• Korean Journal of Construction Engineering and Management
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• v.5 no.3 s.19
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• pp.71-78
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• 2004

In conventional method of supporting soil shuttering wall during excavation a system of struts and wales to provide cross-lot bracing is common in trench excavations and other excavations of limited width. This method, however, becomes difficult and costly to be adopted for large excavations since heavily braced structural systems are required. Another expensive and unsafe situations are expected when temporary struts must be removed for the construction of underground structures. This paper introduces innovative strut systems which can be used as permanent underground structures after its role as brace system to resist earth pressure during excavation phase. Underground structural system suggested from architect is checked against the soil lated pressures before the analysis of stresses developed from gravity loads. In this technology, named SPS(Struts as Permanent System), retaining wall is installed first and excavation proceeds until the first level of bracing is reached. Braces used as struts during excavation will serve as permanent girders when buildings are in operation. Simultaneous construction of underground and superstructure can proceeds when excavation ends with the last level of braces being installed. In this paper, construction sequence and the calculation concept are explained in detail with some photo illustrations. SPS technology was applied to three selected buildings. One of them was completed and two others are being constructed Many sensors were installed to monitor the behavior of retaining wall, braces as column in terms of stress change and displacement. Adjacent ground movement was also obtained. These projects demonstrate that SPS technology contributes to the speed as well as the economy involved in construction.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.6
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• pp.401-412
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• 2016

On Tuesday, January 17, 1995, an earthquake of magnitude 7.2 struck the Port of Kobe. In effect, the port was practically destroyed. After a hazard investigation, researchers reached a consensus to adopt a performance-based design in port and harbor structures in Japan. A residual displacement of geotechnical structures after an earthquake is one of the most important engineering demands in performance-based earthquake-resistant design. Thus, it is essential to provide reliable responses of geotechnical structures after an earthquake through various techniques. Today, a nonlinear explicit response history analysis(NERHA) of geotechnical structures is the most efficient way to achieve this goal. However, verification of the effective stress analysis, including post liquefaction behavior, is difficult to perform at a laboratory scale. This study aims to rigorously verify the NERHA by using well-defined field measurements, existing numerical tools, and constitutive models. The man-made, Port Island, in Kobe provides intensive hazard investigation data, strong motion records of 1995 Kobe earthquake, and sufficient engineering parameters of the soil. Two dimensional numerical analysis was conducted on the caisson quay wall section at Port Island subjected to the 1995 Kobe earthquake. The analysis result matches very well with the hazard investigation data. The NERHA procedure presented in this paper can be used in further studies to explain and examine the effects of other factors on the seismic behavior of gravity quay walls in liquefiable soil areas.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.1
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• pp.21-30
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• 1998

Design parameters which used to analyze the stress distribution on the tank wall were defined to develop the propellant tank and obtain optimal values. 1/4 modeling of total tank was selected to calculate the stress distribution with respect to the variation of the support lug location and the tank wall thickness and 1/2 modeling was selected for the stress distributions with respect to the variation of fuel outlet location. Actually, 350psi was applied as static load and 12 gravity as a dynamic load during launching on the internal tank wall. The structural analysis was done with respect to attaching condition of the tank in the satellite. Also the effect of the variation of the propellant outlet location from $0^{\cire}$ to $25^{\cire}$ on the stress distribution was investigated. The equivalent stress distribution and optimal parameters induced from analysis results of the each condition will be used as the fundamental data to design the propellant tank.

• Wind and Structures
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• v.28 no.3
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• pp.181-190
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• 2019

Light-frame wood structures have the ability to carry gravity loads. However, their performance during severe wind storms has indicated weakness with respect to resisting uplift wind loads exerted on the roofs of residential houses. A common failure mode observed during almost all main hurricane events initiates at the roof-to-wall connections (RTWCs). The toe-nail connections typically used at these locations are weak with regard to resisting uplift loading. This issue has been investigated at the Insurance Research Lab for Better Homes, where full-scale testing was conducted of a house under appropriate simulated uplift wind loads. This paper describes the detailed and sophisticated numerical simulation performed for this full-scale test, following which the numerical predictions were compared with the experimental results. In the numerical model, the nonlinear behavior is concentrated at the RTWCs, which is simulated with the use of a multi-linear plastic element. The analysis was conducted on four sets of uplift loads applied during the physical testing: 30 m/sincreased by 5 m/sincrements to 45 m/s. At this level of uplift loading, the connections exhibited inelastic behavior. A comparison with the experimental results revealed the ability of the sophisticated numerical model to predict the nonlinear response of the roof under wind uplift loads that vary both in time and space. A further component of the study was an evaluation of the load sharing among the trusses under realistic, uniform, and code pressures. Both the numerical model and the tributary area method were used for the load-sharing calculations.

• Journal of the Korean Geosynthetics Society
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• v.22 no.2
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• pp.71-83
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• 2023

It is very important to predict the amount of settlement in order to maintain the function of the coastal structure. Finite element analysis methods and real and model experiments are used as methods for this, but this has the disadvantage of requiring a lot of cost and time. Therefore, this study was conducted for the purpose of a simple formula proposal that can easily predict the amount of settlement of the caisson-type quay wall structure. In the research process, after calculating the PSI (Power Spectrum Intensity) of the velocity, the amount of settlement of the structure is calculated by substituting it into the simple formula of the existing gravity breakwater. By comparing and analyzing the amount of settlement of the structure obtained through numerical analysis, it was confirmed that the error between the amount of settlement of the existing simple formula and the amount of settlement of the numerical analysis was large, and it was confirmed that the background could not be considered in the case of the existing simple formula. Therefore, this study proposed a correction factor for the background of the quay wall structure, indicating a simple formula that can obtain the amount of settlement of the caisson-type quay wall structure. Compared to the numerical analysis settlement amount, it was judged that this simple formula had sufficient precision in calculating the caisson-type quay wall settlement amount. In addition, facilities vulnerable to earthquake resistance can be easily extracted in situations where time and cost are insufficient, and it is expected to be used as a screening technique.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2171-2176
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• 2007

The 3-omega (3-${\omega}$) method is utilized to measure the thermal conductivity of nanofluids. A metal line heater on a silicon nitride membrane bridge structure is microfabricated by a bulk silicon etching method. Localized measurement of the thermal conductivity within the nanofluids droplet is possible by the fabricated 3-${\omega}$ sensor. Time varying AC temperature amplitudes and thermal conductivities are measured to check the stability of the nanofluids containing multi-wall carbon nanotubes (MWCNTs). Stabilities of MWCNT nanofluids prepared with different chemical treatments are compared. Acid treated MWCNT showed best dispersion stability in water while MWCNTs dispersed in water with surfactants such as Gum Arabic and Sodium dodecyl benzene sulfate showed clear sign of gravity dependence.

• Geotechnical Engineering
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• v.12 no.6
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• pp.101-114
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• 1996

Even though the Coulomb's earth pressure theory has been mainly used in practice, the general equation does not exist yet, which is applicable to retaining wall backfilled by cohesive soils. Here, for gravity walls backfilled by cohesive soils, some equations have been derived by newly using the Coulomb's theory, for the cases oi drained and untrained analyses. and for the cases of neglecting and considering the tension crack, respectively. Both the active earth thrust and the depth of tension crack under different conditions were tabulated.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.304-310
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• 2001

A numerical model which simulates the heat and mass transfer processes within a counter-current plate type generator for ammonia/water absorption refrigerators was developed. Ammonia/water solution flows downward under gravity and ammonia/water vapor generated by flow boiling flows upward. The flow pattern within the generator was assumed to be a bubbly flow, and the liquid and vapor phase were assumed to be saturated. It was shown that the boiling of ammonia occurred mainly in the upper part of the generator. The effects of the generator length, the wall temperature and the mass flow rate of ammonia/water solution into the generator on the generation of ammonia/water vapor were investigated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.265-273
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• 2003

Numerical analysis of bubble motion during nucleate boiling is performed by imposing a constant heat flux condition at the base of a heater which occurs in most of boiling experiments. The temporal and spatial variation of a solid surface temperature associated with the bubble growth and departure is investigated by solving a conjugate problem involving conduction in the solid. The vapor-liquid interface is tracked by a level set method which is modified to include the effects of phase change at the interface, contact angle at the wall and evaporative heat flux in a thin liquid micro-layer. Based on the numerical results, the bubble growth pattern and its interaction with the heating solid are discussed. Also, the effect of heating condition on the bubble growth under a micro-gravity condition is investigated.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.570-574
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• 2009

벽 근처에서의 흐름(near wall flow)을 해석하기 위한 낮은 레이놀즈수 수정(low-Reynolds number modification)을 포함하는 통계학적 난류모형을 이용한 3차원 비정상 레이놀즈-평균 나비어-스톡스 (URANS) 계산을 실시하여 사각형 수로에서의 중력류를 모의하였다. 3차원 계산 결과를 2차원 URANS 모의에 의한 계산 결과 그리고 실험결과와 비교하였다. 이 연구 결과는 적정 시 공간적 수치해상도를 가지고 벽 근처에서의 흐름을 주의 깊게 직접 해석하는 3차원 URANS 수치모의는 2차원 계산으로는 해석할 수 없는 대규모 Kelvin-Helmholtz 와구조 (vortical structure)의 붕괴(breakdown) 그리고 중력류 선단부에서 발달하는 Lobe-and-Cleft 흐름 불안정 등을 포함하는 중력류의 동적 특성을 높은 정확도로 재현할 수 있음을 보여준다.