• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.89-98
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• 2017

The offshore plant structure has been transported to the site by barge because it is hard to manufacture in site. When the structure was transported on the sea, offshore plant structures and connection were experienced repetitive submarine load. For this reason, it was known for that the axial force of high-strength bolted connection was declined. Therefore, in this study, high-strength bolted connection was evaluated the shear fatigue performance under longtime fatigue load during marine transport. The experimental variables were selected intial axial force, surface type, and bolt type because they ar important factors in the change of axial force of bolts. As a experimental results of considering various variables, the variation of axial force showed within 1%. Therefore, the high-strength bolted connection was verified structural safety under longtime fatigue load.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.1
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• pp.31-40
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• 2006

The entrance and the exit structures of tunnels are often constructed on unfavorably soft soils (colluvial soils) as a result of environment-friendly design highlighted in recent years. For construction of such a tunnel, it is essential to secure sufficient bearing capacity of the lining supports as well as that of the surrounding soils. In this regard, H-shape steel-ribs with high stiffness are commonly used for lining supports. However, it was the past convention to ignore the effect of the steel-ribs in numerical evaluation of the structural safety. This study is intended to show how the shotcrete stresses are relieved by the steelribs, on the basis of numerical data obtained from 3-dimensional finite element analysis. The effect of steel ribs to shotcrete stresses is examined at different levels of application rates, i.e., 0%, 50%, 75% and 100% of the total stiffness. The data obtained from numerical analysis was compared with in-situ measurement. The effect of st eel ribs to shotcrete stresses was verified and appropriate total stiffness was proposed in the range of 50%~75%.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.37-43
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• 1995

The procedure and the results of the full scale strain measurement of the long-range high-speed foil catamaran are described. The wave induced stresses at the center struts of the foils were measured during the sea trials in order to evaluate the hydrodynamic force acting on the foils and to verify the structural safety of the foil structures. From the statistical properties of the measured response of the stress, the most probable maximum values of the lift force and the stresses at the foils in service life of the ship are predicted and compared with the design parameters of the foils which were applied in the design of the subject ship. The available prediction processes of the measured stress are studied and the results of the applied processes are compared with each other.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1303-1308
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• 2007

Recently, precast concrete tracks are replacing ballast track for efficient and economic maintenance of track. Precast concrete railroad tracks are manufactured in factory, and transported to railroad construction site for installation. Therefore, quality of precast concrete track itself should be sufficiently good. On the contrary to the convenient manufacturing of precast concrete track, the installation of a precast concrete track requires careful steps. Typically, a precast concrete track is placed on an approximately 15-cm thick lean concrete layer. A mortar is filled between lean concrete layer and precast concrete track to adjust the sloping angle of a precast concrete track for a safe train operation at a curvy section. Then, the use of filled mortarproduces a void underneath a precast concrete track, which is harmful to structural safety of a precast concrete track undercyclic loading. Therefore, it is essential to make sure that there is no void left beneath a precast concrete track after mortar filling. In the continuous resonance method, the amplitude of frequency response measured using an instrumented hammer and an accelerometer is plotted against a pseudo-depth, which is half of the wave velocity divided by frequency. The frequency response functions are measured at consecutive measurement locations, 6-cm interval between measurement points, and then combined together to generate a 2-D plot of frequency response. The sections with strong reflections or large amplitude of frequency response are suspicious areas with internal voids and unfilled areas. The 2-D frequency response plot was efficient in locating problematic sections just by examining the color shade of a visualized plot in 2-D format. Some of the problematic sections were drilled to make a visual inspection of mortar filling. The visual image of interface between mortar and precast concrete track was verified using the validity of the continuous resonance technique adopted in this research.

• Journal of the Korean Geophysical Society
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• v.3 no.1
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• pp.49-56
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• 2000

As a part of geophysical studies on segmentation of the Ulsan fault, walkaway refraction seismic data were measured at 17 stations near National Road 7 between Kyungju and Ulsan. Seismic anisotropy was analyzed in the offset range of 1-48 m. The average refraction velocity of 1787 m/s indicates the refractor is the upper boundary of weathered basement. P-wave anisotropy is computed to be 0.056 in average, which may serve as a weak evidence that the strike of major geologic structure coincide with the inferred fault direction. In the south of the province boundary between Kyungsangnam-do and Kyungsangbuk-do, the velocity anisotropy is normal in that P-wave velocity in the strike direction is faster than the one measured in the dip direction. On the contrary, it appears that the fault strikes in many directions or that fractures may be developed better in the dip direction in the northern par. Such a difference in anisotropic pattern is believed to be a seismic evidence indicating that a segmentation boundary of the Ulsan fault locates near the province boundary.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.147-153
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• 2013

Recently the primary water stress corrosion cracking(PWSCC) has occurred in the dissimilar metal weld region between pressurizer nozzle and safe-end in nuclear power plants(NPPs). As material of the pressurizer nozzle, SA508 Gr. 3 low alloy steel was used. F316L stainless steel and Alloy 82/182 were used as safe-end and weld metal, respectively. Although mechanical properties are needed for evaluation of the structural integrity against flaw in the material, material specification and standard don't supply those properties. Therefore, the present study conducted tensile and fracture toughness tests on SA508 Gr.3 and F316L stainless steel at ambient temperature and operating temperature of NPPs and reported the tested results.

• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.85-92
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• 2017

Base isolation system is generally used for low-rise buildings. For high-rise buildings subjected to earthquake loads, a mid-story isolation system was proposed and applied to practical engineering. In this study, seismic responses of high-rise buildings considering the installation story of the mid-story isolation system were evaluated. To do this, the 20-story and 30-story building were used as example structures. Historical earthquakes such as Kobe (1995), Northridge (1994) and Loma Prieta (1989) earthquakes were employed applied as earthquake excitations. The installation location of the mid-story isolation system was changed from the bottom of the $1^{st}$ floor to the bottom of the top floor. The seismic responses of the example building were investigated by changing the location of the isolation layer. Based on the analytical results, when the seismic isolation system is applied, story drift ratio and acceleration response are reduced compared to the case without the isolation system. When the isolation layer is located on the lower part of the building, it is most effective. However, in that case, the possibility that the structure is unstable increases. Therefore, an engineer should consider both structural efficiency and safety when a mid-story isolation system for a high-rise building is designed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.203-210
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• 2012

The main rotor control system is an important structural part of a helicopter that manages the thrust and control force of the helicopter. The main rotor control system consists of a swashplate assembly, scissor assembly, pitch rod assembly, guide, etc. The main rotor control system must endure various loads, such as the thrust and control force, and must meet the optimized fatigue safety life. The rotating swashplate is an important structure influenced by the pitch rod load and rotating scissor load. In this paper, the accuracy of a result about the rotating swashplate part of the main rotor control system is proven through comparison between fatigue test and FEM results. Based on this result, we estimate the lifetime and deduce the fatigue safe lifetime.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.2
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• pp.26-33
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• 2011

Recently, the use of buried glass fiber reinforced plastic (GRP) pipes is widespread and ever increasing trend in the industry. GRP pipes are attractive for use in harsh environments, such as for the collection and transmission of liquids which are abrasive and/or corrosive. The structural behavior of a GRP pipes buried under the ground is different from that of a rigid one made of concrete or clay, for example. A GRP pipe buried under the ground is deflected circumferentially by several percent and the stresses in the pipe are mainly compressive stresses. A GRP pipes has been introduced by a number of manufacturers for selection and used by underground pipeline designers. In all cases, the modified Spangler's equation is recommended by these manufacturers for predicting the ring deflection of these pipes under dead and live loads. In this paper, the ring deflection of buried GRP pipe is evaluated and discussed based on the result of analytical investigation.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.3
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• pp.59-67
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• 2007

This paper proposes potentialities of constructing the information system for earthquake hazard management which can manage and analyse earthquake risk and hazard systematically. The experimental results as well as architectural structure investment data for seismicity assessment are built in database and connected with GIS for assessing earthquake safety of building in urban area. For earthquake-resistant performance assessment, we collected and classified building structural data according to assessment criteria using building register, architectural map, digital map, and then complemented database with field survey data. We also suggest GIS-based information system can cope with and manage earthquake hazard effectively, as evaluating earthquake risk by performing detailed earthquake-resistant assessment and determining final assessment scores. The assessment should be processed quickly and accurately by integrating the earthquake hazard information management system with modularization of assessment procedure and method in the future.