• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.92-101
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• 2020

It is necessary to develop a rational method for evaluating the safety of bridges for the passage of inseparable crane vehicles exceeding the limit weight. In this study, the same method applied to the development of the recently introduced reliability-based highway bridge design code - limit state design method is applied to the calibration of the live load factor for the crane vehicle. Structural analysis was performed on the concrete bridge and the required strengths of the previous design code, the current design code and AASHTO LRFD were compared. When comparing the unfactored live load effect, the live load of the crane was greater than that of the current and previous design code. When comparing the required strength by applying the calibrated live load factor, the previous design code demands the largest strength and the current design code and the crane live load effect yields similar value. The results of safety evaluation of the actual bridges on the candidate route for the crane passage secured the same reliability as the target reliability index required by the design code and the strength of the cross section of the actual bridge is calculated greater than the required strength for the passage of the crane, which confirms the safety for the passage of the crane.

• Journal of the Korean Society for Railway
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• v.7 no.2
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• pp.39-47
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• 2004

연강(mile steel)은 철도차량 차체의 주요 재질로 오랫동안 사용되어 왔으며, 다양한 강도 특성과 저렴한 가격, 용이한 작업성등의 이유로 현재까지도 널리 적용되고 있다. 그러나 연강은 부식에 취약하므로 도장작업이 필수적이고, 부식에 대한 여유로 인해 판두께의 감소가 제한적이므로 경량화가 곤란하고, 정기적인 유지보수가 필요한 단점이 있다. 반면에 스테인레스강(stainless steel)판재는 내부식성이 강하므로 무도장이 가능하고, 차체의 내구 수명이 증가하며, 유지보수가 편리하다는 장점이 있다. 또한 내부식성과 고강도 특성으로 차체 판재의 두께 감소가 가능하므로 경량화에 유리하고, 차체 표면의 다양한 표면처리가 가능하므로 외관의 미려함을 높일 수 있다. 스테인레스강는 연강에 비해 상대적으로 고가의 재질이지만 유지보수 측면과 경량화에 따른 운행비용 측면에서 볼 때 철도차량 차체의 재질로서 유용성을 가지고 있어 활발히 적용되고 있다. 국내에서는 1990년대초 과천선 전동차를 시작으로 스테인레스강 철도차량이 본격적으로 개발되어 상용화되었고, 새마을호를 비롯한객차에도 스테인레스강 차체를 적용하고 있다. 국내의 스테인레스강 철도차량 제작 기술은 이제 상당한 수준에 올라와 있으며 차량의 해외 수출은 물론 기술 이전도 활발히 진행되고 있다. 본 강좌에서는 스테인레스강 철도차량 차체의 특성과 함께 설계 방법을 정리하여 봄으로써, 향후 스테인레스강 철도차량 차체의 개선 및 발전을 위한 기초로 삼고자 한다.(중략)

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.182.2-182.2
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• 2010

설계단계의 풍력발전시스템 하중계산은 20년이 넘는 시스템 수명과 효율을 결정하는 중요한 부분이다. 일반적인 규정서 기반의 설계하중 계산은 실제 풍황 조건인 발전기 상호 간섭, 설치 지형의 특성 등을 상세히 묘사하기 어렵다. 풍력발전기 설계 단계에서 검토된 평균풍속 또는 난류강도 등이 규정(IEC, GL 등)을 만족한다 하더라도 설계값과 실제값은 서로 다른 결과를 나타낼 수 있다. 본 연구에서는 기 설계된 풍력발전기가 최적 효율을 낼 수 있는 풍력단지의 풍황 특성(평균풍속과 난류강도 등)의 범위를 보다 정확하게 제시하여 설치되는 풍력발전기의 수명과 효율을 높이는 방법을 연구하였다. 이를 위하여 당사의 2MW급 IEC Class II-A로 설계된 직접 구동형 풍력발전기에 대해, 다양한 평균 풍속(7m/s~10m/s)과 난류강도(14%~20%)를 고려한 하중 계산을 수행하였다. 하중 분석을 통해 실제 풍황 조건에 따른 극한하중 산출 및 피로수명의 민감도를 검토하여 풍력발전기 운용의 풍속과 난류강도의 최적범위 제시하여 발전단지 설계에 활용할 수 있도록 하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.557-566
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• 2002

This paper presents an optimum deck and girder system design for minimizing the life-cycle cost(LCC) of steel box girder bridges. The problem of optimum LCC design of steel box girder bridges is formulated as that of minimization of the expected total LCC that consists of initial cost, maintenance cost and expected retrofit costs for strength, deflection and crack. To demonstrate the cost effectiveness of LCC design of steel box girder bridges, the LCC optimum design is compared with conventional design method for steel box girder bridges. From the numerical investigations, it may be positively stated that the optimum design of steel box girder bridges based on LCC will lead to mote rational, economical and safer design.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.322-325
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• 2010

철강 플랜트 주요 설비인 전로를 지지하는 장치의 접합부 강도설계를 위해 작용하중은 해석적인 방법으로 신뢰성 있게 계산하였고, 정적하중에 의한 응력은 ASME 규정에 따른 허용응력으로 평가하였다. 한편 피로설계 측면에서는 전로와 같은 대형 용접구조물은 강도상 취약부인 용접부에서 다양한 용접비드 형상에 따라 국부응력이 크게 달라지므로 설계단계에서 피로수명 평가에 어려움이 있었다. 따라서 전로 지지장치 접합부 피로설계는 설계단계에서 피로수명을 평가하는 실용적이고 안전측 방법으로 알려진 Hot Spot 응력을 사용하고 공신력을 갖는 설계규정인 ASME와 영국 PD 5500 절차에 의해 평가하였다. 평가결과 두 규정 모두 안전측에서 평가되는 것을 확인할 수 있었고 이 방법은 피로하중이 지배적인 대형구조물의 설계단계에서 유용한 방법으로 활용할 수 있으리라 판단된다.

• Journal of the KSME
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• v.28 no.4
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• pp.408-414
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• 1988

근년에 항공 산업이 많은 관심을 불러일으키고 있음에 즈음하여 독자적인 항공기 구조개발시 구조적 안전성 확보를 위해서는 구조시험 기술의 확보가 필수적이다. 또한 구조시험 관련기술은 다른 기계 구조물의 초기 설계단계에서 구조 강도 및 피로 강도의 확인을 위해서도 응력될 수 있어 구조물의 설계 및 제작공정 결정에 큰 도움이 될 수 있으므로 기업체나 연구소에서도 충 분히 응용할 수 있도록 노력을 기울여야 할 분야이다.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.659-666
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• 2010

Although the compression splice needs not be longer than the tension slice due to existence of end bearing, current design codes impose a longer compression lap splice than a tension lap splice in high strength concrete. Hence, new criteria for the compression lap splice including the effects of concrete strength need to be sought for economical design involving ultra-high strength concrete. An experimental study has been conducted with column specimens in concrete strength of 80 and 100 MPa. Test results show that the splice strength can be evaluated to be proportional to square root of compressive strength of concrete. Bar stress developed by end bearing is not affected by splice length and is expressed with a function of the square root of concrete strength. Mean value of stresses developed by end bearing is 16.5 square root of $f_{ck}$. The stresses developed by bond in compression splices are nearly identical to those in tension splices and, therefore, strength increment of compression splices is attributed to end bearing only. From regression analysis of 58 tests, a design equation is proposed for compression lap splice in 40 to 100 MPa of compressive strength of concrete. By the proposed equation, the anomaly of lap lengths in tension and compression is got rid of. In addition, the equation has a reliability equivalent to those of the specified strengths of materials.

• Journal of the Korea Concrete Institute
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• v.29 no.4
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• pp.335-343
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• 2017

This paper aims at investigating the bending strength of high-strength concrete beams with compressive strength of 80 MPa. The experimental parameters included nominal yielding strength of rebar with 400 and 600 MPa, rebar ratio ranging from 0.98 to 1.97%, and shear span-effective depth ratios (a/d) of 6.0 and 4.8. Experimental results were discussed regarding load-deflection relationship, ductility, bending strength, and prediction of bending strength of beams. Test results indicate that the use of high-strength rebar increased bending strength but decreased ductility. As span-effective depth ratio increased, the ductility of test beams decreased. In addition, test results of bending strength were compared with predictions from the current KCI code, Eurocode 2 and Korean Highway Design Specification (KHDC). The design code predictions for bending strength underestimated the experimental results. Therefore, the current design code predictions for bending strength of high-strength concrete beams would provide conservative design. Predictions of bending strength from KCI code using strength reduction factors and those from Eurocode 2 as well as KHDC using material factors were similar each other.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.145-150
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• 2019

This paper proposes a model for the calculation of the ultimate torsional strength in normal-strength and high-strength concrete beams which include the concrete contribution strength and use a reasonable thickness of shear flow. The adequacy of the proposed model is evaluated by comparing the calculated torsional strength with the experimentally observed results from 104 test specimens reported in the literature. The results are also compared with the calculations of the KCI and the ACI building code equations, and those of other model which include the concrete contribution strength. The comparisons show that the ultimate torsional strengths calculated by the proposed equation and Rahal's equation are closer to the experimentally observed results than those calculated by the code equations.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.122-131
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• 1992

An expert system is developed which can design the power transmission involute cylindrical gears on the basis of strength and durability. Bending strength, surface durability, scoring, and wear probability are considered as the basis. The basic components of the expert system are knowledge base, inference engine, and working memory. The knowledges in knowledge base are classified hierarchically into the knowledges used in selection of gear type, selection of materials, and determination of K factor and are represented by rules. In the inference engine two inference methods are implemented with the depth first search method. For-ward chaining method is introduced in the selection of gear type and materials and in the determination of K factor. Backward chaining method is introduced in the detailed design of module and face width in accordance with the validation of strength. And inference efficiency is achieved by constructing the part needing a lot of numerical calculations in strength estimation separately from inference mechanism. The working memory is established to save the results during inference temporarily. In addition, design database of past design results is built for consultation during design and knowledge acquisition facility, explanation facility, and user interface are included for the usefulness of user. This expert system is written with the PROLOG programming language and the FORTRAN language in numerical calculation part which interfaced with PROLOG and can also be executed on IBM-PC compatible computer operated by MS-DOS alone.