Maximum Of Wavelet Coefficients Research Articles

An Optimized Damage Identification Method of Beam Using Wavelet and Neural Network

An optimized damage identification method of beam combined wavelet with neural network is presented in an attempt to improve the calculation iterative speed and accuracy damage identification. The mathematical model is developed to identify the structure damage based on the theory of finite elements and rotation modal parameters. The model is integrated with BP neural network optimization approach which utilizes the Genetic algorithm optimization method. The structural rotation modal parameters are performed with the continuous wavelet transform through the Mexico hat wavelet. The location of structure damage is identified by the maximum of wavelet coefficients. Then, the multi-scale wavelet coefficients modulus maxima are used as the inputs of the BP neural network, and through training and updating the optimal weight and threshold value to obtain the ideal output which is used to describe the degree of structural damage. The obtained results demonstrate the effectiveness of the proposed approach in simultaneously improving the structural damage identification precision including the damage locating and severity.

Crack Identification of Frame Structure by Means of Wavelet Analysis of Strain Mode

Based on wavelet transform of strain mode, the damage identification of plane frame was studied in this paper. After solving strain modal parameters of plane frames with cracks by means of the finite element theory, applying the gauss2 wavelet transform to analyze the stain mode of plane frame, and denoising the wavelet coefficients of the strain mode by db3 wavelet, the crack location of the plane frame could be identified by the maximum of wavelet coefficients after denoising. Taking one-story plane frame for example, three finite element models, including a frame beam with a crack, each frame column with a crack, and each frame beam and column with a crack, were set up separately, then the above-mentioned method was applied to identify the location of the crack. The results show the method is effective, and it may be useful in damage identification and diagnosis in structures.

Crack Identification of Plane Frames Based on Wavelet Transform of Rotation Modes

By means of the wavelet analysis theory, the damage identification of plane frame was studied. Based on the finite element analysis of modal parameters, the method using the wavelet analysis of rotation mode was proposed for plane frames crack identification, and the mexh wavelet transform was applied to analyze the rotation mode of plane frame, so the location of crack of the plane frame can be identified by the maximum of wavelet coefficients. Taking one-story plane frame for example, the finite element model, each frame beam and column with a crack, was seperately set up, and the above-mentioned method was applied to identify the location of the crack, and the results validate this method. Finally, compared with the result of the wavelet transform to analysis vibration mode and rotation mode, it can be concluded that the method using the wavelet analysis of rotation mode is more convenient and more effective. This method may be useful in damage identification and diagnosis in structures.

Study on Damage Location of Spatial Structures Based on Wavelet Analysis of Model Strain Energy

The research to identify and locate the damage to the engineering structure mainly aimed at some simple structure forms before, such as beam and framework. Damage shows changes of local characteristics of the signal, while wavelet analysis can reflect local damage traits of the signal in time domain and frequency domain. For confirming the validity and applicability of structural damage identification methods, wavelet analysis is used to spatial structural damage detection. The wavelet analysis technique provides new ideas and methods of spatial steel structural damage detection. Based on the theory of wavelet singularity detection，with the injury signal of modal strain energy as structural damage index，the mixing of the modal strain energy and wavelet method to identify and locate the damage to the spatial structure is considered. The multiplicity of the bars and nodes can be taken into account, and take the destructive and nondestructive modal strain energy of Kiewitt-type reticulated shell with 40m span as an example of numerical simulation，the original damage signal and the damage signal after wavelet transformation is compared. The location of the declining stiffness identified by the maximum of wavelet coefficients，analyzed as signal by db1 wavelet，and calculate the graph relation between coefficients of the wavelets and the damage to the structure by discrete or continuous wavelet transform, and also check the accuracy degree of this method with every damage case. Finally，the conclusion is drawn that the modal strain energy and wavelet method to identify and locate the damage to the long span reticulated shell is practical, effective and accurate, that the present method as a reliable and practical way can be adopted to detect the single and several locations of damage in structures.

Crack Identification of Simple Beam via Wavelet Analysis of Vibration Modes

Based on the finite element theory, a method is proposed for crack identification of simple beam via the wavelet analysis of vibration modal parameters. A cracked simple beam is simulated using finite element method, and its modal parameters, including first three-order vibration modes, are obtained. Then, these modal parameters are analyzed via mexh and db wavelets. The crack location of the simple beam is identified by the maximum of wavelet coefficients, which validates the proposed method. This research may be useful in crack identification of simple beam structures.

Research on Damage Identification of Suspension Bridge by Wavelet Analysis of the Strain Mode

The suspension bridge contained damage was made as the object of study. Three different damage conditions for suspension bridge were calculated(conditions 1, the left midspan contains a damaged zone, condition 2, the left end bay contains two damaged zone, condition 3, both sides midspan contains a damaged zone). Using the wavelet analysis theory, solving strain modal parameters of the suspension bridge with cracks by means of Lanczos method. Then the cracks location of the suspension bridges could be identified by the maximum of wavelet coefficients. It can be concluded that the method using wavelet analysis of strain mode is more accurate and more effective through the calculation and analysis of the suspension bridge damage identification. The method can be useful in the suspension bridge damage identification and diagnosis.

Damage Identification of Arch Bridge Based on Curvature Mode Wavelet Analysis

Based on the curvature modal damage identification of wavelet analysis principle, the finite element method was applied to analyze the vibration characteristics of the damaged deck arch bridge. Take Haar wavelet as the mother wavelet, through the continuous wavelet transform of curvature mode and then identified the damaged position by the maximum of wavelet coefficients. analyze the damage identification problem under three different damaged conditions (condition 1: only the arch 1 contained one damaged location; condition 2: the arch 1 and the arch 2 contained one damaged location respectively; condition 3: the arch 1 contained two damaged locations and the arch 2 contained one damaged location).This paper provided a valuable reference of damage identification and diagnosis for arch bridge.

Research on Surface Cracks Identification of Continuous Steel Box Girder Bridge by Wavelet Analysis of the Strain Mode

The paper chose a three-span continuous steel box girder bridge with horizontal semicircular surface cracks as research object, and the cracks are non-through and unsymmetrical. Solving strain modal parameters of beams with cracks by means of the three-dimensional finite element theory, and applying continuous wavelet transform (CWT) to analyze the strain mode by Haar wavelet, then the position of the cracks could be identified by the maximum of wavelet coefficients. The validity of the method has been proved by numerical calculation and analysis. Some useful conclusions for continuous steel girders bridge have been drawn and it has been useful in surface flaw identification and diagnosis in structures.

Damage Identification of Elastic Plate Based on Strain Mode Wavelet Analysis

By means of the wavelet analysis theory, the damage identification of elastic plate was studied. Adopted the finite element method to analyze the dynamic character of the plate and applied the method of Lanczos for calculating the strain mode, and the strain mode is analyzed by mexh wavelet (Mexican Hat wavelet). The location of the declining stiffness is identified by the place where maximum of wavelet coefficients appears. Therefore, this method is applied to the elastic damaged plate. Three types of damaged regions in rectangular simply supported plate are recognized, which indicates this method is effective and accurate. And this method has a certain value in the project application.

Research on Sheet Crack Identification of Frame Structure Using Wavelet Analysis

This research presented the damage identification problem of frame structure using the wavelet transform of strain mode. Solving strain modal parameters of plane frames with cracks by means of the finite element theory, applying the gauss2 wavelet transform to analyze the stain mode of plane frame, and denoising the wavelet coefficients of the strain mode by db3 wavelet, then the location of crack of the plane frame could be identified by the maximum of wavelet coefficients after denoising. Taking one-layer plane frame as an example, this research gave the finite element model of framework with sheet crack (non-through surface crack and internal crack), calculated the strain mode of the structure, and identified the location of cracks by wavelet analysis of strain mode. Results show that this method is able to identify the damage of frame structure. Numerical calculation shows that the approach is effective. This paper provides a valuable reference of structural damage identification and diagnosis in engineering applications.