• 한국지반공학회논문집
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• 제24권7호
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• pp.25-36
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• 2008

평면변형률 시험기는 실제 지반의 파괴 거동을 보다 근사하게 모사할 수 있다는 장점 때문에 평면변형률 조건을 구현하려는 목적 외에도 흙의 국부적인 변형을 포함하는 전체적인 파괴거동을 관찰하기 위한 목적으로 활용되고 있다. 그러나 대부분의 평면변형률 시험은 시험기 제작과 시험 수행의 어려움 때문에 바닥판이 고정된 단부 구속하에서 수행되는 경우가 일반적이다. 최대 주응력 면의 단부 구속은 주응력 면에 추가적인 전단응력을 유발시켜 의도된 전단 거동을 저해하므로, 시험 결과가 실제 현장에서 발생하는 전단 거동과 다를 수 있다. 본 연구에서는 바닥판 구속을 제어할 수 있는 평면변형률 시험기를 이용하여 단부 구속 여부에 따른 두 가지 시험을 주문진 표준사에 대하여 수행하였다. 시료의 국부적인 변형을 포함하는 전체적인 거동을 측정하기 위해 외부 LVDT와 함께 디지털 이미지 코릴레이션 기법(DIC)을 적용하였다. 평면변형률 시험기의 투명한 측면판을 통하여 서로 다른 시간에 촬영된 두 개의 디지털 이미지를 본 기법으로 해석하여 응력-변형률 거동과 하중 증가에 따라 나타나는 시료 내부 모든 위치에서의 국부적 변형 거동을 파악하였다. 이로써 단부 구속 여부에 따라 발생하는 평면변형률 조건하에서 사질토의 파괴면 형성과 발달과정 그리고 변형 메커니즘을 규명하였다.

• Earthquakes and Structures
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• 제19권6호
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• pp.459-469
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• 2020

An external prestressed steel-bar truss unit was developed as a new strengthening technology to enhance the seismic performance of an in-plane masonry wall structure while taking advantage of the benefits of a prestressed system. The presented method consists of six steel bars: two prestressed vertical bars to introduce a prestressing force on the masonry wall, two diagonal bars to resist shear deformation, and two horizontal bars to maintain the configuration. To evaluate the effects of this new technique, four full-scale specimens, including a control specimen, were tested under combined loadings that included constant-gravity axial loads and cyclic lateral loads. The experimental results were analyzed in terms of the shear strength, initial stiffness, dissipated energy, and strain history. The efficiency of the external prestressed steel-bar truss unit was validated. In particular, a retrofitted specimen with an axial load level of 0.024 exhibited a more stable post behavior and higher energy dissipation than a control specimen with an observed complete sliding failure. The four vertical bars of the adjacent retrofitting units created a virtual column, and their strain values did not change until they reached the peak shear strength. The shear capacity of the masonry wall structure with external prestressed steel-bar truss units could be predicted using the model suggested by Yang et al.

• Steel and Composite Structures
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• 제33권2호
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• pp.245-259
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• 2019

The present study aims to investigate the ultimate strength and geometric nonlinear behavior of composite plates containing initial imperfection subjected to combined end-shortening strain and lateral pressure loading by using a semi-analytical method. In this study, the first order shear deformation plate theory is considered with the assumption of large deflections. Regarding in-plane boundary conditions, two adjacent edges of the laminates are completely held while the two others can move straightly. The formulations are based on the concept of the principle of minimum potential energy and Newton-Raphson technique is employed to solve the nonlinear set of algebraic equations. In addition, Hashin failure criteria are selected to predict the failures. Further, two distinct models are assumed to reduce the mechanical properties of the failure location, complete ply degradation model, and ply region degradation model. Degrading the material properties is assumed to be instantaneous. Finally, laminates having a wide range of thicknesses and initial geometric imperfections with different intensities of pressure load are analyzed and discuss how the ultimate strength of the plates changes.

• 터널과지하공간
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• 제28권4호
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• pp.343-357
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• 2018

절리군 대표방향성에만 의존하는 기존의 평사투영 사면해석의 불확실성을 극복하고 해석결과의 신뢰성을 증진시키기 위하여 확률통계학적으로 도출된 절리극점들의 dense point 및 절리군 대표방향성과 암반구조 분석결과를 종합적으로 고려하여 사면거동양상을 분석하는 알고리즘을 고안하였다. 이를 위하여 절리극점들의 분포양상에 의거하여 절리확산지수를 산정하는 기법을 고안하였으며, 콘각에 따라 상이하게 도출되는 절리확산지수 및 절리군 수효와 방향성을 종합적으로 고려하여 사면해석에 사용될 대표방향성을 추출하였다. 이들 대표방향성을 평사투영분석에 활용하여 신뢰성이 증진된 사면해석을 수행할 수 있었다. 또한 평면파괴가 우려되는 사면에 대해 한계평형이론에 의거하여 민감도 해석을 수행하고, 사면 안정성에 대한 절리강도 및 외부하중 변화의 영향을 심도 있게 분석하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1690-1695
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• 2007

Lightweight metallic truss structures with open, periodic cell are currently being investigated because of their multi-functionality such as thermal management and load bearing. The Kagome truss PCM has been proved that it has higher resistance to plastic buckling, more plastic deformation energy and lower anisotropy than other truss PCMs. The subject of this paper is an examination of the failure mechanism of Wire woven Bulk Kagome(WBK). To address this issue, the out-of-plane compressive responses of the WBK has been measured and compared with theoretical and finite element (FE) predictions. For the experiment, 2 multi-layered WBK are fabricated and 3 specimens are prepared. For the theoretical analysis, the brazed joints of each wire in WBK are modeled as the pin-joint. Then, the peak stress of compressive behavior and elastic modulus are calculated based on the equilibrium equation and energy method. The mechanical structure with five by five cells on the plane are constructed is modeled using the commercial code, PATRAN 2005. and the analysis is achieved by the commercial FE code ABAQUS version 6.5 under the incremental theory of plasticity.

• Geomechanics and Engineering
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• 제17권6호
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• pp.515-525
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• 2019

The calculation of active earth pressure behind retaining wall is a typical three-dimensional (3D) problem with spatial effects. With the help of limit analysis, this paper firstly deduces the internal energy dissipation power equations and various external forces power equations of the 3D retaining wall under the nonlinear strength condition, such as to establish the work-energy balance equation. The pseudo-static method is used to consider the effect of earthquake on active earth pressure in horizontal state. The failure mode is a 3D curvilinear cone failure mechanism. For the different width of the retaining wall, the plane strain block is inserted in the symmetric plane. By optimizing all parameters, the maximum value of active earth pressure is calculated. In order to verify the validity of the new expressions obtained by the paper, the solutions are compared with previously published solutions. Agreement shows that the new expressions are effective. The results of different parameters are given in the forms of figures to analysis the influence caused by nonlinear strength parameters.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.178-201
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• 2019

The appropriate design of a mooring system to maintain the position of an offshore structure in deep sea under various environmental loads is important. Fatigue design of the mooring line considering OPB/IPB(out-of-plane bending/in-plane bending) became an essential factor after the incident of premature fatigue failure of the mooring chain due to OPB/IPB in the Girassol region in West Africa. In this study, mooring line fatigue analysis was performed considering the OPB/IPB of a spread moored FPSO in deep sea. The tension of the mooring line was derived by hydrodynamic analysis using the de-coupled analysis method. The floater motion time histories were calculated under the assumption that the mooring line behaves in quasi-static manner. Additional time domain analysis was carried out by prescribing the obtained motions on top of the selected critical mooring line, which was determined based on spectral fatigue analysis. In addition, nonlinear finite element analysis was performed considering the material nonlinearities, and both the interlink stiffness and stress concentration factors were derived. The fatigue damage to the chain surface was estimated by combining both the hydrodynamic and stress analysis results.

• 한국재난정보학회 논문집
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• 제3권2호
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• pp.147-169
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• 2007

This study investigates the reinforcing effects of the Multi-bar Spring nails with respect to the conventional Soil-nails in artificial slopes. Based on wide experience related to design and construction, soil nails have been widely applied to reinforce slope in the world. Multi-bar spring nails are one of the improved soil nailing methods. These method maximizes bending, shearing, pull-out resistance for those multi-nails, not unit nail, that are inserted in the borehole using special spacer at regular intervals. In addition, because cutting plane is confined effect resulting from a pressured plate at the end of the nails with compression spring equipment, slope stability is secured using MS-nailing method. Analyzing bending, pull-out, shearing condition of MS-nail, it was examined throughly elastic region, load transfer capacity, reinforcing effect on cutting plate of MS-nails. In addition, Pilot and laboratory tests, numerical analysis were carried out to verify the superiority of MS-nailing method. In case, MS nailing method is applied to reinforce artificial slope, it was analyzed that bending, pull-out, shearing resistance was increased more than existing nailing method was applied. In this study, it was shown that surface failure was more or less prevented using MS-nailing method, confining effect on cutting plane using spring stuck to flexible equipment.

• 대한토목학회논문집
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• 제14권4호
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• pp.923-932
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• 1994

얕은기초 및 깊은기초의 지지력에 관한 연구는 여러 분야에서 진전을 이루고 있으며, 다양한 파괴 모델에 따른 지지력 공식들이 발표되었다. 이들 모델들에 대한 얕은기초와 깊은기초의 근입깊이와 기초폭의 비에 따른 구분 방법은 명확하지 않고 지지력계수의 적용에 통일성이 없는 실정이다. 본 실험에서는 탄소봉을 이용하여 평면변형률 상태로 모형지반을 구성하고, 근입깊이에 따른 지반의 파괴 메카니즘과 지지력을 조사하였으며 이로부터 파괴형태에 따른 얕은기초와 깊은기초의 구분을 시도하였다. 또한 여러가지 기존의 기초 파괴형태를 실험으로 검증하였다.

• 대한안전경영과학회지
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• 제16권4호
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• pp.11-19
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• 2014

Modern systems development becomes more and more complicated due to the need on the ever-increasing capability of the systems. In addition to the complexity issue, safety concern is also increasing since the malfunctions of the systems under development may result in the accidents in both the test and evaluation phase and the operation phase. Those accidents can cause disastrous damages if explosiveness gets involved therein such as in weapon systems development. The subject of this paper is on how to incorporate safety requirements in the design of safety-critical systems. As an approach, a useful system structure using the method of design structure matrix (DSM) is studied while reflecting the need on systems safety. Specifically, the effects of system components failure are analyzed and numerically modeled first. Also, the system components are identified and their interfaces are represented using a component DSM. Combining the results of the failure analysis and the component DSM leads to a modified DSM. By rearranging the resultant DSM, a modular structure is derived with safety requirements incorporated. As a case study, application of the approach is also discussed in the development of a military UAV plane.