Research On Structural Damage Identification Of Grid Structure Based On Modern Signal Processing Methods

With the development of the steel structure processing technology and equipment level,large-span space grid structure is developing rapidly,and is widely used in large industrial buildings,railway stations,museums and other important places.In order to meet the demands of the production and living of people,equipment is often lift on space truss structure,and long-term reciprocating random excitation could lead to damage of local area of space grid structure.Space grid structure belongs to multiple statically indeterminate structures,while most local damage would not necessarily cause the overall collapse of the structure,but for the safe operation of the structure,the development of the local damage is often easy to cause catastrophic consequences.The design and construction of space grid structure is often performed by professional grid structure company,it is usually only could satisfy the use and construction requirements;seldom consider long-term safety performance of the space truss structure,especially the local damage caused by external incentives.In addition,due to the large number of space truss structure bar,it is difficult to find damage location of the space truss structure artificially.When modern signal processing methods are used for structural damage detection,to a certain extent,the effect of the detection method could be enhanced;the range of damage detection could also be expanded.Therefore,it is significant to combine with modern signal processing method for structural damage research.In order to avoid the shortage caused by artificial incentive,this paper collects the acceleration response signal directly caused by random excitation and using modern signal processing method to deal with it,and determines damage location of the grid structure through the corresponding damage identification index.In this paper,two kinds of damage detection methods are used to detect the grid structure.The random excitation is defined as the excitation of the suspended equipment on the grid structure and the excitation produced by the moving load in this paper.The first method is based on wavelet packet analysis to identify the damage of different damaged bars and different degrees of a bar,processing the response signals before and after damage of each node by wavelet packet,extracting the wavelet packet energy change rate damage index,analyzing the wavelet packet energy change rate of all nodes by FCM clustering algorithm and determining whether the damage occurs in the position.The second method is based on the empirical mode decomposition to identify the damage of different damaged bars and different degrees of a bar,processing the response signals before and after damage of each node by empirical mode decomposition,analyzing the waveform factor change rate damage index by FCM clustering algorithm and determining whether the damage occurs in the position.The damage indexes are analyzed by FCM clustering algorithm and determining in the two detection methods.In the numerical simulation,the damage of different location and different degree were simulated,five kinds of different damage conditions are analyzed,and the numerical analysis results show that the two methods can accurately identify structure damage.In the experiment,the two methods are also used to analyze the damage index of the grid structure.Only three different damage conditions are analyzed in the experimental part.The results of the numerical simulation analysis and the experimental analysis show that the damage identification method based on wavelet packet analysis and the damage identification method based on empirical mode decomposition of the grid structure damage detection are effective.These two kinds of signal processing methods of damage identification method have some filtering effect to the noise of the signal obtained by sensor.Furthermore,the damage identification method based on empirical mode decomposition is more effective for the damage identification when two damaged locations occur in the grid structure.Because the grid structure is multiple statically indeterminate structure,the damage index of the node of individual non-damaged member is larger when two damaged bars occur,in this case,the node of the first fuzzy partition which is first determined by the FCM clustering algorithm is the node which is most likely to be damaged.And then judge whether the connecting bar connected with the node of the first fuzzy area is damaged.It is necessary to study the damage identification of the grid structure when it occurs three or more than three damaged locations.