• Journal of the Korean earth science society
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• v.21 no.3
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• pp.315-322
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• 2000

In this study, the data used for the models were a set of 56 geologic estimates of long-term fault slip rates. The hest models were those in which mantle drag was convergent on the Transverse Ranges in the San Andreas fault system, and faults had a low friction (${\mu}$= 0.3). It is clearly important to decide whether these cases of low strength are local anomalies or whether they are representative. Furthermore, it would be helpful to determine fault strength in as many tectonic settings as possible. Analysis of data was considered by unsuspected sources of pore pressure, or even to question the relevance of the friction law. To contribute to the solution of this problem, three attempts were tried to apply finite element method that would permit computational experiments with different hypothesized fault rheologies. The computed model has an assumed rheology and plate tectonic boundary conditions, and produces predictions of present surface velocity, strain rate, and stress. The results of model will be acceptably close to reality in its predictions of mean fault slip rates, stress directions and geodetic data. This study suggests some implications of the thermoelastic characteristics to interpret the relationship with very low strength of San Andreas fault system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.542-547
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• 2013

In this study, mechanical property on the composite material of aluminum foam core is investigated by simulation analysis. Impact energies such as 50J, 70J, and 100J are applied to the specimen model. The maximum load occurs at 3.4ms for 50J, 3.2ms for 70J, and 3.2ms for 100J respectively. The striker penetrates the upper face sheet, causing the core to be damaged at 50J test but the lower face sheet remains intact with no damage. It results in occurring with the energy of 52 J. At 70J test, it penetrates the upper face sheet and penetrated the core. And the striker causes the lower face sheet with damage. And it results in occurring with the energy of 65 J. Finally at 100J test, the striker penetrated both the upper face sheet and core and even the lower face sheet. The load becomes maximum at the time when striker penetrates through the upper plate and it rapidly reduced. And then the load increases rapidly when reaching the lower face sheet. And it decreases again. It results in occurring with the energy of 95 J.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.44-57
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• 2008

In this study, a 2D finite-element analysis, using the SEEP/W program, was carried out to estimate the amount of groundwater flawing into a tunnel, as well as the groundwater tables around wetland areas during and after a tunnel excavation through rock mass. Four sites along the Wonhyo-tunnel in Cheonseong Mountain (Gyeongnam, Korea) were analysed, where the model damain of the tunnel included both wetland and fault zone. The anisotropy of the hydraulic conductivities of the rock mass was calculated using the DFN model, and then used as an input parameter for the cantinuum model. Parametric study on the influencing factors was perofrmed to minimize uncertainties in the hydraulic properties. Moreover, the volumetric water content and hydraulic conductivity functions were applied ta the model to reflect the ability of a medium ta store and transport water under both saturated and unsaturated conditions. The conductivity of fault zone was assumed ta be $10^{-5}m/sec\;or\;10^{-6}m/sec$ and the conductivity of grouting zone was assumed as 1/10, 1/50 or 1/100 of the conductivity of rock mass. Totally $6{\sim}8$ cases of transient flow simulation were peformed at each site. The hydraulic conductivities of fault zone showed a significant influence on groundwater inflow when the fault zone crossed the tunnel. Also, groundwater table around wetland maintained in case that the hydraulic conductivity of grouting zone was reduced ta be less than 1/50 of the hydraulic conductivity of rock mass.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1093-1100
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• 2014

The purpose of this paper is to suggest a weight-reduction design method for the hybrid carbody of a high-speed maglev train that uses aluminum extrusion profiles and sandwich composites. A sandwich composite was used on the roof as a secondary member to minimize the weight. In order to assemble the sandwich composite roof and aluminum extrusion side frame of the carbody using welding, a guide aluminum frame located at the four sides of the sandwich composite roof was introduced in this study. The clamping force of this guide aluminum frame was verified by three-point bending test. The structural integrity and crashworthiness of the hybrid carbody of a high-speed maglev train were evaluated and verified according to the Korean Railway Safety Law using a commercial finite element analysis program. The results showed that the hybrid carbody composed of aluminum extrusion frames and a sandwich composite roof was lighter in weight than a carbody made only of aluminum extrusion profiles and had better structural performance.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.171-179
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• 1997

The high-tension bolted joints are clamped by the axial force which approaches the yielding strength. The introduced axial force is transmitted to the connection members pass through washer. The transferred load in connections is balanced to the compressive stress of plates, axial force in bolts and the external loads. In this mechanism, the compressive stress and slip load we dominated by the effective stiffness of bolted joints and plates. In general the effective stiffness is specified to product to the effective area and elasticity modulus in connections. In this reason, the conic projection formular which is assumed that the axial force in bolts is distributed to the cone shape and that region is related to the elastic deformation mechanism in connections, was proposed. But it conclude what kind of formula is justified. Therefore in this paper, the fatigue tests are performed to the high tension bolted joints and inspected to the phase on the friction face. And using the FEM and numerical method, it is analyzed and approximated to the compressive stress distribution and its region. Moreover, it is estimated to the effective area and to the relation the friction area to the effective compressive distribution region.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.63-77
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• 2015

Tsunami take away life, wash houses away and bring devastation to social infrastructures such as breakwaters, bridges and ports. The coastal structure targeted object in this study can be damaged mainly by the wave pressure together with foundation ground failure due to scouring and liquefaction. The increase of excess pore water pressure composed of oscillatory and residual components may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, the bore was generated using the water level difference, its propagation and interaction with a vertical revetment analyzed by applying 2D-NIT(Two-Dimensional Numerical Irregular wave Tank) model, and the dynamic wave pressure acting on the seabed and the surface boundary of the vertical revetment estimated by this model. Simulation results were used as input data in a finite element computer program(FLIP) for elasto-plastic seabed response. The time and spatial variations in excess pore water pressure ratio, effective stress path, seabed deformation, structure displacement and liquefaction potential in the seabed were estimated. From the results of the analysis, the stability of the vertical revetment was evaluated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.1-7
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• 2018

A folding solar power system is a stand-alone system and is a structure with solar panels attached. It consists of supporting parts and folding parts for ease of movement. While the efficiency of solar panels is also important to produce electricity by maximizing the power efficiency of solar panels, the most important thing is structure stability. The folding solar power structure intended to be developed in this study is a collapsible structure that is easy to move and install into systems that can produce electricity from grid to independent. Since these structures are installed outdoors, wind loads, snow cover, etc. In this paper, the wind loads most affected by the folding solar power generation structure were obtained using the MeshFree Finite Element Method. MeshFree is a program that makes it easier for users to interpret by simplifying the mesh tasks required by an existing analysis. The analysis showed that the greater the angle of inclination of the wind to the ground, the greater the wind load. In addition, reliability was ensured by wind load testing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.648-654
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• 2018

In order to maintain manholes installed on the road, the manhole should be easy to open and close. Manhole covers under harsh conditions require that they can be lifted when attempting to open the manhole because the frame and cover are stuck and difficult to open and close. In this study, the design of a lifting mechanism was carried out to improve and integrate the locking type manhole. The mechanism of the locking manhole is that when the bolt located at the center is turned, the hub connected with the bolt descends, and the hook connected to the hub is rotated. The end of the hook is hooked to the manhole frame. The auxiliary device was installed on the hook so that the manhole cover can be lifted. The structure was designed to endure about 300kg of lifting force based on 70% of the yield stress of the hook to perform lifting function. The shape design was performed through the structural analysis using the finite element method. First, the basic design was performed with the simplified 2-dimensional model and the attachment position and shape were designed through the 3-dimensional model. In order to find out the structural problems of the designed shape, the scale downed model was fabricated through 3D printing and confirmed that the lifting function worked. Finally, it was confirmed that both the locking and the average lifting of about 6.1 mm can be done by applying the lifting mechanism through the machining and applying it to the existing locking manhole.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.577-582
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• 2020

Electricity produced at power plants is distributed to consumers through several stages of substations. At this time, an ultra-high voltage transformer is needed in the initial transmission stage to transmit a voltage suitable for each consumer. A high voltage, non-uniform electric field is formed at the end of the winding of the ultra-high voltage transformer, which carries a risk of dielectric breakdown. The winding of the ultra-high voltage transformer is an electrode, which is the key to converting the magnitude of the voltage. A non-uniform electric field is formed along the shape of the winding end, resulting in high electrical stress. The static ring installed at the upper and lower ends of the winding is used to disperse the stress at the winding end. Several variables should be considered when designing a static ring. Among them, this study examined how the curvature of the static ring, the thickness of the insulating paper, the number of barriers, and barrier thickness affect the electrical stress of the static ring using the Finite Element Method. Suggestions to be considered when designing the static ring are proposed through the FEM results.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.433-452
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• 2018

The shield tunneling method can minimize surface settlements by preventing the deformation of tunnel face and tunnel intrados due to tunnel excavation. For this purpose, it is very important to control the operating conditions of shield TBM. The face pressure and backfill pressure for tail void grouting should be the most important and immediate measure not only to restrain surface settlement, but also to influence the effective stress and pore water pressure around the circumstance of tunnel during excavation. The reaction of the ground to the application of face pressure and backfill pressure relies on the stiffness and permeability of ground. Especially, the reaction of saturated clayey ground formations, which shows the time-dependent deformation, is different from the permeable ground. Hence, in this paper it was investigated how the TBM operating conditions, ground stiffness, and permeability impact on the surface settlement of saturated clayey ground. For this purpose, a series of parametric studies were carried out by means of the stress-pore water pressure coupled FE analysis. The results show that the settlement of soft clayey ground is divided into the immediate settlement and consolidation settlement. Especially, the consolidation settlement depends on the ground stiffness and permeability. In addition, the existence of critical face pressure and backfill pressure was identified. The face pressure and backfill pressure above the critical value may cause an unexpected increase in the ground settlement.