• Structural Engineering and Mechanics
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• 제77권4호
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• pp.495-508
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• 2021

This study devises a novel approach, namely quadruple 1D convolutional neural network, for detecting connection stiffness reduction in steel truss bridge structure using experimental and numerical modal data. The method is developed based on expertise in two domains: firstly, in Structural Health Monitoring, the mode shapes and its high-order derivatives, including second, third, and fourth derivatives, are accurate indicators in assessing damages. Secondly, in the Machine Learning literature, the deep convolutional neural networks are able to extract relevant features from input data, then perform classification tasks with high accuracy and reduced time complexity. The efficacy and effectiveness of the present method are supported through an extensive case study with the railway Nam O bridge. It delivers highly accurate results in assessing damage localization and damage severity for single as well as multiple damage scenarios. In addition, the robustness of this method is tested with the presence of white noise reflecting unavoidable uncertainties in signal processing and modeling in reality. The proposed approach is able to provide stable results with data corrupted by noise up to 10%.

• 한국산업융합학회 논문집
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• 제10권3호
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• pp.149-155
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• 2007

Damage assessment and Damage index for RC members failed in flexure was investigated by using the nonlinear finite element analysis, included with nonlocal constitutive law, which is analyzed for the localization of the failure on the post-peak region. In the nonlcal constitutive law, The local strains obtained at gauss points were averaged over a particular length, i.e. characteristic length and it was used to evaluate the damage of RC column member. As the analysis results, The value of nonlocal strain shows less mesh sensibility. In the damage assessment, It was confirmed that evaluations of damage of RC member were able to use nonlocal compressive strain on a cover concrete and a core concrete of the member. Moreover it was confirmed that damage process for the statically indeterminate structure was able to evaluate the damage context of the component members of the structure.

• Computers and Concrete
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• 제20권5호
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• pp.563-572
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• 2017

Ordinary reinforced concrete (RC) and prestressed concrete bridges are two popular and typical types of short- and medium-span bridges that accounts for the vast majority of all existing bridges. The cost of maintaining, repairing or replacing degraded existing RC bridges is immense. Detecting the abnormality of RC bridges at an early stage and taking the protective measures in advance are effective ways to improve maintenance practices and reduce the maintenance cost. This study proposes a systematic method from influence line (IL) identification to damage detection with applications to RC bridges. An IL identification method which integrates the cubic B-spline function with Tikhonov regularization is first proposed based on the vehicle information and the corresponding moving vehicle induced bridge response time history. Subsequently, IL change is defined as a damage index for bridge damage detection, and information fusion technique that synthesizes ILs of multiple locations/sensors is used to improve the efficiency and accuracy of damage localization. Finally, the feasibility of the proposed systematic method is verified through experimental tests on a three-span continuous RC beam. The comparison suggests that the identified ILs can well match with the baseline ILs, and it demonstrates that the proposed IL identification method has a high accuracy and a great potential in engineering applications. Results in this case indicate that deflection ILs are superior than strain ILs for damage detection of RC beams, and the performance of damage localization can be significantly improved with the information fusion of multiple ILs.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2356-2363
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• 2015

Localization of lightning strike point (LSP) in the forest is modeled to mitigate the forest fire damage. Though forest fire ignited by lightning rarely happens, its damage on the forest is grievousness. Therefore, predicting accurate location of LSP becomes crucial in order to control the forest fire. In this paper, we proposed a new hybrid localization algorithm by combining the received signal strength (RSS) and the received signal strength ratio (RSSR) to improve the accuracy by mitigating the environmental effect of lightning strike location in the forest. The proposed hybrid algorithm employs antenna theory (AT) model of cloud-to-ground (CG) return stroke lightning channel to forecast the location of the lightning strike. The obtained results show that the proposed hybrid algorithm achieves better location accuracy compared to the existing RSS method for predicting the lightning strike location considering additive white Gaussian noise (AWGN) environment.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2011년도 정기 학술대회
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• pp.278-281
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• 2011

The global coordinates generated from Isomap algorithm provide a simple way to analyze and manipulate high dimensional observations in terms of their intrinsic nonlinear degrees of freedom. Thus, Isomap can find globally meaningful coordinates and nonlinear structure of complex data sets, while neither principal component analysis (PCA) nor multidimensional scaling (MDS) are successful in many cases. It is demonstrated that the adapted Isomap algorithm successfully enhances the quality of pattern classification for damage identification in various numerical examples.

• Structural Engineering and Mechanics
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• 제46권2호
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• pp.231-244
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• 2013

An efficient method is proposed here to identify multiple damage cases in structural systems using the concepts of flexibility matrix and strain energy of a structure. The flexibility matrix of the structure is accurately estimated from the first few mode shapes and natural frequencies. Then, the change of strain energy of a structural element, due to damage, evaluated by the columnar coefficients of the flexibility matrix is used to construct a damage indicator. This new indicator is named here as flexibility strain energy based index (FSEBI). In order to assess the performance of the proposed method for structural damage detection, two benchmark structures having a number of damage scenarios are considered. Numerical results demonstrate that the method can accurately locate the structural damage induced. It is also revealed that the magnitudes of the FSEBI depend on the damage severity.

• 한국소음진동공학회논문집
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• 제20권3호
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• pp.272-278
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• 2010

A method for damage detection in a plate structure is presented based on strain waves that are generated by impact or damage in the structure. Strain responses from continuous sensors, which are long ribbon-like sensors made from piezoceramic fibers or other materials, were used with a neural network technique to estimate the damage location. The continuous sensor uses only a small number of channels of data acquisition and can cover large areas of the structure. A grid type structural neural system composed of the continuous sensors was developed for effective damage localization in a plate structure. The ratios of maximum strains and arrival times of the maximum strains obtained from the continuous sensors were used as input data to a neural network. Simulated damage localizations on a plate were carried out and the identified damage locations agreed reasonably well with the exact damage locations.

• 한국항공우주학회지
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• 제31권2호
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• pp.41-50
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• 2003

본 논문에서는, 병렬 다중 프런트 해법을 이용한 비선형 병렬 구조해석 과정을 소개하고 이의 응용예제로써 2차원 및 3차원 균열 모델에서의 손상 국부화를 모사하였다. 비선형 유한요소 해석과 연속체 손상역학과 관련된 병렬 알고리듬을 구현하였고, 비선형 손상해석에서 사용되는 많은 변수들을 저장하기 위해서는 메모리가 많이 필요하므로 이를 줄이는 방안을 고려하였다. 그리고 손상 진전으로 인한 변형도 연화가 발생할 때 해를 구하기 위해 사용한 Riks의 연속법도 병렬 계산에 맞도록 수정하였다. 수치예제로써, 최대 약 1백만 자유도를 가진 모델들을 사용하여 손상 국부화 문제를 해석하였는데, 이 예제에서 비선형 병렬 알고리듬의 병렬효율과 자유도 변화에 따른 균열 끝단에서의 손상 변화를 살펴보았다.

• 한국구조물진단유지관리공학회 논문집
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• 제14권1호
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• pp.165-174
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• 2010

본 논문에서는 실물 콘크리트 거더 교량의 가속도 응답 신호를 이용하여 구조물의 상태변화를 경보한 후 그 위치 변화를 검색하는 2단계 구조건전성 모니터링 체계를 제시하였다. 먼저, 2경간 연속 콘크리트 거더 교량인 미호천교를 대상교량으로 선정하였으며, 볼링공을 이용한 강제진동 실험으로부터 동특성을 추출하였다. 다음으로, 미호천교의 2단계 구조건전성 모니터링 체계 구축을 위한 손상 발생 경보 및 손상 위치 검색 기법들을 선정하였다. 손상 경보 기법으로는 시간영역 특징을 이용하는 자기회귀모델과 주파수응답함수의 상관계수, 주파수응답비보증지수를 선정하였다. 손상 위치 검색 기법으로는 모드변형에너지기반 손상지수법을 선정하였다. 마지막으로, 덤프트럭을 이용한 정적 재하 실험을 통해 2단계 손상 모니터링 체계의 적합성을 검증하였다.

• Computers and Concrete
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• 제8권3호
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• pp.243-278
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• 2011

The paper presents simulations of the Brazilian test using two numerical models. Both models are regularized in order to obtain results independent of discretization. The first one, called gradient damage, is refined by additional averaging equation which contains gradient terms and an internal length scale as localization limiter. In the second one, called viscoplastic consistency model, the yield function depends on the viscoplastic strain rate. In this model regularization properties are governed by the assumed strain rate. The two models are implemented in the FEAP finite element package and compared in this paper. Parameter studies of the split test are performed in order to point out the features of each model.