• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 가을 학술발표회 논문집
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• pp.350-357
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• 2002

The scale effect should be considered to determine the bearing capacity and settlement of footings from Plate-Load Test, because of the size difference between a footing and a loading plate. To analyze characteristics of bearing capacity and settlement according to the difference of loading plate sizes, model tests were peformed with four different sizes of square plate, which is B=10, 15, 20 and 25cm respectively, on five different kinds of subsoil, which is pure sand(100:0), sand-clay mixed soil(75:25, 50:50, 25:75), and pure clay(0:100). Based on the analyzed results, this paper also proposed a method of bearing capacity and settlement determination, where scale effect is considered depending on the mixing ratio of sand and clay. Applying the formular proposed in this research to field problems, it is expected that evaluation of bearing capacity and settlement of footings can be more reliable and more economic construction can be achieved.

• Computers and Concrete
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• 제27권1호
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• pp.41-54
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• 2021

This paper introduced three new strengthening systems for isolated footings: BFRP wrapping system, CFRP wrapping system, and steel jacketing system. The proposed systems are more practical than the current traditional methods, which involves installing many dowel bars and splicing reinforcing steels to join new and old concrete segments. In the proposed three new systems, BFRP wraps, CFRP wraps, or steel jackets are installed on the exterior surface of the enlarged footing, with construction adhesive or a few steel dowels being applied to the contact surfaces. To investigate the effectiveness of three systems, forty-four models were constructed in ABAQUS, with different parameters being considered. All footings investigated failed in punching shear, including original and retrofitted footings. According to FEA results and parametric studies, the three strengthening systems were capable of improving the punching shear resistance of footings. By introducing a new factor η, the punching shear equation in Eurocode 2 was modified to predict the punching shear resistances of the strengthened footings. A linear formula was developed to present the relationship between the new factor η and the investigated parameters.

• 한국산학기술학회논문지
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• 제15권10호
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• pp.6322-6328
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• 2014

얕은기초의 하중지지거동을 살펴보기 위해 3종류의 얕은기초를 가정하여 유한요소해석을 수행하였다. 띠기초에 대한 해석을 통해 구한 파괴시의 기초하부지반의 파괴양상은 팽창각이 없는 경우 국부전단파괴양상을 보였으며 팽창각이 있는 경우에는 전반전단파괴양상을 보였다. 팽창각에 따른 극한하중에 있어서는 팽창각이 있는 경우의 극한하중이 팽창각이 없는 경우에 비해 1.5배 큰 값을 보였다. 원형기초와 정사각형 기초에 대한 해석결과에 따르면 팽창각의 존재여부와 관계없이 파괴시 기초 인접지반면에 상향의 변위가 발생하여 전반전단파괴양상을 보였다. 극한하중에 있어서는 팽창각이 있는 경우가 없는 경우에 비해 약 10% 정도 증가하였다. 세 종류의 얕은기초에 대하여 해석을 통해 얻은 하중-침하곡선을 살펴볼 때 팽창각이 클수록 하중지지능력이 큼을 알 수 있었다.

• Geomechanics and Engineering
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• 제9권3호
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• pp.287-311
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• 2015

The ultimate bearing capacity and failure mechanism of square footings resting on a sand layer over clay soil have been investigated numerically by performing a series of three-dimensional non-linear finite element analyses. The parameters investigated are the thickness of upper sand layer, strength of sand, undrained shear strength of lower clay and surcharge effect. The results obtained from finite element analyses were compared with those from previous design methods based on limit equilibrium approach. The results proved that the parameters investigated had considerable effect on the ultimate bearing capacity and failure mechanism occurring. It was also shown that the thickness of upper sand layer, the undrained shear strength of lower clay and the strength of sand are the most important parameters affecting the type of failure will occur. The value of the ultimate bearing capacity could be significantly different depending on the limit equilibrium method used.

• Geomechanics and Engineering
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• 제14권1호
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• pp.51-60
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• 2018

The foundations are classified into shallow and deep, which have important differences: in terms of geometry, the behavior of the soil, its structural functionality, and its constructive systems. The shallow foundations may be of various types according to their function; isolated footings, combined footings, strip footings, and slabs foundation. The isolated footings are of the type rectangular, square and circular. The combined footing may be rectangular, trapezoidal or T-shaped in plan. This paper presents a new model for T-shaped combined footings to obtain the most economical contact surface on the soil (optimal dimensioning) to support an axial load and moment in two directions to each column. The new model considers the soil real pressure, i.e., the pressure varies linearly. The classical model uses the technique of test and error, i.e., a dimension is proposed, and subsequently, the equation of the biaxial bending is used to obtain the stresses acting on each vertex of the T-shaped combined footing, which must meet the conditions following: The minimum stress should be equal or greater than zero, and maximum stress must be equal or less than the allowable capacity that can withstand the soil. To illustrate the validity of the new model, numerical examples are presented to obtain the minimum area of the contact surface on the soil for T-shaped combined footings subjected to an axial load and moments in two directions applied to each column.

• Geomechanics and Engineering
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• 제34권5호
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• pp.561-575
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• 2023

This study investigates to provide a fast solution to the problem of bearing capacity in layered soils with easily obtainable parameters that does not require the use of any charts or calculations of different parameters. Therefore, a hybrid approach including both the finite element (FE) method and machine learning technique have been applied. Firstly, a FE model has been generated which is validated by the results of in-situ loading tests. Then, a total of 192 three-dimensional FE analyses have been performed. A data set has been created utilizing the soil properties, footing sizes, layered conditions used in the FE analyses and the ultimate bearing capacity values obtained from the FE analyses to be used in multigene genetic programming (MGGP). Problem has been modeled with five input and one output parameter to propose a bearing capacity formula. Ultimate bearing capacity values estimated from the proposed formula using data set consisting of 20 data independent of total data set used in MGGP modelling have been compared to the bearing capacities calculated with semi-empirical methods. It was observed that the MGGP method yielded successful results for the problem considered. The proposed formula provides reasonable predictions and efficient enough to be used in practice.

• 한국지반공학회논문집
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• 제18권4호
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• pp.179-188
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• 2002

평판재하시험으로 부터 실제 기초지반의 지지력 및 침하량을 산정할 때, 재하판과 실제기초의 크기가 상이하므로 인해 일어나는 영향, 즉 Scale effect가 고려되어야 한다. 본 논문에서는 재하폭에 따른 지지력 및 침하량의 변화특성을 분석하기 위해 5종류의 모형기초지반을 형성하고, 크기가 각각 l0cm, 15cm, 20cm, 25cm인 4가지 크기의 정사각형 평판으로 재하시험을 실시하여 재하폭에 따른 지지력 및 침하 특성을 분석하였다. 재하시험을 실시하여 분석한 결과, 순수모래 지반에서는 재하폭이 커지면 극한지지력은 증가하였으나 Scale effect에 관한 기존의 식과 같이 비례적으로 증가하지는 않았고, 순수점토 지반에서도 재하폭이 커지면 극한지지력은 약간 증가하여 재하폭에 무관하지 않은 것으로 나타났다. 또한 재하폭과 침하량의 관계를 보면 순수모래 지반은 재하폭이 커지면 침하량은 증가하였으나 Terzaghi and Peck(1967)의 실험식에 의한 값만큼 증가하지는 않았으며, 순수점토 지반에서도 재하폭이 커지면 침하량은 증가하였으나 Scale effect에 관한 기존의 식과 같이 비례적으로 증가하지는 않았다.

• 한국지반공학회논문집
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• 제19권5호
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• pp.343-354
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• 2003

재하판과 실제기초의 크기가 상이하므로 평판재하시험으로부터 실제 기초지반의 지지력 및 침하량을 산정할 때, Scale Effect가 고려되어야 한다. 본 논문에서는 5종류의 모형기초지반을 형성하고, 크기가 각각 l0cm, 15cm, 20cm, 25cm인 4가지 크기의 정사각형 평판으로 재하시험을 실시하여 재하판의 크기에 따른 지지력 및 침하 특성을 분석하였다. 또한 분석된 결과를 토대로 하여, 평판재하시험으로부터 실제기초의 지지력 및 침하량을 산정할 때, 모래와 점토의 혼합비율에 따라 Scale Effect를 합리적으로 고려할 수 있도록 식을 제안하였으며, 식에서 지지력 산정계수(a,b)와 침하량 산정계수(c,d)는 모래와 점토의 혼합비율에 따라 구할 수 있도록 그림으로 제시하였다. 지금까지는 현장기초지반에 대한 지지력 및 침하량을 합리적으로 평가할 수 없어 비경제적인 시공이 되어왔으나, 본 연구에서 제안한 지지력 및 침하량 산정방법에서는 모래와 점토의 혼합비율을 고려하여 기초지반의 지지력 및 침하량을 보다 합리적으로 추정할 수 있으므로 기초지반의 안정성 여부에 대한 확신과, 또한 경제적인 시공이 가능할 것으로 판단된다.

• Geomechanics and Engineering
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• 제1권2호
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• pp.113-120
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• 2009

The results of FLAC3D-based numerical evaluation of the bearing capacity shape factor $s_{\gamma}$ are presented for square and rectangular footings on granular soils. The results confirm a peculiar effect found earlier by Zhu and Michalowski (2005), where for large values of internal friction angle, $s_{\gamma}$ exhibits a peak at some aspect ratio of the footing, and then decreases towards unity at large aspect ratios. The Zhu and Michalowski's results were derived using the finite element program ABAQUS, and the results presented in this note corroborate their earlier findings.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.628-636
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• 2006

This paper presents 3D infinite elements in Cartesian coordinates for the elastodynamic problem in multi-layered half-space. Five kinds of infinite elements are developed by using approximate expressions of multiple wave components for the wave function in exterior far-field soil region. They are horizontal, horizontal-corner, vertical, vertical-corner and vertical-horizontal-corner elements. The elements can be used for the multi-wave propagating problem. Numerical example analyses are presented for rigid disk, square footings and embedded footing on homogeneous and layered half-space. The numerical results obtained show the effectiveness of the proposed infinite elements.