• Special Issue of the Society of Naval Architects of Korea
• /
• 2017.10a
• /
• pp.38-45
• /
• 2017

FPSO is widely used to develop deep sea oil fields and HHI has constructed ten(10) FPSOs. During these constructions, relevant structural design criteria such as yielding, buckling, fatigue, collision and impact strength were applied to verify structural safety. To apply the buckling strength evaluation for structures, the critical buckling stresses and applied stresses of relevant panels should be calculated. The plate and stiffened panels are to be idealized, which are needed much time and efforts by designers. Therefore, program development is necessary in order to evaluate the buckling strength conveniently and accurately. In this study, the buckling strength assessment system by using offshore code, DNV-RP-C201 was developed under MSC/PATRAN, pre-post program of finite element method. Graphic user interface program is written in MSC/PATRAN PCL functions. Source program to evaluate the buckling strength is developed in FORTRAN programming languages. The developed program is verified by comparing with the results of the Nauticus Hull developed by DNV Classification Society, and applied to the marine construction project conducted by Hyundai Heavy Industries LTD.

• Proceedings of the Optical Society of Korea Conference
• /
• 1989.02a
• /
• pp.161-164
• /
• 1989

When an electric (or a magnetic) line source is located near the surface, surface wave type field is generated and the energy associated with this field is guided very close to the impedance surface. In this paper, field strength is calculated by the exact modal and ray methods for a line source excited parallel plate waveguide. The surface wave contribution to the modal and ray solutions is anticipated very strong and must be included in both solutions.

• Journal of Korean Society of Environmental Engineers
• /
• v.35 no.9
• /
• pp.643-653
• /
• 2013

In this study, trend analysis was performed by various runoff analysis method of Non-point Pollution Source(NPS) at the impervious area. The characteristics of rainfall at impervious area appeared to be influenced by rainfall strength and it appeared that first flush phenomenon occurs often if rainfall strength acts largely. It is judged that the measure is required to be prepared against that now that concentration difference of non-point pollution source appeared to be big by precedent number of days of no rainfall. As the result of calculating Decrease Rate (DR) by first flush of non-point pollution source, it is judged that it is important to prepare the measure against the pollutants about initial rain and it is necessary to calculate the capacity of non-point pollution source processing facilities regarding that now that the non-point pollution source integrated at impervious area showed the characteristics that are flowed out in high concentration by initial rain in case of non-rainfall considering the characteristics of non-point pollution source at impervious area. When taking 50% of non-point pollution source as the standard for decrease rate that was evaluated previously, it appeared as 15~60 min in case of TSS and it appeared as 30~90 min in case of organic compound, but the characteristic whose decrease rate is below 50% also appeared even till rainfall-runoff ends. Based on that, it is judged that it could be used as the reference when designing the structural BMPs facilities later.

• Journal of Powder Materials
• /
• v.1 no.2
• /
• pp.119-198
• /
• 1994

The characteristics of various important microstructural factors of WC-base hard- metals (cemented carbides) such as the amount of Co metal binder phase, the carbide grain size, the microstructural defects acting as a fracture source, the solid solubility of tungsten in the binder phase affected by the carbon content, the precipitation of $Co_3W$, the domain size of binder phase, the formation of ${\beta}-free$ layer or Co-rich layer and CVD or PVD coated layer, and the effects of these factors on the flexural strength of the hardmetals are reviewed.

• Nuclear Engineering and Technology
• /
• v.49 no.1
• /
• pp.277-284
• /
• 2017

This paper presents the establishment and characterization of a neutron calibration field using a bare $^{252}Cf$ source of low neutron source strength in Vietnam. The characterization of the field in terms of neutron flux spectra and neutron ambient dose equivalent rates were performed by Monte Carlo simulations using the MCNP5 code. The anisotropy effect of the source was also investigated. The neutron ambient dose equivalent rates at three reference distances of 75, 125, and 150 cm from the source were calculated and compared with the measurements using the Aloka TPS-451C neutron survey meters. The discrepancy between the calculated and measured values is found to be about 10%. To separate the scattered and the direct components from the total neutron flux spectra, an in-house shadow cone of 10% borated polyethylene was used. The shielding efficiency of the shadow cone was estimated using the MCNP5 code. The results confirmed that the shielding efficiency of the shadow cone is acceptable.

• Computers and Concrete
• /
• v.20 no.1
• /
• pp.77-84
• /
• 2017

Shirasu, a pyroclastic flow deposit, showed considerable performance as aluminosilicate source in geopolymer, based on past research. However, the polymerization reactivity was somewhat lower compared to the traditional fly ash based geopolymer even though the long-term strength was fairly good. The present study concentrates on the development of higher initial strength performance of Shirasu based geopolymer by utilizing ground granulated blast furnace slag as an admixture. Mortars with various mix proportions were adopted to study the effect of parametric changes on strength development along with the addition of slag in different percentages. A combination of sodium hydroxide and sodium silicate was used as alkaline activators considering parameters like molar ratios of alkali to geopolymer water and silica to alkali molar ratio. The mortars were cured at elevated temperatures under different curing conditions to analyze the effect on strength development. Compressive strength test, mercury intrusion porosimetry and X-ray powder diffraction were carried out to assess the strength performance and microstructure of slag-Shirasu based geopolymer. Based on the experimental study, it was observed that the initial and long-term strength development of Slag-Shirasu geopolymer were improved by the addition of slag.

• Structural Engineering and Mechanics
• /
• v.81 no.5
• /
• pp.539-550
• /
• 2022

A detailed experimental program was conducted to investigate the flexural behavior of ultra high performance concrete (UHPC) beams reinforced with high strength steel (HSS) rebars with a specified yield strength of 600 MPa via direct tensile test and monotonic four-point bending test. First, two sets of direct tensile test specimens, with the same reinforcement ratio but different yield strength of reinforcement, were fabricated and tested. Subsequently, six simply supported beams, including two plain UHPC beams and four reinforced UHPC beams, were prepared and tested under four-point bending load. The results showed that the balanced-reinforced UHPC beams reinforced with HSS rebars could improve the ultimate load-bearing capacity, deformation capacity, ductility properties, etc. more effectively owing to interaction between high strength of HSS rebar and strain-hardening characteristic of UHPC. In addition, the UHPC with steel rebars kept strain compatibility prior to the yielding of the steel rebar, further satisfied the plane-section assumption. Most importantly, the crack pattern of the UHPC beam reinforced with HSS rebars was prone to transform from single main crack failure corresponding to the normal-strength steel, to multiple main cracks failure under the condition of balanced-reinforced failure, which validated by the conclusion of direct tensile tests cooperated with acoustic emission (AE) source locating technique as well.

• International Journal of Safety
• /
• v.8 no.1
• /
• pp.1-5
• /
• 2009

The CFRP composite has unique properties that offer high strength and stiffness, even though it has light weight. Therefore it can be used in many industrial applications. When mechanical fasteners are used for joining composites, high stress concentrations appear near the edge of holes prepared for accommodating structural bolts and rivets. This presence of high stress concentrations can be a source of damage. The aim of this work is to evaluate fracture behavior and patterns of plain woven CFRP with circular hole and repairing patch element. The maximum strength and pattern for the plain woven carbon composite specimen with the repaired circular hole were examined. From the results, we show that repairing of the CFRP composite specimen with ($\pi$) 3~5 mm of circular hole diameter results in load rising effect and the repairing is more effective as bigger hole specimen.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.15 no.3
• /
• pp.58-65
• /
• 2016

This study analyzed the structural weld strength for a door hinge for a field artillery ammunition support vehicle. In order to determine the optimal conditions, we measured the modal analysis and analyzed the leg length of a rear door hinge. From these methods, we acquired the vibration frequency of normal mode and the optimal welding leg length conditions. It was possible to obtain a structural stability for a rear door hinge of the field artillery ammunition support vehicle. In the future, this should be used as a reference source for the weld strength analysis of high vibration and high weight structures for another welding system design.

• Journal of the Korea Concrete Institute
• /
• v.12 no.1
• /
• pp.45-52
• /
• 2000

The quality of cement mortar products largely depends on various work conditions, specially on the grading and grade shape of aggregates. However, the effect of grading and grade shape on the quality is not considered by both KS codes and production processes, resulting in the increase of the possibility of quality degradation. The objective of this study was to investigate the effect of grading and grade shape on the strength and absorption characteristics of cement mortar products. Flexural and compressive strength increased with the increase of fineness modulus and W/C. The strength increase was measured larger with river sand than with crushed sand. Absorption tended to decrease with the increase of fineness modulus and W/C, but did not affected by the source of sand.