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Study of Girder Bridge’s Damage Identification Based on Modal Strain Energy Method

Author: ZhangJiGang
Tutor: DanDeShan
School: Southwest Jiaotong University
Course: Bridge and Tunnel Engineering
Keywords: Damage Identification The rate of change of modal strain energy Noise Recognition rate Monte Carlo method Girder bridge
CLC: U446.3
Type: Master's thesis
Year: 2007
Downloads: 323
Quote: 4
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Abstract

Because of the role of various factors, the civil engineering structure will inevitably produce damage that may lead to serious consequences, health monitoring is necessary, for the civil engineering structures. Theories and methods of structural damage identification is the core of the study of the structural health monitoring, structural damage identification problem is to judge according to the behavior of the structure showed structural damage location and degree of injury. Based on the basic theory of modal strain energy, calculated according to the change of the structure before and after the injury modal modal strain energy rate of change, as indicators of Bridge Structural Damage Identification and applied. In this paper, the damage index coagulation on the simply supported beam and continuous beam damage numerical simulation and computational analysis. By reducing the modulus of elasticity to simulate the stiffness reduction by MIDAS software the modal model before and after the injury, self MATLAB program to obtain the unit modal strain energy rate of change in order to identify injury. Numerical results show that one or multiple injuries, varying degrees of damage, the identification of the different locations injury, can be found using the first-order mode shapes to the first five orders of mode shapes, can be used to identify simply supported beam or continuous beam damage location, damage location modal strain energy rate of change is greater than the undamaged location; applying the same order modal calculation, with the increase of the degree of injury, damage element modal strain energy rate of change along with the increases, whereby qualitative estimate of the size of the degree of injury. The numerical results also show that the Charpy the effect of damage identification in continuous beam. Noise immunity modal strain energy method is the focus of this paper. In this paper, the introduction of the Monte Carlo method to simulate the measured error by adding noise injury modes are performed with sufficient test, statistical total identification number and rate of change of each unit modal strain energy self recognition algorithm Matlab procedures, you can get stable under the influence of the noise and the degree of injury, damage identification and modal strain energy rate of change of the average, which can meet their variation, recognizing the different levels of damage in the same noise when the unit modal strain energy average rate of change changes in the law. Numerical results show that under the influence of noise under the same conditions, the better the modal combination order of more recognition effect;, the better the damage greater the degree of recognition rate; the noise level the greater the degree of injury, damage to the unit mode the greater the rate of change of strain energy. Various degree of injury, damage identification rate is large, the unit modal strain energy rate of change of the relative size and noise is basically the same.

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