• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2006년도 학술발표회 논문집
• /
• pp.300-307
• /
• 2006

Integral pile shaft-column foundations are increasingly popular thanks to not only the comparative advantage of economy in constructing large cast-in-drilled-hole(CIDH) piles compared with driven piles with pile cap footings but also being free from problems associated with the critical column-footing connection. In this paper, the structural characteristics of integral pile shaft-column foundations as well as seismic analysis methodology and reinforcement details for seismic design are introduced.

• Structural Engineering and Mechanics
• /
• 제58권6호
• /
• pp.1045-1075
• /
• 2016

Shallow footings are one of the most common types of foundations used to support mid-rise buildings in high risk seismic zones. Recent findings have revealed that the dynamic interaction between the soil, foundation, and the superstructure can influence the seismic response of the building during earthquakes. Accordingly, the properties of a foundation can alter the dynamic characteristics (natural frequency and damping) of the soil-foundation-structure system. In this paper the influence that shallow foundations have on the seismic response of a mid-rise moment resisting building is investigated. For this purpose, a fifteen storey moment resisting frame sitting on shallow footings with different sizes was simulated numerically using ABAQUS software. By adopting a direct calculation method, the numerical model can perform a fully nonlinear time history dynamic analysis to realistically simulate the dynamic behaviour of soil, foundation, and structure under seismic excitations. This three-dimensional numerical model accounts for the nonlinear behaviour of the soil medium and structural elements. Infinite boundary conditions were assigned to the numerical model to simulate free field boundaries, and appropriate contact elements capable of modelling sliding and separation between the foundation and soil elements are also considered. The influence of foundation size on the natural frequency of the system and structural response spectrum was also studied. The numerical results for cases of soil-foundation-structure systems with different sized foundations and fixed base conditions (excluding soil-foundation-structure interaction) in terms of lateral deformations, inter-storey drifts, rocking, and shear force distribution of the structure were then compared. Due to natural period lengthening, there was a significant reduction in the base shears when the size of the foundation was reduced. It was concluded that the size of a shallow foundation influences the dynamic characteristics and the seismic response of the building due to interaction between the soil, foundation, and structure, and therefore design engineer should carefully consider these parameters in order to ensure a safe and cost effective seismic design.

• 한국지반공학회논문집
• /
• 제20권8호
• /
• pp.5-14
• /
• 2004

얕은기초의 설계에 있어 작용하중에 의한 침하량 산정은 기초의 지지력 산정과 함께 매우 중요한 고려사항이다. 상부구조물에 의한 설계하중이 지표면의 기초지반에 직접 작용하는 얕은기초의 경우, 기초지반의 거동은 일반적으로 완전 선형탕성도 아니며, 파괴에 도달한 소성상태도 아닌 비선형 응력-변형률의 거동을 보이게 된다. 이러한 지반의 비선형성은 침하량 산정에 있어 매우 중요한 요소로 간주될 수 있으나, 실제 설계에 있어서는 대표탄성계수의 적용에 의한 간편법이 보편적으로 적용되고 있다. 일반적으로 사질토지반에 놓인 얕은기초 침하량 산정은 표준관입시험(SPT)나 콘관입시헙(CPT) 등의 현장시험 결과를 토대로 이루어진다. 본 연구에서는 비선형 유한요소해석에 의한 얕은기초 하중-침하량 분석을 수행하였으며, 기존의 탄성론에 근거한 침하량 산정법과의 비교분석 또한 수행하였다. 이와 같은 해석을 통하여 콘관입시헙(CPT) 결과에 근거한 새로운 얕은기초 침하량 산정법 및 얕은기초 설계법을 제안하였다.

• 한국지반공학회지:지반
• /
• 제13권1호
• /
• pp.75-84
• /
• 1997

본 고에서는 지하공동위에 위치한 확대기초의 지지력 산정기법을 제시하였다. 지지력 산정기법의 개발을 위해서 필자에의해 개발된 3차원 탄소성 유한요소해석 프로그램을 이용하여 지하공동위에 위치한 확대기초의 지지력에 대한 매개변수 변환연구를 수행하였다. 매개변수 변환연구의 결과를 이용하여 각 경계조건의 지지력을 평가하고 이를 지지력 산정기법 개발에 필요한 데 이터 베이스로 활용하였으며, 수집된 데이터 베이스에 대한 다중회귀분석을 통해 반 경험적 지지력 산정기법을 개발하였다. 개발된 지지력 산정기법은 기존의 모형기초실험 및 유한요소해석 결과와의 비교를 통해 그 타당성이 검증되었으며, 그 결과 본 연구의 범위내에 해당하는 실제 현장문제에 효율적으로 적용될 수 있을 것으로 사료된다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2002년도 기초기술위원회 워크샵
• /
• pp.102-117
• /
• 2002

The general design practice for piled footings is based on the assumption that the piles are free-standing, and that all the external loads are carried by the piles, with any contribution of the footing being ignored. This approach is not reasonable, because the footing itself is actually in direct contact with the soil, and thus carries a significant fraction of the loads. In the case of not considering the bearing capacity of footing, the bearing capacity of group piles can be evaluated conservatively in the designing the group piles. There are a number of reasons why the idea of piled raft design with considering the capacity of footing has not become widely used. One of the reasons is the lack of reliable calculation methods for estimating the behavior of piled raft. In this study the bearing capacity, settlement, load distribution, etc. of piled raft footing are studied.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2003년도 봄 학술발표회 논문집
• /
• pp.455-462
• /
• 2003

The current practice of estimating bearing capacity usually employs the conventional bearing capacity formula originally developed for strip footings under vertical central loading, In order account for the effect of footing shape and eccentricity and inclination of loads, correction factors are introduced in the formula, which are derived based on a number of small-scale model test observations. In this paper, comparison of several formulations of bearing capacity factors, as well as values of these factors, are presented. And the conventional bearing capacity equations are compared with some of other failure loci proposed for cohesive soil. Also, the bearing capacity of shallow foundation estimated by the conventional bearing capacity equations are compared with the experimental load test results.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
• /
• pp.333-336
• /
• 1999

The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as mat-slab of nuclear reactor buildings, dams or large footings, foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, pre-cooling which lowers the initial temperature of fresh concrete with ice flake, pipe cooling which cools the temperature of concrete with flowing water, design change which considers steel bar reinforcement, operation control and so on. The Aim of this paper is to verify the effect of low heat blended cement in reducing thermal stress in slab type's mass concrete such as container harbor structures.

• Geomechanics and Engineering
• /
• 제15권2호
• /
• pp.739-744
• /
• 2018

This paper presents the results of numerical modeling studies on the effect of displacements of tunneling in granular soils. Presence of building loads is considered, to find displacement generated at the surface on tunnel. Effect of varying eccentricities of building is simulated, to find influence of building on vertical and horizontal displacement. Studies were carried out in two cases of with and without a geosynthetic layer installed at the bottom of the footing. Results of analysis revealed, the presence of geosynthetic layer under footing, with building placed on centre line, reduced the surface displacements compared to displacement generated without geosynthetic layer. Presence of geosynthetic layer under footing had a dominant effect in reducing displacements in high storey structures. However, when the building was shifted to greater eccentricities from centre line, presence of geosynthetic layer, led to insignificant reduction of displacements on the centre line at the surface.

• 한국안전학회지
• /
• 제10권4호
• /
• pp.3-8
• /
• 1995

Anchors find their use in providing tie-back resistance for submerged footings, transmission towers, tunnels and ocean structures. Laboratory model teats were performed for the short-term net ultimate uplift capacity of a circular anchors with respect to various embedment depths and moisture content in saturated bentonite. The tests have been conducted with the anchor at two different moisture contents. Based an the model test results, empirical relationships between the net load, rate of strain, and time have been developed. Test results are as follows. 1) In creep tests for load versus ultimate uplift capacity, the displacement of plate anchors rapidly increases during the primary stage but thereafter becomes constant over a period of time. 2) Displacement increased with the increase of the sustain load and embedded ratio in soil. 3) If the load is less than or equal to 75% of the short-term ultimate uplift capacity, a complete pullout does not occur due to creep.

• 대한토목학회논문집
• /
• 제11권3호
• /
• pp.47-58
• /
• 1991

본 논문에서는 무한요소를 이용한 지반-구조물 상호작용 해석에 대하여 연구하였다. 적층지반(Layered Soil)과 같이 여러 가지 응력파가 동시에 전파되는 탄성지반의 외부영역을 효과적으로 모형화할 수 있는 동적무한요소를 개발하였으며, 요소행렬 구성시 수반되는 무한대 방향으로의 적분을 효과적으로 수행하기 위하여 Gauss-Laguerre 적분방법을 기초로 하여 새로이 고안된 적분방법을 제시하였다. 이 방법의 타당성은 반무한 탄성지반과 적층된 반무한 탄성지반 위에 놓여 있는 원형강판의 임피던스(Impedance) 함수를 구하여 해석적으로 구한 값들과 비교함으로써 검토하였다.