• International Journal of Highway Engineering
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• v.12 no.4
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• pp.211-218
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• 2010

Volume of concrete slab changes by temperature and moisture effects. At that time, tensile stress develops because the slab volume change is restrained by friction resistance between the slab and subbase, and then crack occurs occasionally. Accordingly, researchers have made efforts to figure out the friction characteristics between the slab and subbase by performing push-off tests. Lately, researches to analyze concrete pavement behavior by the friction characteristics have been performed by finite element method. In this study, The friction characteristics between the slab and subbase were investigated based on the friction test results for lean concrete, aggregate, and asphalt subase widely used in Korean concrete pavements. The energy method bilinearizing relation between nonlinear friction resistance and displacement were suggested. The friction test was modeled by 3-D finite element program, ABAQUS, and the model was verified by comparing the analyzed results to the test results. The bilinear model developed by the energy method was validated by comparing analysis results obtained by using the nonlinear and bilinear friction resistance displacement relation as input data. A typical Korean concrete pavement was modeled by ABAQUS and EverFE and analyzed results were compared to evaluate applicability of the bilinear model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.5
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• pp.429-436
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• 2014

This paper presents the seismic performance of a geometrically unsymmetrical reinforced concrete building considering torsional effect and material nonlinearity of concrete and steel. The reinforced concrete building is a structure for seismic performance evaluation in the SMART-2013 international benchmark program. Nonlinear constitutive models for concrete and steel were constructed, and their numerical performance was demonstrated by various local tests. Modal analysis showed that the first three natural frequencies and mode shapes were close to the experimental results from the SMART-2013 program. In the time history analysis for low-intensity seismic loadings, displacement and acceleration responses at sampling points were similar to the experimental results. In the end, nonlinear time history analysis was conducted for Northridge earthquake to predict the behavior of the reinforced concrete structure under high-intensity seismic loadings.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.9-16
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• 2014

This paper presents the theoretical analysis of a flow driven by surface tension and gravity in an inclined circular tube. A governing equation is developed for describing the displacement of a non-Newtonian fluid(Power-law model) that continuously flows into a circular tube owing to surface tension, which represents a second-order, nonlinear, non-homogeneous, and ordinary differential form. It was found that quantitatively, the theoretical predictions of the governing equation were in excellent agreement with the solutions of the equation for horizontal tubes and the past experimental data. In addition, the predictions compared very well with the results of the force balance equation for steady.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.10
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• pp.4642-4647
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• 2011

Solution for elastic foundation of plane strain state was derived by the application of variational method. Functions of the transverse distribution of the displacements for the analysis were chosen as linear functions. Loading conditions considered for the analysis were concentrated load and distributed load. Under the loading condition of the concentrated load, surface displacement was decreased drastically as the distance from the point of the loading increased. Under the loading condition of the distributed load, surface displacements were more uniformly distributed beneath the loading area when the ratio of the half of the loading width to the depth(B/H) of the compressible layer was greater. The surface displacement was more quickly converged from the edge of the loading area as the ratio(B/H) increased.

• Geotechnical Engineering
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• v.13 no.1
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• pp.123-136
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• 1997

By applying the finite element theory which is capable of handling the geometrically altered structure in a successive manner, the linear relationship between incremental displacements and the magnitude of the initial stress field was derived. Based on this relationship, back analysis code having the capability of dealing multi-step excavation problem was built and verified With this back analysis code, the measurements of the incremental displacements in a particular excavation step make it possible to back-calculate the initial stress state. illustrative examples showed the applicability of this code to a practical problem.

• 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.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.109-119
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• 2004

A design procedure for velocity-dependent supplemental dampers, such as viscous or viscoelastic dampers, required to meet the desired performance objectives was developed using displacement spectra. The amount of supplemental damping required to satisfy given performance limit state was obtained first from the nonlinear static procedure using displacement spectra, then dampers were appropriately distributed throughout the stories to realize the required damping. The proposed method was applied to multi-story steel frames, and the structures were analyzed by time history analysis to validate the accuracy of the design procedure. According to the analysis results the maximum displacements of the model structures retrofitted by the supplemental dampers turned out to be restrained well within the given target values.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.667-674
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• 2011

This paper discusses the analysis method of prestressed concrete girder integral abutment bridges for a 75-year bridge life and the development of prediction models for abutment displacements under thermal loading due to annual temperature fluctuation and time-dependent loading. The developed nonlinear numerical modeling methodologies considered soil-structure interaction between supporting piles and surrounding soils and between abutment and backfills. Material nonlinearity was also considered to simulate differential rotation in construction joints between abutment and backwall. Based on the numerical modeling methodologies, a parametric study of 243 analysis cases, considering five parameters: (1) thermal expansion coefficient, (2) bridge length, (3) backfill height, (4) backfill stiffness, and (5) pile soil stiffness, was performed to established prediction models for abutment displacements over a bridge life. The parametric study results revealed that thermal expansion coefficient, bridge length, and pile-soil stiffness significantly influenced the abutment displacement. Bridge length parameter significantly influenced the abutment top displacement at the centroid of the superstructure, which is similar to the free expansion analysis results. Developed prediction model can be used for a preliminary design of integral abutment bridges.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.432-437
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• 2016

The behavior of a bellows for an electromagnetic control valve was investigated. The bellows consists of an outer metal bellows, inner spring, and metal caps. The bellows needs to have sensitive and precise motion against external loads and pressure loads in order to control the position of the valve accurately. The spring constant of the inner spring and load-displacement curve of the bellows set were measured using a test machine. The inner spring showed a linear relation between load and displacement. The bellows set showed small stiffness at small displacement, and then the stiffness slightly increased upon subsequent displacement. Based on the measured data, finite element analysis was performed. Axisymmetric conditions were applied, and shell elements were used. The effective material properties of the outer bellows material were extracted. Additional analysis was performed, and the behavior of the bellows was analyzed using the finite element model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.11
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• pp.919-925
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• 2016

In this study, the Lamb wave mixing technique, which is basised on advanced research on the nonlinear bulk wave mixing technique, is applied for corrosion detection. To demonstrate the validity of the Lamb wave mixing technique, an experiment was performed with normal and corroded specimens. Comparison group in an experimentation are selected to mode and frequency with dominant in-plane displacement and out-of-plane displacement of Lamb waves. The results showed that the Lamb wave mixing technique can monitor corrosion defects, and it has a trend similar to that of the conventional Lamb wave technique. It was confirmed that the dominant displacement and mode matching the theory were generated. Flaw detectability is determined depending on displacement ratio instead of using the measurement method and mode selection.