• 한국지반환경공학회 논문집
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• 제3권2호
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• pp.61-70
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• 2002

본 논문은 폐 Styrofoam과 현장발생토를 활용하여 경량 성토재로서의 특성을 파악하고자 하는데 목적이 있다. 폐 Styrofoam 입자는 가볍고 단열성이 좋으며 진동차단효과도 우수하기 때문에 경량 성토재로서의 활용이 가능하다. 특히 Styrofoam은 1996년 재활용 품목으로 선정되어 토공재료로서의 적합성만 확인된다면 체계적인 공급이 가능하다. 따라서 본 논문에서는 폐 Styrofoam 혼합토의 동적 다짐시험, 정적 다짐시험, pH 및 용출실험을 하였으며, 그 결과 효율적인 다짐관리를 위해서는 정적 다짐방식으로 다짐관리가 이루어져야 하며, 경량 성토재의 환경적 위해성 평가결과 pH는 지정폐기물 판정기준을 만족하는 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2010년도 춘계 학술논문 발표대회 1부
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• pp.25-27
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• 2010

Helical steel piles are being widely used in foundation for the buildings in urban areas because of their high compressive and tensile capacities. Helical steel piles have many advantages; ease installation, a vibration-free and low level of noise process, and so on. However, the most researches are about the capacity of helical steel piles under uplift condition. Therefore, this paper focuses on the capacity under compressive loading according to the soil condition. The bearing capacity of helical steel piles varies with the diameter of the helix and shaft and the bearing area of helical steel piles is not always identical with the sum of helix and shaft area due to the difference of each bearing mechanism. Therefore, the experiment with the parameters of the ratio of helix and shaft diameter and soil condition will be carried out to survey the effective helix area under a given soil condition for the bearing capacity of helical steel piles.

• Structural Engineering and Mechanics
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• 제3권2호
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• pp.107-120
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• 1995

A soil-structure interaction formulation is used here which is based on consideration of the dynamics of the structure with a free, rather than a fixed, base. This approach is shown to give a quite simple procedure for coupling the dynamic characteristics of the structure to those of the foundation and soil in order to obtain a matrix formulation for the complete system. In fixed-base studies it is common to presume that each natural mode of the structure has a given fraction of critical damping, and since the interaction formulation uses a free-base model, it seems natural for this situation to assign the equal modal damping values to free-base modes. It is shown, though, that this gives a structural model which is significantly different than the one having equal modal damping in the fixed-base modes. In particular, it is found that the damping matrix resulting in equal modal damping values for free-based modes will give a very significantly smaller damping value for the fundamental distortional mode of the fixed-base structure. Ignoring this fact could lead one to attribute dynamic effects to interaction which are actually due to the choice of damping.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.810-818
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• 2020

A moored floating structure may exhibit resonant motion responses to low-frequency excitations. Similar to the resonant responses of many vibration systems, the motion amplitude of a moored floating structure is significantly affected by the damping of the entire system. In such cases, the damping contributed by the mooring lines sometimes accounts for as much as 80% of the total damping. While the damping induced by catenary mooring lines is well-investigated, few studies have been conducted on the damping induced by taut mooring lines, especially one partly embedded in soil. The present study develops a simple but accurate model for estimating the damping contributed by mooring lines. A typical type of taut mooring line was used as the reference and the hydrodynamic drag force and soil resistance were taken into consideration. The proposed model was validated by comparing its predictions with those of a previously developed model and experimental measurements obtained by a physical model. Case studies and sensitivity studies were also conducted using the validated model. The damping induced by the soil resistance was found to be considerably smaller than the hydrodynamic damping. The superposition of the wave frequency motion on the low-frequency motion was also observed to significantly amplify the damping induced by the mooring lines.

• 한국토양비료학회지
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• 제46권6호
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• pp.610-614
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• 2013

Massive intercalation of urea into montmorillonite (MUCH) was recently proposed to enhance urea use efficiency through smart suppression of emission of $NH_3$ and NOx. This study was to synthesize citrate-incorporated MUCH (Cit-MUCH) which can enhance suppression of $NH_3$ volatilization. The XRD pattern of Cit-MUCH was very similar to that of MUCH to indicate successful incorporation of citric acid into MUCH. Incorporation of citric acid was confirmed by the existence of $COO^-$ symmetric stretching vibration. During the initial 4 days after application, $NH_3$ volatilization from both bare and perilla-planted soils was much more suppressed by application of Cit-MUCH than MUCH. A peak volatilization rate decreased from 28.3 N mg $m^{-2}\;h^{-1}$ of MUCH-broadcasted soil to 22.2 N mg $m^{-2}\;h^{-1}$ of Cit-MUCH-broadcast soil. $NH_3$ volatilization was less in planted soil than bare soil for 72 hrs after application. These results showed that incorporation of citric acid led to increase in suppression of ammonia volatilization from urea-applied soils.

• Geomechanics and Engineering
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• 제19권5호
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• pp.463-472
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• 2019

The mode perturbation method (MPM) is suitable and efficient for solving the eigenvalue problem of a nonuniform soil deposit whose property varies with depth. However, results of the MPM do not always converge to the exact solution, when the variation of soil deposit property is discontinuous. This discontinuity is typical because soil is usually made up of sedimentary layers of different geologic materials. Based on the energy integral of the variational principle, a new mode perturbation method, the energy-based mode perturbation method (EMPM), is proposed to address the convergence of the perturbation solution on the natural frequencies and the corresponding mode shapes and is able to find solution whether the soil properties are continuous or not. First, the variational principle is used to transform the variable coefficient differential equation into an equivalent energy integral equation. Then, the natural mode shapes of the uniform shear beam with same height and boundary conditions are used as Ritz function. The EMPM transforms the energy integral equation into a set of nonlinear algebraic equations which significantly simplifies the eigenvalue solution of the soil layer with variable properties. Finally, the accuracy and convergence of this new method are illustrated with two case study examples. Numerical results show that the EMPM is more accurate and convergent than the MPM. As for the mode shapes of the uniform shear beam included in the EMPM, the additional 8 modes of vibration are sufficient in engineering applications.

• 한국지반공학회지:지반
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• 제12권5호
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• pp.103-116
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• 1996

교통하중이나 건설 작업에 의해 야기되는 지반진동은 인접구조물에 손상을 입힐 수 있으므로 중요하게 관리되어야 한다. 최근 문헌에 의하면 도심지에서 구조물 손상의 주요 원인은 진동파의 직접 전달에 의한 손상보다 지반다짐으로 야기되는 부등침하에 의한 것으로 알려져 있다. 덕 논문에서는 지반진동에 의한 주변침하 예측기 법을 사례 연구를 충심으로 소개하였다. 실험실에서 개발된 침하예측모델의 현장적용기법을 설명하였으며, 사례연구에서 계측된 침하량과 모델에서 예측된 침하량을 비교하였다. 모델에서 예측한 침하량은 실제침하량과 비교적 잘 일치하였다. 전형적인 도심지 상황에서 영향요소 연구를 수행하여 침하예민요소들을 살펴보고 현장에서의 신뢰성있는 진동 계측 및 평가 방법을 제안하였다. 이상의 연구를 통해 사직토 지반에서 진동에 의한 침하평가 및 예측을 위해 개발된 모델의 사용 가능성을 입증하였다.

• 한국지반공학회논문집
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• 제36권11호
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• pp.157-165
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• 2020

현재 국내외에서는 진동기계기초에 진동으로 발생하는 추가 연직 동하중을 산정하고 설계함에 있어서 명확하게 제시된 기준이나 이론이 정립되어 있지 않아 국내의 경우, 심각한 진동조건이 아님에도 불구하고 진동에 의한 추가 동하중을 정적하중의 최대 100%로 간주하는 극히 보수적인 설계가 이루어지고 있다. 본 연구의 목적은 연직 기계진동으로 인하여 정하중외에 추가적으로 발생하는 동적하중의 정량적 크기를 평가하기 위한 모형실험 방안을 제시하는 것이다. 실내 모형실험의 기초실험으로, 제한된 크기의 모형 토조 내에서 발생할 수 있는 진동 반사파의 영향을 분석 및 보완하였고, 제작한 모형 진동기계기초의 고유진동수를 산정하여 실험 시 공진영향을 최소화하였다. 제안된 기법을 적용한 본 모형실험을 수행하여, 중간 조밀도의 모래 기초지반에 놓인 기계진동 얕은 기초에 기계진동에 의해 발생하는 추가적인 동하중의 정량적 크기를 평가해 보았다. 모형실험결과로부터, 현재 국내외에서 제시하고 있는 설계기법의 적합성을 논의해 보았다.

• 한국지반환경공학회 논문집
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• 제15권5호
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• pp.23-29
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• 2014

압력주입에 의한 그라우팅은 지반교란 및 인접지반에 미치는 영향이 적어 현재까지 광범위하게 활용되어 왔다. 반면 저압주입의 한계로 확산범위가 제한적이므로 그 단점을 보완하고자 최근 시멘트 입자에 주파수를 도입하여 주입효과를 개선한 진동주입공법이 개발되었다. 본 연구에서는 진동주입 방식에 의한 시멘트 그라우팅 공법의 주입효과를 기존의 압력주입방식과 비교하기 위하여 현장시험을 실시하였다. 점토코어 및 풍화토 지반으로 구성된 제방에서 진동주입 및 기존의 압력주입 방식으로 주입하고 그 효과를 비교하기 위하여 주입량, 표준관입시험, 현장투수시험과 전기비저항탐사를 실시하였다. 주입량을 비교한 결과 가진주입 시 일반주입 대비 약 15 % 주입량이 증가하여 확산 효과가 큰 것으로 분석되었다. 가진주입한 지반의 투수계수는 일반주입 대비 평균 50 %까지 감소하여 균질한 주입이 이루어짐이 확인되었다. 표준관입시험 결과 일반주입과 비교하여 가진주입 시 평균 17.4 %가량 N치가 증가하였고, 특히 풍화토층에서 개선효과는 일반주입 대비 19 %로 주입효과가 큰 것으로 나타났다. 전기비저항탐사를 이용하여 전체적인 주입효과를 판단한 결과 진동주입 구간의 경우 상대적으로 높은 비저항을 나타내어 균일하고 광범위하게 주입이 이루어진 것으로 나타났다. 이상의 주입효과 비교를 통하여 동일한 지반에서 압력주입을 진동주입으로 대체할 경우 주입공당 주입재의 양은 증가하지만, 주입재의 확산반경이 커짐에 따라 주입공의 천공간격이 감소함으로써 경제성 개선이 가능할 것으로 판단되었다.

• Steel and Composite Structures
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• 제49권1호
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• pp.81-89
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• 2023

A simplified calculation method of natural vibration characteristics of high-speed railway multi-span bridge-longitudinal ballastless track system is proposed. The rail, track slab, base slab, main beam, bearing, pier, cap and pile foundation are taken into account, and the multi-span longitudinal ballastless track-beam-bearing-pier-cap-pile foundation integrated model (MBTIM) is established. The energy equation of each component of the MBTIM based on Timoshenko beam theory is constructed. Using the improved Fourier series, and the Rayleigh-Ritz method and Hamilton principle are combined to obtain the extremum of the total energy function. The simplified calculation formula of the natural vibration frequency of the MBTIM under the influence of vertical and longitudinal vibration is derived and verified by numerical methods. The influence law of the natural vibration frequency of the MBTIM is analyzed considering and not considering the participation of each component of the MBTIM, the damage of the track interlayer component and the stiffness change of each layer component. The results show that the error between the calculation results of the formula and the numerical method in this paper is less than 3%, which verifies the correctness of the method in this paper. The high-order frequency of the MBTIM is significantly affected considering the track, bridge pier, pile soil and pile cap, while considering the influence of pile cap on the low-order and high-order frequency of the MBTIM is large. The influence of component damage such as void beneath slab, mortar debonding and fastener failure on each order frequency of the MBTIM is basically the same, and the influence of component damage less than 10m on the first fourteen order frequency of the MBTIM is small. The bending stiffness of track slab and rail has no obvious influence on the natural frequency of the MBTIM, and the bending stiffness of main beam has influence on the natural frequency of the MBTIM. The bending stiffness of pier and base slab only has obvious influence on the high-order frequency of the MBTIM. The natural vibration characteristics of the MBTIM play an important guiding role in the safety analysis of high-speed train running, the damage detection of track-bridge structure and the seismic design of railway bridge.