• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.159-170
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• 2005

The grid structure is parallel main girders intersected with crossgirder. It distribute the loads to adjoining main girder through the crossgirder when a girder is subjected to a load. grillage girder bridge has high load-carrying capacity, it can save materials and become more economical type of bridge. In this paper, the grillage girder bridge analysis program developed by using the transfer matrix method deals with following problems: the comparision with Leonhardt, Szabo, FEM yang and jung in the analysis of grillage girder bridges, quality of straight and curved bridges with skew angle, forces of straight and curved bridges according to skew angle and bending stiffness/torsional stiffness ratio.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.105-111
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• 2005

Shaking table tests are performed to investigate the seismic behavior of the batter pile and to bring up the countermeasures to improve the seismic performance of the batter pile. First of all, this study demonstrates how batter piles and vertical piles behave under static lateral loadings. Secondly, the vulnerability of batter plies under dynamic lateral loadings is demonstrated showing the axial forces and bending moments mobilized at the pile heads during shaking table tests. Thirdly, countermeasures to overcome the vulnerability of behavior piles during earthquakes are pursued. The countermeasures investigated in this study include introduction of a rubber element at the pile head and the deck plate connection, and introduction of hinge connection. Finally, the slope of batter piles which induces the minimum pile forces during the dynamic loadings are investigated and found to be 8:3 (Vertical to Horizontal).

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.538-542
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• 2015

The transverse moment of inertia is an indispensable factor in analyzing the roll motion characteristics of ships and the calculating method needs to be based on the more reasonable theories when deciding the value as the results and reliability of analysis could be much affected by the correctness. However, the mass distribution and shape of hulls are quite complicated and give much difficulties in case of calculating the value directly from the ship design data, furthermore even acquiring the detailed design data for calculation is almost impossible. Therefore some simpler ways are practically adopted in the assumption that the gyradius of roll moment can be decided by a given ratio and hull width. It is well known that the responses of the free roll decay are varied according to the value of roll moment in view of roll period and amplitude decay ratio, so that the general formula to get the moment value can be derived also from the observation of roll decay responses. This study presents how the roll period and decay ratio are interrelated each other from the roll motion characteristics with suggesting a general formula to be able to calculate roll moment from it. Finally, the obtained general formula has been applied to a ship data to check the resultant characteristics through analyzing graphs and showed that the roll moment becomes more accurate when rolling period and decay ratio are considered together in calculation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.75-77
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• 2016

IMO는 해상에서의 선박 안전 향상을 위해 선박의 복원성능과 조종성능에 관한 국제적 기준을 제시하고 있다. 이러한 기준은 선박 연구자가 수행하는 연구의 방향에도 영향을 미치고 있다. 기존의 수행된 연구는 복원성능과 조종성능의 각각의 분야에서 독립적으로 수행되어 왔으며, 아직 두 분야의 상호 관계에 관한 연구는 미비한 실정이다. 이에 본 논문에서는 선박의 복원성능과 조종성능의 상호 관계를 정량적으로 규명하고자 기초적인 실험 연구를 수행하였다. 이를 위해 복원성능을 나타내는 지표인 GM과 선박의 조종성능을 나타내는 지표인 선회성능을 통해 두 항복 간 상호 관계의 정량적 분석을 시도하였다. 자유항주 모형선을 이용한 선회 시험을 실시하였고, 그 결과 GM 감소에 따른 선회반경 감소 및 초기 횡경사 각도 증가를 확인했으며, 그 변화의 경향은 서로 다르게 나타나는 것을 확인하였다.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.202-213
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• 1992

For the analysis and design of ship structures the generalized slope deflection method(GSDM) taking account of axial elongation effect as well as the bending and shearing deformation is developed. Using the span point concept, the existing slope deflection method is easy to transform the variable section to the equivalent uniform one under the bending moment and the shear force, but it is difficult to analyze the web frame with inclined members because the axial deformation effect is not considered. In the present method, the equilibrium conditions including all force components(i.e. axial force, shear force, bending moment) are formulated at the both ends of the variable section beam, such that the usual space frame stiffness equation which can be solved easily by the matrix method is derived. The accuracy and applicability of the present method is demonstrated by analyzing the ship web frame structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.231-238
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• 2012

The rockbolt functions as a main support, which restricts enlargement of the plasticity area and increases stability in the original ground around tunnels, and prevents a second deformation of an excavated surface by supplementing vulnerability arising from opening of the excavated surface. System bolting is generally applied if ground conditions are bad. System bolting is generally installed perpendicular to the excavation direction in every span. If a place is narrow, or it is difficult to insert bolts due to construction conditions, it may be connected and used with short bolts, or installed obliquely. In this study, laboratory model tests were performed to analyze the effect of the ground being reinforced by inclined bolts, based on a bending theory that assumes that the reinforced ground is a simple beam. In all test cases, deflections and vertical earth pressures induced by overburden soil pressure were measured. Total of 99 model tests were carried out, by changing the installation angle of bolts, lateral and longitudinal distance of bolts, and soil height. The model test results indicated that when the installation angle of bolts was less than $75^{\circ}$, deflections of model beams tended to increase rapidly. Also, the relaxed load that was calculated by earth pressure was rapidly increased when the installation angle of bolts was less than $75^{\circ}$. However, the optimum installation angle of inclined bolts was judged to be in the range of $90^{\circ}{\sim}75^{\circ}$. Also, as might be expected, the reinforcement effect of bolts was increased when the longitudinal and lateral distance of bolts was decreased.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.131-137
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• 2014

The SUV has a risk of rollover because of the highness of center of mass. In this paper the roll-behavior of a SUV in turning motion is analyzed. Dynamic model of the vehicle on the slope is developed and simulation is carried out using the software ADAMS/Car. The results show that the relational expression between the ground force acting on the tire and the roll motion is well established. It is also identified that the driving state of the vehicle becomes unstable at the lower or upper position of the slope.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.465-471
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• 2003

A coastwise chemical tanker sailing at full speed has capsized during turning in calm water. In the previous paper, we investigated the reasons of the accident by demonstrating the proper correction for the free surface effect of the liquid cargo and the bow-sinkage effect. In this paper, we also carry out model experiments of a transverse pressure under the seawater and an outward heel moment according to the heel angle and rudder angle, on the basis of radius of turning circle, ship's speed and drift angle of model ship occurring in turning. It is also shown that the flooding of seawater onto the deck occurring in turning generated a significant outward heel moment and increased the vertical distance between the center of gravity of the ship and the center of lateral water drag.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.19-27
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• 2018

Terzaghi proposed a 2D formula for arching based on the assumption of a vertical sliding surface induced in the upper part due to the downward movement of a trapdoor. The formula was later expanded to consider 3D tunnel excavation conditions under inclined sliding surfaces. This study further extends the expanded formula to consider the effects of different ground properties and inclined sliding conditions in the transverse and longitudinal directions considering anisotropic ground conditions, as well as 3D tunnel excavation conditions. The 3D formula proposed in this study was examined of the induced vertical stress under various conditions (ground property, inclined sliding surface, excavation condition, surcharge pressure, earth pressure coefficient) and compared with the 2D Terzaghi formula. The examination indicated that the induced vertical stress increased as the excavation width and length increased, the inclination angle increased, the cohesion and friction angle decreased, the earth pressure coefficient decreased, and the surcharge pressure increased. Under the conditions examined, the stress was more affected at low excavation lengths and by the ground properties in the transverse direction. In addition, The comparison with the 2D Terzaghi formula showed that the induced vertical stress was lower and the difference was highly affected by the ground properties, inclined sliding conditions, and 3D tunnel excavation conditions. The proposed 3D arching formula could help to provide better understanding of complex arching phenomena in tunnel construction.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.235-239
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• 2016

The capsizing speed of an unstable vessel with a lost restoring moment can be understood as a unique response to an accident situation, and is naturally affected by such parameters as moment of inertia, metacentric height, and transverse damping coefficient of the hull in the case of free roll motion. Additionally, it is supposed that the analysis of capsize accidents can be further simplified when a vessel's leaning velocity is shown to be quite low. Therefore, capsize accidents with low leaning speeds are desirably categorized in view of rescuing strategies, as opposed to fast capsize accidents, since the attitude of the declining hull can be properly estimated, which allows rescuers to have more time for helping accident cases. This study focuses on deriving some analytical equations based on the roll decay ratio parameter, which describes how a hull under a low-speed capsize is related to the situational hull characteristics. The suggested equations are applied to a particular ship to disclose the analytical responses from the model ship. It was confirmed that the results show the general characteristics of slow capsizing ships.