Study On The Grey Correlation Of The Strain Modal In The Structural Damage Identification Of The Beam

Due to the load and service environment and as well as other factors, the structural damages usually occured in engineering structures during operation. Some damage may even lead to catastrophic accidents. So, structure detection to identify the damage has important engineering value. Structural damage identification technique could be divided into identification based on static response and dynamic response. Including, the dynamic paramters were various in damage identification based on dynamic response. Recently research always focused on how to insure that parameter variation reflected the real condition of the structure correctly. The structural strain model is one kind of model parameter that is sensitive to the local change of structure. Grey correlation theory was widely used in system identification, because of its consistency with qualitative analysis and correction in quantitative analysis of small samples data. This paper based on the combination of strain model and grey correlation theory, its validity and effectiveness on recognition were studied by using the simple supported beam and continuous beam as subjects.Firstly this paper systematically introduced the strain modal theory and its application in structural damage identification, and also expounds grey correlation theory and its advantage in dealing with the small samples data with poor information. On this basis, the method on the structural damage identification based on the combination of the strain model and grey correlation theory was studied, and the numerical formula about the correlation coefficient is deduced in this article.Secondly with simply supported beam and continuous beam as example, using ANSYS software to simulate and Matlab to complete data processing, based on the correlation coefficient of strain modal, the vibration strain model to different damage location and damage degree were systematically researched. The results show that:the damage location could be effectively determined by the grey correlation coefficient of the modal vibration test points, except the damage location was on the modal nodes, the relative degree of damage could be identified on a certain extend.Finally, the simply supported beams with different damage locations were made out in the work of this paper. The validity and effectiveness of grey correlation coefficient on recognition of structural damage were verified under the conditions of different number of test points by the modal test of these beams. There are two experiment schemes. One is that sparse strain measuring points were set on the beams. The other was that encryption strain measuring points were fixed. The results showed that the damage location could be determined effectively by two experiment schemes, the more measuring points the beam has, the more precisely the damage located.