Damage Identification Method Of Bridge Structures Using Curvature Characteristics

In practical operation,the routine safety inspection of bridge mostly adopts the method of manual inspection of bridge deck or long-distance observation with telescope,which is lack of quantifiable scientific basis,and it is difficult to find the hidden danger of bridge structure in time.In the case of "serious injury" of bridge structure,the changes of bridge deck geometry are easy to be ignored by naked eyes,and these abnormal changes can be detected by three-dimensional laser scanning.Using these change data to distinguish the safety state of bridge structure can make the regular safety inspection have objective quantitative data and historical experience data accumulation.In this paper,two kinds of characteristic curves of bridge deformation response,deflection curve and displacement influence curve,are proposed to calculate the characteristic curvature,and the flexural rigidity EI of the structure is selected as the damage variable to identify the damage of the bridge structure.The main work is as follows:(1)the method of damage identification of bridge structure based on the curvature feature of deflection curve is studied,and the damage identification index based on the curvature mutation feature is established by obtaining the point cloud data of bridge geometry shape,extracting the characteristic curve of typical section;(2)the structure model is established by numerical simulation and finite element method,and the damage identification analysis of the structure is carried out to verify the established structure The validity of damage identification index.Thirdly,according to the characteristics of the displacement influence line,the measured displacement influence line data are analyzed,and the damage identification method based on the measured displacement influence line curvature characteristic data is established.Based on the actual project of Wen Xing Wan bridge in Beibei District,Chongqing,the method proposed in this paper is explored.The conclusions are as follows:1.The difference curvature of displacement curve is only related to the damage degree in the damage area and damage position,which can clearly identify the damage position and damage degree to a certain extent;2.The abrupt position of the deformation curvature of the characteristic section of the side span girder of the model bridge will change with the change of the different crack positions in the side span girder span,and the corresponding abrupt peak value of the curvature will change with the different crack positions of the bridge structure,and the peak value and the degree of the crack are roughly quadratic parabola distribution;3.Using the ratio of the square of curvature influence line element area difference before and after the damage to the sum of the square of each element area difference(AD value)to locate the local stiffness damage in the structure from a small degree(18.47%)to a serious degree(96.51%).This parameter shows a strong effect on different degrees of damage and different types of member damage in the structure Sensitivity.In this paper,the curvature characteristic indexes of deformation curve and displacement influence line are analyzed,which can lay a technical foundation for intelligent,efficient and quantitative daily safety inspection.