• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.454-457
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• 2006

This study presents a strut-and-tie model for the development of headed bars in an exterior beam-column joint with transverse reinforcements. The tensile force of a headed bar is considered to be developed by head bearing together with bond along a bonded length as a partial embedment length. The model requires construction of struts with biaxially compressed nodal zones for head bearing and fan-shaped stress fields against neighboring nodal zones for bond stresses along the bonded length. Due to the existence of transverse reinforcements, the fan-shaped stress fields are divided into direct and indirect fan-shaped stress fields. A required development length and head size of a headed bar can be optimally designed by adjusting a proportion between a bond contribution and bearing contribution.

• Computers and Concrete
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• 제22권6호
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• pp.539-550
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• 2018

Concrete is highly non-linear material which is originating from the transition zone in the form of micro-cracks, governs material response under various loadings. In this paper, the constitutive models published by many researchers have been used to generate novel stiffness parameters and constitutive curves for concrete. Following such linear material formulations, where the energy is conservative during the curvature, and a nonlinear contribution to the concrete has been made and investigated. In which, nonlinear concrete elastic modulus modeling has been developed that is capable-of representing concrete elasticity for grades ranging from 10 to 140 MPa. Thus, covering the grades range of concrete up to the ultra-high strength concrete, and replacing many concrete models that are valid for narrow ranges of concrete strength grades. This has been followed by the introduction of the nonlinear Hooke's law for the concrete material through the replacement of the Young constant modulus with the nonlinear modulus. In addition, the concept of concrete elasticity index (${\varphi}$) has been proposed and this factor has been introduced to account for the degradation of concrete stiffness in compression under increased loading as well as the multi-stages micro-cracking behavior of concrete under uniaxial compression. Finally, a sub-routine artificial neural network model has been developed to capture the concrete behavior that has been introduced to facilitate the prediction of concrete properties under increased loading.

• 콘크리트학회논문집
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• 제19권6호
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• pp.745-754
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• 2007

이 논문은 철근콘크리트 구조 부재의 인장증강효과에 대한 해석적 모델을 제안한 것이다. 이 모델의 정식화를 위해 철근과 콘크리트 경계면에서 발생하는 실제와 유사한 형태의 부착응력과 미끌림 특성과 쪼갬균열의 영향을 고려하였다. 균열 안정화 단계에서의 철근 경계면 미끌림 분포를 선형으로 가정하고, 균열이 발생한 부재의 중앙 단면에서 콘크리트의 분담력이 일정하다는 조건을 CEB-FIP Model Code 1990 및 Eurocode 2에서 제시하고 있는 부착응력-미끌림 관계에 적용하였다. 이로부터 균열 안정화단계에서 부착응력에 의해 철근의 매입길이 방향으로 변화하는 철근의 변형률과 콘크리트 분담력을 계산할 수 있는 평형방정식을 유도하고, 변형적합조건을 고려하여 철근의 평균 변형률과 콘크리트 평균 분담력으로 동시에 표현이 가능한 인장강성 계수를 제안하였다. 이로부터 새롭게 정식화된 인장증강효과 모델을 기존 문헌에 발표된 여러 연구자들의 실험 자료에 적용하여 그 정확성을 검증한 결과, 제안식에 의한 예측값은 실험값을 비교적 정확하게 예측하는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제63권4호
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• pp.521-536
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• 2017

Reinforced concrete core-wall structures with buckling-restrained brace outriggers are interesting systems which have the ability to absorb and dissipate energy during strong earthquakes. Outriggers can change the energy demand in a tall building. In this paper, the energy demand was studied by using the nonlinear time history analysis for the mentioned systems. First, the structures were designed according to the prescriptive codes. In the dynamic analysis, three approaches for the core-wall were investigated: single plastic hinge (SPH), three plastic hinge (TPH) and extended plastic hinge (EPH). For SPH approach, only one plastic hinge is allowed at the core-wall base. For TPH approach, three plastic hinges are allowed, one at the base and two others at the upper levels. For EPH approach, the plasticity can extend anywhere in the wall. The kinetic, elastic strain, inelastic and damping energy demand subjected to forward directivity near-fault and ordinary far-fault earthquakes were studied. In SPH approach for all near-fault and far-fault events, on average, more than 65 percent of inelastic energy is absorbed by buckling-restrained braces in outrigger. While in TPH and EPH approaches, outrigger contribution to inelastic energy demand is reduced. The contribution of outrigger to inelastic energy absorption for the TPH and EPH approaches does not differ significantly. The values are approximately 25 and 30 percent, respectively.

• 한국지진공학회논문집
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• 제14권6호
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• pp.23-31
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• 2010

우리나라 공동주택의 대부분을 이루는 철근콘크리트(RC) 벽식 구조의 지진에 대한 거동을 예측하기 위해 신뢰성이 있으며 사용하기 간편한 해석모델의 수립이 필요하다. 본 논문은 기 수행된 RC 전단벽 부분구조의 횡 하중 반전주기 실험결과를 기준으로 하여 PERFORM 3D에서 가용한 RC벽 요소 및 보 기둥 요소 해석모델을 응용하여 최대한 실험결과와 근접한 결과를 주는 모델을 수립하였다. 전체 및 국부거동에 있어서 이 해석결과를 실험결과와 비교함으로써 해석의 신뢰성과 한계성을 확인함과 동시에, 실험에서 파악하기 어려운 내부 저항력의 구성, 전체 구조물의 저항 메카니즘에 대한 정량적인 분석을 제시한다.

• Steel and Composite Structures
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• 제20권2호
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• pp.251-266
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• 2016

The paper combines two distinct parts. First the behavior of welded headed studs with small diameters of 10 and 13 mm acting as shear connectors (which are not embraced in current standards) is studied. Based on standard push tests the load-slip relationships and strengths are evaluated. While the current standard (Eurocode 4 and AISC) formulas used for such studs give reasonable but too conservative strengths, less conservative and full load-slip rigidities are evaluated and recommended for a subsequent investigation or design. In the second part of the paper the partially encased beams under bending are analyzed. Following former experiments showing rather indistinct role of studs used for shear connection in such beams their role is studied. Numerical model employing ANSYS software is presented and validated using former experimental data. Subsequent parametric studies investigate the longitudinal shear between steel and concrete parts of the beams with respect to friction at the steel and concrete interface and contribution of studs with small diameters required predominantly for assembly stages (concreting). Substantial influence of the friction and effect of concrete confinement was observed with rather less noticeable contribution of the studs. Distribution of the longitudinal shear and its sharing between friction and studs is presented with concluding remarks.

• Steel and Composite Structures
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• 제45권2호
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• pp.193-204
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• 2022

The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.564-567
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• 2015

The incorporation of sustainability principles into the structural engineering design of buildings is increasingly important. Historically the focus of improvements to the environmental performance of structures has been operational energy considerations. Current research has highlighted the requirement for changing the approach by increasing the consideration of embodied energy in structures. This research was conducted to build on previous research by the authors in quantifying the contribution of column optimization to the embodied energy performance of concrete framed buildings. Ultimately, the authors intend to develop mechanisms through which sustainable design can be quantified, enabling alleviation prior to construction. Columns are a key structural element to consider as part of this development process. The outcomes of this assessment reinforced previous findings, observing that reduced structural weight as a result of other sustainable design measures carries manifold benefits include column design savings. Through the quantification of the embodied energy outcomes during this research phase, the columns were shown to contribute up to 19.71% of the total embodied energy of the structural system dependent upon construction technique used.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.179-184
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• 2002

The evaluation equation of torsional moment for prestressed concrete members in ACI 318-95 ignores the contribution of concrete, T$_{c}$. Several research indicates that the current ACI code is not successful in predicting the observed torsional moment of the PSC beams with reasonable accuracy. This paper proposes an evaluation equation of torsional moment taking into account the inter-effects between concrete and torsional reinforcement on the torsional resistance of the PSC beams. According to the comparison with the 31 test results, the torsion equation in ACI code underestimated or overestimated the real torsional moment of prestressed concrete beams. On the other hand, the proposed torsional equation is shown to be in a good agreement with experimental results.s.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.805-808
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• 1999

According to the results of this research, Production of Fold Concret Permanent-Form, was found to be possible by Concrete. The FCP-Form (Fold Concret Permanent-Form) Concrete had Compress strength 300kg/$\textrm{cm}^2$ and banding strength 120kg/$\textrm{cm}^2$. FCP-Form Model was made by the result of the first research. There was no mimute-crack on beam form and The outer surface of form was very smooth, and Those qualities it were made possible hand-made by experiment. With these results, The Production of FCP-Form seemed possible. In the banding load test, P-S showed increase of maxim load 12% than P-R. At the first stage of minute crack, under continuing loading size of crack increased. These phenomena seemed to be based on contribution of stress of inner bars in FCP-Form. In the test of defection. P-S shower about 10% banding load increase than P-R. FCP-Form Concrete was found to be efficient in compressibleness, defection, safety and use of material.