• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.113-113
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• 2004

실제 사용중인 기계나 기계구조물은 다양한 환경 및 복잡한 설계조건으로 인하여 변동하중과 다축에서 작용하는 혼합모드 하중 상태에 놓이는 경우가 대부분이다. 하지만, 순수 모드 I 하중상태 하에서의 연구는 활발히 이루어졌으나, 실제 구조물에서 대부분 발생하는 혼합모드 하중상태 하에서의 연구는 아직 부족한 실정이다. 또한 기계구조물내의 많은 성분요소에 존재하는 작용 하중 방향에 수직적이지 않게 되며, 초기균열의 균열선상에서 성장하지 않는다.(중략)

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.757-764
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• 2014

In this study, the effect of shape parameters on the J-R curves of curved CT specimens was evaluated using the limit load method. Fracture toughness tests considering the shape factors L/W and $R_m/t$ of the specimens were also performed. Thereafter, the J-R curves of the curved CT specimens were compared using the J-integral equation proposed in the ASTM (American Society for Testing and Materials) and limit load solution. The J-R curves of the curved CT specimens were also compared with those of the CWP (curved wide plate), which is regarded to be similar to real pipe and standard specimens. Finally, the effectiveness of the J-R curve of each curved CT specimen was evaluated. The results of this study can be used for assessing the applicability of curved CT specimens in the accurate evaluation of the fracture toughness of real pipes.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.293-297
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• 2021

Calibration of load-resistance factors for the limit state design of front covered caisson breakwaters were presented. Reliability analysis of the breakwaters which are constructed in Korean coast was conducted. Then, partial safety factors and load-resistance factors were sequentially calculated according to target reliability index. Load resistance factors were optimized to give one set of factor for limit state design of breakwater. The breakwaters were redesigned by using the optimal load resistance factor and verified whether reliability indices larger than the target value. Finally, load-resistance factors were compared with foreign country's code for verification.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.458-464
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• 2020

Calibration of load-resistance factors for the limit state design of perforated caisson breakwaters are presented. Reliability analysis of 12 breakwaters in nationwide ports was conducted. Then, partial safety factors and load-resistance factors were sequentially calculated according to target reliability index. Load resistance factors were optimized to give one set of factor for limit state design of breakwater. The breakwaters were redesigned by using the optimal load resistance factor and verified whether reliability indices larger than the target value. Finally, some load-resistance factors were proposed by changing target reliability index.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.6
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• pp.1-10
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• 2013

Probabilistic nonlinear first ply failure loads of flat composite panels and nonlinear buckling loads of curved composite panels with cutouts are estimated to provide the more reliable main load carrying structure in the renewable energy industry and offshore structures. The response surface method approximates limit state surface to a second order polynomial form of random variables with the results of deterministic finite element analyses at given sampling design points. Furthermore, the iterative linear interpolation scheme is used to obtain a more accurate approximation of the limit state surface near the most probable failure point (MPFP). The advanced first order second moment method and the Monte Carlo method are performed on an approximated limit state surface to evaluate the probability of failure. Finally, the sensitivity of the reliability index with respect to transformed random variables is investigated to figure out the main random variables that have an effect on failures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.13-24
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• 2019

This paper brings up fallacy of material factors specified for the design of concrete members in the current Korean limit state design code for highway bridges, and proposes new material factors based on a robust optimization scheme to overcome the fallacy. It is shown that the current load factors in the code and the proposed material factors lead to a much higher reliability index than the target index. The load factors are adjusted to yield the target reliability index using the inverse reliability analysis. A reliability-based approach following the basic concept of Eurocode is formulated to determine material factors as well as load factors. The load-material factors obtained by the proposed reliability-based approach yield a lower reliability level than the target index. Drawbacks of the basic concept of Eurocode are discussed. It is pointed out that differences in the uncertainties between materials and members may cause the lower reliability index of concrete member than the target.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.99-118
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• 2018

Recently, the limit state design method in the design of the structure is in global trend, but it is limited to a few structures in Korea. Since the introduction of the limit state design method has recently been attempted for tunnels, which are the main underground structures, it is surely necessary to understand the latest limit state design method. Therefore, based on the recently published AASHTO LRFD Road Tunnel Design and Construction Guide Specification (2017), structural load factors and load combinations were reviewed, and various factors which should be applied for the review of structures have been analyzed. In this study, utility tunnel section and subway tunnel sections used in Korea were analyzed by the limit state design method, and we have analyzed the direction of application of limit state design method through studying the tendency of member force by various influential factors such as ground conditions, load modifier and joint stiffness.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.187-196
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• 2003

Today, the Working Stress Rating (WSR) is being widely used for the capacity-rating and the safety assessment of railroad steel bridges. Since it cannot incorporate the uncertainties, several studies have been carried out in order to get over the incompleteness of the conventional capacity-rating and safety assessment. A system reliability-based equivalent capacity-rating method, which can evaluate the capacity of existing bridges, has been recently proposed. For more efficient reliability analysis, probabilistic parameters of the random variables in the limit-state models should be reasonably evaluated. Especially, uncertainties for live load effects must be realistically included. In this study, an improved limit-state model was used for the system reliability-based equivalent strength method. This model can incorporate the probabilistic parameters obtained from ambient measurement data. To demonstrate the applicability of the improved system reliability-based equivalent capacity rating method, this was applied to the existing steel plate girder bridge for comparison with the conventional capacity-rating and safety assessment.

• Proceedings of the Korean Geotechical Society Conference
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• 1995.10a
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• pp.17.2-25
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• 1995

한계상태설계법이 지반공학에 도입되었다. 하중과 지지계력수법 그리고 우로코드로 되어있는 본 설계법에서 신뢰성이론을 토대로 한 전자는 북미지역에서, 반통계론적인 후자는 최근에 통합된 유럽연합에서 오래동안 연구 후 채택하였다. 본 논문은 이러한 설계법을 방법론적으로 검토접근하며 다른 선진국의 연구활동을 알아봤으며, 하중과 지지력계수설계법에서 관입말뚝에 대한 지지력계수를 결정하는 합리적인 방법론을 제시하는데 있다.

• Journal of the Korean Society for Railway
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• v.19 no.2
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• pp.187-194
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• 2016

It is necessary to determine reliability indexes of existing railway bridges prior to setting up a proper target reliability index that can be used to introduce a reliability based limit state design method to design practice. Reliability is evaluated for a six PSC-I girder railway bridge, which is one of many representative types of double-track railway bridges. The reliability assessment is carried out for an edge girder subjected to bending moment. In the assessment, the flexural resistance and the fixed-load effect were obtained using existing statistical values from previous research on the introduction of limit state design to road bridge design. On the other hand, the live-load effect was determined using statistical values obtained from field measurement for the Joong-ang corridor, on which heavy freight trains are frequently passing. The reliability assessment is performed by AFOSM(Advanced First Order Second Moment method) for the limit state equation, and a sensitivity analysis for the reliability is performed for each factor of the load and resistance effects.