Structural Damage Quantification Research Articles

Model-based damage identification of railway bridges using genetic algorithms

The assessment of structural integrity via numerical model updating has been drawing attention in several areas of engineering over the last years. Basically, it consists in an optimization process based on the minimization of the residuals between measured and estimated numerical responses. In such methodologies, several factors influence the success of both localization and quantification of structural damage, such as: the damage features used in the formulation of the objective function, the optimization algorithm and the adopted updating parameters. Many existing studies using these methods are applied to simple structural systems, e.g., beams, frames and trusses. However, few studies applied to large and complex structures are found in the literature. In this context, this work proposes to assess the performance of a genetic algorithm-based approach applied to two case studies. The first case refers to a two-dimensional model of a hypothetical railway bridge, where the efficiency and robustness of five different indicators are assessed considering three damage scenarios. In the second case, a real railway bridge is considered. The results obtained show that the proposed approach is able to detect, locate and quantify multiple damage with several updating parameters and few target responses.

Data-driven damage tracking and hysteresis evaluation of earthquake-excited structures with test validation

A data-driven damage tracking and hysteresis evaluation method for earthquake-excited structures that adopts the model-reference concept is presented in this paper. A series of target substructures with local interstory hysteresis is first decentralized from the global structure system adopting the Rayleigh damping model. A linear reference model, designed to be identified from nondestructive seismic events, is used to represent the desired healthy behaviors. The tracking error of structural responses with a substructure-level loading reconstruction is subsequently introduced to quantify the potential behavior deviation during a disastrous earthquake. Such a structural behavior deviation, in terms of a normalized form, has been proposed in a novel data-driven damage model; accordingly, a logistic framework has been presented for the quantification of structural damage of interests. Two illustrative examples, including a numerical simulation of a three degree-of-freedom degradation model and an experimental investigation of a large-scale reinforced concrete frame through a shaking table test, have been employed. Comprehensive results and detailed discussion are presented to illustrate the damage tracking and quantification performances of the proposed data-driven evaluation method.

Seismic reliability assessment of structures using artificial neural network

Localization and quantification of structural damage and estimating the failure probability are key outputs in the reliability assessment of structures. In this study, an Artificial Neural Network (ANN) is used to reduce the computational effort required for reliability analysis and damage detection. Toward this end, one demonstrative structure is modeled and then several damage scenarios are defined. These scenarios are considered as training data sets for establishing an ANN model. In this regard, the relationship between structural response (input) and structural stiffness (output) is established using ANN models. The established ANN is more economical and achieves reasonable accuracy in detection of structural damage under a set of ground motions. Furthermore, in order to assess the reliability of a structure, five random variables are considered. These are columns’ area of the first, second, and third floor, elasticity modulus, and gravity loads. The ANN is trained by suing the Monte Carlo Simulation (MCS) technique. Finally, the trained neural network specifies the failure probability of the proposed structure. Although MCS can predict the failure probability for a given structure, the ANN model helps simulation techniques to receive an acceptable accuracy and reduce computational effort.

Diagnosis and Longitudinal Assessment of Osteoarthritis: Review of Available Imaging Techniques.

Osteoarthritis (OA) is a major chronic and global health care problem. Recent technological advances in imaging and postprocessing techniques have enhanced the understanding and characterization of the pathophysiology of this chronic and prevalent disease. Although plain radiograph remains the modality of choice for initial assessment of OA, recent studies have shown that advanced cross-sectional imaging can improve the early detection, grading, structural damage quantification, and risk stratification of OA. This article discusses the currently available evidence regarding both the conventional and novel imaging modalities that can be used for evaluation of patients with OA and its longitudinal assessment.

Damage recovery of FIB modified Si for directed-assembly of semiconductor nanostructures

Focused ion beam (FIB) techniques have previously been shown to have applications in templating semiconductor nanostructure growth on Si. To assess crystalline quality in this method, or in other FIB-based nano-fabrication methods in Si, we assess in this work FIB-implantation damage in Si and subsequent recovery by annealing. Specifically, we study Si substrates implanted to 1 × 1012–5 × 1015 ions cm−2 fluences of 30 kV Si2+, Ge2+ and Ga+ incident normally at room temperature, covering a structural damage regime from almost no damage to amorphization. Raman spectroscopy with incident photons of wavelength 405 and 514 nm were used for probing structural damage in different depths in as-implanted and thermally annealed substrates. Annealing was performed for varying times at 730–900 °C in ultra-high purity nitrogen ambient. Structural damage quantification was performed through measurements of peak height and position of the crystalline Si peak at 520 cm−1. Our analysis shows that a structural damage parameter, D, (defined by subtracting from unity, the ratio of the height of the Si Raman peak in implanted/annealed samples to that for the Si peak in an unimplanted standard, such that D = 0.00 and D = 1.00 correspond to pristine single crystal and amorphous Si respectively) is 0.05 or less in all the Si and Ge implants after annealing to 900 °C, 1800 s. However, D for the Ga implants is close to zero for Ga fluences up to 3 × 1013 cm−2 but increases steadily to 0.19 for 5 × 1015 Ga cm−2 under these annealing conditions. The underlying damage recovery mechanisms are discussed.

Fault Isolation and Quantification from Gaussian Residuals with Application to Structural Damage Quantification

Fault detection for structural health monitoring has been a topic of much research during the last decade. Localization and quantification of damages, which are linked to fault isolation, have proven to be more challenging, and at the same time of higher practical impact. While damage detection can be essentially handled as a data-driven approach, localization and quantification require a strong connection between data analysis and physical models. This paper builds upon a hypothesis test that checks if the mean of a Gaussian residual vector - whose parameterization is linked to possible damage locations - has become non-zero in the faulty state. It is shown how the damage location and extent can be inferred and robust numerical schemes for their estimation are derived based on QR decompositions and minmax approaches. Finally, the relevance of the approach is assessed in numerical simulations of two structures.

Damage-based optimization of large-scale steel structures

A damage-based seismic design procedure for steel frame structures is formulated as an optimization problem, in which minimization of the initial construction cost is treated as the objective of the problem. The performance constraint of the design procedure is to achieve repairable damage state for earthquake demands that are less severe than the design ground motions. The Park-Ang damage index is selected as the seismic damage measure for the quantification of structural damage. The charged system search (CSS) algorithm is employed as the optimization algorithm to search the optimum solutions. To improve the time efficiency of the solution algorithm, two simplifying strategies are adopted: first, SDOF idealization of multi-story building structures capable of estimating the actual seismic response in a very short time; second, fitness approximation decreasing the number of fitness function evaluations. The results from a numerical application of the proposed framework for designing a twelve-story 3D steel frame structure demonstrate its efficiency in solving the present optimization problem.

Detection and quantification of structural damage under ambient vibration environment

In this paper, a new damage detection and quantification method has been presented to perform detection and quantification of structural damage under ambient vibration loadings. To extract modal properties of the structural system under ambient excitation, natural excitation technique (NExT) and eigensystem realization algorithm (ERA) are employed. Sensitivity matrices of the dynamic residual force vector have been derived and used in the parameter subset selection method to identify multiple damaged locations. In the sequel, the steady state genetic algorithm (SSGA) is used to determine quantified levels of the identified damage by minimizing errors in the modal flexibility matrix. In this study, performance of the proposed damage detection and quantification methodology is evaluated using a finite element model of a truss structure with considerations of possible experimental errors and noises. A series of numerical examples with five different damage scenarios including a challengingly small damage level demonstrates that the proposed methodology can efficaciously detect and quantify damage under noisy ambient vibrations.

A Structural Damage Quantification Method for HFR-Video-Based Modal Testing

In this study, we introduce the concept of “modal radar” as a novel structural damage analysis methodology for HFR (high-frame-rate)-video-based modal testing that can accurately quantify both the degrees and positions of structural damage. Our modal radar method consists of four parts: (1) vibration displacement measurement using an HFR video camera, (2) stochastic subspace identification to estimate modal parameters, (3) improved local Fisher discriminant analysis for supervised learning based on modal parameters, and (4) feature space normalization for damage quantification. Based on our modal radar method, numerical simulations were performed for beam-shaped cantilevers with different weights as structural damage, and the positions and degrees of the weights were accurately estimated in the normalized feature space, even when the objects to be observed were not involved in the sample set for supervised learning. These tendencies were also confirmed in HFR-video-based modal testing of actual steel cantilever beams with different weights, which were excited by human finger tapping. These experimental results demonstrated the effectiveness of our concept of “modal radar” for accurate structural damage quantification.

EC8-based earthquake record selection procedure evaluation: Validation study based on observed damage of an irregular R/C building

This study investigates the applicability and limitations of the Eurocode 8 earthquake ground motion selection framework for the assessment of both elastic and inelastic structural response of multi-storey, irregular R/C buildings subjected to bi-directional loading. In order to minimize modelling uncertainties inherent in the quantification of structural damage and the consideration of the supporting soil–foundation system for complex structural systems, an existing building damaged by the 2003 Lefkada earthquake was adopted as case study. This selection has an advantage in that ground excitation, soil profile and damage observations are all available, thus permitting calibration of the finite element model with the observed response, especially in terms of use of appropriate plasticity models and damage indices, plus the assessment of soil–structure interaction effects. After establishing a reliable finite element model of the structure under study, extensive parametric analyses for different EC8 compliant sets of records were conducted, permitting quantification of the discrepancy of the structural response due to record-to-record and set-to-set variability (i.e., intra-set and inter-set scatter, respectively). The results confirm that many of the observations found in the literature regarding the effect of ground motion selection on the predicted seismic performance of SDOF systems are also valid for bi-directionally excited, multi-storey, irregular buildings. Finally, the results also highlight specific limitations of the EC8 provisions that may lead to erroneous results in many practical cases.

Frequency–wavenumber domain analysis of guided wavefields

Full wavefield measurements obtained with either an air-coupled transducer mounted on a scanning stage or a scanning laser vibrometer can be combined with effective signal and imaging processing algorithms to support characterization of guided waves as well as detection, localization and quantification of structural damage. These wavefield images contain a wealth of information that clearly shows details of guided waves as they propagate outward from the source, reflect from specimen boundaries, and scatter from discontinuities within the structure. The analysis of weaker scattered waves is facilitated by the removal of source waves and the separation of wave modes, which is effectively achieved via frequency–wavenumber domain filtering in conjunction with the subsequent analysis of the resulting residual signals. Incident wave removal highlights the presence and the location of weak scatterers, while the separation of individual guided wave modes allows the characterization of their separate contribution to the scattered field and the evaluation of mode conversion phenomena. The effectiveness of these methods is demonstrated through their application to detection of a delamination in a composite plate and detection of a crack emanating from a hole.

Identification of structural damage in buildings using iterative procedure and regularisation method

PurposeThe paper aims to identify both the location and severity of damage in complex framed buildings using limited noisy vibration measurements. The study aims to directly adopt incomplete measured mode shapes in structural damage identification and effectively reduce the influence of measurement errors on predictions of structural damage.Design/methodology/approachDamage indicators are properly chosen to reflect both the location and severity of damage in framed buildings at element level for braces and at critical point level for beams and columns. Basic equations for an iterative solution procedure are provided to be solved for the chosen damage indicators. The Tikhonov regularisation method incorporating the L‐curve criterion for determining the regularisation parameter is employed to produce stable and robust solutions for damage indicators.FindingsThe proposed method can correctly assess the quantification of structural damage at specific locations in complex framed buildings using only limited information on modal data measurements with errors, without requiring mode shape expansion techniques or model reduction processes.Research limitations/implicationsFurther work may be needed to improve the accuracy of inverse predictions for very small structural damage from noisy measurements.Practical implicationsThe paper includes implications for the development of reliable techniques for rapid and on‐line damage assessment and health monitoring of framed buildings.Originality/valueThe paper offers a practical approach and procedure for correctly detecting structural damage and assessing structural condition from limited noisy vibration measurements.

Damage analysis of a steel–concrete composite frame by finite element model updating

In the last two decades, many studies have reported the effectiveness of Experimental Modal Analysis and Finite Element Model Updating in mechanical and aerospace engineering, where they represent useful tools for Structural Health recognition and can provide an information base for detection, assessment and quantification of structural damage due to exercise actions and exceptional events. The applications of Damage Detection techniques to civil constructions left some still not well clarified points, due to the great variety of structural typologies, material properties, boundary conditions and possible damage patterns, as in the case of seismic damage. In order to design post-earthquake rehabilitation interventions, in fact a careful knowledge of the damage distribution and residual structural capacity is obviously needed and this can be very expensive and time consuming. However, the application of vibration based damage identification techniques to high ductile structures designed according to seismic capacity approach can improve the feasibility, reliability and efficiency of these methods. In the present study, Finite Element Model Updating procedures based on vibration measurements were used to detect, assess and quantify the structural damage of a high ductile steel–concrete composite frame subjected to increasing seismic damage by means of pseudo dynamic and cyclic test at the Joint Research Centre (Ispra, Italy). The updating process, repeated for three damage levels, has been applied to different finite element structural models (addressing different modelling strategies), allowing a comprehensive description and quantification of the progressive degradation of beam-to-column joints, devoted to dissipate the seismic energy by design.

Detection and Quantification of Structural Damage of a Beam-Like Structure Using Natural Frequencies

Need for developing efficient non-destructive damage detection procedures for civil engineering structures is growing rapidly. This paper presents a methodology for detection and quantification of structural damage using modal information obtained from transfer matrix technique. Vibration characteristics of beam-like structure have been determined using the computer program developed based on the formulations presented in the paper. It has been noted from reported literature that detection and quantification of damage using mode shape information is difficult and further, extraction of mode shape information has practical difficulties and limitations. Hence, a methodology for detection and quantification of damage in structure using tranfer matrix technique based on the changes in the natural frequencies has been developed. With an assumption of damage at a particular segment of the beam-like structure, an iterative procedure has been formulated to converge the calculated and measured frequencies by adjusting flexural rigidity of elements and then, the intersections are used for detection and quantification of damage. Eventhough the developed methodology is iterative, computational effort is reduced considerably by using transfer matrix technique. It is observed that the methodology is capable of predicting the location and magnitude of damage quite accurately.

Structural crack detection without updated baseline model by single and multiobjective optimization

Identification, localization and quantification of structural damage can be performed through a model-updating procedure. Model-updating methods require a baseline finite element (FE) model of the undamaged structure, which imposes a restriction on their applicability and can become very problematic especially for large and complex civil structures. Modeling errors in the baseline model whose effects exceed the modal sensitivity to damage are critical and make an accurate estimation of damage impossible. This paper presents an identification algorithm using modal data for assessing structural damage that is based on FE-updating procedures and takes modeling error into account. To overcome its influence, differences of mode shapes and frequencies before and after damage for both numerical model and experimental measurements are used instead of the mode shapes and frequencies themselves. To formulate the objective function, two different approaches have been considered taking into account how these differences are grouped: a single-objective approach and a multiobjective approach. The effectiveness of both approaches is verified against numerical and experimental results.

Instantaneous damage detection of bridge structures and experimental verification

An extended Kalman filtering (EKF) method was developed and applied to instantaneously identify elemental stiffness values of a structure during damaging seismic events based on vibration measurement. This method is capable of dealing with nonlinear as well as linear structural responses. Identification of the structural elemental stiffness enables location as well as quantification of structural damage. The instantaneous stiffness values during an event can provide highly useful information for post-event capacity estimation. In this study, a large-scale shaking table test of a three-bent concrete bridge model was performed in order to verify the proposed damage detection method. The bridge model was shaken to different damage levels by a sequence of earthquake motions with increasing intensities. The elemental stiffness values of the structure were instantaneously identified in real time during the damaging earthquake excitations using the EKF method. The identified stiffness degradations and their locations agreed well with the structural damage observed by visual inspection and strain measurements. More importantly, the seismic response accelerations analytically simulated using the instantaneous stiffness values thus identified agreed well with the measured accelerations, demonstrating the accuracy of the identified stiffness. This study presents an experimental verification of a structural damage detection method using a realistic bridge model subjected to realistic seismic damage. Copyright © 2007 John Wiley & Sons, Ltd.

Damage detection of coupled bridge deck-girder system

An equation error based approach of structural damage quantification at element level is presented in this paper. The proposed equation error approach is found to be efficient for identifying the properties of structure at element level directly without iterations. But its application in literature is limited to truss type structures only. The equation error based identification algorithm is readily developed for structural system coupled with beam and plate element so that it can be applied to assess the damage of bridge deck-girder system. The inverse method proposed here utilize modal frequencies and mode shapes of the damaged structure to identify the structural properties locally. The formulation is elucidated through a typical longitudinal and cross girder system monolithic with deck slab. Various feasible damage scenarios are considered to establish the identifiability of the proposed algorithm using numerically simulated modal data obtained through finite element analysis software. A Monte Carlo based error sensitivity analysis is also performed to study the robustness of the algorithm.

Improved Damage Quantification from Elemental Modal Strain Energy Change

An improved structural damage quantification algorithm is presented based on the elemental modal strain energy change before and after the occurrence of damage in a structure. The algorithm include...

Determination of storey stiffness of three-dimensional frame buildings

Few past system identification studies have attempted structural models with many degrees-of-freedom (DOFs) owing to the numerical difficulty with regard to convergence and computational speed. Even fewer studies have considered a three-dimensional building with the torsional response taken into consideration. In this respect, an ‘improved condensation’ method for the system identification of multistorey three-dimensional frame buildings is developed. Specifically, reductions in storey stiffnesses are determined for the quantification of structural damage or deterioration in each storey of a building. Both static and kinematic condensations are employed to reduce the DOFs of a (complete) mathematical model for the building, resulting in a condensed model of much fewer DOFs. The modelling error is minimized by introducing a remedial model whose parameters are identified by using the extended Kalman filtering technique. A stiffness correction factor is computed to successively update the complete model. Finally the method yields integrity indices to quantify changes in the respective storey stiffnesses. A numerical simulation example of an asymmetric three-storey frame building which has a total of 270 DOFs is presented. Three cases of different damage status of the building are considered. The proposed method is implemented to identify the storey damages, under the influence of input and output noise. The numerical results show that this method accurately reports the extent of stiffness reduction at each storey of the building and is computationally efficient because of a smaller system used for identification in the remedial model.