• Journal of the Society of Disaster Information
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• v.13 no.2
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• pp.130-138
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• 2017

The connector of the complex behavior is to connect the individual piles of the pile to the lower foundation of the oil sand plant where the floating foundation is used. In this study, to verify the shape of a connector of the complex behavior for applying the advantages of existing group pile and piled raft foundation to an oil sand plant, a scaled model was constructed to measure the behavior of the load.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.3
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• pp.155-164
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• 2019

In this study, the soil-structure interaction(SSI) effect on the seismic response of LNG storage tanks was investigated according to the type of foundation. For this purpose, a typical of LNG storage tank with a diameter of 71m, which is constructed on a 30m thick clay layer over bedrock was selected, and nonlinearity of the soil was taken into account by the equivalent linearization method. Four different types of foundations including shallow foundation, piled raft foundation, and pile foundations(surface and floating types) were considered. In addition, the effect of soil compaction in group piles on seismic response of the tank was investigated. The KIESSI-3D, which is a SSI analysis package in the frequency domain, was used for the SSI analysis. Stresses in the outer tank, and base shear and overturning moment in the inner tank were calculated. From the comparisons, the following conclusions could be made: (1) Conventional fixed base seismic responses of outer tank and inner tank can be much larger than those of considering the SSI effect; (2) The influence of SSI on the dynamic response of the inner tank and the outer tank depends on the foundation types; and (3) Change in the seismic response of the structure by soil compaction in the piled raft foundation is about 10% and its effect is not negligible in the seismic design of the structure.

• Journal of the Korean Geotechnical Society
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• v.26 no.12
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• pp.31-40
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• 2010

This study describes the three-dimensional behavior of pile foundations based on a numerical study. A series of numerical analyses were performed for connectivity conditions between piles and cap under vertical and lateral loadings. It is shown that a fixed connection between pile and cap is able to transfer significant bending moment through the connection and increases the pile lateral stiffness and the bending moment. Based on the results obtained, it was found that the cross sectional shear force in the raft with fixed head condition was larger than that of pinned head condition. Thus, the reinforcement of pile head and thickness of the raft also increases in fixed pile head condition. From the results, it is found that the overall behavior and cross sectional forces of pile foundations is affected significantly by the pile head conditions. Furthermore, the design of pile foundations with pinned head condition was judged to be less costly and very useful for preliminary design stages.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.25-34
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• 2008

An application of concrete track is being actively processed for the construction of Korean high speed railway. The concrete track has an advantage in decreasing the maintenance cost, whereas it has much difficulty controlling the long term settlement after settlement occurred. Therefore, the management and control of settlement are very important for the successful construction of concrete track. The purpose of this paper is to verify the allowable settlement between concrete track and ballast track, and piled raft foundation installation effects as settlement reducers for concrete track. Therefore, a series of 3D finite element analyses that take into account the allowable settlement were performed for major parameters such as soil condition, pile installation and loading type. Based on the analysis, it is shown that concrete track causes much smaller settlement than ballast track, and the effect of installation is necessary to effectively reduce the settlement of concrete track.

• The Journal of Engineering Geology
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• v.29 no.4
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• pp.451-460
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• 2019

In this study, a complex behavior connector is proposed to overcome the problems that may occur when small pile pipe and micro pile is used as a friction pile concept in the lower foundation of an oil sand plant where a piloti foundation is used. The individual settlement and heaving of piles were connected in one group to allow the composite behavior. This study performed to analyze the load carrying capacity to identify a complex behavior. In addition, the shape of the composite behavior connector was examined to apply the advantages of pile-group and piled raft foundations to oil sand plants. A scale model was constructed to measure the behavior of the load. The stability and weakness of the device were selected to determine the shape of the connector using the scale model testing.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.367-374
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• 2019

We investigate the effect of soil-structure interaction (SSI) on the response of LNG storage tanks to vertical seismic excitation depending on the type of foundation. An LNG storage tank with a diameter of 71 m on a clay layer with a thickness of 30 m upon bedrock, was selected as an example. The nonlinear behavior of the soil was considered in an equivalent linear method. Four types of foundation were considered, including shallow, piled raft, and pile foundations (surface and floating types). In addition, the effect of soil compaction within the group pile on the seismic response of the tank was investigated. KIESSI-3D, an analysis package in the frequency domain, was used to study the SSI and the stress in the outer tank was calculated. Based on an analysis of the numerical results, we arrived at three main conclusions: (1) for a shallow foundation, the vertical stress in the outer tank is less than the fixed base response due to the SSI effect; (2) for foundations supported by piles, the vertical stress can be greater than the fixed base stress due to the increase in the vertical impedance due to the piles and the decrease in radiation damping; and (3) soil compaction had a miniscule impact on the seismic response of the outer tank.

• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.41-53
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• 2024

Micropiles are small, cast-in-place piles with a diameter of 300 mm or less, primarily used to reinforce existing structures and support new constructions. As the application of these piles has expanded, extensive research has been conducted on their bearing characteristics, particularly in micropiled rafts. These studies have consistently demonstrated the positive impact of micropiles on foundation reinforcement. However, previous research often overlooked the potential variations in behavior between micropiled and conventional piled rafts based on different pile conditions. Furthermore, the influence of the cohesive characteristics of the soil layer beneath the foundation on the reinforcing effect of the micropiles has not been adequately addressed. This study, therefore, undertook 3D numerical analysis to assess the reinforcing effect of micropiles, considering both pile conditions and the cohesive characteristics of the soil layer beneath the foundation. The findings revealed that micropiles are significantly more effective in non-cohesive soil layers compared to cohesive ones, with the potential to increase the bearing capacity of the raft by up to 3.7 times.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.1
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• pp.21-32
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• 2024

This study performed the seismic response analysis of an LNG storage tank supported by a disconnected piled raft foundation (DPRF) with a load transfer platform (LTP). For this purpose, a precise analytical model with simultaneous consideration of Fluid-Structure Interaction (FSI) and Soil-Structure Interaction (SSI) was used. The effect of the LTP characteristics (thickness, stiffness) of the DPRF system on the seismic response of the superstructure (inner and outer tanks) and piles was analyzed. The analytical results were compared with the response of the piled raft foundation (PRF) system. The following conclusions can be drawn from the numerical results: (1) The DPRF system has a smaller bending moment and axial force at the head of the pile than the PRF system, even if the thickness and stiffness of the LTP change; (2) The DPRF system has a slight stiffness of the LTP and the superstructure member force can increase with increasing thickness. This is because as the stiffness of the LTP decreases and the thickness increases, the natural frequency of the LTP becomes closer to the natural frequency of the superstructure, which may affect the response of the superstructure. Therefore, when applying the DPRF system, it is recommended that the sensitivity analysis of the seismic response to the thickness and stiffness of the LTP must be performed.

• Journal of the Korean Geotechnical Society
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• v.35 no.1
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• pp.17-30
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• 2019

This study presents the application of the numerical and analytical technique to simulate the Load Distribution Ratio (LDR) and to define axial stiffness on reinforcing pile foundation ($K_{vr}$) in vertical extension remodeling structure. The main objective of this study was to investigate the LDR between existing piles and reinforcing piles. Therefore, to analyze the LDR, 3D FEM analysis was performed as variable for elastic modulus, pile end-bearing condition, raft contacts, and relative position of reinforcing pile in a group. Also, using the axial stiffness ($K_{ve}$) of existing piles, the axial stiffness of reinforcing pile was defined by 3D approximate computer-based method, YSPR (Yonsei Piled Raft). In addition $K_{vr}$ was defined by reducing the $K_{ve}$considering the degradation of the existing piles.

• Journal of the Korean Geotechnical Society
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• v.36 no.8
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• pp.61-72
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• 2020

It is generally considered that differences of axial stiffness between exiting pile and reinforcing pile affect the load distribution ratio during vertical extension remodeling. But there are few cases to verify the effect of stiffness by field load test on load distribution ratio in Korea. In this paper, a series of load tests for micropiles were carried out to evaluate the effect of axial stiffness on the load distribution ratio. First, different types of micropiles were constructed so that conventional micropiles simulated existing piles and waveform micropiles simulated reinforcing piles. Secondly, load tests were performed to evaluate the stiffness of each piles. After then, the raft was installed to make a piled raft system and load tests were applied on foundation to verify the effect of axial stiffness on the load distribution ratio. The experimental results show that the stiffness of waveform micropiles were 2.5 times larger than that of conventional micropiles, and the load distribution ratio between existing and reinforcing piles was increased according to axial stiffness of piles.