• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.889-893
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• 2004

This work presents a study on development of a practical and quantitative technique for assessment of the structural health condition by piezoelectric impedance-based technique associated with longitudinal wave propagation method. The bolt fastening condition is adjusted by torque wrench. In order to estimate the damage condition numerically, three damage indices, impedance peak frequency shift ${\Delta}F$ is proposed in this paper. Furthermore, an assessment method is described for estimation of the damage by using these three damage indices.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.870-874
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• 2004

This work presents a study on development of a practical and quantitative technique for assessment of the structural health condition by Piezoelectric impedance-based technique associated with longitudinal wave propagation method. The bolt fastening condition is adjusted by torque wrench. In order to estimate the damage condition numerically, three damage indices, impedance peak frequency shift ${\Delta}F$, peak amplitude ratio $\delta$ and quality factor ratio $\gamma$, are proposed in this paper. Furthermore, an assessment method is described for estimation of the damage by using these three damage indices.

• Structural Monitoring and Maintenance
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• 제2권3호
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• pp.269-282
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• 2015

Civil structures should be designed with the lowest cost and longest lifetime possible and without service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber is one of the best contenders for these purposes particularly in terms of aesthetics; fire protection; strength-to-weight ratio; acoustic properties and seismic resistance. In recent years, timber has been used in commercial and taller buildings due to these significant advantages. It should be noted that, since the launch of the modern building standards and codes, a number of different structural systems have been developed to stabilise steel or concrete multistorey buildings, however, structural analysis of high-rise and multi-storey timber frame buildings subjected to lateral loads has not yet been fully understood. Additionally, timber degradation can occur as a result of biological decay of the elements and overloading that can result in structural damage. In such structures, the deficient members and joints require strengthening in order to satisfy new code requirements; determine acceptable level of safety; and avoid brittle failure following earthquake actions. This paper investigates performance assessment and damage assessment of older multi-storey timber buildings. One approach is to retrofit the beams in order to increase the ductility of the frame. Experimental studies indicate that Sprayed Fibre Reinforced Polymer (SFRP) repairing/retrofitting not only updates the integrity of the joint, but also increases its strength; stiffness; and ductility in such a way that the joint remains elastic. Non-linear finite element analysis ('pushover') is carried out to study the behaviour of the structure subjected to simulated gravity and lateral loads. A new global index is re-assessed for damage assessment of the plain and SFRP-retrofitted frames using capacity curves obtained from pushover analysis. This study shows that the proposed method is suitable for structural damage assessment of aged timber buildings. Also SFRP retrofitting can potentially improve the performance and load carrying capacity of the structure.

• 한국환경복원기술학회지
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• 제23권6호
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• pp.15-28
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• 2020

Urbanization and industrialization have caused increasing damage to national lands, and ecological restoration has proceeded without any specific assessment of this damage. The purpose of this study is to select indices to assess damaged areas through literature review and panel discussions, and to derive the importance of damaged area assessment indices by analyzing them through the Analytic Hierarchy Process (AHP). This study has derived, via literature review, six types of damage and a total of 18 related assessment indices. A total of 51 responses were collected from surveys and given to experts, and an AHP analysis conducted. As a result of the analysis, "Landform change (0.268)" was of the highest importance, with associated damage types as follows: "Soil contamination (0.193)", "Vegetation damaged (0.149)", "Surface soil loss (0.143)", "Change in soil physiochemical property (0.125)", and "Vegetation decline (0.122)". The analysis determined that the item of the highest importance in the overall assessment of damage was "Slope occurred area (0.100)", and that "Conductivity (0.022)" was of the lowest importance. This study can be presented as a criterion in determining the type and degree of damage in setting priorities for future ecological restoration projects.

• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.251-261
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• 2007

본 연구는 터널굴착 공사에 의한 지반거동을 평가하여, 구조물의 형상, 위치, 굴착공정 변화등의 다양한 조건과 지반/구조물의 상호작용이 고려된 모형실험을 기본으로 수행하였다. 굴착진행 단계에 따른 구조물의 손상 거동 평가시 인접 구조물이 밀집된 도심지 굴착에서는 보다 안전하고 보수적인 평가가 나타나는 각변위와 수평변형율에 의한 손상도표를 활용하는 것이 보다 안전할 것으로 판단된다. 모형실험시 구조물에 발생된 균열의 손상수준을 손상도표에서 평가해 본 결과, 균열손상 수준이 적용된 평가가 각변위와 수평변형율만 적용된 손상수준보다 안전측으로 평가되는 것을 확인할 수 있었다. 그러므로, 각변위와 수평변형율 뿐만 아니라 균열이 고려된 손상평가를 수행하는 것이 보다 바람직할 것으로 판단된다.

• 대한조선학회논문집
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• 제55권3호
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• pp.274-280
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• 2018

This paper deals with the calculation of vulnerable areas of critical components required for the assessment of naval ship's vulnerability. Taking into account the effectiveness of threatening weapons, the probability density function of damage was used to assess vulnerable areas or vulnerabilities of critical components. It is shown that the vulnerable area of critical component can be simply computed from the damage function. Considering the weapon effectiveness of fragmentation and explosion on the target, both Carleton Damage Function and Rectangular Cookie Cutter Function representing the probability of damage are applied to the vulnerable area assessment. Carleton damage function is utilized to describe the weapon-target interaction in the vulnerability analyses. A problem of blast effect against an assumed naval ship is chosen as a case study. Vulnerability is evaluated by applying the suggested method to the equipments arranged in the engine room of the virtual ship.

• Nuclear Engineering and Technology
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• 제50권5호
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• pp.673-682
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• 2018

One of the most widely used methods to estimate core damage during a nuclear power plant accident is containment radiation measurement. The evolution of severe accidents is extremely complex, leading to uncertainty in the containment dose rate (CDR). Therefore, it is difficult to accurately determine core damage. This study proposes to conduct uncertainty analysis of CDR for core damage assessment. First, based on source term estimation, the Monte Carlo (MC) and point-kernel integration methods were used to estimate the probability density function of the CDR under different extents of core damage in accident scenarios with late containment failure. Second, the results were verified by comparing the results of both methods. The point-kernel integration method results were more dispersed than the MC results, and the MC method was used for both quantitative and qualitative analyses. Quantitative analysis indicated a linear relationship, rather than the expected proportional relationship, between the CDR and core damage fraction. The CDR distribution obeyed a logarithmic normal distribution in accidents with a small break in containment, but not in accidents with a large break in containment. A possible application of our analysis is a real-time core damage estimation program based on the CDR.

• 한국산학기술학회논문지
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• 제16권1호
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• pp.769-777
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• 2015

본 논문에서는 교량 구조의 유지관리에서 계측정보 부족 문제를 극복하기 위하여 주행하중 시험법과 광변위 계측을 이용하는 손상도 추정기법에 대한 연구를 수행하였다. 이 방법을 통한 연속적 계측 변위는 손상 추정을 보다 간단하며 실제적이도록 할 수 있다. 제안된 기법에 의한 대형 사회기간시설물에 대한 보다 현실적인 손상 추정 방법으로의 가능성과 이 방법의 효율성과 정확도를 보이기 위하여 수치모의실험과 실험적 연구가 수행되었다. 예제해석 결과는 실험적 방법에서도 구해진 손상도들이 충분한 정확도를 가지고 있고 특히 실제 손상위치에서는 정확한 값과 거의 같음을 나타내고 있다. 이는 제안된 방법이 손상위치 추정이나 손상정도 추정에 모두 유용하고 실제 현장에서 구현 가능한 실용성이 충분하다는 의미로 해석된다.

• 한국CDE학회논문집
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• 제13권3호
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• pp.227-234
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• 2008

The number of marine accidents have been decreased since various equipments for navigation control have been introduced to the marine vessels. However, disastrous marine accidents such as ship collisions are occurred more frequently. Therefore, IMO(International Maritime Organization) is enforcing the design requirement of structural strength for marine vessel. Also EU countries are developing new design methodologies and design tools to suggest the design guidance which can minimize the damage of commercial vessels in case of marine collision accidents. In this study, an integrated design system for the safety assessment has been presented to enhance the safety of damaged ships in marine collision accidents. The architecture of system is described by use-cases and IDEF functional analysis. Then an integrated system for safety assessment of damaged ship which is considering both damage stability and structural safety has been developed to support the ship design in early stage.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.60-64
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• 2008

According to previous research, welding-induced stress in steel structures can significantly affect the fatigue behaviour; it produces initial damage of weldiug part of structure locally and residual stresses reduce the fatigue strength after welding precess. In this study, through continuum damage mechanics, we can estimate the weldiug damage using the stress and strain history during welding process and the effect of welding residual stress for assessment of fatigue life. The variation of welding-induced stresses and strains need be traced precisely in advance for a reliable weldiug damage assessment. In this study, a damage and fatigue analysis techniques for steel structures with welding-induced residual stress are presented. First, We calculate the history of temperature according with welding process. And residual stress with a welding thermal history was evaluated by non-linear thermal stress analysis. Secondly, welding damage and fatigue life are estimated with kinetic damage law.