• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.713-716
• /
• 1999

The presence of voids under pavements or behind tunnel linings results in the deterioration. One method of detecting such voids by non-destructive means is radar. This research is devoted to quantitatively evaluating the efficiency of such non-destructive tests with radar. As a foundation to this ongoing research, which aims to estimate the thickness of voids using radar, an analysis method based on radar signal processing using convolution technique is carried out with various void thicknesses in embedded layer which has different electromagnetic properties. The computed results were verified by comparing the test results. As a result, a proposed method in this study has a possibilty of estimating the thickness of voids with good accuracy.

• Structural Engineering and Mechanics
• /
• v.44 no.5
• /
• pp.571-584
• /
• 2012

Appropriate assessment of lateral capacity of pile foundation is known to be a complex problem involving soil-structure interaction. Having reviewed the available methods in brief, relative paucity of simple and rational technique to evaluate lateral capacity of pile in layered soil is identified. In this context, two efficient approaches for the assessment of lateral capacity of short pile embedded in bi-layer cohesive deposit is developed. It is presumed that the allowable lateral capacity of short pile is generally dictated by the permissible lateral displacement within which pile-soil system may be assumed to be elastic. The applicability of the scheme, depicted through illustration, is believed to be of ample help at least for practical purpose.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.687-696
• /
• 2005

Safety diagnosis was conducted to evaluate the long-term stability evaluation of power transmission tower of which deformation of the upper structural elements occurred. To assess the cause of the structural deformation, field investigation including BIPS, down-hole test, concrete pile coring and finite element analysis were carried out. From these studies, the major cause of deformation was found due to the heavily fractured layer and weathered soil topography at the pile tip area. The cement-milk grouting method was proposed to reinforce these weak zone around the pile tip area. Also, the increase of cross-section and stiffness for steel members of upper tower structures was suggested. Instrumental monitoring was proposed as well to verify reinforcing effect.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.5 no.2
• /
• pp.23-31
• /
• 2001

지반 위에 세워진 구조물의 지진응답해석시 지반-구조물 상호작용 영향은 지반으 선형특성을 고려하여 간주되었는데 최근 연구결과에 의하면 구조물 지진해석에서 연약지반의 비선형 특성이 중요한 요소로서 인식되었다. 하지만 지반-구조물계의 복잡한 비선형 특성 때문에 내진설계 기준에서 비선형 지반특성을 고려하기에는 아직도 어려움이 많다. 이 논문에서는 UBC 지반종류 $S_{D}$ 지반 위에 놓인 중규모의 얕은 온통기초와 묻힌 온통기초위에 세워진 건물에 대한 단자유도계 선형 지진해석을 연약지반의 비선형성을 고려하여 최대가속도가 0.17g 과 0.36g 인 Taft E-W 및 El Centro N-S 지진기록을 사용하여 수행하였다. 비선형 지진해석을 결과를 선형해석 결과와 비교하였을 때, 비선형 응답스펙트럼의 최대가속도가 지반의 비선형성 때문에 상당히 줄어드는 것으로 나타나 지반의 비선형성을 고려한 더효율적인 내진설계의 가능성을 보여준다.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.4
• /
• pp.721-726
• /
• 2017

We fabricated stretchable thin-film transistors(TFTs) on a polydimethylsiloxane substrate with patterned polyimide island structures by using an amorphous InGaZnO semiconductor and parylene gate insulator. The TFTs exhibited a field- effect mobility of $5cm^2V^{-1}s^{-1}$ and a current on/off ratio of $10^5$ at a relatively low operating voltage. Furthermore, the fabricated transistors showed no noticeable changes in their electrical performance for large strains of up to 50 %.

• Wind and Structures
• /
• v.24 no.1
• /
• pp.43-57
• /
• 2017

The use of nanotechnology materials and applications in the construction industry should be considered for enhancing material properties. However, the nonlinear buckling of an embedded straight concrete columns reinforced with silicon dioxide ($SiO_2$) nanoparticles is investigated in the present study. The column is simulated mathematically with Euler-Bernoulli and Timoshenko beam models. Agglomeration effects and the characteristics of the equivalent composite are determined using Mori-Tanaka approach. The foundation around the column is simulated with spring and shear layer. The governing equations are derived using energy method and Hamilton's principal. Differential quadrature method (DQM) is used in order to obtain the buckling load of structure. The influences of volume percent of $SiO_2$ nanoparticles, geometrical parameters and agglomeration on the buckling of column are investigated. Numerical results indicate that considering agglomeration effects leads to decrease in buckling load of structure.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.05a
• /
• pp.216-217
• /
• 2017

Slag cement or ternary blended cement is mainly used for non-structural lean concrete for the purpose of foundation work or protection of the waterproof layer on the roof of buildings. However, such non-structural lean concrete has a lot of drying shrinkage cracks, which makes it difficult to maintain the quality of the structure. Therefore, in this study, the compressive strength and the drying shrinkage of ternary blended cement(blended of portland cement, blast furnace slag, fly ash from combined heat and power Plant) for non-structural lean concrete were examined. As a result, it was confirmed that this non-structural lean concrete reduced drying shrinkage compared to the conventional ternary blended cement using fly ash from power plant.

• Journal of the Korea Society for Simulation
• /
• v.8 no.2
• /
• pp.111-122
• /
• 1999

The paper presents a stability analysis of uniform Timoshenko beams resting on two-parameter elastic foundations. The two-parameter elastic foundations were considered as a shearing layer and Winkler springs in soil models. Governing equations of motion were derived using the Hamilton's principle and finite element analysis was performed and the eigenvalues were obtained for the stability analysis. The numerical results for the buckling stability of beams under axial forces are demonstrated and compared with the exact or available confirmed solutions. Finally, several examples were given for Euler-Bernoulli and Timoshenko beams with various boundary conditions.

• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.1519-1524
• /
• 2009

Construction of high-speed concrete track embankments over soft ground needs many of the ground improvement techniques. Drains, surcharge loading, and geosynthetic reinforcement, have all been used to solve the settlement and embankment stability issues associated with construction on soft soils. However, when time constraints are critical to the success of the project, another measures should be considered. Especially, since the design criteria of residual settlement is limited as 30mm for concrete track embankment, it is very difficult to satisfy this allowable settlement by using the former construction method. Pile net method consist of vertical columns that are designed to transfer the load of the embankment through the soft compressible soil layer to a firm foundation and one or more layers of geosynthetic reinforcement placed between the top of the columns and the bottom of the embankment. In this paper, three cases with different embankment height and number of geosynthetic reinforcement, were studied through FEM analysis for efficient use of pile net method.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.467-474
• /
• 2002

Colluvial sell has a very unique deformation property, particularly when it is subject to the cutting work entailed in a variety of construction. In this study, the cut slope tying on a colluvial layer in which the transmission tower had been installed were investigated to find out the cause of deformation. In-situ tests such as boring, surface-wave analysis (MASW) were employed to look into the physical composition of underground layers and FEM including LEM were carried out to simulate the construction steps. The result shows that the stress relaxation followed by road construction induced the deformation of the slope and damage in the foundation of the transmission tower.