Research On Damage Identification Method Of Bridge Structures Based On Curvature Features

Regular safety inspections of bridges are now mostly in the form of manual visual scoring assessments,the effectiveness of which relies heavily on maintaining the professionalism of the custodial workers.In order to find a more efficient,objective and quantifiable alternative method of manual safety inspection than manual regular inspection,intelligent perception of bridge safety status and prevention of disaster accidents,based on the National Natural Science Foundation Project,"Research on obtaining holographic deformation and structural state deduction method based on image contour superposition analysis"(51778094)" hosted by the tutor,and combined with the finite element analysis and the indoor model bridge tests,the damage identification methods based on the curvature of the characteristic deflection curves and the Gaussian curvature of the deflection surface are studied respectively in this paper.The main research works are as follows:Based on the theoretical relationship between the deflection,angle and curvature of beam structure,the area enclosed by the load curvature curve of main girder under different working conditions is divided into several units,and the ratio of the square of each unit area to the sum of the square of all units is defined as the "curvature area unit variance ratio".The position and degree of the sudden change of this value represents the position and degree of the structure damage under the previous and subsequent working conditions Degree.Based on the finite element simulation analysis of a simple supported T-beam bridge with a span of 20 meters,the correctness of the location and degree of multiple damage of the structure before and after the identification of the location and degree of the mutation in the bridge according to the "curvature area element variance ratio" is verified.In this paper,the theoretical relationship between the Gaussian curvature of the curved surface of the bridge and the structural stiffness is derived,the sensitivity of the Gauss curvature of the curved surface of the bridge to the structural stiffness is demonstrated,and the method of calculating the Gaussian curvature of the curved surface calculation point is proposed;the solid finite element analysis model is established for a simple supported T-beam bridge with a span of 40 meters,and the multi working condition simulation is carried out by setting different degrees of structural damage at different positions Through the real analysis,the correctness of identifying the location and extent of structural damage before and after working condition is verified according to the location and extent of abrupt change of Gaussian curvature of curved surface of bridge.A PMMA model bridge was loaded before and after the damage.The point cloud data of the model bridge was obtained by using a three-dimensional laser scanner.Through noise reduction,coordinate transformation and surface interpolation of the point cloud data,the characteristic deflection surface of the model bridge under the load was obtained.The curvature area difference before and after the damage was calculated based on the curvature area single the "variance ratio of elements" is used to verify the effective damage identification of the model bridge,and the influence of the length of the curvature area calculation element on the identification effect is analyzed.The stack difference analysis of the curved surface before and after the damage is carried out to obtain the deflection change cloud chart,and then the Gauss curvature value of the deflection change of the characteristic points of the bridge deck element is calculated.Based on the mutation of the Gauss curvature value,the effective damage identification of the model bridge is carried out Verification.The research results of this paper explore a practical and effective technical and theoretical new way for high-efficiency quantitative damage identification of bridge structures.