• 한국해양공학회지
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• 제11권1호
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• pp.65-73
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• 1997

본 연구는 부유식 파랑제어구조물의 계류방식을 말뚝계류식으로 하여 종래의 부유식 파랑제어구조물의 파랑제어기능을 보완하고, 친수성 구조물로 이용할 수 있는 다용도 구조물의 개발을 목표로 하고 있다. 본 연구에서는 부유체의 계류장치에 초기반력을 작용시킴으로써 발생하는 파랑제어 효과의 개선과 부유체의 동요제어 효과를 수치계산법을 통하여 논의하였다. 이 때 계류부에서 발생하는 비선형 마찰력을 선형모델화하는 이론을 전개한 다음 수치계산 및 실험값을 통하여 본 수치모델의 적용성에 관하여 논의한 결과 양호한 일치성을 보였다. 또한, 파랑제어 효과 및 부유체의 동요저감 효과를 동시에 만족할 수 있는 초기반력에 관하여 논의하였다.

• 한국터널지하공간학회 논문집
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• 제19권3호
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• pp.355-373
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• 2017

도심지에서의 터널굴착은 상부구조물과의 상호거동에 대한 이해가 필수적이다. 도심지에 사용중인 대부분의 구조물은 말뚝기초로 상부의 하중을 지지하고 있어, 터널 굴착 시 반드시 영향을 받는다. 따라서 본 연구에서는 실내모형시험을 통해 기존의 군말뚝 기초 하부 터널굴착에 따른 축력 분포와 지반의 거동을 분석하였다. 말뚝 기초는 2, 3 열 말뚝으로 가정되었으며, 말뚝 선단부와 터널 천단부의 이격거리는 터널직경에 대한 일반화를 위해 터널 직경(D) 대비 0.5D, 1.0D 그리고 1.5D로 고려되었다. 지반은 약 30%의 상대밀도(Dr)를 가지는 느슨한 사질토로 형성되었으며, 말뚝의 축력 분포를 측정하기 위해 말뚝에 변형률게이지(strain gauge)를 부착하였다. 또한, 이격거리에 따른 군말뚝의 침하와 인접지반의 침하를 변위센서(linear variable differential transformer; LVDT)와 다이얼게이지(dial gauge)를 통해 측정였으며, 터널굴착에 따른 지중의 변형을 근거리사진계측기법(close range photogrammetric technique)을 통해 측정하였다. 수치 해석을 통해 실내모형시험 및 근거리사진계측 결과와 비교 분석하였다. 본 연구에서는 체적손실율(volume loss; $V_L$) 개념을 이용하여 터널굴착을 모사하였으며, 1.5%로 적용되었다. 연구결과, 이격거리가 멀어질수록 말뚝의 축력감소는 작게 나타났으며, 침하량은 모두 유사한 경향을 나타내었다. 특히, 말뚝 선단부와 터널 천단부의 이격거리가 0.5D에서 1.0D로 증가할 때 축력과 침하량의 가장 큰 감소율이 가장 큰 것으로 나타났다.

• Wind and Structures
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• 제21권6호
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• pp.625-639
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• 2015

Monopiles have been most widely used for supporting offshore wind turbines (OWTs) in shallow water areas. However, multi-member lattice-type structures such as jackets and tripods are also considered good alternatives to monopile foundations for relatively deep water areas with depth ranging from 25-50 m owing to their technical and economic feasibility. Moreover, jacket structures have been popular in the oil and gas industry for a long time. However, several unsolved technical issues still persist in the utilization of multi-member lattice-type supporting structures for OWTs; these problems include pile-soil-interaction (PSI) effects, realization of dynamically stable designs to avoid resonances, and quick and safe installation in remote areas. In this study, the effects of PSI on the dynamic properties of bottom-fixed OWTs, including monopile-, tripod- and jacket-supported OWTs, were investigated intensively. The tower and substructure were modeled using conventional beam elements with added mass, and pile foundations were modeled with beam and nonlinear spring elements. The effects of PSI on the dynamic properties of the structure were evaluated using Monte Carlo simulation considering the load amplitude, scouring depth, and the uncertainties in soil properties.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.698-705
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• 2004

Application of structural load on soft ground can cause lateral movement as well as ground break due to pressing and shearing of ground. Especially, abutment supported by pile foundation can make pile deformed due to lateral movement of ground in order to have harmful effect on structure. According to the result of this study, it is required to consider disturbance of weak soil layer when using lateral movement countermeasure method by EPS construction method as a result of performing study on safety review and EPS construction method with respect to this based on site where lateral movement occurs due to backside soil filling load at bridge abutment installed on weak ground, and it is required to sufficiently consider soil reduction during design of EPS construction method due to lateral movement deformation of soft clay layer by losing ground horizontal resistance force due to plasticity of ground around pile as well as combination part damage with pile head and expansion foundation.

• 한국지진공학회논문집
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• 제28권1호
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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.

• Wind and Structures
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• 제29권2호
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• pp.99-110
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• 2019

This paper provides a simple numerical method to determine the optimal parameters of tuned mass damper (TMD) and viscoelastic dampers (VEDs) in frame structure for wind vibration control considering the soil-structure interation (SSI) effect in frequency domain. Firstly, the numerical model of frame structure equipped with TMD and VEDs considering SSI effect is established in frequency domain. Then, the genetic algorithm (GA) is applied to obtain the optimal parameters of VEDs and TMD. The optimization process is demonstrated by a 20-storey frame structure supported by pile group for different soil conditions. Two wind resistant systems are considered in the analysis, the Structure-TMD system and the Structure-TMD-VEDs system. The example proves that this method can quickly determine the optimal parameters of energy dissipation devices compared with the traditional finite element method, thus is practically valuable.

• 산업기술연구
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• 제27권B호
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• pp.209-214
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• 2007

This paper is the research result about centrifuge model experiments of investigating the behavior of bridge abutment on the sloped ground. Ground condition of the studied site was the bridge abutment with pile foundation adjacent to the slope. The pile foundations was supported on the soft rocks covered with the embankment. Evaluating the behavior of such a complicate ground and structure conditions was not easy so that the centrifuge modelling was performed to find the overall behavior of them. Layout of centrifuge model experiment was simplified to simulate easily the actual behavior of very complicate site condition. Construction process in field such as ground excavation for footing foundation, installation of piles, placement of footing and bridge abutment, backfilling and surcharge loading eas duplicated in the centrifuge model experiment. Consequently, the stability of the piled bridge abutment adjacent to the slope of embankment was evaluated throughout centrifuge modelling.

• 한국지반공학회논문집
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• 제32권8호
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• pp.35-46
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• 2016

본 연구에서는 지반조건에 따른 실제 piled raft 기초의 거동을 실규모 시험을 통해 분석하기가 어려운 점을 감안하여 수치해석을 이용한 민감도분석을 수행하고자 하였다. 수치해석에 사용한 프로그램은 유한차분법 기반의 FLAC 3D이다. 말뚝의 수치해석 모델링은 FLAC의 구조요소 중 하나인 말뚝요소를 사용하여 모델링하였고, 지반과 래프트는 연속체 요소를 이용하여 모사하였다. 말뚝의 배열은 $3{\times}3$으로 고정하고 말뚝직경, 말뚝길이, 말뚝간격 그리고 지반조건을 민감도 매개변수로 선정하고 상관관계를 규명하였다. 그 결과, 말뚝직경이 크고 말뚝의 길이가 길수록, 그리고 말뚝의 간격이 넓을수록 piled raft 기초의 전체 지지력은 증가하는 것으로 나타났다. 그러나 지반조건에 따라 말뚝간격이 일정 간격 이상이 될 경우, piled raft 기초의 거동이 래프트만으로 지지되는 얕은기초와 유사한 거동을 보였다. 또한 지반조건이 좋아질수록, piled raft 기초의 전체 지지력은 증가함을 확인할 수 있었다.

• Structural Engineering and Mechanics
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• 제43권5호
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• pp.637-655
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• 2012

In this study, stochastic responses of a cable-stayed bridge subjected to the spatially varying earthquake ground motion are investigated by the finite element method taking into account soil-structure interaction (SSI) effects. The considered bridge in the analysis is Quincy Bay-view Bridge built on the Mississippi River in between 1983-1987 in Illinois, USA. The bridge is composed of two H-shaped concrete towers, double plane fan type cables and a composite concrete-steel girder deck. In order to determine the stochastic response of the bridge, a two-dimensional lumped masses model is considered. Incoherence, wave-passage and site response effects are taken into account for the spatially varying earthquake ground motion. Depending on variation in the earthquake motion, the response values of the cable-stayed bridge supported on firm, medium and soft foundation soil are obtained, separately. The effects of SSI on the stochastic response of the cable-stayed bridge are also investigated including foundation as a rigidly capped vertical pile groups. In this approach, piles closely grouped together beneath the towers are viewed as a single equivalent upright beam. The soil-pile interaction is linearly idealized as an upright beam on Winkler foundation model which is commonly used to study the response of single piles. A sufficient number of springs on the beam should be used along the length of the piles. The springs near the surface are usually the most important to characterize the response of the piles surrounded by the soil; thus a closer spacing may be used in that region. However, in generally springs are evenly spaced at about half the diameter of the pile. The results of the stochastic analysis with and without the SSI are compared each other while the bridge is under the sway of the spatially varying earthquake ground motion. Specifically, in case of rigid towers and soft soil condition, it is pointed out that the SSI should be significantly taken into account for the design of such bridges.

• Geomechanics and Engineering
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• 제29권2호
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• pp.155-170
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• 2022

An accurate analysis of structures supported on soft soils and subjected to seismic loading requires the consideration of the soil-foundation-structure interaction. An important aspect of this interaction lies with the energy dissipation due to soil material damping. Unlike advanced constitutive models that can induce energy loss, the use of simple elastoplastic constitutive models requires additional damping. The frequency dependent Rayleigh damping is a formulation that is frequently used in dynamic analysis. The main concern of this formulation is the correct selection of the target damping ratio and the frequency range where the response is frequency independent. The objective of this study is to investigate the effects of the Rayleigh damping parameters in soil-pile-structure and soil-inclusion-platform-structure systems in the presence of soft soil under seismic loading. Three-dimensional analyses of both systems are carried out using the finite difference software Flac3D. Different values of target damping ratios and minimum frequencies are utilized. Several earthquakes are used to study the influence of different excitation frequencies in the systems. The soil response in terms of accelerations, displacements and strains is obtained. For the rigid elements, the results are presented in terms of bending moments and normal forces. The results show that when the frequency of the input motion is close to the minimum (central) frequency in the Rayleigh damping formulation, the overdamping amount is reduced, and the surface spectral acceleration of the analyzed pile and inclusion systems increases. Thus, the bending moments and normal forces throughout the piles and inclusions also increase.