• The Journal of Engineering Geology
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• v.26 no.3
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• pp.339-352
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• 2016

The best way of investigating the physical and mechanical properties of subsurface materials is the combined interpretation of data from borehole geophysical surveys and geotechnical experiments with rock samples. In this study two surface seismic surveys with refraction and surface-wave method are alternatively conducted for downhole seismic surveys in test site for geological field trip in Jeungpyung, Chungbuk. P- and S-wave velocity structures are delineated by refraction and MASW (multichannel analysis of shear waves) methods, respectively. Possion's ratio section, reconstructed from P- and S-wave velocities, is correlated to the outcrop geological features consisting of reddish sedimentary rock, gray volcanic rock, and joints/fractures. In addition, rock samples representative for reddish sedimentary and gray volcanic features are geotechnically analyzed to provide physical, mechanical properties, and elastic modulus. Dynamic elastic moduli estimated from geophysical data is found to be higher than the one from geotechnical data. Reddish sedimentary rock characterized with low porosity and moisture content corresponds to the zone of low electrical resistivities and their small variations in the resistivity sections between the rainy and dry days. This trend suggests that the weathered gray volcanic rock and the nearby fractures with higher low porosity and moisture content are interpreted to be good carrier especially in rainy season.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1119-1127
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• 2010

In this paper, the design and nonlinear simulation of a multistable electromagnetic microactuator, which provides four stable equilibrium positions within its operating range, have been discussed. Quadstable actuator motion has been made possible by using both X- and Y-directional bistable structures with snapping curved beams. Two pairs of the curved beams are attached to an inner frame in both X- and Y-directions to realize independent bistable behavior in each direction. For the actuation of the actuator at the micrometer scale, an electromagnetic actuation method in which Lorentz force is taken into consideration was used. By using this method, micrometer-stroke quadstability in a plane parallel to a substrate was possible. The feasibility of designing an actuator that can realize quadstable motion by using the electromagnetic actuation method has been thoroughly clarified by performing nonlinear static and dynamic analyses and electrothermal coupled-field analysis of the multistable microactuator.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2219-2228
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• 2015

The proposed RDT(Reversed Double T) girder bridge is suitable to eco corridor, because of its cross section which resembles Korean alphabet vowel "ㅛ". The total height and cost of bridge would be reduced for its inner space containing some of plant soil. In this study, the performance of the RDT girder was assessed by comparing results of static test with those of nonlinear analysis. The cracking load of the RDT girder was evaluated more than two times of design load.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.807-812
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• 2009

Most structure engineers give the casting components over-estimated factor of safety without any reasonable foundation due to the worries about the unavoidable defects such as shrinkages and porosity in castings; the engineers have little knowledge on the relation between the defect and structural behavior. And the workers in casting field also do not know how to control the defects by manufacturing; they do not know to where the defects move or until how size they reduce the defects. In this study, shrinkage defect was scanned by industrial computerized tomography instrument (CT), and subsequently was modeled to a spheroid primitive for structural analysis. Using these simplified models of shrinkage, we observed the effects of the defect on the results of the structural analysis. A commercial structural analysis code was used to do the analysis works. Considering the conclusions, it is possible to manage the shrinkages effectively in casting process and to design the products with more reliable

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.289-299
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• 2012

The goal of this paper is to apply the multi-step Taylor method to a space truss, a non-linear discrete dynamic system, and analyze the non-linear dynamic response and unstable behavior of the structures. The accurate solution based on an analytical approach is needed to deal with the inverse problem, or the dynamic instability of a space truss, because the governing equation has geometrical non-linearity. Therefore, the governing motion equations of the space truss were formulated by considering non-linearity, where an accurate analytical solution could be obtained using the Taylor method. To verify the accuracy of the applied method, an SDOF model was adopted, and the analysis using the Taylor method was compared with the result of the 4th order Runge-Kutta method. Moreover, the dynamic instability and buckling characteristics of the adopted model under step excitation was investigated. The result of the comparison between the two methods of analysis was well matched, and the investigation shows that the dynamic response and the attractors in the phase space can also delineate dynamic snapping under step excitation, and damping affects the displacement of the truss. The analysis shows that dynamic buckling occurs at approximately 77% and 83% of the static buckling in the undamped and damped systems, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1A
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• pp.31-43
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• 2009

In this study, the numerical method is presented, which can consider the various train types and can solve the equations of motion for a vehicle-bridge interaction analysis by non-iteration procedure through formulating the coupled equations of motion. The coupled equations of motion for the vehicle-bridge interaction are solved by the Newmark ${\beta}$ of a direct integration method, and by composing the effective stiffness matrix and the effective force vector according to a analysis step, those can be solved with the same manner of the solving procedure of equilibrium equations in static analysis. Also, the effective stiffness matrix is reconstructed by the Skyline method for increasing the analysis effectiveness. The Cholesky's matrix decomposition scheme is applied to the analysis procedure for minimizing the numerical errors that can be generated in directly calculating the inverse matrix. The equations of motion for the conventional trains are derived, and the numerical models of the conventional trains are idealized by a set of linear springs and dashpots with 16 degrees of freedom. The bridge models are simplified by the 3 dimensional space frame element which is based on the Euler-Bernoulli theory. The rail irregularities of vertical and lateral directions are generated by the PSD functions of the Federal Railroad Administration (FRA). The results of the vehicle-bridge interaction analysis are verified by the experimental results for the railway plate girder bridges of a span length with 12 m, 18 m, and the experimental and analytical data are applied to the low pass filtering scheme, and the basis frequency of the filtering is a 2 times of the 1st fundamental frequency of a bridge bending.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.727-734
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• 2005

High-rise residential buildings these days tend to adopt a building frame system as primary earthquake resisting structural system for some architectural reasons. But there exist several ambiguities in designing such building frame systems according to current codes with regards to : the effective stiffness property of RC cracked section in static and dynamic analyses, analytical model to evaluate story drift ratio, and deformation compatibility requirements of frames. The comparative study for these issues by appling KBC 2005 to a typical building frame system shows that demands of member strength and story drift ratio can be different significantly depending on engineer's Interpretation and application of code requirements. And a building frame system can be noneconomical, compared with the dual system, because of higher demands on strength or ductility in both frames and shear walls.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.989-1000
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• 2002

As advanced earthquake design methods using nonlinear static analysis are developed, it is required to estimate precisely the cyclic behavior of reinforced concrete members that is characterized by strength, deformability, and energy dissipation. In a recent study, a simplified method which can estimate accurately the energy dissipation capacity of flexure-dominated RC members subjected to repeated cyclic load was developed. Based on the previously developed method, in the present study, simple equations that can be used for calculating the energy dissipation capacity were derived and verified by the comparison with experimental results. Through parametric study using the proposed equations, effects of axial load, reinforcement ratio, rebar arrangement, md ductility on the dissipated energy were investigated. The proposed equations can accurately estimate the energy dissipation capacity compared with the existing empirical equations, and therefore they will be useful for the nonlinear static analysis/design methods.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.92-100
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• 2002

In this study, transonic/supersonic nonlinear flutter analysis system of a complete aircraft including forced harmonic motion pf control surfaces has been effectively developed using the modified transonic small disturbance (TSD) equation. To consider the nonlinear effects, the coupled time marching method (CTM) combining computational structural dynamics (CFD) has been directly applied for aeroelastic computations. The grid system for a complex full aircraft configuration is effectively generated by the developed inhouse code. Intransonic and supersonic flight regimes, the characteristics of static and dynamic aeroelastic effect has been investigated for a complete aircraft model. Also, nonlinear flutter flight simulations for the forced harmonic motion of control surfaces are practically presented in detail.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.429-438
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• 2011

In this paper, experiment of thermal conductivity among thermal properties for CCS insulation material was carried out under the condition ranged from room temperature to cryogenic temperature. CCS insulation system should be sustained under cryogenic temperature($-163^{\circ}C$), and lots of investigations will be conducted how to block the heat to insulation material. CCS components which consist of various materials are especially the main interests, and how the temperature of the entire CCS along the location is should be investigated through these studies. With the experimental thermal properties, the steady state thermal analysis of the entire cargo system was conducted. When the LNG leaked through the insulation system with external impact, temperature distribution and thermal safety of secondary barrier, especially plywood and hull structure, was observed.