Damage Diagnosis Method Research Articles

Time series-based SHM using PCA with application to ASCE benchmark structure

Detecting damage at an early stage can avoid a serious catastrophic failure of structures due to inevitable cause, such as fatigue, environmental corrosion, and natural disasters. Various damage detection algorithms have been proposed based on autoregressive model using time series data, which are computationally expensive, and the selection of an optimal order of the model requires extra expertise. In this paper, computationally efficient algorithm is proposed to process the time series data using principal component analysis (PCA) in an effective way. PCA is utilized to model a feature space to compute damage sensitive features insensitive to environmental variations and measurement noise. The modeled feature space preserves the damage information along with eliminates the consequences of environmental variations and measurement noise. Furthermore, Mahalanobis squared distance is adopted to compute damage index as the severity of the damage. The proposed method is validated on analytical models of IASC–ASCE benchmark structure. The test results show that the proposed damage diagnosis method can be useful for wireless sensor network-based structural health monitoring with less computation and low data transmission rate.

Output-only damage diagnosis for plan-symmetric buildings with asymmetric damage using modal flexibility-based deflections

Effective methods for vibration-based damage diagnosis in building structures are based on the estimation of structural deflections from identified modal flexibility (MF) matrices. However, most of the existing methods and previous studies that use MF-based deflections were developed by considering the case of buildings that can be modeled as planar structures (e.g. plan-symmetric buildings) both in the baseline and possibly damaged states. In an attempt to fill this research gap, a deflection-based method for output-only damage diagnosis in building structures tested under ambient vibrations is proposed in this paper. The method is applicable for simple rectangular plan-symmetric “box type” 3D building structures which may experience asymmetric damage, and it can be used for detecting, localizing and quantifying the damage. One of the main differences between the proposed and the existing methods is related to the inspection loads adopted to estimate the MF-based deflections. The inspection loads of the proposed method are more complex than the uniform translational loads adopted in the existing methods. Such proposed loads in fact can be assembled only after having estimated the position of the center of stiffness for each story of the structure. According to the proposed approach, the locations of the centers of stiffness are extracted from the experimentally-derived modal flexibility matrices, before performing the damage diagnosis process. The effectiveness and validity of the proposed method was demonstrated both through numerical analyses and by executing experimental ambient vibration tests on a frame building. The results of the proposed method were also compared with the existing approach which was developed for planar structures. This comparison (made both through numerical and experimental analyses) demonstrated that only the proposed approach can be used to perform a correct damage diagnosis process in plan-symmetric buildings which may experience asymmetric damage, especially when considering the damage quantification problem.

A Reference Matching-Based Temperature Compensation Method for Ultrasonic Guided Wave Signals.

The ultrasonic guided wave-based structural damage diagnosis method has broad application prospects in different fields. However, some environmental factors such as temperature and loads will significantly affect the monitoring results. In this paper, a reference matching-based temperature compensation for ultrasonic guided wave signals is proposed to eliminate the effect of temperature. Firstly, the guided wave signals measured at different temperatures are used as reference signals to establish the relationship between the features of the reference signals and temperature. Then the matching algorithm based on Gabor function is used to establish the relationship between the amplitude influence coefficient obtained by the reference signal and the corresponding temperature. Finally, through these two relationships, the values of the phase and amplitude influence coefficients of the guided wave signals at other temperatures are obtained in a way of interpolation in order to reconstruct the compensation signals at the temperature. The effect of temperature on the amplitude and phase of the guided wave signal is eliminated. The proposed temperature compensation method is featured such that the compensation performance can be improved by multiple iteration compensation of the residual signal. The ultrasonic guided wave test results at different temperatures show that the first iterative compensation of the proposed method can achieve compensation within the temperature range greater than 7 °C, and the compensation within the temperature range greater than 18 °C can be achieved after three iterations.

A new synthesis aperture-MUSIC algorithm for damage diagnosis on complex aircraft structures

Abstract Multiple signal classification (MUSIC) algorithm has gradually been applied to guided wave based structural health monitoring (SHM) as a novel promising method, which is able to realize directional scanning and has the potential to monitor multiple signal sources. However, on complex structures, the low signal-to-noise ratio (SNR) of damage scattered signals and structural anisotropy usually result in the poor localization performance of MUSIC algorithm based damage diagnosis method. To solve these problems for applying the MUSIC algorithm on complex structures, this paper presents a new synthesis aperture-MUSIC algorithm for damage diagnosis with array error compensation. This method enhanced the damage scattered signals and compensate the phase delay perturbations caused by structural anisotropy, which realized damage localization on complex structures. The proposed method is verified on an aircraft structure with T-stiffeners, ribs and rivets to detect corrosion damages with five severity levels. Application results show the advantage and effectiveness of the presented method.

A novel electromechanical impedance model for surface-bonded circular piezoelectric transducer

The electromechanical impedance (EMI) technique is one of common used methods for damage diagnosis. However, the mechanism of EMI-based damage diagnosing is usually complicated and difficult to be comprehensively described. To solve this problem to a certain extent, a novel EMI model for describing the interaction between piezoelectric transducer (PZT) and host structure is developed in this paper. The developed EMI model has advantages of simplicity in formula and excellent precision in signatures prediction. An efficaciously equivalent SMD (Spring-Mass-Damping) system is adopted to obtain the local structural mechanical impedance (LSMI) and to calculate the equivalent parameters ( ) in the vicinity of PZT. To verify the effectiveness of the novel model, a series of experiments are separately conducted on the specimen under healthy condition and damage condition. Through comparing the predicted curves with the experimental ones, the effectiveness of the developed model is demonstrated when used for predicting signatures, especially for resistance signatures. The developed EMI model has shown the potential application in the field of structural health monitoring and damage diagnosis.

Experimental research of nonlinear damage diagnosis using ARMA/GARCH method

Nonlinear damage such as fatigue crack often occurs in some engineering structures, which brings challenges in structural damage diagnosis. A nonlinear damage diagnosis method based on ARMA/GARCH model is proposed to extract the nonlinear characteristic caused by cracks. First, the background description of ARMA/GARCH model is given and a damage diagnosis index based on this model is proposed to detect nonlinear damage location. The main advantage of ARMA/GARCH model is that this hybrid model can well simulate structural time domain acceleration response and effectively extract the nonlinear damage feature. An experiment of three-storey frame structure, which utilized a mechanism constituted of a bumper and a center column to model breathing crack, is studied. The results show that the damage diagnosis index based on ARMA/GARCH model exhibits good accuracy.

Damage location diagnosis of urban rail transit bridge based on vehicle-induced vibration responses

For the urban rail transit bridges, vehicle load has obvious repeatability and regularity, and the vibration amplitude of the bridges under the vehicle action is much larger than that during the period of not being open to traffic, which is more conducive to the appearance of structural damage. This paper attempts to use vehicle-induced vibration responses to diagnose damages for urban rail transit bridges. Firstly, the vehicle-rail-bridge coupling finite element model was established based on the engineering background of a typical urban rail transit bridge. Then, through dynamic time history analysis, the vibration responses of bridge and vehicle before and after damage were obtained. Finally, the sensitivity to damage of acceleration responses from measuring points on both bridge and vehicle was compared, and a damage diagnosis method based on the difference of acceleration responses from different measuring points of bridge and vehicle structure was proposed. The results show that the difference of acceleration response between the measured points of bridge, wheelset and bogie before and after damage can be used to locate damage, and the vehicle-induced vibration data as a medium can provide a new way for rapid diagnosis of damage location for urban rail transit bridges.

Structural health monitoring for long-term aircraft storage tanks under cryogenic temperature

In order to monitor the structural conditions, an SHM technology is necessary for long-term aircraft storage tanks under cryogenic conditions. In this paper, a PZT-based Lamb waves SHM technology is developed for such storage tanks. In order to determine the survivability, durability of different PZT-epoxy sensor systems and functionality of the damage diagnosis method under cryogenic conditions of long-term storage tanks, a series of tests have been conducted. First, the durability of PZT-epoxy sensor systems under cryogenic environment was considered by cryogenic durability tests. Simultaneously, performance tests of different PZT-epoxy sensor systems were performed, include high strain performance test and Lamb waves propagation tests under different temperature environments. The high strain performance of different epoxy adhesives under cryogenic environments was investigated by lap shear strength tests. The functionality of different PZT-epoxy sensor systems was investigated by Lamb waves propagation tests. At last, the damage diagnosis ability of the SHM technology was evaluated in a composite damage diagnosis experiment under cryogenic temperature. Experimental results demonstrated that the developed SHM technology can withstand operational levels of high strain and long-term under cryogenic/room temperature on cryogenic storage tanks, and is functional in the cryogenic environment.

Investigation of Damage Diagnosis of Retaining Wall Structures Based on the Hilbert Damage Feature Vector Spectrum

To diagnose damages within the retaining wall structure, the Hilbert marginal energy spectrum was acquired via the Hilbert–Huang transformation of virtual impulse response functions of responses to the retaining wall under ambient excitations. Based on the Hilbert marginal energy spectrum, the Hilbert damage feature vector spectrum was created. On the basis of the damage feature vector spectrum, a damage identification index was proposed. Based on the damage feature vector spectrum and damage index, the damage state of the retaining wall was detected by the damage feature vector spectrum, damage locations of the wall were diagnosed by the damage index trend surface, and the damage intensity of the wall was identified by the quantitative relationship between the damage index and damage intensity. Based on this, a damage diagnosis method for retaining wall structures was proposed. To verify the feasibility and validity of the damage diagnosis method, both model tests and field tests on a pile plate retaining wall are performed under ambient excitations. Test results show that the damage state of the wall can be detected sensitively, damage locations can be diagnosed validly, and damage intensity can be identified quantitatively via this damage diagnosis method.

A novel mode shape reconstruction method for damage diagnosis of cracked beam

Abstract This paper presents a novel mode shape reconstruction method for damage diagnosis of cracked beam. The proposed method uses output-only data of damaged structure to identify and reconstruct the mode shape of healthy structure. Following that, the curvature mode shapes (CMS) is employed as a damage sensitive feature to locate the damage. In order to identify the mode shape of a target structure with measurement noises, EMD with intermittency criteria is applied to separate dynamic responses into individual modal responses of all grid points on the target structure. A statistical analysis is proposed to evaluate mode shapes from obtained modal responses. Then the Fourier series fitting is employed to mathematically represent the mode shape of the healthy structure. After that, the curvature mode shapes (CMS) which has been investigated as a promising feature for damage identification are acquired by a central difference approximation. Numerical studies are conducted for methodology illustration and validation. Effects of broader damage, multiple damage and measurement noise level are investigated in detail. The accuracy and effectiveness of the proposed method are demonstrated and verified by comparison with conventional method. Finally, a two-span continuous steel I-girder bridge is used to demonstrate the proposed method for more practical applications.

Fire Damage Assessment of Reinforced Concrete Structures Using Fuzzy Theory

Once a reinforced concrete (RC) structure is damaged by fire, the fire damage assessment should proceed to take appropriate post-fire actions, including the decision-making of whether it can be repaired for reuse or not. Since the assessment results of current fire damage diagnosis methods, however, highly depend on the subjective judgment of inspectors, it is hard to ensure their objectiveness and reliability. This study, therefore, aims to develop a new fire damage diagnosis system (FDDS) based on fuzzy theory that can provide objective and comprehensive evaluation results by considering all of the damage conditions observed from the inspection on RC structural members exposed to fire. In addition, the FDDS was applied to an actual fire-damaged case reported by the Architectural Institute of Japan (AIJ, 2009), and it appears that the proposed method provides a reasonable estimation on the fire damage grade of the fire-damaged RC members.

A new damage diagnosis approach for NC machine tools based on hybrid Stationary subspace analysis

This paper focused on the damage diagnosis for NC machine tools and put forward a damage diagnosis method based on hybrid Stationary subspace analysis (SSA), for improving the accuracy and visibility of damage identification. First, the observed single sensor signal was reconstructed to multi-dimensional signals by the phase space reconstruction technique, as the inputs of SSA. SSA method was introduced to separate the reconstructed data into stationary components and non-stationary components without the need for independency and prior information of the origin signals. Subsequently, the selected non-stationary components were analysed for training LS-SVM (Least Squares Support Vector Machine) classifier model, in which several statistic parameters in the time and frequency domains were exacted as the sample of LS-SVM. An empirical analysis in NC milling machine tools is developed, and the result shows high accuracy of the proposed approach.

Seismic damage diagnosis of a masonry building using short-term damping measurements

It is of considerable importance to perform dynamic identification and detect damage in existing structures. This paper describes a new and practical method for damage diagnosis of masonry buildings requiring minimum computational effort. The method is based on the relative variation of modal damping and validated against experimental data from a full scale two storey shake table test. The experiment involves a building subjected to uniaxial vibrations of progressively increasing intensity at the facilities of EUCENTRE laboratory (Pavia, Italy) up to a near collapse damage state. Five time-histories are applied scaling the Montenegro (1979) accelerogram. These strong motion tests are preceded by random vibration tests (RVT's) which are used to perform modal analysis. Two deterministic methods are applied: the single degree of freedom (SDOF) assumption together with the peak-picking method in the discrete frequency domain and the Eigen realisation algorithm with data correlations (ERA-DC) in the discrete time domain. Regarding the former procedure, some improvements are incorporated to locate rigorously the natural frequencies and estimate the modal damping. The progressive evolution of the modal damping is used as a key indicator to characterise damage on the building. Modal damping is connected to the structural mass and stiffness. A square integrated but only with two components expression for proportional (classical) damping is proposed to fit better with the experimental measurements of modal damping ratios. Using this Rayleigh order formulation the contribution of each of the damping components is evaluated. The stiffness component coefficient is proposed as an effective index to detect damage and quantify its intensity.

Structural damage diagnosis with uncertainties quantified using interval analysis

The in situ structural assessment by means of structural health monitoring (SHM) has received a great attention in all sorts of civil engineering applications. However, SHM implementations especially damage detections for real-world infrastructures are always overwhelmed with uncertainties of high dimensionality. A nonprobabilistic uncertainty-quantification-enhanced damage diagnosis method is proposed in this study with respect to interval analysis on SHM features. The diagonal elements of the vector auto-regressive model, constructed from the data measurements, are firstly extracted to form a vector, and this vector's Mahalanobis distance between pristine and unknown conditions is used as a damage-sensitive feature. Subsequently, the uncertainty sources, such as measurement inaccuracy and physical variability, are considered as influencing variables. A differential evolution algorithm is thereby introduced to convert the fluctuating interval of those variables into the uncertainty interval of Mahalanobis distance estimation. Finally, inspired by the idea of receiver operating characteristics when probability of detection is available, a modified mathematic metric is defined suited for interval analysis, and area under the modified receiver operating characteristics curve is employed to detect and localize damages. A contrived numerical mass-spring system and a laboratory-scale frame structure are used to validate the proposed framework; and in addition, the damage severity is able to be quantified via a proposed interval distance between pristine and inspection conditions.

Exploring the limits of the Truncated SPRT method for vibration-response-only damage diagnosis in a lab-scale wind turbine jacket foundation structure

The performance limits of the truncated Sequential Probability Ratio Test (SPRT) method for damage diagnosis via vibration-response-only signals are explored. This is accomplished by considering damage detection and identification (classification) in a laboratory-scale wind turbine jacket foundation structure subject to damage scenarios ranging from minor to mild in terms of their effects on the dynamics. Low and limited frequency bandwidth (~ 3.5—200 Hz) signals are employed in order to better reflect actual excitation conditions. As an additional challenge, only a single vibration signal, measured via laser vibrometer or accelerometer, is employed. The results indicate moderate damage diagnosis performance for the minor damage scenarios, but good for mild ones. Expectedly, the overall performance is similar to that of the residual variance based method, but inferior to that of the model parameter based method.

Analytical and experimental investigation on eigenfrequency-based damage diagnosis of cantilever beam

This paper presents two eigenfrequency-based damage diagnosis methods in a cantilever beam. The analytical relationship has been established between the eigenfrequency and damage parameters, including relative damage location and severity. On the premise that pre-damaged eigenfrequencies are known, a diagnosis algorithm without requirement of material properties is proposed based on change ratios of the first three eigenfrequencies. If pre-damaged eigenfrequencies are unfeasible to be acquired, a three-contour method based on only post-damaged eigenfrequencies is introduced to estimate damage parameters. The uniqueness of solution is discussed. Both the numerical simulation by the finite element method and the experiment on real beams are conducted and result in a good agreement between actual damage parameters and calculated values by using the proposed methods.

Experimental and numerical studies on a test method for damage diagnosis of stay cables

To diagnose the state of stay cables, a vibration-based model-free damage diagnosis method of stay cables using the changes in natural frequencies is further proposed and validated. The structural frequency is rapidly and easily acquired; moreover, it is simple and reliable for damage diagnosis. The frequency would change after the stay cable is damaged, so the frequency change could be used as the damage index. However, the stay cables are very long in long-span cable-stayed bridges, and their frequencies are very small; the frequency change due to small damage of the stay cable would be submerged by the surrounding noise and error of parameter identification process. A temporary diagonal steel bar–based method is used to solve this issue. The steel bar is installed with one end on the stay cable close to the bottom anchor head and the other end on the bridge deck; thus, the stay cable is divided into a short part and a long part by the steel bar. The frequency of a stay cable with a given tension force increases with the decrease in its length; according to the qualitative analysis, the frequency of the short part increases dramatically, and the local frequency change of the short part due to the same damage in the whole stay cable is amplified dramatically; thus, the small damage of a stay cable can be diagnosed easily. Numerical simulations of a stay cable selected from a cable-stayed bridge and a laboratorial stay cable are used to validate the method and also give a recommended rule for design of the temporary diagonal steel bar; experimental validation has also been conducted. All the results indicate that the proposed method works very well in damage diagnosis of stay cables. The proposed method is an output-only, model-free, fast and economical damage diagnosis method for stay cables.

A two-step method composed of wavelet transform and model updating method for multiple damage diagnosis in beams

In the present study, a two-step approach comprised of wavelet transform and model updating method for multiple structural damage localization and quantification in beams is proposed. The first step is commenced with applying wavelet transform to axial components of mode shapes so as to predict where the damages are located. During this step, wavelet transform might mistakenly detect a number of elements as impaired due to both sampling interval and middle support effect. In the next step, by defining a damage sensitive objective function consisting of natural frequencies and mode shapes, damage intensities at predicted locations will be computed via model updating method employing ECBO (Enhanced Colliding Bodies Optimization) algorithm. The problem with mistakenly predicted damaged locations will be addressed by reported damage intensities during the second step. The present study also indicates that this two-step method greatly assists in reducing the number of variables during model updating process leading to more precise results. Three numerical examples with multiple damages and noisy modal data are studied in order to guarantee the efficacy of the method. Moreover, one numerical example is solved with a number of other Meta-Heuristic algorithms including GA (Genetic Algorithm), CSS (Charged System Search), Pattern Search and Cuckoo algorithm whose results are compared to ECBO algorithm with the intention of ensuring the veracity of ECBO results. The results vividly demonstrate that this method is highly efficient even in the presence of noise.

Reconstruction of baseline time-trace under changing environmental and operational conditions

Compensation of changing environmental and operational conditions (EOC) is often necessary when using guided-wave based techniques for structural health monitoring in real-world applications. Many studies have demonstrated that the effect of changing EOC can mask damage to a degree that a critical defect might not be detected. Several effective strategies, specifically for compensating the temperature variations, have been developed in recent years. However, many other factors, such as changing humidity and boundary conditions or degradation of material properties, have not received much attention. This paper describes a practical method for reconstruction of the baseline time-trace corresponding to the current EOC. Thus, there is no need for differentiation or compensation procedures when using this method for damage diagnosis. It is based on 3D surface measurements of the velocity field near the actuator using laser vibrometry, in conjunction with high-fidelity finite element simulations of guided wave propagation in free from defects structure. To demonstrate the feasibility and efficiency of the proposed method we provide several examples of the reconstruction and damage detection.

An electromechanical impedance-based method for tensile force estimation and damage diagnosis of post-tensioning systems

We propose an effective methodology using electromechanical impedance characteristics for estimating the remaining tensile force of tendons and simultaneously detecting damages of the anchorage blocks. Once one piezoelectric patch is attached on the anchor head and the other is bonded on the bearing plate, impedance responses are measured through these two patches under varying tensile force conditions. Then statistical indices are calculated from the impedances, and two types of relationship curves between the tensile force and the statistical index (TE Curve) and between statistical indices of two patches (SR Curve) are established. Those are considered as database for monitoring both the tendon and the anchorage system. If damage exists on the bearing plate, the statistical index of patch on the bearing plate would be out of bounds of the SR curve and damage can be detected. A change in the statistical index by damage is calibrated with the SR curve, and the tensile force can be estimated with the corrected index and the TE Curve. For validation of the developed methodology, experimental studies are performed on the scaled model of an anchorage system that is simplified only with 3 solid wedges, a 3-hole anchor head, and a bearing plate. Then, the methodology is applied to a real scale anchorage system that has 19 strands, wedges, an anchor head, a bearing plate, and a steel duct. It is observed that the proposed scheme gives quite accurate estimation of the remaining tensile forces. Therefore, this methodology has great potential for practical use to evaluate the remaining tensile forces and damage status in the post-tensioned structural members.