Damage Identification Of Beam String Structure Based On Frequency Changes

Beam string structure is widely used in bridge, terminal building, stadium and other large span projects. Have an important influence on the safe use of key projects. So it is very important to ensure the normal use of the beam string structure. At present, the research on the damage identification of the beam string structure is less. How to detect the use of the string structure in service need to be further studied. This paper is according to the theory of structural damage identification based on frequency change. The damage identification method for beam string structure is researched, By setting different damage conditions, studying the method of damage location and damage extent identification method, analysising the contact between the frequency variation and ultimate bearing capacity. The main contents and related conclusions of this paper are as follows:Firstly, introducing the ratio of frequency changes and the square ratio of frequency changes, ratio of frequency change ratio, normalized ratio of frequency changes four kinds of damage identification index based on the changes in frequency, Calculation and analysis are done at a T-shaped beam, comparing the applicability of several damage index. Compared with the other three indicators, Normalized ratio of frequency changes showed good monotonicity, peak change highlights, the damage sensitive with the flaw detection of a beam. As a damage location index, it has good stability. According to a practical project, A beam string structure model is established, By setting four damage conditions:damage of bottom cable, loss of bottom cable prestress, damage of struts and damage of lower chord, It is analysised the change rule of the normalized ratio of frequency changes along with different damage location under each damage condition. The normalized ratio of frequency changes damage index is proposed for the damage location. It is suggested that the theory and method of damage identification by using the square damage index of natural frequency change. Finally, the relationship between the natural frequency and the ultimate bearing capacity of the string structure is analyzed. The relationship between the frequency variation of the structure and the residual ultimate bearing capacity is got. The research of this paper provides reference for the damage detection of the beam string structure.