• 한국안전학회지
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• 제22권5호
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• pp.65-70
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• 2007

This paper is estimation of structure damage caused by VCE(Vapor Cloud Explosion) in enclosure. As we estimate the influence of damage which occur at gas facility in factory. We can utilize the elementary data of safety distance. In this study, the influence of over-pressure caused by VCE in enclosure was calculated by using the Hopkinson's scaling law and the accident damage was estimated by applying the influence on the adjacent structure into the probit model. As a result of the damage estimation conducted by using the probit model, both the damage possibility of explosion overpressure to structures of 20 meters away and to glass bursting of 80 meters away was nearly zero in open space explosion.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.148-151
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• 2009

In these days it is important to secure the life and stability of the structure such as aircrafts, automobiles and building. So the structural health monitoring is needed. In conventional lamb wave techniques, damage is identified by comparing the measured data (baseline signals) and the current data. But this method can lead to high false signal in the intact condition of the structure due to environmental conditions of the structure. As a solution to resolve it, the structural health monitoring method which doesn't use baseline signals is necessary. Damaged structure has unusual elastic wave. This paper proposed a PC(pitch-catch) method which doesn't use baseline signal. New baseline signals can get from detection signal. Damage signals based on new baseline signals. This paper made an image includes damage information by applying damage-signals to beamformming.

• Structural Engineering and Mechanics
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• 제32권2호
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• pp.301-320
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• 2009

Damage assessment for buried structures against an internal blast is conducted by considering the soil-structure interaction. The structural element under analysis is assumed to be rigid-plastic and simply-supported at both ends. Shear failure, bending failure and combined failure modes are included based on five possible transverse velocity profiles. The maximum deflections with respect to shear and bending failure are derived respectively by employing proper failure criteria of the structural element. Pressure-Impulse diagrams to assess damage of the buried structures are subsequently developed. Comparisons have been done to evaluate the influences of the soil-structure interaction and the shear-to-bending strength ratio of the structural element. A case study for a buried reinforced concrete structure has been conducted to show the applicability of the proposed damage assessment method.

• 한국해양공학회지
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• 제30권4호
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• pp.287-293
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• 2016

This paper presents an effective damage detection method for offshore jackets using natural frequency change ratios. Two parameters, cosine similarity and magnitude index, are considered to estimate the location and severity of the damage in the structure. A numerical jacket structure model is considered to verify the performance of the proposed method. As observed through analysis, the damages in the structure are detected accurately.

• 콘크리트학회지
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• 제6권6호
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• pp.180-189
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• 1994

철근콘크리트 구조물의 손상을 진동반응특성치의 변화를 측정한 자료로부터 예측할 수 있는 실용적인 방법론이 제시되었다. 먼저, 구조물에 발생한 손상의 위치를 구조물 모드형상의 변화로부터 결정할 수 있는 알고리즘이 요약되었다. 다음으로, 실물크기 1/3 촉소 건조된 철근콘크리트 구조물을 사용한 실험에서 알고리즘을 이용하여 손상의 위치를 예측하였다. 이 실험과정에는 손상발생 전$\cdot$후의 소수의 진동반응특성치가 사용되었다. 구조물의 손상을 예측한 결과로부터 알고리즘이 손상을 정확하게 발견하는 것으로 판명되었다.

• Smart Structures and Systems
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• 제25권3호
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• pp.345-368
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• 2020

The present work proposes a self-controlled multi-stage optimization method for damage identification of structures utilizing standard particle swarm optimization (PSO) algorithm. Damage identification problem is formulated as an inverse optimization problem where damage severity in each element of the structure is considered as optimization variables. An efficient objective function is formed using the first few frequencies and mode shapes of the structure. This objective function is minimized by a self-controlled multi-stage strategy to identify and quantify the damage extent of the structural members. In the first stage, standard PSO is utilized to get an initial solution to the problem. Subsequently, the algorithm identifies the most damage-prone elements of the structure using an adaptable threshold value of damage severity. These identified elements are included in the search space of the standard PSO at the next stage. Thus, the algorithm reduces the dimension of the search space and subsequently increases the accuracy of damage prediction with a considerable reduction in computational cost. The efficiency of the proposed method is investigated and compared with available results through three numerical examples considering both with and without noise. The obtained results demonstrate the accuracy of the present method can accurately estimate the location and severity of multi-damage cases in the structural systems with less computational cost.

• 한국BIM학회 논문집
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• 제9권1호
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• pp.42-51
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• 2019

Maintenance of aging structures has attracted societal attention. Maintenance of the aging structure can be efficiently performed with a digital twin. In order to maintain the structure based on the digital twin, it is required to accurately detect the damage of the structure. Meanwhile, deep learning-based damage detection approaches have shown good performance for detecting damage of structures. However, in order to develop such deep learning-based damage detection approaches, it is necessary to use a large number of data before and after damage, but there is a problem that the amount of data before and after the damage is unbalanced in reality. In order to solve this problem, this study proposed a method based on Generative adversarial network, one of Generative Model, for generating acceleration data usually used for damage detection approaches. As results, it is confirmed that the acceleration data generated by the GAN has a very similar pattern to the acceleration generated by the simulation with structural analysis software. These results show that not only the pattern of the macroscopic data but also the frequency domain of the acceleration data can be reproduced. Therefore, these findings show that the GAN model can analyze complex acceleration data on its own, and it is thought that this data can help training of the deep learning-based damage detection approaches.

• Smart Structures and Systems
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• 제18권6호
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• pp.1189-1202
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• 2016

This paper describes an application of wavelet analysis for damage detection of a steel frame structure with bolted connections. The wavelet coefficients of the acceleration response for the healthy and loosened connection structure were calculated at each measurement point. The difference of the wavelet coefficients of the response of the healthy and loosened connection structure is selected as an indicator of the damage. At each node of structure the norm of the difference of the wavelet coefficients matrix is then calculated. The point for which the norm has the higher value is a candidate for location of the damage. The above procedure was experimentally verified on a laboratory-scale 2-meter-long steel frame. The structure consists of 11 steel beams forming a four-bay frame, which is subjected to impact loads using a modal hammer. The accelerations are measured at 20 different locations on the frame, including joints and beam elements. Two states of the structure are considered: healthy and damaged one. The damage is introduced by means of loosening two out of three bolts at one of the frame connections. Calculating the norm of the difference of the wavelet coefficients matrix at each node the higher value was found to be at the same location where the bolts were loosened. The presented experiment showed the effectiveness of the wavelet approach to damage detection of frame structures assembled using bolted connections.

• Smart Structures and Systems
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• 제1권1호
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• pp.29-46
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• 2005

In this study, a wavelet packet based method is proposed for identifying damage occurrence and damage location for beam-like structures. This method assumes that the displacement or the acceleration response time histories at various locations along a beam-like structure both before and after damage are available for damage assessment. These responses are processed through a proper level of wavelet packet decomposition. The wavelet packet signature (WPS) that consists of wavelet packet component signal energies is calculated. The change of the WPS curvature between the baseline state and the current state is then used to identify the locations of possible damage in the structure. Two numerical studies, one on a 15-storey shear-beam building frame and another on a simply-supported steel beam, and an experimental study on a simply-supported reinforced concrete beam are performed to validate the proposed method. Results show the WPS curvature change can be used to locate both single and sparsely-distributed multiple damages that exist in the structure. Also the accuracy of assessment does not seem to be affected by the presence of 20-15dB measurement noise. One advantage of the proposed method is that it does not require any mathematical model for the structure being monitored and hence can potentially be used for practical application.

• Structural Engineering and Mechanics
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• 제15권1호
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• pp.53-70
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• 2003

The motivation of this paper is to introduce the modern technology of large-scale cooling tower design. Thereby the innovative design concept for the world's largest cooling tower with a height of 200 m is briefly presented (Harte & Kr$\ddot{a}$tzig 2002, Bush et al. 2002). The new concept was considered not only for safety, but also for preservation of the durability of the structure, because cracking damage in large cooling towers in general cause extremely high cost of maintenance and repair. The paper demonstrates numerically the damage process in large cooling towers (Kr$\ddot{a}$tzig et al. 2001), and describes some basics of the numerical finite element approach for damage propagation modelling of shell structure. A prototype is analysed to trace the progressive damage process, whereby the changes in the dynamical behaviour of the structure, as mirrored in its natural frequencies and the corresponding mode shapes, are presented and discussed. Finally, the example shows that such damage processes develop progressively over the life-time of the shell structure.