• Structural Engineering and Mechanics
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• 제59권6호
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• pp.951-972
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• 2016

The purpose of this study is to illustrate the propagation of the shear waves (SH-waves) in a prestressed hetrogeneous orthotropic media overlying a pre-stressed anisotropic porous half-space with self weight. It is considered that the compressive initial stress, mass density and moduli of rigidity of the upper layer are space dependent. The proposed model is solved to obtain the different dispersion relations for the SH-wave in the elastic-porous medium of different properties. The effects of compressive and tensile stresses along with the heterogeneity, porosity, Biot's gravity parameter on the dispersion of SH-wave are shown numerically. The wave analysis further indicates that the technical parameters of upper and lower half-space affect the wave velocity significantly. The results may be useful to understand the nature of seismic wave propagation in geophysical applications and in the field of earthquake and material science engineering.

• Computers and Concrete
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• 제24권2호
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• pp.173-183
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• 2019

This study presents experimental and numerical results of prestressed concrete composite beams with different casting and stressing sequence. The beams were tested under three-point bending and it was found that prestressed concrete composite beams could not achieve monolith behavior due to interface slippage between two layers. The initial stress distribution due to different construction sequence has little effect on the maximum load of composite beams. The multi-step FE analyses could simulate different casting and stressing sequence thus correctly capturing the initial stress distribution induced by staged construction. Three contact algorithms were considered for interaction between concrete layers in the FE models namely tie constraint, cohesive contact and surface-to-surface contact. It was found that both cohesive contact and surface-to-surface contact could simulate the interface slip even though each algorithm considers different shear transfer mechanism. The use of surface-to-surface contact for beams with more than 2 layers of concrete is not recommended as it underestimates the maximum load in this study.

• 한국해안해양공학회지
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• 제1권1호
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• pp.44-49
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• 1989

점성토의 퇴적현상에는 여러가지 물리화학적 인자가 작용하기 때문에 최근까지의 연구경향은 주로 현장관측이나 수리실험에 의존하고 있는 실정이다. 본 연구에서는 금강하구에서 채취한 시료를 사용하여 정성토의 침식 및 퇴적에 관한 개수로 실험을 하였다. 침식에 대한 실험에서는 여러가지 수리조건에서의 시간에 따른 부유농도 변화를 측정하여 침식률 및 침식계수를 구하여 침식에 대한 한계소류력을 결정하였으며, 퇴적에 대한 실험에서는 수리조건을 변화시키면서 각 소류력에 대한 평형농도를 결정하여 평형농도와 초기농도와의 비와 소류력과의 관계를 얻었다. 본 연구의 결과를 다른 자료와 비교 검토하여 정상적으로 유사한 경향을 나타내고 있음을 알 수 있었다.

• 대한기계학회논문집
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• 제15권2호
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• pp.413-423
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• 1991

Multiaxial loading by combinations of tension-torsion-internal pressure have been applied to the thins-walled tubular specimens prepared from cold drawn tubes of SAE 1020 steel. Prior to the multiaxial loading, each specimen has been twisted to different shear strains. Uniaxial tensile yield stresses measured at different angles to the tube axis clearly show that the initial orthotropic symmetry is maintained during twisting. The orthotropy axes are observed to rotate with shear strains. The plane stress yield locus measured for each twisted specimens show that yield surface shape does not remain similar during twisting and thus anisotropic work hardening is not a function of only plastic work.

• 대한기계학회논문집A
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• 제21권2호
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• pp.317-326
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• 1997

An investigation was performed to study the matrix cracking and delamination in laminated composite plates due to transverse impact. A model was developed for predicting the initiation of the matrix cracking and the shape and size of impact-induced delamination in laminated composite plates resulting from the ballistic impact. The model consists of a stress analysis and a failure analysis. A transient finite element analysis which was based on the higher-order shear deformation theory was adopted for calculating the stresses inside the laminated composite plates during impact. A failure analysis was used to predict the initial intraply matrix cracking and the shape and size of the interface delamination in the laminates. As a results, a shear matrix cracking which was governed by the transverse interlaminar shear stress occured at the middle layer near the midplane of laminates and a bending matrix cracking which was governed by the transverse inplane stress occured at the bottom layer near the surface of laminates. In a thick laminates, a shear matrix cracking generated first at the middle layer of laminates, but in a thin laminates, a bending matrix cracking generated first at the bottom layer of laminates.

• 한국지반공학회논문집
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• 제22권4호
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• pp.61-71
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• 2006

본 논문에서는 유효응력모델을 이용하여 포화된 사면의 동적거동에 관한 연구를 수행하였다. 수치해석에는 저자가 개발한 연성 유효응력모델인 UBSSAND모델을 이용하였으며, 이 모델은 초기전단응력이 수평면에 작용하는 경우와 작용하지 않는 경우를 포함한 반복 직접단순전단시험 자료를 이용하여 검증하였다. 검증된 모델은 느슨한 Fraser River 모래로 성형된 사면을 가진 원심모형모델의 동적거동을 예측하였다. 예측된 과잉간극수압, 가속도 및 변위를 계측치와 서로 비교하였으며, 예측치와 계측치는 비교적 서로 잘 일치하였다. 전단응력도의 응력전환형태는 초기전단응력과 반복전단응력의 크기에 따라 달라지며, 이는 지진시 포화된 사면의 안정해석에 아주 중요한 역할을 하고 있음을 알 수 있었다. 전단응력도의 응력전환이 발생하지 않을 경우에 사면근처의 모래는 낮은 유효응력 구속압과 그에 따른 팽창성으로(부의 과잉간극수압발생) 유효응력이 증가하여, 동적하중 하의 사면의 변위를 저지하였다. 이와 같은 유효응력모델은 액상화를 고려한 지반구조물의 내진해석에 유용하게 사용될 수 있다.

• Steel and Composite Structures
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• 제23권3호
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• pp.251-261
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• 2017

In this paper, thermal effect on the vibration and stability of initially stressed sandwich plates with functionally graded material (FGM) face sheets is analyzed. Material properties of FGM face sheet are graded continuously in the thickness direction. The variation of FGM properties assumes a simple power law distribution in terms of the volume fractions of the constituents. The governing equations of arbitrarily initially-stressed sandwich plates including the effects of transverse shear deformation and rotary inertia are derived. The initial stress is taken to be a combination of a uniaxial extensional stress and a pure bending stress in the examples. The eigenvalue problems are formed to study the vibration and buckling characteristics of simple supported initially stressed FGM/metal/FGM plates. The effects of volume fraction index, temperature rise, initial stress and layer thickness of metal on the natural frequencies and buckling loads are investigated. The results reveal that the volume fraction index, initial stresses and layer thickness of metal have significant influence on the vibration and stability of sandwich plates with FGM face sheets.

• 한국지진공학회논문집
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• 제25권5호
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• pp.191-199
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• 2021

In seismic design, hollow section concrete columns offer advantages by reducing the weight and seismic mass compared to concrete section RC bridge columns. However, the flexure-shear behavior and spirals strain of hollow section concrete columns are not well-understood. Octagonal RC bridge columns of a small-scale model were tested under cyclic lateral load with constant axial load. The volumetric ratio of the transverse spiral hoop of all specimens is 0.00206. The test results showed that the structural performance of the hollow specimen, such as the initial crack pattern, initial stiffness, and diagonal crack pattern, was comparable to that of the solid specimen. However, the lateral strength and ultimate displacement of the hollow specimen noticeably decreased after the drift ratio of 3%. The columns showed flexure-shear failure at the final stage. Analytical and experimental investigations are presented in this study to understand a correlation confinement steel ratio with neutral axis and a correlation between the strain of spirals and the shear resistance capacity of steel in hollow and solid section concrete columns. Furthermore, shear strength components (V_c, V_s·, V_p) and concrete stress were investigated.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2001년도 봄 학술발표회 논문집
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• pp.139-146
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• 2001

Undrained triaxial tests were peformed for a weathered soil, which includes local measurement using LVDT The behavior from small In large strain conditions could be evaluated consistently through a triaxial test, The stress-strain relationship of undisturbed samples were compared with the disturbed and the shear moduli in the small strain level had the almost same values. Especially the shear moduli were mostly affected by the initial condition of water contents. An anisotropic hardening model based on the total stress concept could predict the stress-strain relationship accurately, which makes it possible to analyze the geotechnical problem reasonably for the weathered soil.

• 터널과지하공간
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• 제27권2호
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• pp.89-99
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• 2017

이산화탄소 지중저장 사업의 성공적인 수행을 위해서는 저장시스템의 안정성을 확보할 수 있는 대상 지층을 선정하고 현장 지질조건에 최적화된 주입 조건을 설계해야 한다. 본 연구에서는 국내 실증실험 대상 예상후보지의 하나인 장기분지의 지질구조를 바탕으로 2차원 간략해석모델을 구축하고 TOUGH-FLAC 연계해석기법을 사용하여 초기응력조건과 주입량이 이산화탄소 격리저장시스템에 미치는 영향을 분석하였다. 기초해석 결과, 수직응력이 수평응력보다 우세한 정단층 응력조건에서 전단미끄러짐 가능성이 가장 높은 결과를 보였으며, 단위시간당 주입량을 달리하는 주입량 시나리오 해석에서는 주입량을 단계적으로 증가시켜 주입하는 경우가 공극압의 증가폭이 가장 크고 활동마찰계수를 이용한 전단미끄러짐 가능성 평가 결과에서도 가장 불리한 것으로 평가되었다.