• Structural Engineering and Mechanics
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• 제66권4호
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• pp.423-438
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• 2018

This pioneer study focuses on finite element modeling and numerical modeling of three types of Reinforced Concrete Haunched Beams (RCHBs). Firstly, twenty RCHBs, consisting of three types, and four prismatic beams which had been tested experimentally were modeled via a nonlinear finite element method (NFEM) based software named as, ATENA. The modeling results were compared with experimental results including load capacity, deflection, crack pattern and mode of failure. The comparison showed a good agreement between the results and thus the model used can be effectively used for further studies of RCHB with high accuracy. Afterwards, new mechanism modes and design code equations were proposed to improve the shear design equation of ACI-318 and to predict the critical effective depth. These equations are the first comprehensive formulas in the literature involving all types of RCHBs. The statistical analysis showed the superiority of the proposed equation to their predecessors where the correlation coefficient, $R^2$ was found to be 0.89 for the proposed equation. Moreover, the new equation was validated using parametric and reliability analyses. The parametric analysis of both experimental and predicted results shows that the inclination angle and the compressive strength were the most influential parameters on the shear strength. The reliability analysis indicates that the accuracy of the new formulation is significantly higher as compared to available design equations and its reliability index is within acceptable limits.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.126-129
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• 2006

A bending moment $M_u$ transferred at slab-column connection is resisted at the slab critical section by flexure and shear. The ACI 318-05 Building Code(1) gives an empirical equation for the fraction ${\gamma}_{\upsilon}$ of the moment $M_u$ to be transferred by shear at the slab critical section at d/2 from the column face and also the effective wide(c+3h). The equation is based on tests of interior slab-column connections without shear reinforcement. In order to investigate the data eight test specimens were examined. The test shows that increased slab load substantially reduces both the unbalanced moment capacity and the lateral drift capacity of the connection. Especially, the specimens with the bottom reinforcement existence and nonexistence, appears remarkable differences. Studies also show that the code equation for ${\gamma}_{\upsilon}$ does not apply to all cases. The purpose of this study is to compare the test results with present ACI 318-05 Building Code provisions for design of slab-column connections and with the analysis of the experimental data for a new limitation of strength equation without shear reinforcement and bottom reinforcement.

• Steel and Composite Structures
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• 제38권6호
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• pp.739-749
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• 2021

This paper introduces an improved design equation to evaluate the resisting capacity of circular reinforced concrete (RC) columns partially strengthened with outer steel tube. When RC column members are required to be strengthened according to the change in the loadings considered and/or the deterioration progress in columns, wrapping up RC column with steel circular tube, which takes the form of concrete filled steel tube (CFST), has been popularly considered because of its structural advantage induced from the confinement effect. However, the relatively high construction cost of steel tube is restricting its use to the required region, while deriving the shape of a partial CFST column. To evaluate the resisting capacity of a partial CFST column, numerical analyses need to be performed, and a numerical model proposed in the previous study for the numerical analysis of full CFST columns is used to conduct parametric studies for the introduction of a design equation. The bond-slip effect developed along the interface between the in-filled concrete and the exterior steel tube is taken into consideration and the validity of the numerical model has been established through correlation studies between experimental data and numerical results for partial CFST circular columns. Moreover, parametric studies make it possible to introduce a design equation for determining the optimum length of outer steel tube which produces partial CFST circular columns.

• Steel and Composite Structures
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• 제28권4호
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• pp.483-494
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• 2018

In this research the effect of high strength concrete (HSC) on shear capability of the channel shear connectors (CSC) in the steel concrete composite floor system was estimated experimentally and analytically. The push-out test was carried out for assessing the accurateness of the proposed model (nonlinear and finite element model) for the test specimens. A parametric analysis was conducted for predicting the shear capacity of the connectors (CSC) in the HSC. Eight push-out specimens of different sizes with different strength levels were tested under the monotonic loading system. The aim of this study was to evaluate the efficacy of the National Building Code of Canada (NBC) of Canada for analysing the loading abilities of the CSC in the HSC. Using the experimental tests results and verifying the finite element results with them, it was then confirmed by the extended parametric studies that the Canadian Design Code was less efficient for predicting the capacity of the CSC in the HSC. Hence, an alternative equation was formulated for predicting the shear capacity of these connectors during the inclusion of HSC for designing the codes.

• Tribology and Lubricants
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• 제30권5호
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• pp.284-290
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• 2014

The influence of round embossed surface on slider bearing characteristics and its load carrying capacity is discussed for thin film effect of embossed slider bearing. For the numerical computation of lubrication parameters such as pressure, load capacity and shear stress that are normalized and a Reynolds equation is used for the analysis of embossed slider bearing characteristics. For this purpose, the finite difference method of central difference scheme is used in this study. In a slider bearing with embossed form, several simulation parameters such as pressure, load capacity and shear stress of the bearing can be obtained according to independent parameters such as the slope of the slider bearing and number of embossing in the upper slider. Also this results can be summarized and be stored in sequential data file for latter analysis. After all, their distribution of the pressure and shear stress parameters can be displayed and be analyzed easily by using the developed program with matlab GUI technique. The independent parameters such as a number of embossing and a slope of the embossed surface slider are used for discussing simulation parameters of pressure distribution, shear stress and load carrying capacity of the round embossing. These study results reported in this paper should be applied to the other shaped slider bearing with a rectangular embossed surface or rectangular waved surface.

• Journal of Advanced Marine Engineering and Technology
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• 제9권4호
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• pp.317-327
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• 1985

In the case of temperature control of air conditioning and refrigerating system, it is possible to operate the system continuously by controlling the cooling capacity of refrigerating machines. But on-off control system has been adopted for refrigerating system which has more large capacity than that required to remove the generated heat. In this on-off control system, it can be considered that there exists some optimum condition for the refrigerating capacity, operating cycle, running hour, and the temperature difference between thermostat setting value and real one. In this paper, an equation was derived to express the temperature variation of the refrigerated object (Nybrine) and later two evaluating functions were derived. One is for the temperature difference and another is for operating cycle and running hour. The weighted sum of these two functions is defined as the criterion function for the evaluation of the control performance of the system, and then the optimum running condition is investigated in the sense of minimizing the criterion function. Experiments showed that the heat balance equation derived for the temperature variation and the estimation of the time constant of the refrigerated system are appropriate. By conclusion, if a proper weighting factor D is selected, the optimum conditions exist for the refrigerating capacity, running hour, and operating cycle in the on-off temperature control of the refrigerating system.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2006년도 하계학술발표대회 논문집
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• pp.953-958
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• 2006

Perimeter zone has been reinforced by active systems, such as fan-coil units, because it causes an increase in heating and cooling loads, dew condensation in winter, or discomfort with cold-draft to residents in buildings, through poor insulation by light-weighed skin due to progressing multi-storied buildings and skyscrapers. However, because these active systems raise Its capacity so that fossil fuel is used as much as they are added, and ultimately, greenhouse effect is urged, we proposed BIPV system functioned as solar collector which can substitute active system. As an early stage, heat balance equation in steady-state by Fortran was used not only for pre-heating effect and electric power capacity during the day in winter, but also for electric power capacity during day in slimmer and sky radiation effect during night in summer. Especially, we should have considered shading on PV, since even a little bit of it makes the efficiency too low for the PV to work. Still, when the flux of pre-heated air was increased to make air-barrier, its temperature was not enough to make it because the speed of heat exchange was too fast to warm up the air, thus the capacity to meet the condition was evaluated, and electric power from PV was made used for it.

• 한국지반공학회논문집
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• 제23권12호
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• pp.5-11
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• 2007

국내에서는 조립토를 이용한 연약지반 처리공법 중 모래다짐말뚝공법이 많이 활용되고 있으나, 모래자원의 고갈과 단가상승으로 인해 적용이 제한되고 있어 대체공법이 필요한 실정이다. 본 연구에서는 육상부 현장에 시험시공된 단일쇄석다짐말뚝에 대한 정재하시험을 수행하였다. 시험시 말뚝의 직경을 700mm로 고정하구 재하판의 면적을 변화시켰으며, 치환율 20, 30, 40%에 대하여 정재하시험을 실시하였다. 그 결과를 토대로 하여 단일쇄석다짐말뚝의 지지력 증가효과를 평가하였다. 치환율이 증가할수록 침하량이 작아지는 경향을 보였다. 또한, 치환율이 고려된 단일쇄석다짐말뚝의 항복지지력 공식을 제안하였다.

• 대한공간정보학회지
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• 제24권3호
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• pp.93-101
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• 2016

용수공급이나 수질관리 등과 같은 저수지 운영을 위해서는 최신의 수위별 저수면적과 저수량을 평가해야 한다. 본 연구에서는 괴연저수지를 대상으로 UAV 촬영 및 GCP 측량을 통해 정사영상과 DSM 자료를 구축하였으며, 저수지 영역에 대한 TIN 데이터모델을 구축함으로써 실제 저수구간인 149~156 EL.m에 대한 수위별 저수면적과 저수량을 계산할 수 있었다. 또한 수위별 저수면적과 저수량 자료에 대해 다양한 함수식을 적용한 결과, 수위별 저수면적은 4차 다항식을 적용한 곡선식의 결정계수가 0.97로 가장 높게 나타났으며 수위별 저수량은 2차 다항식을 적용한 곡선식의 결정계수가 0.99로 가장 높게 나타남을 알 수 있었다. 이와 같이 UAV 사진측량을 통해 저수면적과 저수량 곡선식을 산정함으로서 효율적인 저수지 관리가 가능할 것으로 판단된다.

• 한국지반공학회논문집
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• 제15권2호
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• pp.95-104
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• 1999

Set-up현상이 나타나는 지반에 항타된 말뚝의 지지력은 시간경과에 따라 지지력이 증가하게 된다. 파동이론해석법(WEAP해석법)은 말뚝의 항타관입성을 평가하는데 매우 유용한 것으로 평가되고 있다. 그러나 기존의 WEAP해석법은 항타후 변화하는 지반의 강도특성을 고려할 수 없다는 측면에서 재항타시의 신뢰도 있는 지지력을 예측하는데 한계가 있다고 평가된다. WEAP에 의한 항타말뚝의 지지력 평가가 신뢰성 있기 위해서는 set-up효과가 반영되어야만 한다. 그러나 아직까지 이를 고려할 수 있는 만족할 만한 방법이 없다. 본 논문에서는 항타시와 재항타시의 동재하시험 결과들을 통계분석하여 WEAP해석시 set-up효과를 반영할 수 있는 방안을 제시하였다. 또한 현장 시험결과와의 비교를 통해서, 제안된 변수(quake, damping)를 적용한 파동이론해석 결과는 기존의 방법보다 신뢰성이 있음을 알 수 있었다.