Research Of Orthogonal Pyramid Space Truss Damage Detection Based On Wavelet And Vibration Modal Analysis

Recently, with the rapid development of national economy and driven by constantly improved architecture technology, a large number of magnificent and innovative long-span spatial structure, such as, gymnasia, terminals, exhibition centers, etc has built in our country. Because of the gathered crowd and many important facilities, serious casualty accidents may happen when the long-span spatial structures were severely damaged. During design working life, the long-span spatial structures, such as, grid structures, net shell structures etc, are to bear the long-term constant load weight and suffer the environmental damages including erosions, explosions, earthquakes, impacts and vibrations., which is to lead to the fatigue of the structural elements accumulated, resistance attenuation, and materials, aging damage. What's more, nanotechnology-finding practical rigidity degradation accumulates to a certain degree, which will cause the overall destruction of the structures. Indeed, a lot of long-span space structures collapsed events in history were caused by these. Therefore, in order to prevent structure collapsed incidents and avoid major economic and safety accidents, it is necessary to carry on regular testing about load-bearing components of long-span space structure.In view of above reasons, the main structure of the thesis as follows:1) Analyze the steel cantilever structure damage with finite element software ANSYS. first, using transient incentive and extract useful information, build index parameters of structural damage (difference of the unit strain modal and rate of the unit mode strain energy), and then extract the wavelet transform, finally, determine the location of structural damage.In order to verify the effectiveness of the numerical simulation, this paper also utilizing laboratory equipment for steel cantilever beam to do dynamic modal test, and uses the comparison of the numerical simulation and experimental results of the damage to explain the applicability of the numerical simulation.2) Because of getting the actual detection of useful information often mingled with noise signals, in order to obtain better damage detection signal, this paper adopts the combination method of wavelet threshold and MATLAB software to simulate signal de-noising, using de-noising method to the collected signal in experiment, restore the original signal and determine the location of structural damage. 3) Analyze the orthogonal pyramid space truss damage with finite element software ANSYS. first, pick the best excitation position through analysis of orthogonal pyramid space truss, using transient excitation to conduct dynamical modal numerical simulation about intact structure and damage structural, and then collect test signals, use rate of unit mode strain energy as damage parameter, finally, alternate index parameters with the wavelet transform, and determine the location of structural damage.