• 한국강구조학회 논문집
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• 제21권3호
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• pp.331-342
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• 2009

Miner의 피로손상법칙을 적용하여 피로파괴에 대한 한계상태함수를 표현하고, 실제 국내 통행차량의 통계적 특성을 반영하여 LRFD 설계기준(안)의 피로설계트럭모형과 현 도로교설계기준의 DB-24 하중에 대한 피로파괴 신뢰도해석을 수행하였다. 피로한계상태함수는 Miner의 피로손상법칙을 확률변수의 함수로 나타내고 이들 확률변수에 대하여 국내 통행트럭 등의 실측 통계자료를 분석하여 구한 통계치와 문헌에 보고된 결과를 조사하여 구한 통계치를 적용하여 지간별 및 피로상세별 신뢰도지수를 Rackwitz-Fiessler법으로 구하고, 신뢰도해석 결과를 분석하여 LRFD 설계기준(안)의 피로설계트럭모형을 제안하였다. 아울러, 제안된 피로설계트럭모형을 적용하여 단경간 및 3경간 연속 플레이트 및 박스 거더교의 총 16개 실교량에 대한 피로설계를 수행하고, 설계결과를 현 도로교설계기준의 DB-24 하중에 의한 피로설계 결과와 비교하여 LRFD 피로설계트럭 모형의 적용성을 검토하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.359-362
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• 1999

Partially prestressed concrete members are concrete members reinforced with a combination of prestressed and non-prestressed reinforcement, and also can offer advantages of reinforced concrete. The objective of this study is to develop a design program using Visual Basic language according to the limit state design method which controls crack and check fatigue effectively for partially concrete members.

• 대한조선학회 특별논문집
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• 대한조선학회 2015년도 특별논문집
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• pp.69-73
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• 2015

An evaluation of the accidental limit state (ALS) for design of a semi-submersible drilling rig is one of the essential design requirements as well as ultimate limit state (ULS) and fatigue limit state (FLS). This paper describes the ALS evaluation on the explosion accident at shale shaker room of semi-submersible drilling rig. There are three steps for the ALS evaluation such as structural analysis at concept design, risk based safety design and structural analysis at detailed design. For the ALS evaluation at concept design, conceptual explosion overpressure from the Rule guided by the classification society was used in the structural analysis that was carried out using LS-DYNA. To set up the design accidental load (DAL), explosion analysis was carried out using FLACS taking safety barriers into consideration. Then, the structural analysis was carried out applying DAL for the ALS evaluation at detailed design. Through the ALS evaluation on the explosion at shale shaker room, the importance of the risk based safety design was described.

• 한국방재학회 논문집
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• 제7권4호
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• pp.1-12
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• 2007

본 연구에서는 강교 부재를 대상으로 시간에 따른 부식과 교통량(트럭통행량)의 변화 영향을 반영한 피로 취약도 평가 방법을 제안하였다. 제안된 방법을 통해 부식과 교통량 변화를 고려할 수 있는 피로에 대한 한계상태함수를 설정하였다. 부식의 영향은 평균부식깊이와 피로강도감소계수와의 관계를 이용하여 한계상태함수에서 피로저항의 감소로써 반영되었다. 트럭통행량의 변화는 세 가지 대표적인 변화양상을 설정하여 기간별로 실제 변화에 맞게 모델링함으로써 한계상태함수에서 하중의 증가로 반영되었다. Monte-Carlo 시뮬레이션을 이용하여 신뢰성 해석을 수행하도록 하였으며, 이를 바탕으로 시간이력 피로 취약도 곡선을 도출하였다. 검증예제와 실제 국내 강교에 적용하여 제안된 피로 취약도 평가방법을 검증하였다.

• Structural Engineering and Mechanics
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• 제49권2호
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• pp.203-223
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• 2014

The extensive use of prestressed reinforced concrete (PSC) highway bridges in marine environment drastically increases the sensitivity to both fatigue-and corrosion-induced damage of their critical structural components during their service lives. Within this scenario, an integrated method that is capable of evaluating the fatigue reliability, identifying a condition-based maintenance, and predicting the remaining service life of its critical components is therefore needed. To accomplish this goal, a procedure for fatigue reliability prediction of PSC highway bridges is proposed in the present study. Vehicle-bridge coupling vibration analysis is performed for obtaining the equivalent moment ranges of critical section of bridges under typical fatigue truck models. Three-dimensional nonlinear mathematical models of fatigue trucks are simplified as an eleven-degree-of-freedom system. Road surface roughness is simulated as zero-mean stationary Gaussian random processes using the trigonometric series method. The time-dependent stress-concentration factors of reinforcing bars and prestressing tendons are accounted for more accurate stress ranges determination. The limit state functions are constructed according to the Miner's linear damage rule, the time-dependent S-N curves of prestressing tendons and the site-specific stress cycle prediction. The effectiveness of the methodology framework is demonstrated to a T-type simple supported multi-girder bridge for fatigue reliability evaluation.

• 국제강구조저널
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• 제18권4호
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• pp.1242-1251
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• 2018

Not all loads contribute to fatigue crack propagation in the welded detail of steel bridges when they are subjected to variable amplitude loading. For fatigue assessment, therefore, non-contributing stress cycles should be truncated. However, stress range truncation is not considered during typical fatigue reliability assessment. When applying the first order reliability method, stress range truncation occurs mismatch between the expected number of cycles to failure and the number of cycles obtained at the time of evaluation, because the expected number of cycles only counts the stress cycles that contribute to fatigue crack growth. Herein, we introduce a calibration factor to coordinate the expected number of cycles to failure to the equivalent value which includes both contributing and non-contributing stress cycles. The effectiveness of stress range truncation and the proposed calibration factor was validated via case studies.

• 한국구조물진단유지관리공학회 논문집
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• 제26권4호
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• pp.30-39
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• 2022

원자력발전소 주요기기의 건전성 유지는 구조물의 안전성과 관련하여 매우 중요한 문제로 인식되고 있으며 배관시스템의 건전성은 원자력발전소의 안전과 관련된 매우 중요한 문제이다. 지진하중으로 인한 배관시스템의 실제 파괴모드는 피로균열에 의한 누수이며 구조적인 손상 메커니즘은 소성변형을 발생할 수 있는 큰 상대변위로 인한 저주기 피로이다. 이 연구에서는 원자력발전소의 배관시스템에서 3인치의 강재 직관과 강재 배관 Tee로 구성된 시험체에 대하여 다양한 크기의 일정한 진폭에 대하여 면내반복가력실험을 수행하였다. 지진하중으로 인한 배관시스템에서 발생하는 상대변위를 고려하기 위하여 하중진폭을 증가시켰으며, 강재 배관 Tee의 한계상태인 피로균열에 의한 누수가 발생할 때까지 수행하였다. 힘과 변위의 관계에 대하여 손상모델에 기반을 둔 손상지수를 이용하여 한계상태를 표현하였다. 그 결과 손상지수를 이용하여 강재 배관 Tee의 한계상태를 정량적으로 표현할 수 있음을 확인할 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권6호
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• pp.577-588
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• 2016

Due to the uncertainties related to the flaw assessment parameters, such as flaw size, fracture toughness, loading spectrum and so on, the probability concept is preferred over deterministic one in flaw assessment. In this study, efforts have been made to develop the reliability based flaw assessment procedure which combines the flaw assessment procedure of BS7910 and first-and second-order reliability methods (FORM/SORM). Both crack length and depth of semi-elliptical surface crack at weld toe were handled as random variable whose probability distribution was defined as Gaussian with certain means and standard deviations. Then the limit state functions from static rupture and fatigue perspective were estimated using FORM and SORM in joint probability space of crack depth and length. The validity of predicted limit state functions were checked by comparing it with those obtained by Monte Carlo simulation. It was confirmed that the developed methodology worked perfectly in predicting the limit state functions without time-consuming Monte Carlo simulation.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.201-206
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• 2003

This study is test for STS304 specimen using bending and torsion state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed If summarize STS304 torsion result of fatigue test, is as following. Fatigue life prediction was available by Weibull statistics distribution, and 50% breakdown probability correlation equation was appeared as following.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.199-204
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• 2001

Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frenquently. Therefore many people are suffering harm of property. The destruction cause of macaine components is almost accused by fatigue. This study is test for STS304 specimen using pure and cantilever bending state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed.