• Journal of the Society of Disaster Information
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• v.15 no.4
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• pp.524-530
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• 2019

Purpose: In this paper, we construct a detailed three-dimensional interface element using a three-dimensional analysis program, and evaluate the composite behavior stability of the connector by applying physical properties such as the characteristics of general members and those of reinforced members Method: The analytical model uses solid elements, including non-linear material behavior, to complete the modeling of beam structures, circular flanges, bolting systems, etc. to the same dimensions as the design drawing, with each member assembled into one composite behavior linkage. In order to more effectively control the uniformity and mesh generation of other element type contact surfaces, the partitioning was performed. Modeled with 50 carbon steel materials. Results: It shows the displacement, deformation, and stress state of each load stage by the contact adjoining part, load loading part, fixed end part, and vulnerable anticipated part by member, and after displacement, deformation, The effect of the stress distribution was verified and the validity of the design was verified. Conclusion: Therefore, if the design support of the micro pile is determined based on this result, it is possible to identify the Vulnerable Parts of the composite behavior connector and the degree of reinforcement.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.541-549
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• 2008

The fatigue analysis is performed to avoid structural failure in aerospace structures under repeated loads. In this paper, the fatigue life is estimated for the design of tilt rotor UAV. First of all, the fatigue load spectrum for tilt rotor UAV is generated. Fatigue analysis is done for the flaperon joint which may have FCL(fracture critical location). Tilt rotor UAV operates at two modes: helicopter mode such as taking off and landing; fixed wing mode like cruising. To make overall fatigue load spectrum, FELIX is used for helicopter mode and TWIST is used for fixed wing mode. The other hand, the Kriging meta model is used to get S-N regression curve for whole range of material life when S-N test data are analyzed. And then, the second order of S-N curve is accomplished by the least square method. In addition, the coefficient of determination method is used to ensure how accuracy it has. Finally, the fatigue life of flaperon joint is compared with that obtained by MSC. Fatigue.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.1999-2010
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• 1992

The fixed slab analogy device which can measure stress intensity factors(S.I.F) experimentally by slab analogy theory is developed in this paper. The margin of errors resulted from the new testing apparatus are between 0.02% and 8.25%. Therefore, it is assured that this one can be effectively used for the more accurate measurement of S.I.F.( $k_{I}$, $k_{I I}$) than conventional apparatus. The pitch of master grating used in this experiment is 0.1mm It is known that the ratio of the distance from crack tip to the crack length on obtaining the accurate stress intensity factor is between 0.4 and 0.7. The optimum curvature radius of slab is about 125mm. The thickness of slab(plate) used in the fixed slab analogy device is 0.05mm(P.V.C. ; E = 64 MN/ $m^{2}$, .nu.=0.38), which is proved to be suitable for the test. The optimum material for the frame(slab`s external boundary) is a alloy tool steel(SKS 5) plate and its thickness is 1mm. In this research, the rigid cracks are directly bonded to the slab surface by cyanoacrylate adhesive for the easiness of slab making and conformity to the practical crack figure. The material of rigid crack is thin steel plate. It is expected that the developed method can be used effectively for the analysis of $k_{I}$ and $k_{I I}$ of arbitrary shaped or distributed cracks.cks.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.4
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• pp.266-272
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• 2010

Purpose: The purpose of this study was to investigate the effects of the surface morphology of the implant neck on marginal bone stress measured by using finite element analysis in six implant models. Materials and methods: The submerged type rescue implant system (Dentis co., Daegu, Korea) was selected as an experimental model. The implants were divided into six groups whose implant necks were differently designed in terms of height (h, 0.4 and 1.0 mm) and width (platform width, w = 3.34 + 2b [b, 0.2, 0.3 and 0.4 mm]). Finite element models of implant/bone complex were created using an axisymmetric scheme. A load of 100 N was applied to the central node on the top of crown in parallel with the implant axis. The maximum compression stress was calculated and compared. Results: Stress concentration commonly observed around dental implants did not occur in the marginal bone around all six test implant models. Marginal bone stress varied according to the implant neck bevel which had different width and height. The stress was affected more markedly by the difference in height than in width. Conclusion: This result indicates that the implant neck bevel may play an important role in improving stress distribution in the marginal bone area.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.115-122
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• 1992

A sandwich element is a special Hybrid structural form of the composite construction, which is consisted of three main parts : thin, stiff and relatively high density faces separated by a thick, light, and weaker core material. In a sandwich construction, the shear deformation of the faces. Therefore, in the calculation of the bending stiffness, the shear effect should be included. In this paper, the minimum weight is selected as an object function, as the weight critical structures are usually composed of these kind of construction. To obtain the minimum weight of sandwich panel, the principle of minimum potential energy is used and as for the design constraints, the allowable bending stress of face material, the allowable shear stress of core material, the allowable value of panel deflection and the wrinkling stress of faces are adopted, as well as the different boundary conditions. For the engineering purpose of sandwich panel design, the results are tabulated, which are calculated by using the nonlinear optimization technique SUMT.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.127-149
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• 2003

The bridge tested was 3 spans 90m-long PSC beam concrete bridge with a stub-type abutment which had a skew of 60$^{\circ}$ about the axis of bridge. A cement concrete was placed at the superstructural slab of the bridge. Inclinometers and straingauges were installed at piles as well. During 7 days-curing of superstructural slab, the pile behavior in response to hydration heat and drying shrinkage of the slab was monitored. Then monitored values were compared with the horizontal movement obtained from the HACOM program and the calculated lateral behavior obtained from the nonlinear p-y curves of pile. As a result, lateral behavior of H-piles by the field measurement occurred due to the influence of hydration heat and drying shrinkage obtained during curing of superstructural concrete. The lateral displacements by hydration heat and drying shrinkage were 2.2mmand 1.4mm respectively. It was observed as well that the inflection point of lateral displacement of pile was shown at 1.3m down from footing base. It means that the horizontal movement of stub abutment did not behave as the fixed head condition of a pile but behave as a similar condition. The measured bending stress did not show the same behavior as the fixed head condition of pile but showed a similar condition. The increment of maximum bending stress obtained from the nonlinear p-y curves of pile was about 300(kgf/$\textrm{km}^2$) and was 2 times larger than measured values regardless of installation places of straingauges. Meanwhile, lateral load, maximum lateral displacement, maximum bending stress and maximum bending moment of pile showed a linear behavior as curing of superstructural concrete slab.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.116-122
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• 2021

This study quantitatively evaluated the performance improvement of a circular reinforced concrete pier under dynamic load with strengthening using a steel plate. Various three-dimensional elements were applied using the finite element program ABAQUS. The analytical parameters included the ratios of the steel cover length to the pier's total height and the ratios of the steel cover thickness to the pier diameter for inelastic-nonlinear analysis. The lower part of the pier had fixed boundary conditions, and lateral repetitive loads were applied at the top of the pier. The pier was investigated to evaluate the dynamic performance based on the load-displacement curve, stress-strain curve, ductility, energy absorption capability, and energy ratio. The yield and ultimate loads of piers with steel covers increased by 3.76 times, and the energy absorption capability increased by 4 times due to the confinement effects caused by the steel plate. A plastic hinge part of the column with a steel plate improved the ductility, and the thicker the steel plate was, the greater the energy absorption capacity. This study shows that the reinforced pier should be improved in terms of the seismic performance.

• Geotechnical Engineering
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• v.7 no.1
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• pp.33-40
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• 1991

This paper reports the application study of the ground reinforcement under a pipe joint. The soil-reinforcement interaction helps to minimize the stress concentration at joint. The settlement pattern and the earth pressure variation have been evaluated under the pipeline subjected to differential settlement. The pipeline is fixed at one side with the other side set free being loaded with a uniform surface loading. The problem has been studied by means of laboratory model test and flite element technique, and the analysis results are compared for both non-reinforced and reinforced cases to evaluate the effectiveness of the soil reinforcement for restraining the settlement of the pipeline.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.27-37
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• 2001

본 연구에서는 지금까지 수행한 건조토 지반에 대한 말뚝의 수평거동 연구의 연속된 연구로서 지반내에 함수비가 존재하는 포화토 및 습윤토 지반에서의 수평거동에 대한 지반내 함수비의 영향성을 평가하고자 함이 목적이다. 말뚝의 수평거동을 고찰하기 위하여 각각 다른 함수비를 갖는 네 종류의 지반과 말뚝의 두부 및 선단 구속조건이 다른 네 종류의 말뚝조건으로 모형실험을 수행하였다. 본 연구에서 1회의 지하수 상승과 하강을 반복하는 모형실험결과에 의하면, 포화토와 습윤토 지반의 수평지지력은 건조토 지반에 비하여 각각 26%~45% 감소와 20%~36%정도 증가하는 것으로 나타났다. 말뚝두부 고정과 선단 자유조건의 경우, 동일 수평변위 1mm에서의 최대 휨모멘트는 건조토 지반에 비하여 25%의 함수비를 갖는 습윤토 지반에서 약 48% 증가하나, 34.06%의 함수비를 갖는 포화토 지반에서는 반대로 68% 감소하였다. 이는 지하수의 존재로 인한 입자간 인력에 의한 유효응력과 겉보기강도의 증가 그리고 단위중량의 증가로 설명할 수가 있다. 지속수평하중에 대한 수평변위와 최대 휨모멘트의 변화를 포화토 및 습윤토 지반에서 관찰할 수 있었다.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.717-726
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• 2006

Traditional external post-tensioning method using either steel bars or tendons is commonly used as a retrofitting method for steel composite bridges. However, the method has some disadvantages such as stress concentration at anchorages and inefficient load-carrying capability of live loads. Multi-stepwise prestressing method using thermal expanded coverplate is a newly proposed prestressing method, which was originally developed for prestressing steel structures. A new retrofitting method for steel girder bridges founded on a simple concept of thermal expansion and contraction of cover plate, the method is a hybrid of and combines the advantages of external post-tensioning and thermal prestressing. In this paper, basic concepts of the method are presented and an illustrative experiment is introduced. From actual experimental data, the thermal prestressing effect was substantiated and the FEM approach for its analysis was verified. The retrofitting effects ofa single-span bridge were analyzed and the feasibility of the developed method was examined.