• Geotechnical Engineering
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• v.6 no.4
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• pp.43-52
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• 1990

To investigate the effects of soil properties of the soft zone around a pile subjected 1,o the horizontal harmonic vibration, the parametric study is perfomed. The determination of the soil reaction or stiffness of the Winkler springs representing the soil around a pile is performed by dividing the soil profile into a number of homogeneous obtained from this study are as follows : 1) The real and imaginary parts of the stiffness show clear variations for the different shear modulus ratios, poisson's ratios, and distance retios to outer boundary as the dimensionless frequency increases. The differences are more pronounced for the imaginary part of the stiffness. 2) The stiffness of soil shows clear decrease. The real parts of the stiffness show larger as the frequency increases. On the other hand, the imaginary parts of the stiffness show smaller.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.205-215
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• 1992

Load tests for fourteen small-scale foundation models combined with geotextile, sand mat and rigid mat were conducted to study the effect of geotextile(G/T), sand mat(S/M), and foundation types on deformation of foundation soils. In addition, the experimental results were compared with those obtained from numerical analysis using a software program. The main conclusions were summarized as follows: 1. The restraint effect on G/T is more outstanding on the lateral displacement than on the vertical one. 2. The single use of S/M has better effect on the restraint of vertical displacement than lateral one. 3. The use of both S/M and G/T is required for the restraint of lateral and vertical displacement. 4. Multi-layered foundation with large rigidity shows similar tendency to that of foundation reinforced with S/M and G/T.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.461-466
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• 2020

In this study, the relationship between the track support stiffness and the track impact factor for a sleeper floating track and a turnout system with wood ties currently employed in Korean urban transit was assessed by performing field tests using actual vehicles running along the service lines. Field tests were performed on four track systems (i.e., sleeper floating track, and point, lead and crossing sections of turnout system). The theoretically designed track impact factor and track support stiffness were compared with the corresponding track impact factor and track support stiffness measured through field tests for the target tracks on the service line. The track impact factor for the service line appeared to increase with the deviation of track support stiffness according to vehicle driving direction; therefore, it was inferred that the deviation of track support stiffness between each track section directly affected the track impact factor.

• Journal of the Korean Wood Science and Technology
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• v.20 no.1
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• pp.72-78
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• 1992

지진과 관련있는 하중 속도에서 damping을 측정하기 위하여 합판과 목재 사이에 한개의 못을 사용한 접합에 대하여 조사 했다. 조사된 하중은 sine function 의 15Hz와 ASTM하중 속도 사이에서 행했다. Damping 율은 4Hz까지의 하중 속도에서는 증가를 보였으며 그후 15Hz 까지는 점진적으로 감소하였다. 강성은 높은 하중 범위에서 slip moduli가 지속적으로 증가 하였다. 낮은 하중 범위에서 2.5Hz까지 증가 하였으며 그후는 감소 하였다. Damping 율과 slip modulus는 하중 속도와 상관 관계가 낮은 반면 work capacity와 dissipated energy는 높은 상관 관계를 보았다.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.327-335
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• 2011

This study has two objectives: (1) to evaluate the degradation characteristics of symmetric unbraced steel frames by using analytical approach, and (2) to suggest equation which can approximately estimate the effect of degradation during the schematic design stage. For the analytical approach, the refined plastic hinge method with an arc length algorithm was adopted. The subject of analysis was one story one-bay, multistory one-bay, and multistory three-bay unbraced steel frames. The main parameters of the analytical approach include the stiffness ratio of column to beam and the axial force ratio. The study led to the following conclusions. The normalized stiffness of degradations is affected by both stiffness ratio of column to beam and the axial load ratio; however, the major influence on degradations is the axial force ratio. The equation, which can approximately estimate the effect of degradation, was suggested together with the research results.

• Journal of the korean Society of Automotive Engineers
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• v.3 no.1
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• pp.32-37
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• 1981

모든 차형을 간단한 이상형으로 가정하여 그들을 수치적인 값으로 비교할 수 있다면 승용차 차 체의 설계상 매우 큰 도움이 될 것이다. 실제로 새로운 모델의 차가 개발되었을 때에는 다음과 같은 이유 때문에 그 prototype body에 대한 정적 시험이 실시되고 있다. 1) 조기에 설계의 문제점이나 차체의 주결함을 발견할 수 있어 시간과 경비를 절약할 수 있다. 2) 계속적인 정적 시험을 통하여 구조적으로 만족할 만한 road car를 만들 수 있다. 3) 과설계를 방지하여 차체의 경량화에 기여하고, 최적설계의 개발을 위한 길을 제시해 준다. 차체에 대한 정적 시험은 위와 같은 이유 때문에 발전되어 왔으며, 정적 시험의 효과를 ㅊ대로 하기 위하여 그것은 순수한 공학적 원리에 기초를 두어 실제의 사용조건과 충분히 일치되는 시 험으로서 고안되었다. 차체구조는 그 사명의 다양성뿐만 아니라 제작, 개수에 상당한 노력과 시 간이 필요하기 때문에 조기에 문제점을 발견하여 결함을 제지하지 않으면 안된다. 구조체로서의 많은 필요조건 중에서 특히 중요시되는 것은 강도, 강성 및 내구성이다. 그 때문에 차체의 강도, 강성시험은 이론적인 해석(탄성학, 구조역학, 강도학 등)에 앞서 여러가지 방법이 개발되어 왔 으며, 여기에서는 그 중 가장 대표적인 방법인 비틀림시험(torsion test)과 굽힘시험(bending test) 에 관하여 Pony 4-door Sedan 차체의 시험 결과를 토대로 하여 기술하고자 한다.

• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.527-535
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• 2000

Accurate determination of the relative restraint of beam-to-column connections is important for both the strength and the serviceability of structural frames. But steel frame analysis is carried out under the assumption that the connections are either fixed or pinned. Overestimating the connection restraint can result in underestimating lateral sway and underestimating the connection restraint can lead to underestimating forces developed in the beams and columns. This implies that the exact stiffness of connections as well as the geometric effects should be considered in the frame analysis and the overall behavior of connections could be described adequately. Therefore, the stiffness matrix which is able to consider the moment-rotation of connection was derived previously and the modified exponential model, power model and the proposed log model are adopted for modeling the semi-rigid connections. The main purpose of this study is to examine the feasibility of the derived stiffness matrix and to show the validity of log model proposed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.81-87
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• 2017

This paper describes the dynamic behavior and enhancement of Korean high-speed trains. The tail vibration reduction method of the yaw damper installation method change, which was derived from previous research, was applied to the running test of high-speed train. In addition, the vibration reduction method for the entire vehicle was derived by a numerical method and its effect was confirmed by a running test. The improved design was applied to the double-deck high-speed train coaches and the commissioning proceeded without problems in dynamic behavior. Sensitivity analysis of the suspension parameters affecting the critical speed of Korean next-generation high-speed trains was performed and four design variables that greatly affected the critical speed were derived. These were in the order of the primary elastic joint x-directional stiffness, the secondary yaw damper series stiffness, the secondary lateral damper damping coefficient, and the carbody damper damping coefficient. By optimizing the design variables, the suspension parameter that improves the critical speed by 23.3% can be used in the commercial designs of Korean next-generation high-speed trains.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.293-303
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• 2010

The purpose of this study was to evaluate the influence of the methods of application of the direct analysis method, using the load amplification factor suggested by the KBC 2009 design code, for the evaluation of frame stability. For this purpose, the direct analysis method was performed for three-story-one-bay and five-story-three-bay unbraced steel frames with various notional loads, bending stiffness reductions, and factor B2s. The results of the analyses were compared with the results of the second-order inelastic analysis to evaluate the influence of the applied methods. The scale of the frame, the axial load ratio, and the axial load distribution pattern were added to the main parameters to investigate the external effects. The research results showed that the influence of the methods of application of the direct analysis method is not significant in the case of the required axial strength and the application of the additional notional loads; and that the application of the factor B2 with the story stiffness concept to the direct analysis method is appropriate for the required flexural strength.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.1-10
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• 2004

A study on the evaluation of proper spacing and required flexural rigidity of cross beams in composite two I-section steel girder bridges without a lateral and sway bracing system was performed. Specifically, a 2-lane, 40-m simple span bridge and a 3-span continuous (40+50+10m) bridge were designed, and structural analyses under dead load before and after composite, live, wind, and seismic loads were performed using spacing and flexural rigidity or cross beams as parameters. Through parametric analysis, the effect on the stresses due to the combination of loads and live load distribution was investigated. In addition. material and geometric nonlinear analyses under dead load before composite were performed to evaluate the lateral buckling strength of the steel girders and cross beam. Based on the results or such analyses, the proper spacing and flexural rigidity of cross beams at intermediate points and supports were proposed.