Experimental Study On Damage Identification Of The Steel-concrete Composite Beams Based On 3D Image Reconstruction

In view of the low efficiency of manual safety inspections and the lack of quantitative scientific basis,the use of digital images for structural holographic form monitoring has the obvious advantages of economic convenience,high efficiency and credibility,that is a research hotspot in the field of bridge structure health monitoring.This article relies on the National Natural Science Foundation projects undertaken by the instructor "Exploration of deduction methods for obtaining bridge holographic deformation and structural state based on image contour overlap analysis(51778094)" and "Cross-scale analysis of damage evolution and failure process of bridge structures based on surface spatio-temporal data Method(51708068)",systematically carried out the theoretical exploration of the method of bridge structure damage identification based on digital image sets.The main research contents are as follows:1.By studying the method of using multi-view sequence images to reconstruct the structural three-dimensional digital model,established the mathematical transformation geometric model of the three-dimensional scene and the two-dimensional digital image,analyzed the spatial transformation relationship between the spatial point and the pixel point under the ideal linear projection.Aiming at the problem of large image distortion in the actual measurement process of civil non-measurement cameras,analyzes the distortion cause and distortion mathematical model,collects the steel truss-concrete composite test beam sequence images,and obtains a high-resolution digital model through reconstruction,can complete characterization of the test beam morphology information.2.The static load test of the steel truss-concrete composite test beam under multidamage conditions was carried out;the three-dimensional holographic morphological data recovery of the test beam under different disturbance deformations was carried out respectively,aiming at the problem of non-deterministic spatial attitude of the threedimensional reconstruction model,a point cloud model data registration method based on feature rigid domain is proposed,and the global optimal registration of the digital model is achieved by using the sum of squared Euclidean distances between the pair of points as the objective function.The registration completes the spatial posture of the overall structure,and a digital model for high-precision deformation analysis of the test beam is constructed.3.Proposed the use of the bidirectional European shortest layered stripping method to achieve the same-named point tracking between the model data characterized by three-dimensional feature points,and proposed to construct the deformation recognition constraint conditions of spatial data by point set neighborhood normal estimation,eliminating the Mismatched point pairs in point tracking with the same name,a highprecision structural full-field displacement distribution model is obtained.4.Explored the theoretical method of structural damage identification based on structural abnormal deformation,analyzed the sensitivity and feasibility of displacement vector rotation angle and curvature to structural damage information,studied the abnormal distribution of vector rotation angle under structural holographic deformation,and analyzed it by numerical model theoretical verification is completed,the displacement vector data of the lower edge of the transverse steel plate in the compression zone of the test beam is extracted,the linear change of the damage condition is analyzed using the angle change curvature,and the effective identification of the structural damage location is completed by tracking the peak change.