• 대한토목학회논문집
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• 제34권1호
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• pp.73-85
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• 2014

CFT 기둥은 시공이 간단하고 경제적이며 구조성능이 우수한 현장타설 매입형 연결 형식이다. 본 연구에서는 모듈러 교각에 적용되는 CFT 기둥-기초 연결부 형식을 제안하고, 실험을 통하여 구조성능을 평가하였다. 기둥-기초 연결부의 구조성능을 평가하기 위해서 기초부 콘크리트에 매입되는 CFT 기둥의 매입깊이를 변수로 총 4개의 실험체를 제작하여 실험을 수행하였다. 준정적 실험결과, 매입깊이가 0.6D인 실험체에서는 낮은 하중단계에서 기초부의 콘파괴로 인하여 상대적으로 낮은 연성능력을 보였다. 그러나 매입깊이가 0.9D 이상인 실험체에서는 기초부의 콘파괴가 방지되고 CFT 기둥 하단부에서 전형적인 휨파괴 거동을 보이며 높은 연성능력을 발휘하였다. 하중-변위 이력곡선, 변위 연성도 및 에너지 소산능력 등을 분석한 결과, 제안된 CFT 기둥-기초 연결부의 매입깊이는 0.9D~1.2D 수준이 내진성능을 발휘하는 합리적인 수준인 것으로 평가되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.853-860
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• 1999

A large concentrated load is often transferred to reinforced concrete footing in a tall building. In this study, a foundation system which used high strength precast concrete bearing plate was proposed. This concrete bearing plate has to be strong enough to resist the column load. However, a sufficient bearing strength may not be provided if the column load is too high and the concrete of bearing plate does not have enough strength.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.953-958
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• 2001

A retrofit method “Steel Ring Confinement Retrofit” was proposed and discussed on the material and member characteristics through experiments. Steel Ring Confinement Retrofit consist of confining steel ring and expansive concrete. The steel ring is set on the footing, surrounding the base of the pier. By placing expansive concrete between the pier and steel ring, chemical prestress is introduced in the members. Chemical prestressed ring concrete enlarge the pier section and enhance both the strength and ductility of the pier. It was confirmed that Various Ring Confinement Retrofit improved the strength of the pier up to 30% ~ 100% with experiments.

• 한국산학기술학회논문지
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• 제6권3호
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• pp.223-230
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• 2005

최근 들어 매스콘크리트 구조물의 해석에 대한 연구가 증가 추세에 있다. 대형 콘크리트 구조물은 일괄 타설하지 않고 분할하여 타설하기 때문에 서로 다른 발열특성 및 시간의존적 특성을 지닌 콘크리트로 구성된 구조물이 됩니다 따라서 실제 구조물과 근접한 수화열해석 모델을 만들기 위해서는 시공단계를 고려한 모델이 필요합니다. 본 연구에서는 교각 기초의 온도균열을 방지하기 위하여 열응력 검토를 실시하였으며, 이때 기초는 보통 콘크리트를 사용하고 $12m\times14m$의 면적과 3m 높이를 가지는 것을 모델로 하였다. 2단계로 분할하여 타설된 기초구조물에 대해서 별 해석을 수행하고 그 결과를 분석합니다.

• Advances in Computational Design
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• 제4권3호
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• pp.273-294
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• 2019

In this paper is presented the minimum cost (optimal design) for reinforced concrete circular isolated footings based on an analytic model. This model considers a load and two moments in directions of the X and Y axes, and the pressure has a variation linear, these are the effects that act on the footing. The minimum cost (optimal design) and the Maple program are shown in Flowcharts. Two numerical experiments are shown to obtain the minimum cost design of the two materials that are used for a circular footing supporting an axial load and moments in two directions in accordance to the code of the ACI (American Concrete Institute), and it is compared against the current design (uniform pressure). Also, the same examples are developed through the normal procedure to verify the minimum cost (optimal design) presented in this document, i.e., the equations of moment, bending shear and punching shear are used to check the thickness, and after, the steel areas of the footing are obtained, and it is compared against the current design (uniform pressure). Results section show that the optimal design is more accurate and more economical than to any other model. Therefore, it is concluded that the optimized design model presented in this paper should be used to obtain the minimum cost design for the circular isolated footings.

• 한국방재학회 논문집
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• 제6권2호
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• pp.1-7
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• 2006

콘크리트 댐, 원자력발전소 및 항만구조물등의 대형구조물을 시공하기 위해서는 짧은 기간에 막대한 양의 콘크리트를 타설하게 된다. 매스콘크리트 구조물을 시공하는 단계에서 발생되는 수화열은 심각한 온도균열을 발생시켜 본래의 기능수행능력과 사용수명에 있어서 심각한 저하를 초래할 수 있다. 본 연구에서는 매스콘크리트 구조물의 대표적인 예라고 할 수 있는 교대구조물에 대하여 수화열 및 온도응력을 사전해석하고 그 결과를 바탕으로 구조물 성능확보를 위한 온도균열제어대책을 제시하였으며, 제시된 대책을 바탕으로 이루어진 시공현장에서 교대기초부 및 본체부에서의 온도분포와 응력을 계측하고 온도균열 발생양상을 관찰하여 제시된 대책의 타당성을 단계별로 확인하였다.

• 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.

• Geomechanics and Engineering
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• 제1권3호
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• pp.219-239
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• 2009

Vertical vibration tests were conducted using model footings of different size and mass resting on the surface of finite sand layer with different height to width ratios and underlain by either rigid concrete base or natural red-earth base. A comparative study of the ratio of predicted and observed natural frequency ratio of the finite sand stratum was made using the calculated values of equivalent stiffness suggested by Gazetas (1983) and Baidya and Muralikrishna (2001). Comparison of results between model footings resting on finite sand stratum underlain by the rigid concrete base and the natural red-earth base showed that, the presence of a finite base of higher rigidity increases the resonant frequency significantly. With increase in H/B ratio beyond 2.0, the influence of both the rigid concrete and natural red-earth base decreases. Increase in the contact area of the footing increases the resonant frequency of the model footings resting on finite sand stratum underlain by both the types of finite bases. Both the predicted and the observed resonant frequency ratio decreases with increase in force rating and height to width ratio for a given series of model footing.

• Earthquakes and Structures
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• 제7권6호
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• pp.1001-1024
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• 2014

The size of spread footings was found to be unnecessarily large from some actual engineering practices constructed in Taiwan, due to the strict design provisions related to footing uplift. According to the earlier design code in Taiwan, the footing uplift involving separation of footing from subsoil was permitted to be only up to one-half of the foundation base area, as the applied moment reaches the value of plastic moment capacity of the column. The reason for this provision was that rocking of spread footings was not a favorable mechanism. However, recent research has indicated that rocking itself may not be detrimental to seismic performance and, in fact, may act as a form of seismic isolation mechanism. In order to clarify the effects of the relative strength between column and foundation on the rocking behavior of a column, six circular reinforced concrete (RC) columns were designed and constructed and a series of rocking experiments were performed. During the tests, columns rested on a rubber pad to allow rocking to take place. Experimental variables included the dimensions of the footings, the strength and ductility capacity of the columns and the intensity of the applied earthquake. Experimental data for the six circular RC columns subjected to quasi-static and pseudo-dynamic loading are presented. Results of each cyclic loading test are compared against the benchmark test with fixed-base conditions. By comparing the experimental responses of the specimens with different design details, a key parameter of rocking behavior related to footing size and column strength is identified. For a properly designed column with the parameter higher than 1, the beneficial effects of rocking in reducing ductility and the strength demand of columns is verified.

• Geomechanics and Engineering
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• 제30권6호
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• pp.525-538
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• 2022

This paper presents a more general model for T-shaped combined footings that support two columns aligned on a longitudinal axis and each column provides an axial load and two orthogonal moments. This model can be applied to the following conditions: (1) without restrictions on its sides, (2) a restricted side and (3) two opposite sides restricted. This model considers the linear soil pressure. The recently published works have been developed for a restricted side and for two opposite sides restricted by Luévanos-Rojas et al. (2018a, b). The current model considers the uniform pressure distribution because the position of the resultant force coincides with the center of gravity of the surface of the footing in contact with the soil in direction of the longitudinal axis where the columns are located. This paper shows three numerical examples. Example 1 is for a T-shaped combined footing with a limited side (one column is located on the property boundary). Example 2 is for a T-shaped combined footing with two limited opposite sides (the two columns are located on the property boundary). Example 3 is for a T-shaped combined footing with two limited opposite sides, one column is located in the center of the width of the upper flange (b₁/2=L₁), and other column is located at a distance half the width of the strip from the free end of the footing (b₂/2=b-L₁-L). The main advantage of this work over other works is that this model can be applied to T-shaped combined footings without restrictions on its sides, a restricted side and two opposite sides restricted. It also shows the deficiencies of the current model over the new model.