• 대한토목학회논문집
• /
• 제32권4C호
• /
• pp.159-167
• /
• 2012

본 연구는 실내 모형말뚝 재하실험과 유한요소해석을 통해 모형말뚝 선단부 주변 흙의 변형률 거동을 비교 분석하였다. 모형말뚝의 하중을 모사하기 위해 LCM(load control method) 기법과 DCM(displacement control method) 기법을 소개하고, 이 중 수치해석에 타당한 기법을 제안하였다. 유한요소해석에 있어서 말뚝의 미끄럼 거동을 모사하기 위해 기존과는 달리 두 가지 경계면 요소를 사용하여 모형실험 결과와 비교하였다. 본 연구를 통해 비연관 흐름의 정도(degree of non-associated flow)가 수치해석 값 수렴에 중요한 요소임을 알 수 있었다. 또한 수치해석에 있어 대칭인 최대전단변형률 분포를 얻기 위해서는 새로이 개선된 유한요소망(finite element mesh)의 도입이 필요함을 알 수 있었다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2008년도 추계 학술발표회
• /
• pp.1144-1156
• /
• 2008

In this paper, heaving phenomenon is analyzed by laboratory tests. A laboratory test is consist of building soft clay foundation in plane-strain soil tank, construction of retaining wall, and excavation work. And range of shear strain, and destruction shape about soft clay foundation is compared, and analyzed with results of proposal formula. Using this study, safety factor is suggested for heaving phenomenon in the construction of wall on the soft clay. Actual theory is suggested by this suggested safety factor. There are various proposal formula for heaving phenomenon. For example, Terzaghi & Peck, Tschebotarioff, Bjerrum & Eide(Experience formula) and so on. Terzaghi & Peck's proposal formula is chosen, compared with laboratory test's result and analyzed in this study. A soft clay used in study is assumed homogeneous. A Depth of foundation is enough to observe shear strain by heaving phenomenon. Retaining wall is enough hard not to have vertical displacement.

• 한국농공학회지
• /
• 제42권3호
• /
• pp.97-106
• /
• 2000

The study is closely relevant to Lade's single work hardening model. This model has been shown to have good applicability to cohesive soils. However the validation of this model on the clayey soils has not been satisfactorily reported. To scrutinize the applicability of this model on clayey foundation the laboratory tests for Kwangyang clayey soils were performed using the improved cubical triaxial test apparatus designed originally by Lade. A computer program was developed by which soil parameters for the single work-hardening model can be rationally determined by deleting some dispersed test data generated usually at the initial stage of laboratory tests. And using the program numerical analysis of the cubical clayey specimens using intermediate principal stress was carried out and a good agreement between observed values and numerical results was found.

• 항공우주시스템공학회지
• /
• 제14권6호
• /
• pp.91-99
• /
• 2020

This study proposes a finite element (FE) model for predicting the bending strength of small gears used in electro-mechanical actuators for aircraft. First, a strain gauge was attached to the tooth root of test gear, and the strain was measured. Subsequently, the FE model was applied to calculate the strain of the test gear, and the modeled strain was compared with the experimental strain. The results confirmed that the FE strain was very close to the experimental strain and the FE model was valid. This FE model was extended to the bending strength analysis of several small gear tooth models. The bending strengths of all the tooth models were almost identical to the ISO theoretical bending strength. Finally, the FE model was validated and the reliability of the modeled bending strength was evaluated through the strain measurement experiment.

• Earthquakes and Structures
• /
• 제13권3호
• /
• pp.299-307
• /
• 2017

High Damping Rubber bearings (HDR bearings) have been used in the seismic design of bridge structures widely in China. In earthquakes, structural natural periods will be extended, seismic energy will be dissipated by this kind of bearing. Previously, cyclic loading method was used mainly for test studies on mechanical properties of HDR bearings, which cannot simulate real seismic responses. In this paper, Real-Time Substructure (RTS) test study on mechanical properties of HDR bearings was conducted and it was found that the loading rate effect was not negligible. Then the influence of peak acceleration of ground motion was studied. At last test results were compared with a numerical simulation in the OpenSees software framework with the Kikuchi model. It is found that the Kikuchi model can simulate real mechanical properties of HDR bearings in earthquakes accurately.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회 2차
• /
• pp.38-44
• /
• 2010

Shaking table tests were performed to reproduce the dynamic behavior of estuary barrage and its subbase soil which can be potentially damaged during earthquake loading. For understanding the vibration effect to the ground during earthquake, the model was formulated with 1/300 scale of prototype estuary barrage and subbase soil. Scott and Iai(1989) proposed the law of the similarity for similar experimental conditions. The laboratory model shaking table test was conducted under the vibration condition of simulated earthquake of 0.154g. The horizontal displacement on the structure was measured during the shaking table test. The pore water pressure was also monitored for the underground layers of soil. The field horizontal displacement and the pore water pressure can be predicted by using the results of the laboratory shaking table test.

• Steel and Composite Structures
• /
• 제25권1호
• /
• pp.79-92
• /
• 2017

Initial damage to a stud due to corrosion, fatigue, unexpected overloading, a weld defect or other factors could degrade the shear capacity of the stud. Based on typical push-out tests, a FEM model and theoretical formulations were proposed in this study. Six specimens with the same geometric dimensions were tested to investigate the effect of the damage degree and location on the static behavior and shear capacity of stud shear connectors. The test results indicated that a reduction of up to 36.6% and 62.9% of the section area of the shank could result in a dropping rate of 7.9% and 57.2%, respectively, compared to the standard specimen shear capacity. Numerical analysis was performed to simulate the push-out test and validated against test results. A parametrical study was performed to further investigate the damage degree and location on the shear capacity of studs based on the proposed numerical model. It was demonstrated that the shear capacity was not sensitive to the damage degree when the damage section was located at 0.5d, where d is the shank diameter, from the stud root, even if the stud had a significant reduction in area. Finally, a theoretical formula with a reduction factor K was proposed to consider the reduction of the shear capacity due to the presence of initial damage. Calculating K was accomplished in two ways: a linear relationship and a square relationship with the damage degree corresponding to the shear capacity dominated by the section area and the nominal diameter of the damaged stud. This coefficient was applied using Eurocode 4, AASHTO LRFD (2014) and GB50017-2003 (2003) and compared with the test results found in the literature. It was found that the proposed method produced good predictions of the shear capacity of stud shear connectors with initial damage.

• Geomechanics and Engineering
• /
• 제8권1호
• /
• pp.33-52
• /
• 2015

Based on the Mohr-Coulomb failure criterion, a gradient-dependent plastic model that considers the strain-softening behavior is presented in this study. Both triaxial shear tests on conventional specimen and precut-specimen, which were obtained from an ancient landslide, are performed to plot the post-peak stress-strain entire-process curves. According to the test results of the soil strength, which reduces from peak to residual strength, the Mohr-Coulomb criterion that considers strain-softening under gradient plastic theory is deduced, where strength reduction depends on the hardening parameter and the Laplacian thereof. The validity of the model is evaluated by the simulation of the results of triaxial shear test, and the computed and measured curves are consistent and independent of the adopted mesh. Finally, a progressive failure of the ancient landslide, which was triggered by slide of the toe, is simulated using this model, and the effects of the strain-softening process on the landslide stability are discussed.

• Geomechanics and Engineering
• /
• 제13권6호
• /
• pp.1027-1044
• /
• 2017

Membrane penetration is the most important factor influencing the measurement of volume change for triaxial consolidated-drained shear test for coarse-grained soil. The effective pressure p, average particle size $d_{50}$, thickness $t_m$ and elastic modulus $E_m$ of membrane, contact area between membrane and soil $A_m$ as well as the initial void ratio e are the major factors influencing membrane penetration. According to the membrane deformation model given by Kramer and Sivaneswaran, an analytical solution of the membrane penetration considering the initial void ratio is deduced using the energy conservation law. The basic equations from theory of plates and shells and the elastic mechanics are employed during the derivation. To verify the presented solution, isotropic consolidation tests of a coarse-grained soil are performed by using the method of embedding different diameter of iron rods in the triaxial samples, and volume changes due to membrane penetration are obtained. The predictions from presented solution and previous analytical solutions are compared with the test results. It is found that the prediction from presented analytical solution agrees well with the test results.

• Water Engineering Research
• /
• 제1권4호
• /
• pp.309-320
• /
• 2000

In this study, laboratory study of the behavior of wastewater discharged from the Boston ocean outfall was compared with the predictions of mathematical models. The dta sets cover broad ranges of discharge conditions and oceanic conditions, and are associated with a typical type of outfall discharges with multiport diffusers. The laboratory data sets were obtained in density stratified towing tanks. These data sets were used to evaluate four commonly used models: UM, UDKHDEN, RSB and CORMI$\times$2 for minimum dilution, the height to the top of the wastefield, and wastefield thickness. For minimum diluation and height to the top of the wastefield, UM and RSB predictions agree well with laboratory data. UDKHDEN overestimated the minimum dilution and height to the top of the wastefield while CORMI$\times$2 underestimated these values. All of the model predictions for the wastefield thickness were widely scattered. about the measured values. The hydraulic model study reproduced the major features observed in the laboratory. It also afforded considerable insight into the mechanics of mixing of multiport risers which could not have been obtained either from the laboratory test or the mathematical models.