• Magazine of the Korea Concrete Institute
• /
• v.10 no.2
• /
• pp.167-178
• /
• 1998

횡방향철근에 의하여 적절히 구속된 콘크리트 기둥은 강도증가 및 연성의 확보면에서 유리하다. 본 연구의 목적은 횡방향철근에 의하여 구속된 코아콘크리트의 크기,횡방향철근의 간격비 및 체적철근비 등의 변화에 따른 콘크리트 기둥의 극한강도를 포함한 최대하중 이전의 거동 및 최대하중 이후의 거동을 실험적, 해석적으로 고찰함으로써 콘크리트 기둥의 구속효과정도를 규명하려는데 있다. 본 연구에서는 횡구속된 콘크리트 기둥모형의 압축재하실험을 수행하였으며, 최대하중 이전의 거동에 대하여 연속체적 파괴와 소성을 고려한 3차원 모델링을 통한유한요소해석을 실시하였다. 또한 횡구속된 콘크리트 기둥의 변형률국소화 모델에 의한 파괴해석을 통하여 구속된 콘크리트 기둥의 최대하중 이후의 거동을 재현하였다. 해석결과는 압축재하실험의 결과와 비교, 분석되었으며, 이에 따른 구속효과를 규명하였다.

• Journal of Korean Society of Transportation
• /
• v.6 no.2
• /
• pp.21-33
• /
• 1988

부적정한 도로포장 구조물의 설정 및 유지보수의 적정관리 미흡으로 표면의 피해와 소성변형이 장기간 발생된다. 이로 인한 가요성 통제 구조물의 파괴 원인은 일반적으로 포 장재료의 동질성, 선형탄성 상태의 가정 하에서 분석되었다. 그러나 아스팔트 재료의 특성은 엄밀히 분석해서 완전한 선형탄성이라고는 볼 수 없음은 잘 알려져 있다. 따라서 근본적으 로 포장체의 수명과 파양 예측에 오류 발생가능성이 높다 하겠다. 금번 연구는 이와 같은 종전의 경험적인 선형탄성 방법이 아닌 탄성일소성 상태하의 격자(mechano-lattice) 이론이란 새로운 기법을 도입하였다. 특히 마이너(Miner's Law) 이론의 누적손실과 확률을 적용하여 포장체의 피노수명과 손실을 예측할 수 있다. 금번 이론은 실제로 호주 빅토리아주의 멜보른(Melbourne)시 일부 지역구간을 모형으 로 선정되었다. 분석결과 가장 최적화된 도로포장 각층의 두께와 재료 선정을 하기 위하여 일정기간의 교통량, 상대적 손실지수와 잔여응력 및 표면 변위, 대기온도 그리고 습도의 영 향을 종합적으로 고려하여야 한다.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.1705-1711
• /
• 2008

Analysis of settlement of foundation under the cyclic loading is very important element in the field construction. The fatigue of construct is inflicted by wheel load of mobile unit with railroad and superhighway. The settlement behavior under the cyclic loading is investigated through Power Model by Li and Selig. However, the settlement tendency of foundation appears to be the settlement of general Europe cohesive soil. In this study, the Power Model was used to determine the plastic deformation for sandy soil. Based on the laboratory cyclic loading test a, m, b parameters, for using in the Power Model were presented.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.4 no.2
• /
• pp.73-82
• /
• 2000

본연구의 목적은 반복하중을 받는 철근콘크리트 교량 교각의 비선형 이력거동을 해석적으로 예측하는 것이다 이를 위해서 반복적인 횡하중이 작용하는 경우에 실험결과와 일치하는 교각의 하중-변위 이력곡선을 도출하고자 수정된 trilinar 이력거동모델을 이용하였다 철근과 콘크리트의 비선형 거동특성과 각 하중단계에 따른 교각의 중립축을 구하여 소성힌지부의 모멘트와 변형률을 구하고 반복하중하에서의 강성의 변화를 해석적으로 모형화하기 위하여 각기 다른 강성을 갖는 5가지 지선을 갖춘 형태의 이력거동모델식을 제안하였다 본 연구에서는 실험적으로 구한 하중-변위 이력곡선을 이용하여 축하중비 주철근비 및 구속철근비에 따른 강도감소지수와 강성감소지수의 영향을 회귀분석을 이용하여 일반식으로 제안하였다 새로운 이력거동 해석 모델을 프로그램 SARCF III에 적용함으로써 기존 철근콘크리트 교각에 강도 및 강성감소 현상을 정확하게 예측하였다

• Korean Journal of Food Science and Technology
• /
• v.18 no.3
• /
• pp.215-220
• /
• 1986

Mechanical properties of 9-30% starch gels from naked and covered barley were investigated with rheometer or rotation viscosimeter. The compression-penetration curves of 20 and 30% gels were characterized by deformations containing elastic, plastic and fracture regions under the load of 0-2kg. The compressive stress relaxation test showed that the viscoelastic properties of 20% gels may be represented by four element Maxwell model consisting of two Maxwell element in parallel. Also, stress-decay under the steady shear of 9% covered starch gel was able to be interpreted by linear viscoelastic model and stress-decay process was suggested to be effective to investigate the effect of temperature or additives on gel structure.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.2 s.54
• /
• pp.81-94
• /
• 2007

In most experimental researches on the liquefaction phenomenon, an earthquake as a random vibration has been regraded as a sinusoidal wave or a triangular wave with an equivalent amplitude. Together with the development in the part of signal control and data acquisition, dynamic experimental equipments in the soil dynamics have also developed rapidly and further more, several real earthquakes have been simulated in the large model test such as shaking table tests and centrifuge tests. In Korea, several elementary laboratory tests to simulate the real earthquake load were performed. From these test results, it was reported that the sinusoidal wave cannot reliably reflect the soil dynamic behavior under the real earthquake motion. In this study, 4 types of dynamic motions such as the sinusoidal wave, the triangular wave, the incremental triangular wave and several real earthquake motions which were classified with shock-type and vibration-type were loaded to find something new to explain the change of the excess pore water pressure under the real earthquake load. Through the detailed investigation and comparison on all test results, it is found that the dynamic flow is generated by the soil plastic deformation and the velocity head of dynamic flow is changed the pressure head in the un-drained condition. It can be concluded that the change of the excess pore water pressure is related to the pressure head of dynamic flow. Lastly, a new hypothesis to explain such a liquefaction initiation phenomenon under the real earthquake load is also proposed and verified.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.2
• /
• pp.121-128
• /
• 2020

The purpose of this study is to investigate the distribution patterns of displacement and acceleration fields in a nonlinear soil ground based on the interaction of high-speed train, wheel, rail, and ground. For this purpose, a high-speed train in motion was modeled as the actual wheel, and the vertical contact of wheel and rail and the lateral contact, caused by meandering motion, were simulated; this simulation was based on the moving mass analysis. The soil ground part was given the nonlinear behavior of the upper ground part by using the modified the Drucker-Prager model, and the changes in displacement and acceleration were compared with the behavior of the elastic and inelastic grounds. Using this analysis, the displacement and acceleration ranges close to the actual ground behavior were addressed. Additionally, the von-Mises stress and equivalent plastic strain at the ground were examined. Further, the equivalent plastic and total volumetric strains at each failure surface were examined. The variation in stresses, such as vertical stress, transverse pressure, and longitudinal restraint pressure of wheel-rail contact, with the time history was investigated using moving mass. In the case of nonlinear ground model, the displacement difference obtained based on the train travel is not large when compared to that of the elastic ground model, while the acceleration is caused to generate a large decrease.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.6
• /
• pp.57-69
• /
• 1999

This study investigates the existing theoretical backgrounds for bearing capacity determination according to the plasticity of soils when unsymmetrical surcharge is loaded on polluted soft soils. It also investigates the behavior of the displacement and bearing capacity by unsymmetrical surcharge on the Polluted soft soils. by comparing the analytical results and the actual measurements performed through the model test. Model tests were carried out as follows : soil tank, bearing frame and bearing plate are made for the test ; the water content in soil tank was kept constant while the contaminants in natural soils and polluted material were gradually increased ; unsymmetrical surcharge is increased at regular intervals and then the amounts of settlement, lateral displacement and upheaval are observed. In conclusion, the value of critical surcharge was expressed as $q_{ cr}= 2.78_{Cu}$ which was similar to those $Tschebotarioff(q_{cr}=3.0_{Cu)$ and $Meyerhof(q_{cr}=(B/2H+\pi/2_{Cu})$ had proposed. The value of ultimate capacity was expressed as $q_{ult}=4.84_{Cu}$ which was similar to that of Prandtl.

• Journal of the Korean Geotechnical Society
• /
• v.22 no.9
• /
• pp.23-36
• /
• 2006

This study presents the development of a new closed-form analytical solution for the ultimate bearing capacity of an embedded wall in a granular mass. The closed-form analytical solution consists of upper and lower bound solutions (UB and LB). The calculated values from these bound solutions were compared with the author's two-dimensional laboratory wall model loading test and finite element analysis in the plastic region. The comparison showed that ultimate bearing loads from both the model test and finite element analysis are located between UB and LB. In particular, the ultimate bearing load from LB showed good agreement with the ultimate bearing load values from both the model test and finite element analysis. However, the calculated value from the conventional empirical form subjected to plane-strain conditions was shown to be much smaller than the LB.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.5C
• /
• pp.231-238
• /
• 2012

The rockbolt functions as a main support, which restricts enlargement of the plasticity area and increases stability in the original ground around tunnels, and prevents a second deformation of an excavated surface by supplementing vulnerability arising from opening of the excavated surface. System bolting is generally applied if ground conditions are bad. System bolting is generally installed perpendicular to the excavation direction in every span. If a place is narrow, or it is difficult to insert bolts due to construction conditions, it may be connected and used with short bolts, or installed obliquely. In this study, laboratory model tests were performed to analyze the effect of the ground being reinforced by inclined bolts, based on a bending theory that assumes that the reinforced ground is a simple beam. In all test cases, deflections and vertical earth pressures induced by overburden soil pressure were measured. Total of 99 model tests were carried out, by changing the installation angle of bolts, lateral and longitudinal distance of bolts, and soil height. The model test results indicated that when the installation angle of bolts was less than $75^{\circ}$, deflections of model beams tended to increase rapidly. Also, the relaxed load that was calculated by earth pressure was rapidly increased when the installation angle of bolts was less than $75^{\circ}$. However, the optimum installation angle of inclined bolts was judged to be in the range of $90^{\circ}{\sim}75^{\circ}$. Also, as might be expected, the reinforcement effect of bolts was increased when the longitudinal and lateral distance of bolts was decreased.