• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.1
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• pp.63-72
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• 2001

상부 벽체와 하부 골조로 구성되는 주상복합건물은 전이층에서 수직적인 강성과 강도의 불연속성을 갖는다. 이러한 복합구조는 전이층에서 춤이 큰 보에 의하여 하중이 전달되면 설계시 매우 중요하게 고려하여야 하는 사항이다. 그러나 이에 대한 연구가 충분히 이루어져 있지 않으며 실제 전이보의 설계시 춤을 매우 크게 하여 요구되는 강도보다 큰 안전율이 고려되고 있다. 본 연구에서는 전이층의 단순화모델을 이용하여 보의 높이 및 지지면의 길이에 따른 아치거동의 변화를 조사하였다. 유한요소법을 이용하여 구조물을 분석하고 두 변수를 포함하는 헌치부재를 이용하여 그 효과를 기존 시스템과 비교하였다. 중요 변수와 헌치의 기울기는 1:1의 비율에서 사장 효율이 좋은 것으로 나타났으며, 이러한 결과를 전이보를 대신하여 사용한 결과 중력방향의 상부 아치거동에 대하여 효과적으로 작용하는 것으로 나타났다. 또한 응력 집중부위에서의 응력 감소와 깊이 전이보의 높이감소에 효과적으로 작용하는 것으로 나타났다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.999-1012
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• 2017

Theoretical, empirical and numerical methods are used to evaluate the rock load due to tunnelling. Theoretical and empirical methods do not consider ground conditions, tunnel shape, and construction conditions. However, through numerical analysis, it is possible to analyze the displacement and stresses around tunnel due to its excavation, and evaluate the rock load considering ground and construction conditions. The stress transfer ratio(e) which is defined as a ratio of the difference between the major and minor principal stresses to major principal stress is used in order to understand the stress transfer effect around the tunnel excavation using numerical analysis results. The loosend area around tunnel periphery was found based on this approach. The difference of rock load from stress transfer effect was found according to the ground grade. From comparison, rock load obtained from stress transfer effect (e = 10%) were somewhat larger than the results obtained from the critical strain method, but smaller than those obtained from theoretical and empirical methods. The stress transfer effect approach considers the ground condition, tunnel shape; therefore, it can be applied to evaluate the rock load in concrete lining design.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.10a
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• pp.282-284
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• 2012

해양플랜트의 관심의 증가로 사업의 수요가 많아지고 플랜트 사업이 활발해지고 있다. 플로팅구조물의 상부구조물과 하부구조물간의 발생 할 수 있는 집중응력으로 인한 구조적인 문제를 제기하며, 이 문제를 해결할 수 있는 효율적인 전이보시스템을 제안한다. 전이보시스템이 주각부에 발생하는 집중하중을 분산시키는 효과가 있는지 유한요소 프로그램인 ABAQUS를 통해 구조해석을 수행한다.

• Journal of the Korean Geotechnical Society
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• v.27 no.2
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• pp.35-42
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• 2011

The residual stress on drilled shafts is often neglected. Neglect of the existence of locked-in loads in the shaft is the main reason for conclusions of instrumented tests which suggest that shaft resistance is smaller when the shaft is loaded in tension than when it is loaded in compression. A few researchers studied the residual stress and mentioned that the residual stress is influenced by either the physical expansion/contraction of concrete during the curing or site stratigraphy. In this study, field measurements of residual stress on test shafts were conducted and the factors influencing the residual stress were figured out.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.431-438
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• 2012

The mechanical behavior of the polymeric material, HDPE depends on both time and temperature. The study of the tensile behavior at different strain rates is important in engineering design of the orthopedics device such as X-band plate. The mechanical properties and deformation mechanisms of HDPE are strongly dependent on the applied strain rate. Generally, the deformation behavior of HDPE based on the stress-strain curve is complex because of the highly inhomogeneous nature of plastic deformation, particularly that of necking. Therefore, we attempted to determine the mechanical behavior of HDPE in this study. Normally, tensile testing under various strain rates of the HDPE has been used to determine the mechanical behavior. We performed tensile tests at various strain rates (1 to 500 %/min) to analyze the viscoelastic behavior on increasing the strain rate. A tensile stress-strain curve was plotted from the data, and the point of transition was marked to calculate the transition stress, strain, and modulus.

• Journal of Korean Association for Spatial Structures
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• v.4 no.2 s.12
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• pp.53-61
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• 2004

Recently, most of residential-commercial buildings and apartment houses which are being constructed in the downtown area mainly adopt hybrid structural systems to compose various spaces. Especially, column-supported wall system which is one of the hybrid systems includes shear wall and rigid frame structure and these structures are connected by the transfer floor. But this system is very disadvantageous from the viewpoint of structural safety and is difficult to find out the stress distribution at the transfer floor. Therefore, this study analyzes the behavior and stress distribution according to the shear wall layout of transfer girder system subject to vertical and static lateral loads. Also, this study recognizes load paths and stress concentration based on the analysis results nearby the transfer floor and presents guidelines for the effective design of wall and transfer girder.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1C
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• pp.33-39
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• 2009

Vertical soil stress near a pile subjected to negative skin friction (NSF) may be reduced due to shear transfer at the pile-soil interface. A three-dimensional finite difference analysis has been performed to clarify the influence of vertical and horizontal stress reductions on the pile behavour. In addition, a simple equation has been proposed to estimate vertical stress reduction of the soil near the pile. The vertical and horizontal stresses are reduced by substantial amount compared to corresponding stress components at the Greenfield condition. The horizontal extent of vertical stress reduction of the soil near the pile is rather limited to about up to 4-8 D, where D is the pile diameter. The findings from the current research indicate that widely used $\beta$-method may result in over-estimation of dragload (compressive force on piles due to NSF) and hence stress reduction needs to be incorporated in the original equation.

• Korean Journal of Materials Research
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• v.2 no.5
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• pp.320-329
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• 1992

In 2Y-TZP powders calcined at temperature range of 80$0^{\circ}C$0 to 150$0^{\circ}C$, the effect of stabilization and the transformability of tetragonal phase on the tetragonal to monoclinic transformation have been investigated. The transformability of tetragonal phase in calcined powders shows maximum at the calcination temperature of 130$0^{\circ}C$. This result is explained by a combined effect of the increase of particle size and of constrained force among the particles with increasing the calcination temperature. The amount of transformed monoclinic phase with calcination temperature after quenching in liquid nitrogen, stress induction and isothermal aging at 25$0^{\circ}C$is also explained by the transformability of tetragonal phase determined by the sum of particle size effect and constraint effect.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.825-835
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• 2019

When the tunnel is designed, the ground is classified into several grades and the corresponding support system is applied according to the support pattern table. However, a simple pattern application based on rock grade does not take into account the longitudinal stress transitions occurring at rock grade boundaries. In this study, three-dimensional numerical analysis was performed to estimate the stress change in the longitudinal rock grade change of NATM tunnel, and the influence zone of load transfer was investigated using the influence line and trend line. As a result, the downward change of rock grade in the direction of tunnel excavation occurs in the range of 0.35~0.7D from low-strength rock to high-strength rock around the grade change boundary. It is necessary to apply a downward pattern of about 1.0D to the safety direction in consideration of the influence range of 0.35D to 0.7D.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.5-13
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• 2000

모래지반의 상대밀도, 말뚝의 시공방법, 일정근입깊이에 따른 소요향타 에너지 그리고 지하수 조건에 따라 말뚝의 지지력과 하중전이를 연구하기 위하여 강관말뚝을 이용한 모형실험을 수행하였다. 매입말뚝은 말뚝을 미리 설치한후에 지반성형을 실시하였고, 타입말뚝은 매입말뚝과 같은 깊이까지 항타높이를 5, 10, 15cm로 달리하여 말뚝을 관입하였다. 그 뒤 정적하중을 단계적으로 가하여 하중-침하 곡선에 의한 모형 말뚝의 지지력과ㅏ 말뚝내의 등간격으로 설치된 변형 게이지를 이용하여 타입말뚝 의 하중전이에 대해 살펴보았다. 타입말뚝의 하중전이시험에서는 항타 전과 항타 후 말뚝내 하중전의 소효항타 에너지에 따른 변화를 관찰하였다. 매입말뚝의 시험결과는 현재 가장 많이 사용하고 있는 대표적인 정적 지지력 공식들에 의하여 계산되어진 값들과 비교 분석하였다. 그 결과 상대밀도가 작은 느슨한모래지반에서는 Vesic 공식이 그리고 상대밀도가 큰 조밀한 모래지반에서는 Hanbu 공식이 가장 근접한 평가를 나타내었다. 하중전이시험에 의한 항타시 잔류응력은 모든 경우에서 지표면과 선단부위에서 아주 큰 잔류응력이 나타났고. 말뚝의 선단 지지력비는 상대밀도에 비례하게 증가하였다.