• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.63-63
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• 2021

Bed shear stress is important variable in river flow analysis. The bed shear stress has an effects on bed erosion, sediment transport, and mean flow characteristics. Quadratic formula to estimate bed shear stress is widely used, 𝜏=𝜌c_fu|u| in which friction coefficient, c_f, needs to be assigned to numerical models. The aim of this study is to estimate Chezy coefficient using bathymetry data measured by ADCP. Bed form geometry variables will be estimated form bed profile, then Chezy coefficient will be determined using estimated bed form geometry variables in order to set friction coefficient to numerical model. From the probability density function obtained from the bathymetry data, Chezy coefficient will be randomly generated since Chezy coefficient is not uniform over the space and it does not depend on spatial variables such as water depth and distance from river bank. Numerical test will be performed to find to demonstrate randomly extracted Chezy coefficient is appropriate. The result of this study is valuable in that the friction coefficient is estimated in consideration of the bed profile, and as a result, uncertainty of the friction coefficient can be reduced.

• 콘크리트학회지
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• 제6권4호
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• pp.161-168
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• 1994

반두께 P.C. 슬래브는 슬래브의 일부분(하부)을 프리캐스트로 제작하고 상부에 현장 콘크리트를 타설하는 공법으로서 반두께 슬래브가 휨변형을 일으킬 때 접합면사이에서는 수평전단력이 발생하게 된다. 본 연구에서는 이러한 수평전단력에 저항하기 위한 방법으로 스크랫치 방법을 도입하였다. 주요 변수로서는 상부콘크리트의 압축강도, 전단철근의 유무, 콘크리트 표면거칠기, 그리고 용접철망과 전단철근의 결합유무등으로 되어있다. 모든 실험체의 접합면의 면적(A$_c$)은 3,2000$cm^2$으로 동일하다. 실험결과, 콘크리트 표면처리 깊이가 증가할수록 전단강도는 증가하였으며 전단철근이 없이 표면거칠기만에 의해 수평전단강도를 확보할 수 있었다. 콘크리트의 압축강도가 증가함에 따라 수평전단강도는 증가하였다. 또한 전단강도를 예측하기 위한 전단계수 결정식을 도출하였다.

• Steel and Composite Structures
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• 제25권6호
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• pp.671-684
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• 2017

Elastic-plastic shear buckling behaviors of the web-post in a Castellated Steel Beam (CSB) with hexagonal web openings under vertical shear force were investigated further using Finite Element Model (FEM) based on a sub-model, which took the upper part of the web-post under horizontal shear force to represent the whole web-post under vertical shear force. A simplified design method for the web-post elastic-plastic shear buckling strength was proposed based on simulation results of the sub-model. Proper boundary conditions were applied to the sub-model to assure that its behaviors were identical to those of the whole web-post. The equation to calculate the thin plate elastic shear buckling strength was adopted as the basic form to build the design equation for elastic-plastic buckling strength of the sub-model. Parameters that might affect the elastic-plastic shear buckling strength of the whole web-post were studied. After obtaining the vertical shear buckling strength of a sub-model through FEM, the shear buckling coefficient k can be obtained through the back analysis. A practical calculation method for k was proposed through curving fitting the parameter study results. The elastic-plastic shear buckling strength of the web-post calculated using the proposed shear buckling coefficient k agreed well with that obtained from the FEM and test results. And it was more precise than those obtained from EC3 based on the strut model.

• 대한건축학회논문집:구조계
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• 제34권1호
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• pp.79-87
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• 2018

The purpose of this study was to analyze factors influencing insulation performance of inorganic Autoclaved Lightweight Concrete(ALC) sandwich wall panels with the application of shear connectors. To analyze the effect of shear connectors on the thermal performance of sandwich wall panels, heat transfer analysis was conducted by using the three-dimensional heat transfer simulation software. Four types of shear connector such as Pin, Clip, Grid, and Truss were selected for insulation performance analysis. Thermal bridge coefficient was calculated by varying typical panel thickness and shear connector thickness and materials such as steel, aluminum, and stainless steel. The results showed that Grid and Truss type widely distributed along the section of sandwich wall panel had a great influence on the thermal bridge coefficient by changing the influence factors. Based on the results of thermal and structural performance analysis, effective heat transmission coefficient of the sandwich wall panel satisfying the passive house insulation criteria was calculated. As a result, it was found that heat transmission coefficient was increased from $0.132W/m^2{\cdot}K$ to $0.141{\sim}0.306W/m^2{\cdot}K$ depending on the shear connector types and materials. In the majority of cases, the passive house insulation criteria was not satisfied after using shear connectors. The results of this study were likely to vary according to how influence factors were set, but it is important to apply the methods that reduce the thermal bridge when there would be a possibility of greatly affecting the insulation performance.

• 한국지반공학회논문집
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• 제36권4호
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• pp.31-39
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• 2020

지진 하중 하에서 필댐의 거동은 필댐 구성 재료의 전단파 속도(또는 전단 탄성계수) 분포에 많은 영향을 받는다. 일반적으로 필댐의 전단파 속도 분포는 전단파 속도 주상도를 통해 나타낼 수 있다. 이때 댐 구성 재료의 전단파 속도는 일반적으로 필댐 내부에서 공간에 따른 변동성을 가지며, 댐에서 허용되는 한정된 수의 실험에서는 이러한 재료 물성치 공간 변동성을 결정론적으로 규명할 수 없다. 따라서 실험에서 얻어진 전단파 속도 주상도는 불확실성을 가지게 되며, 재료 물성치의 불확실성은 해석결과에 불확실성을 야기하게 된다. 신뢰성 기반 해석은 이러한 재료 물성치 불확실성에 의한 해석결과의 영향을 평가 할 수 있다. 신뢰성 기반 해석에서는 변동계수를 통해 재료 물성치의 불확실성을 평가하고, 이러한 불확실성에 의한 영향을 해석에 반영할 수 있다. 본 연구에서는 국내 필댐 심벽부와 사력부 구성 재료의 전단파 속도 변동계수(COV, Coefficient Of Variation)를 결정하였다. 이를 위해 국내 필댐 심벽부와 사력부에서 표면파 시험을 통해 결정된 전단파 속도 주상도들에 대해 Hwang and Park(2013)에 의해 개발된 랜덤 전단파 속도 주상도 생성 기법을 적용하여 국내 필댐 심벽부와 사력부에 존재 가능한 전단파 속도 주상도 600개를 생성하고 이에 대한 통계처리를 통하여 필댐 심벽부와 사력부의 깊이별 전단파 속도 변동계수를 결정하였다.

• Wind and Structures
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• 제17권4호
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• pp.379-397
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• 2013

Large Eddy Simulations (LES) were carried out to investigate the aerodynamic characteristics of a rectangular cylinder with side ratio B/D=5 at Reynolds number Re=22,000 (based on cylinder thickness). Particular attention was devoted to the effects of velocity shear in the oncoming flow. Time-averaged and unsteady flow patterns around the cylinder were studied to enhance understanding of the effects of velocity shear. The simulation results showed that the Strouhal number has no significant variation with oncoming velocity shear, while the peak fluctuation frequency of the drag coefficient becomes identical to that of the lift coefficient with increase in velocity shear. The intermittently-reattached flow that features the aerodynamics of the 5:1 rectangular cylinder in non-shear flow becomes more stably reattached on the high-velocity side, and more stably separated on the low-velocity side. Both the mean and fluctuating drag coefficients increase slightly with increase in velocity shear. The mean and fluctuating lift and moment coefficients increase almost linearly with velocity shear. Lift force acts from the high-velocity side to the low-velocity side, which is similar to that of a circular cylinder but opposite to that of a square cylinder under the same oncoming shear flow.

• 지질공학
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• 제23권4호
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• pp.503-510
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• 2013

전단파 속도는 그 자체로 지층의 구조적인 특성을 확인할 수 있으며 상관관계 식들을 활용하면 타 공학적인 지표로 도출할 수 있다. 본 연구에서는 전단파 속도의 활용성에 발맞춰 부산 점토의 전단파 속도 관련 계수를 산정하는 것이다. 계수를 산정하기 위하여 실내 실험이 수행되었다. 실내 실험은 10 m, 12 m, 15 m, 20 m, 22 m, 25 m, 30 m 그리고 31 m에서 채취한 시료를 활용하였으며 압밀실험으로 유효응력과 전단파 속도 간의 관계를 도출하였다. 그 관계는 선행적으로 제시된 연구와 유사하게 비선형적인 특성을 보여주었으며 최종적으로는 전단파 속도에 활용 가능한 계수 값들을 도출하였다. 도출된 상수 값은 일정한 범위내에 속하는 것으로 나타났으며 두 상수 간의 관계도 제시하였다. 본 연구에서 제시한 계수 값들은 부산 점토의 참고 값이 될 것으로 판단되며, 향후 전단파 속도를 이용하여 공학적인 지표 전환시 다양하게 활용 될 것으로 판단된다.

• 국제초고층학회논문집
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• 제3권2호
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• pp.121-145
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• 2014

The story shear force distributions of most seismic design codes generally reflect the influences of higher vibration modes based on the elastic deformations of structures. However, as the seismic design allows for the plastic behavior of a structure, the story shear force distribution shall be effective after it is yielded due to earthquake excitation. Hence this study conducted numerical analyses on the story shear force distributions of most seismic design codes to find out the characteristics of how a structure is damaged between stories. Analysis results show that the more forces are distributed onto high stories, the lower its concentration is and the more energy is absorbed. From the results, this study proposes the optimum story shear force distribution and its calculation formula that make the damages uniformly distributed onto whole stories. Consequently, the story damage distribution from the optimum calculation formula was considerably more stable than existing seismic design codes.

• 한국지반공학회논문집
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• 제33권4호
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• pp.17-24
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• 2017

지진과 같은 외부 하중하에서 CFRD 거동은 사력존의 전단파 속도(또는 전단 탄성계수)분포에 큰 영향을 받는다. 일반적으로 사력존의 전단파 속도 분포는 주상도의 형태로 표면파 시험과 같은 비파괴 시험에 의해 결정될 수 있다. 이때 한정된 수의 실험에서 결정된 전단파 속도 주상도에는 불확실성이 존재하며, 이러한 불확실성은 사력존에 존재하는 물성치 공간 변동성에 의해 발생하게 된다. 내진 해석과 같은 다양한 해석에서 물성치 변동성에 의해 발생할 수 있는 해석 결과의 불확실성은 신뢰성 기반 해석을 통해 고려될 수 있다. 신뢰성 기반해석에서는 재료 물성치의 변동계수 결정을 통해 이러한 불확실성을 해석에 반영한다. 본 연구에서는 국내 CFRD 사력존을 위한 전단파 속도변동계수를 결정하였다. 이를 위해 국내 CFRD 사력존에서 결정된 전단파 속도 주상도들과 하모닉 웨이브릿 해석에 기반한 기법을 사용하여 국내 CFRD 사력존에 존재 가능한 600개의 전단파 속도 주상도를 생성하고 이를 이용하여 사력존 전단파 속도 분포의 깊이별 변동계수를 결정하였다.

• Geomechanics and Engineering
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• 제9권1호
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• pp.39-55
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• 2015

Usually the analyses of structures are carried out by assuming the base of structures to be fixed. However, the soil beneath foundation alters the earthquake loading and varies the response of structure. Hence, it is not realistic to analyze structures by considering it to be fixed. The importance of soil-structure interaction was realized from the past failures of massive structures by neglecting the effect of soil in seismic analysis. The analysis of massive structures requires soil flexibility to be considered to avoid failure and ensure safety. Present study, considers the seismic behavior of multi-storey reinforced concrete narrow and wide buildings of various heights with and without shear wall supported on raft foundation incorporating the effect of soil flexibility. Analysis of the three dimensional models of six different shear wall positions founded on four different soils has been carried out using finite element software LS DYNA. The study investigates the differences in spectral acceleration coefficient (Sa/g), base shear and storey shear obtained following the seismic provisions of Indian standard code IS: 1893 (2002) (IS) and International building code IBC: 2012 (IBC). The base shear values obtained as per IBC provisions are higher than IS values.