The Numerical Simulation Research Of Orthogonal Pyramid Space Truss Damage Dectection Based On Wavelet Analysis

The spatial steel structure is widely used in industry and civil construction based of the advantages of big stiffness, light weight, reasonable loading, well seismic performance and so on. The truss structure as a kind of spatial steel structure becomes the main structural form of large span roof, and covers in and abroad. But, most truss structures in service exist damages after longtime working, becauce of excessive loading, disaster and other reasons. With using, the damages become more serious and collapse may occur at any time. So it is very necessary to find some methods to forbid these problems. Now, the studies focus on which parameters are sensitive to the damages of truss structures and which methods can accurately find the damage location and damage degree. While some works have been done around the sensitive parameters to damage and the damage identification methods in this paper.A method made of mode analysis and wavelet analysis is used to judge the damages of steel truss structures for the first time in this article. At the same time, some studies also have been done including how to obtain the damage fearures and reduce noise using wavelet method, and how to define the damage location and damage degree of orthogonal pyramid space trussstructures through these features. These researchs are shown as follows:1) The mechanics performances of cantilever, plane truss and spatial truss structure are analyzed by the numerical simulation software ANSYS. Given the damage location and damage degree in the structure, the strain energy of damage structure will be obtained as the original damage signal. With wavelet transformation, the wavelet transformation coefficient figure of this signal will be found. The results show as: the singular point of this figure might determine the damage region initially.2) In practice, the damage signal often mixed with the noise information because of the outside effects. To find the accurate damage signal, the wavelet and wavelet packet analysis were adopted to remove the noise information in this paper. A series of noise reduction model experiments by MATLAB software, the results indicate that the wavelet packet analysis used to reduce the signal noise has the superiority.3) The feasibility of the damage judging method was analyzed in this paper and this method is combined modal analysis and wavelet analysis. The strain mode difference and curvature mode difference of the intact and damage truss structure are considered as damage index. Through wavelet transformation, the singular point location in the wavelet transformation coefficient figure is same to the given damage location. So, the feasibility of the method combined modal analysis and wavelet analysis is effective.4) The method combined the wavelet transformation and the modal analysis is also used to identify the damage location of the orthogonal pyramid space truss structure in this paper. The single link is the force unit of the spatial truss structure, and every link joins many nodes. So the node damage information can not test the damage location accurately. And it is necessary to gain the element damage message to discern the damage location. In order to solve this problem, the element strain mode differences and the element curvature mode differences from the intact and damage structure were considered as the structural damage index. Through the wavelet analysis, the single and multiple damage locations can be distinguished by this method and the damage degree can be preliminary judgement. These researches have some guideness to the practicle project.