• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.27-36
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• 2010

It is well known that the shear strength of an RC column subjected to a lateral force decreases with the increase of the displacement ductility of column. This decreasing rate of shear strength is quite dependent on the initial shear strength. Therefore, the evaluation of the initial shear strength is important to predict the shear strength with reasonable accuracy. The shear behavior is complex because many parameters, such as the sectional shape, aspect ratio, axial force, longitudinal bars and ductility, are mutually interactive. In this study, the initial shear strength has been investigated by experiments varying parameters such as the aspect ratios, void ratios, ratio of longitudinal bars and sectional types. A new empirical equation for the initial shear strength, considering the ratio of the longitudinal bars, has been proposed and its validity has been assessed.

• Journal of Korean Society of Steel Construction
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• v.14 no.3
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• pp.423-432
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• 2002

This study presented analytical and numerical solutions for spatial free vibration of nonsymmetric thin-walled circular curved beams. The closed-form solutions were obtained for in-plane free vibration analylsis of monosymmetric curved beams. Likewise, two types of thin-walled curved beam elements were developed using the third and the fifth order Hermitian polynomials. In order to illustrate the accuracy and usefulness of the present method, this study presented analytical and numerical solution and compared these with the results using the ABAQUS's shell elements. In particular, effects of the thickness-curvature as well as the inextensional condition were investigated on the free vibration of curved beams with nonsymmetric sections.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.725-726
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• 2008

This paper proposes elastic stress intensity factors and crack opening displacements (CODs) for a slanted axial through-wall cracked cylinder under an internal pressure based on detailed 3-dimensional (3-D) elastic finite element (FE) analyses. Based on the elastic FE results, the stress intensity factors along the crack front and CODs through the thickness at the center of the crack were provided. These values were also tabulated for three selected points, i.e., the inner and outer surfaces and at the mid-thickness. The present results can be used to evaluate the crack growth rate and leak rate of a slanted axial through-wall crack due to stress corrosion cracking and fatigue. Moreover, the present results can be used to perform a detailed Leak-Before-Break analysis considering more realistic crack shape development.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.2
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• pp.161-166
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• 1999

The GPS ability for detecting the deformation is experimently tested by analyzing how precisely GPS can detect the true movement value of the GPS test bed with three axis. As the result, we found that GPS can detect the deformation with the precision of 2 mm in horizontal componts and 8 mm in vertical component for the short baseline of 16 km. The applicable possibilities of GPS for measuring the structure deformation are discussed on the base of this result.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.153-156
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• 2009

The pitch and yaw axis controls of Kick Motor, KLSV-I second propulsion system, was provided by the flexible seal that consists of alternate laminate of natural rubber and composite reinforcements between forward and aft ring. A hydrostatic actuating test has been conducted to evaluate a performance of the manufactured flexibke seal before it is assembled at the nozzle. Through the tests, we have verified an actuation torque and axial displacement of the flexible seal according to pressure variation. The actuation torque and axial displacement of all flexible seal is shown below 60kgf-m/deg at without pressure and 6mm at MEOP respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.521-526
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• 2014

In this study, closed-cell aluminum foam with an initial crack was investigated to produce an axial load-time graph. Using the 10-kN Landmarks of MTS Corporation, a 15-mm/min velocity of mode I shape was applied to the aluminum foam specimen using the displacement control method. ABAQUS 6.10 simulation was used to model and analyze the identical model in three dimensions under conditions identical to those of the experiment. The energy release rate was calculated on the basis of an axial load-displacement graph obtained from the experiment and a transient image of the crack length, and then an FE model was analyzed on the basis of this fracture energy condition. The relation between load and displacement was discussed; it was found that the aluminum foam deformed somewhat less than the adhesive layer owing to the difference in elastic modulus.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.191-199
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• 2007

This paper presents a closing method for a cable-stayed bridge erected by the free cantilever method to produce the initial equilibrium configuration at the final construction stage. To realize the initial equilibrium condition in cable-stayed bridge by the cantilever method, compatibility conditions for vertical displacements, rotational angles, and axial displacements at the closing section of both side girders should be satisfied. In this paper, it was shown that it can be accomplished by using some applicable loads during construction such as the pull-up force of the derrick crane, some cable tension forces, and jacking force at the pylon. The proposed method was applied to a construction stage analysis of a sample bridge to demonstrate its validity, and it was acknowledged that the tower was considerably affected by the compatibility condition for axial displacement in the closing step.

• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.201-210
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• 2007

Double-angle connections should be designed with enough stiffness and strength to properly resist various applied loads. Therefore, structural engineers should be able to predict some influential variables and take their effects into account in design. This study was performed to establish the effects of the number of bolts and bolt gage distance on the stiffness and strength of a double-angle connection under tension. Six experimental tests were conducted to describe the effects of these variables by comparing load-displacement relationship curves. In addition, two prediction models were proposed to estimate the initial stiffness and the maximum allowable tensile load based on the results of experimental tests. In the development of these prediction models, the effect of prying action was considered.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.407-412
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• 2004

본 연구에서는 PMN-PT bimorph actuator를 이용하여 초소형 광디스크 드라이브용 광픽업 구동기를 제작하였다. 최근에 휴대용 기기에서의 고용량 정보 저장기기에 대한 필요성이 대두됨에 따라 착탈식이 가능한 수 기가급 초소형 광디스크 드라이브가 개발중에 있다. PMN-PT는 약 1.5kV/cm 이하의 전기장에서는 PZT같은 압전 소자와 마찬가지로 입력 전압에 대한 변형률이 선형성을 나타내는데, 사용된 PMN-PT는 PZT의 약 3배 가까운 압전 상수값을 나타내었다. 보 끝단에 외부 힘이 작용할 때 PMN-PT bimorph 구동기가 낼 수 있는 수직 방향의 힘과 변위에 대해서 일반적인 적층 형태로 이론적인 해석을 수행 하였다. 그리고 이 bimorph로 구동될 Cymbal 형태의 변위 확대 기구의 변위에 대한 이론적인 모델을 제시하고, 이를 이용하여 2개의 bimorph로 2축을 동시에 구동하는 픽업 구동기를 제작하였다. 3개의 제작된 prototype으로 실험을 수행하여 예상 변위량과 잘 일치함을 보였다. 또한, 상용 해석 프로그램인 Matlab과 Ansys를 이용하여 Cymbal 확대 기구의 여러 파라미터에 따른 구동 성능의 민감도를 확인해 보았다.

• Elastomers and Composites
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• v.37 no.3
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• pp.151-158
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• 2002

An elastomeric bushing which has been considered in this research is a device used in automotive suspension systems to reduce the forte transmitted iron the wheel to the frame of the vehicle. A bushing is modeled at a hollow cylinder which is bonded to a solid metal shaft at its inner surface and a metal sleeve at its outer surface. Lianis constitutive equation for a nonlinear viscoelastic incompressible material is used to model the elastomeric material of the bushing. It is used to derive a force-displacement relation for axial response of the bushing. The displacement dependent force relaxation function for the bushing is obtained from the ramp displacement control tests with an extrapolation method. This is compared with the exact result obtained from the step displacement control test and the results are in very good agreement.