The Study For The Method Of Damage Identification Based On The Strain Modal Theory

Civil engineering, as the basis of living and acting of human-beings, its safety is an eternal topic. But the engineering structures are so large and systematic that it is impossible to detect the damage and monitor the safety like mechanical structures.Nevertheless, the structural health monitoring have gained some achievements on megastructures such as large span bridges, offshore drilling platforms and large stadium.Currently, the academia have no agreement on the damage identifcation in structural health monitoring.This paper summarizes the existing experience in engineering and the academic firstly and try to use an indicator based on the strain to identificate the damage. This paper includes three parts: 1) establishing damage index based on impulse response function of the structure and using it to locate the damage position; extracting the response data under the impulse of random impulse, and thus build the damage strain type index to identificate the location and degree of the damage, while compared with the displacement type data based index. 2) establishing the index based on strain mode shapes and using it to analy the damage of a simple beam; firstly, analyzing the damage sensitive of the order of the mode, then use these mode to build objective function and then optimized by ANSYS analysis to achieve the purpose of damage identification; 3) using these two types of strain on index to identificate the damage of a cable-stayed bridge; the first method is used to judge the location of the injury, and then analyzing the order of sensitivity to damage, and finally carrying on the optimizing analysis to complete the specific location of the damage location and degree of recognition.The results show that based on the local damage-sensitive strain type, injury index can be a good indicator of structural damage identification, while the paper also proposes a set of structural damage identification method for structural damage detection. It also has reference value for structural health monitoring.