• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.26-35
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• 2012

Until now, study on the hydraulic resistance characteristics of the ground at the river and the ocean current has been focused on the behavior under uni-directional flow without the direction change of flow. However, recent research result shows that scour rate which were measured under the bi-directional flow was much higher than those measured under uni-directional flow for both fine grained and coarse soil. Since the direction of inflow and return flow at the shore, where the structure will be constructed, is not always $180^{\circ}$, effect of the incidence angle on the hydraulic resistance capacity of the ground should be examined. Using the improved EFA which can consider the direction change of flow, hydraulic resistance capacities of the artificially composed clayey fine grained soil and clayey sandy soil under $0^{\circ}$, $90^{\circ}$, $135^{\circ}$, $180^{\circ}$ flow angle of incidence were assessed. Test result shows that hydraulic resistance capacity decreases and scour rate increase with the increase of the incidence angle between inflow and return flow. For the low consolidation pressure condition, hydraulic resistance capacity of the fine grained soil decreases rapidly. While the hydraulic resistance capacity of the coarse grained soil decreases more rapidly than fine grained soil under high consolidation pressure. Eventually since the larger the incidence angle between inflow and return flow, the larger the scour rate. Hydraulic resistance capacity under bi-directional flow($0^{\circ}{\longleftrightarrow}180^{\circ}$) should be examined for the design purpose.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.3-4
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• 2009

This study predicts the structural behavior of RC beams using high strength shear reinforcement and evaluates current design codes restricting the strength of shear reinforcement steel. Under the present design codes, the yield strength of shear reinforcement steel is restricted to 400MPa. In case that use high yield strength reinforcement steel, could incure heavily crack and deflection at the members of structure, and have not verified ductility capacity, fatigue resisting capacity, shear and torsion resisting capacity, anchoring capacity and seismic capacity. To this end, we evaluate structural behavior of reinforced concrete beams using high strength shear reinforcement.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.145-148
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• 2008

Recently, most of the international design code for concrete structures are trying to develope performance-based design specification with the limit state concept. To accomplish this object, it is necessary to define required performance and to measure the performance level of structure. The reliability index is one of the most attractive indexes to express the level of performance. In this paper, prestressed concrete beam is designed following member resistance factor and material resistance factor format and the reliability indexes are obtained and compared for different sets of resistance factors. Compatible sets of safety factors could be calibrated for given level of target reliability index applying the similar method presented in this paper.

• Bulletin of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.18-21
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• 1994

시제품을 만들어 본 후 대량 생산에 들어가는 여느 공업과는 달리, 조선공업에서는 시제품을 미리 만들어 볼 수가 없으므로 실선의 성능을 미리 추정하는 것은 참으로 중요한 과제 중의 하 나이다. 그 가운데 하나인 저항추진성능을 추정하는 데에는 통계해석 방법이 널리 쓰이고 있다. 여기서 통계해석은 모형시험 결과를 표본자료로 한 통계해석을 말한다. 실선의 저항추진성능을 추정하는 것이므로 실선 속력시운전 자료를 사용하는 것이 좋겠으나, 실선 속력시운전에서 정 확한 값을 얻는다는 것이 거의 불가능하므로 대부분 모형시험 값을 이용하곤 한다. 본 고에서는 기존에 발표된 여러 가지 도표와 회귀식을 요약하여 본 후, 표본자료를 이용하여 새로운 회귀 식을 만드는 과정을 소개하고자 한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.4
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• pp.426-434
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• 2014

The research developed twin keel yacht for everyone which is able to stand erectly on mud flat without list and intended to commercialize the development product for popularization of west coast's marine leisure industry. Yacht's linear was utilized by "Blue Water21" has superior performance among the existing sailing yachts and twin keel model has been tested by calculation of mono keel's extent and its center of gravity. The result was that only 4 % of difference have been identified between mono keel and twin keel's hydrodynamic resistance which was smaller difference than predicted.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.9-16
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• 2006

The design practice of the lateral resisting system has been traditionally dependent on the experience and know-how of a structural engineer. And the method to reflect the evaluation results of building's capacity on design process doesn't exist. The proposal of a rational design of the lateral load resisting system is based on the available full capacity $(R_{ac})$ of a building and the minimum required capacity $(R_{code})$ suggested in the code. This study suggests thai nonlinear static analysis, which is the estimation of the lateral capacity with the pushover analysis, be included in the existing design procedure of the structure. After finishing the basic structural design, the lateral resisting capacity ol a building is estimated. At the phase of nonlinear static analysis, pushover analysis is peformed to define the fully yielded baseshear $(V_Y)$. When the design wind baseshear $(V_{wind})$ is bigger than the design seismic baseshear $(V_D)$, the value is checked to determine whether or not it is smaller than the $V_Y$. After confirming that it is smaller, the $R_{ac}$ of the structure is computed. If the $V_D$ is bigger at first, only the $R_{ac}$ is computed. When the value of the estimation shows remarkable differences with the $R_{code}$, repetition of the design modification is needed for those approximate to the $R_{code}$. Application of the proposed design procedure to 2-D steel braced RC buildings has proven to be efficient.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.672-680
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• 2023

Weight is a critical factor in the ship design process given that it has a substantial impact on the hydrodynamic performance of ships. Typically, ships are optimally designed for specific conditions with a fixed draft and displacement. However, in reality, weight and draft can vary within a certain range owing to operational activities, such as fuel consumption, ballast adjustments, and loading conditions . Therefore, we investigated how resistance changes under three different loading conditions, namely overload, design-load, and lightship, for small craft, using both model experiments and numerical simulations. Additionally, we examined the sensitivity of weight changes to resistance to enhance the performance of ships, ultimately reducing power requirements in support of the International Maritime Organization's (IMO) goal of reducing CO2 emissions by 50% by 2050. We found that weight changes have a more significant impact at low Froude Numbers. Operating under overload conditions, which correspond to a 5% increase in draft and an 11.1% increase in displacement, can lead to a relatively substantial increase in total resistance, up to 15.97% and 14.31% in towing tests and CFD simulations, respectively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.656-665
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• 2021

In this study, trim tabs were attached to end of stern hull of a small high-speed vessel of length approximately 10 m and Froude number 1.0 to improve resistance performance and passenger comfort. Before computational fluid dynamics (CFD) simulations to assess the performance according to various geometries of the trim tab, the scale effect had been found through a previous study, so full-scale simulations were performed. The trim tab chord length was set to 0.5 %, 1.0 % and 1.5 % of L_PP, and its angle to base line was varied in intervals of 5°. It decreased trim by stern and flotation: the greater the angle and length, the greater was the effect. Then it had pressure resistance decreased and shear resistance increased, and reduction ratio of total resistance varied accordingly. The results of this study indicated that the resistance performance was improved about 27 % at optimal running attitude that was the trim by stern about 1.5°.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.4
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• pp.538-549
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• 2021

In this study, a trim tab on the stern hull of a small high-speed vessel of approximately 10 m length sailing at a Froude number of 1.0 was designed for energy efficiency. The running attitude and resistance performance of the bare hull and trim tab hull at several angles to the base line were analyzed for model and full scale ships using computational fluid dynamics, and compared to investigate the scale effect. The analysis results for the bare hull were quite similar, but a difference in the attitude control under same conditions of the trim tab was observed, resulting in the total resistance error. However, there was no significant difference in tendency of the variation in the resistance with the attitude. Thus, the optimum running attitude could be determined from the tendency despite the scale effect, but a full scale analysis is required to analyze the control of the attitude by the trim tab and flow characteristics near the full scale ship.

• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.253-253
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• 2017

본 연구에서는 연륙연도 사업에 대응하는 경제성 및 안정성을 갖춘 쌍동선형 차도선의 개발을 위해 U형과 V형의 서로 다른 쌍동선형을 CFD 해석을 수행하여 저항성능을 비교하였다. CFD 해석 결과 U형 쌍동선형의 경우 14kts 이상의 고속에서 선수부 파형에 이상이 발생하여 정상적인 운행이 불가능하다 판단되었으며, 이에 비해 V형은 동일한 속도에서도 이상이 발생하지 않았으며, 또한 U형 쌍동선형 대비 V형 쌍동선형의 경우, 저속에서는 U형 대비 높은 침수표면적에도 불구하고 거의 같은 $R_{TS}$값을 보이지만, 고속으로 넘어가면 U형에 비해 확연히 낮은 $R_{TS}$값을 보임을 확인, V형의 쌍동선형이 U형에 비해 저항성능이 개선됨을 확인하였다.