• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.819-826
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• 2022

Recently, interest in smart port systems for linking with autonomous ships is increasing. To build a smart port system, primarily, a system that can automatically moor a vessel is required. To calculate the allowable mooring capacity of the automatic mooring system in a port, the characteristics of the vessel must be considered, and the external force generated from environmental disturbances in the sea must be accurately calculated. Accurately estimating the magnitude of these environmental disturbances is an extremely important factor for designing an automatic mooring system. In this study, the mooring capacity of the HANBADA was estimated according to the port and fishing port design criteria of the Ministry of Ocean and Fisheries. The longitudinal and lateral forces of the mooring force acting on the HANBADA were 18 kN and 248 kN, respectively, under the most extreme ocean conditions (BF 6).

• Journal of the Korean Geotechnical Society
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• v.26 no.11
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• pp.111-123
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• 2010

The steel pipe of steel-concrete composite drilled shafts increases the pile strength and induces the ductile failure by constraining the deformation of the inner concrete. In this research, pile loading tests were performed to analyze the field applicability of a steel-concrete composite drilled shafts. The test ground consisted of 5~7 m thick soil underlying rock mass. The test piles consisted of two steel-concrete composite drilled shafts, which were the concrete filled steel pipe piles with the diameter of 0.508 m, and a concrete pile with the same diameter. The test results showed that the boundary between the upper steel composite section and the lower concrete section was structurally weak and needs to be reinforced by using a inner steel cage. If the boundary is located in deep depth, which is not influenced by lateral load, the allowable strength of the lower concrete section increases, so an economical design can be performed by increasing the design load of steel-concrete composite drilled shafts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.531-542
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• 2017

The structural safety of small craft, such as steel ships and FRP ships, can be estimated using the measurement test of the hull plate thickness or the longitudinal bending strength test. A polyethylene boat is made using inexpensive HDPE and can be mass produced. The structural safety of a polyethylene boat cannot be guaranteed because a polyethylene boat hull is notspecified in the KR technical rules. The inspection procedure of sailing yachts and pleasure boats and drop test method of ISO standard 12215-5 propose the structural strength required for small crafts as the drop test height. Therefore, in this study, the drop test of a polyethylene boat hull was carried out based on the inspection procedure of a sailing yacht and pleasure boat and the drop test method of ISO standard 12215-5. The drop load was acquired by the drop acceleration ofa boat hull. Structural analysis and safety of a polyethylene boat were performed by the drop load and allowable stress criteria. The calculation results of the hull plate thickness by structural design specification of ISO standard 12215-5 showed that polyethylene boat hull was more than two times thicker than a steel ship hull and the boat hull determined by the inspection procedure of sailing yacht and pleasure boat and drop test method of ISO standard 12215-5 was more than 1.2 times thicker than the boat hull determined by structural design specification of ISO standard 12215-5. Therefore, inspection procedure of sailing yachts and pleasure boats and drop test method of ISO standard 12215-5 was much more conservative than the structural design specification of ISO standard 12215-5 and could be used as the structural design method of a polyethylene boat.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.1-8
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• 2014

Using the level set and the meshfree methods, we develop a topological shape optimization method applied to linear elasticity problems. Design gradients are computed using an efficient adjoint design sensitivity analysis(DSA) method. The boundaries are represented by an implicit moving boundary(IMB) embedded in the level set function obtainable from the "Hamilton-Jacobi type" equation with the "Up-wind scheme". Then, using the implicit function, explicit boundaries are generated to obtain the response and sensitivity of the structures. Global nodal shape function derived on a basis of the reproducing kernel(RK) method is employed to discretize the displacement field in the governing continuum equation. Thus, the material points can be located everywhere in the continuum domain, which enables to generate the explicit boundaries and leads to a precise design result. The developed method defines a Lagrangian functional for the constrained optimization. It minimizes the compliance, satisfying the constraint of allowable volume through the variations of boundary. During the optimization, the velocity to integrate the Hamilton-Jacobi equation is obtained from the optimality condition for the Lagrangian functional. Compared with the conventional shape optimization method, the developed one can easily represent the topological shape variations.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.5
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• pp.305-318
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• 2012

Although the existing performance-based design method for the vertical breakwater evaluates an average sliding distance during an arbitrary time, it does not calculate the probability of the first occurrence of an event exceeding an allowable sliding distance(i.e. the first-passage probability). Designers need information about the probability that the structure is damaged for the first time for not only design but also maintenance and operation of the structure. Therefore, in this study, a time-dependent reliability design method based on a stochastic process is developed to evaluate the first-passage probability of caisson sliding. Caisson sliding can be formulated by the Poisson spike process because both occurrence time and intensity of severe waves causing caisson sliding are random processes. The occurrence rate of severe waves is expressed as a function of the distribution function of sliding distance and mean occurrence rate of severe waves. These values simulated by a performance-based design method are expressed as multivariate regression functions of design variables. As a result, because the distribution function of sliding distance and the mean occurrence rate of severe waves are expressed as functions of significant wave height, caisson width, and water depth, the first-passage probability of caisson sliding can be easily evaluated.

• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.5-15
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• 2014

Target reliability index in the limit state design indicated the safety margin and it is important to determine the partial factor. To determine the target reliability index which is needed in the limit state design, the six design and construction case histories of gravel compaction piles (GCP) were investigated. The limit state functions were defined by bulging failure for the major failure mode of GCP. The reliability analysis were performed using the first order reliability method (FORM) and the reliability index was calculated for each ultimate bearing capacity formulation. The reliability index of GCP tended to be penportional to the safety factor of allowable stress design and average value was ${\beta}$=2.30. Reliability level that was assessed by reliability analysis and target reliability index for existing structure foundations were compared and analyzed. As a result, The GCP was required a relatively low level of safety compared with deep and shallow foundations and the currd t reliability level were similar to the target reliability in the reinforced earth retaining-wall and soil-nailing. Therefore the target reliability index of GCP suggested as ${\beta}_T$=2.33 by various literatures together with the computed reliability level in this study.

• Journal of the Korean Geotechnical Society
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• v.35 no.8
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• pp.17-30
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• 2019

Based on pile load test results for various pile types that were constructed in-situ and pile design data of prebored PHC piles, the ratio of skin friction to total capacity (SRF) was analyzed. A SRF distribution range from the pile load test results for pilot test prebored PHC piles was 42~99% regardless of relative penetration lengths, soil types, and pile load test types. However, a SRF distribution range from the pile design data for prebored PHC piles was 20~53% regardless of relative penetration lengths and pile diameters. Also, a SRF distribution range from the restrike dynamic pile load test results for pretest working prebored PHC piles was a scattered range of 4~83% regardless of pile diameters, relative penetration lengths and soil types. The scattered SRF of pretest working piles was caused to the quality control issue on the filling of cement milk around piles and this quality control issue should be improved. The average SRF calculated by the current design method was estimated to be 2.2 times lower than the average SRF of the pilot test piles. It is because skin friction resistance is calculated at a very low level. Therefore, a new design method for skin friction will be proposed based on this study.

• Journal of the Korean Wood Science and Technology
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• v.43 no.4
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• pp.446-455
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• 2015

Based on comparative studies on standards and grading procedures of machine graded lumber in Korea and other countries, this study proposed a procedure of determining the grade classification and design strengths of domestic machine graded lumber. Differences between machine stress rated lumber and E-rated laminations were detailed in order to clarify the need for the procedure improvement. To this improvement the use of average MOE requirement for grading was introduced instead of the fixed minimum MOE requirement which is currently used in the Korean standards. It was found that the fixed minimum MOE requirement method was easier for an inspector to grade but, less efficient as a strength predictor than the average MOE requirement method. The advantage of average MOE requirement method is statistically MOR-MOE regression-based MOR prediction and highly efficient in quality control though it requires a computer-aided operation system in an initial setup. A major weakness of the current Korean grading system was found that different strength characteristics depending on wood species were not reflected on the grade classification and the tabulated allowable design stress. The proposed procedures were developed taking advantages of respective merits of both methods and based on MOR-MOE regression analysis. Through this procedure, the grades of machine stress rated lumber should be revised to become interchangeable with E-rated lamination, which would be beneficial to the cost competitiveness of domestic machine graded lumber and glued laminated timber industry.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.91-96
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• 2015

In this study, we performed a study on prevention of the escape hoist heavy objects on the basis of the case of a disaster occurring during crane operations. A safety hook of the automatic fastening and coupling method by the conventional coupling method, the weight of the outside consisting of a combination of a safety ring structure was designed and manufactured. The main mechanism three-dimensional detail design and structural analysis confirmed the structure and stability of small strain than the allowable stress of the Safety Hook with X-jog through. Safety factor was confirmed to represent the average 1.5 to 1.2 higher than the safety factor to be considered in the general design structure. Therefore, Safety Hook and X-jog in the present study is to be operated upon structural stability is a structure attached to the hoist and crane are considered sufficient.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1915-1933
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• 2013

In this study, the virtual fixed point analysis and 3D fully modeling analysis for bent pile structures are conducted by considering various influencing factors and the applicability of the virtual fixed point theory is discussed. Also, the optimized column-pile length ratio is analyzed for supplementing virtual fixed point design and examining a more exact behavior of bent pile structures by taking into account the major influencing parameters such as pile length, column and pile diameter, reinforcement ratio and soil conditions. To obtain the detailed information, the settlement and lateral deflection of the virtual fixed point theory are smaller than those of 3D fully modeling analysis. On the other hand, the virtual fixed point analysis overestimates the axial force and bending moment compared with 3D fully modeling analysis. It is shown that the virtual fixed point analysis cannot adequately predict the real behavior of bent pile structures. Therefore, it is necessary that 3D fully modeling analysis is considered for the exact design of bent pile structures. In this study, the emphasis is on quantifying an improved design method (optimized column-pile length ratio) of bent pile structures developed by considering the relation between the column-pile length ratio and allowable lateral deflection criteria. It can be effectively used to perform a more economical and improved design of bent pile structures.