which verifies the accuracy of the holographic deformation curve and the structure shape of the test beam Digital Orthophoto Image.4.A damage identification method based on the matrix similarity of structural digital orthophoto images is proposed.Through the establishment of the finite element model of simply supported beam,the theoretical analysis of the matrix similarity damage identification method is carried out,and the feasibility of using the image matrix similarity to identify the structural damage location is verified;the experimental research on the image matrix similarity damage identification method is carried out;the maximum similarity measurement curve under each damage condition is obtained by calculating the similarity of the image matrix before and after the damage;the experimental research is carried out The experimental results show that the maximum similarity measurement curve has obvious response at the damage location,which verifies the effectiveness of the damage identification method in single damage and multiple damage states. |
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