Dynamic Characteristics Calculation And Damage Identification Method Of Cracked Simply Supported Bridge

Crack is one of the common diseases of simply supported bridge, and it will lead to the deterioration of bridge structures. The dynamic characteristic test technique has strong objectivity, and it can discover the cracks of the hidden parts and has no additional damage to the bridge structure. So people try to apply the dynamic characteristics to cracked bridge structures, and the application of dynamic characteristics in cracked structures has two aspects: the direct problem and the inverse problem. For the direct problem, on the one hand, the dynamic characteristics of cracked bridge structures is the basic data of bridge maintenance and reinforcement. On the other hand, the accurate calculation method of dynamic characteristics can provide theoretical support for bridge condition assessment based on dynamic parameters. For the inverse problem, cracks will lead to the local stiffness change of bridge structure and dynamic characteristics can reflect the local stiffness changes, so it is imperative to apply dynamic characteristics to crack damage identification of bridge structure.Based on the above reasons, this paper carried out the dynamic characteristics calculation of cracked simply supported bridge and damage identification method based on dynamic characteristics, the main research work is as follows:1. Based on the basic theory of structural vibration and the basic principle of the stress characteristics of cracked beam structure, the dynamic characteristics calculation method of cracked simple supported beam based on the piecewise vibration function and the transfer matrix method is formed.2. Under the assumption that the number of crack is known, based on dynamic characteristics calculation method of cracked simply supported beam, identification algorithm of crack location and depth based on the self-vibration frequencies and the lower order dynamic parameters is formed using perturbation theory.3. Under the condition that the number of crack is unknown, two step method for damage identification is presented. Firstly, the approximate location of the crack is determined by using the continuous wavelet transform and fractal theory, and then to identify the exact location and depth of the crack by using the damage identification method for the condition that the number of crack is known.