• 콘크리트학회논문집
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• 제28권4호
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• pp.419-426
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• 2016

이 연구에서는 다양한 콘크리트를 갖는 전단계면에서의 전단마찰거동에 대한 횡보강근 및 압축응력의 영향을 평가하였다. 12개 직접전단실험체로부터 균열진전, 전단하중-상대 미끄러짐 관계, 균열발생시 전단응력, 최대전단내력 및 횡보강근의 전단저항력 등이 측정되었다. 실험결과 동일 전단하중에서 상대 미끄러짐 제어에 대한 횡보강근 배근형상 및 콘크리트 압축강도의 영향은 미미하였다. 작용 압축응력의 증가와 함께 콘크리트의 전단전달력을 증가하는 반면, 횡보강근의 전단전달력은 감소하였는데, 횡보강근의 전단저항은 배근형태에 의해 영향을 받지 않았다. AASHTO-LRFD, Mattock 및 Hwang and Yang의 모델은 콘크리트의 전단마찰내력을 과소평가하였다. 반면, Hwang and Yang의 모델은 실험결과와의 비교에 대한 평균과 표준편차 값이 각각 1.02과 0.23으로서 기존 모델에 비해 다양한 변수의 영향을 적절히 고려하면서 콘크리트의 전단마찰내력을 잘 예측하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.897-902
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• 2001

The purpose of this experimental study is to investigate the shear behavior of high-strength concrete deep beam and to grasp the conservatism of ACI Building Code. Experimental results on 12 deep beams under two equal symmetrically placed point loads are reported. Main variables are vertical and horizontal web reinforcement and shear span-to-overall depth ratio. Test results indicated that web reinforcement dose not affect on formation of inclined cracks but shear span-to-overall depth ratio affect on inclined shear cracks and ultimate shear strength. Addition of vertical web reinforcement improves ultimate shear strength of H.S.C. deep beams that shear span-to-overall depth ratio is 1.0. Considerable increase in ultimate shear strength of H.S.C. deep beams with increasing horizontal web reinforcement that shear span-to-overall depth ratio is 0.5. Especially with increasing concrete strength($f_{ck}$) the ACI code is conservative in estamating the ultimate shear strength of deep beams.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.37-40
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• 2008

The study is an experimental test on full-scale flat plate slab-column interior connection. The punching shear on the flat plate slab-column connection can bring about the reason of the brittle punching shear failure which may result of collapsing the whole structure. From the development of residential flat plate system, the shear reinforcement is developed for preventing the punching shear. For making sure of the punching shear capacity, developed for shear reinforcement in slab-column connection, the structural test is performed. The dimension of the slabs was 2620*2725*180mm with square column (600*800mm). The slabs were tested up to failure monotonic vertical shear forces. The presences of S/S bar and wire mesh substantially increased the punching shear capacity and the ductility of the slab-column connections.

• Computers and Concrete
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• 제18권2호
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• pp.165-178
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• 2016

The present work is concerned with a numerical investigation of the behaviour of reinforced-concrete beams with non-bonded flexural tension reinforcement. The numerically-established behaviour of such beams with and without transverse reinforcement is compared with its counterpart of similar beams with bonded reinforcement. From the comparison, it is found that the development of bond anywhere within the shear span inevitably leads to inclined cracking which is the cause of 'shear' failure. On the other hand, the lack of bond within the shear span of the beams is found, not only to prevent cracking within the shear span, but, also, to lead to a flexural type of failure preceded by the formation of horizontal splitting of concrete in the compressive zone. It is also found that delaying the extension of horizontal splitting through the provision of transverse reinforcement in the beam mid span can lead to flexural failure after yielding of the tension reinforcement. Yielding of the tension reinforcement before the horizontal splitting of the compressive zone may also be achieved by reducing the amount of the latter reinforcement.

• Computers and Concrete
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• 제14권3호
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• pp.211-231
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• 2014

Prestressed hollow-core slabs (HCS) are widely used for modern lightweight precast floor structures because they are cost-efficient by reducing materials, and have excellent flexural strength and stiffness by using prestressing tendons, compared to reinforced concrete (RC) floor system. According to the recently revised ACI318-08, the web-shear capacity of HCS members exceeding 315 mm in depth without the minimum shear reinforcement should be reduced by half. It is, however, difficult to provide shear reinforcement in HCS members produced by the extrusion method due to their unique concrete casting methods, and thus, their shear design is significantly affected by the minimum shear reinforcement provision in ACI318-08. In this study, a large number of shear test data on HCS members has been collected and analyzed to examine their web-shear capacity with consideration on the minimum shear reinforcement requirement in ACI318-08. The analysis results indicates that the minimum shear reinforcement requirement for deep HCS members are too severe, and that the web-shear strength equation in ACI318-08 does not provide good estimation of shear strengths for HCS members. Thus, in this paper, a rational web-shear strength equation for HCS members was derived in a simple manner, which provides a consistent margin of safety on shear strength for the HCS members up to 500 mm deep. More shear test data would be required to apply the proposed shear strength equation for the HCS members over 500 mm in depth though.

• 대한건축학회논문집:구조계
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• 제35권6호
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• pp.111-119
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• 2019

The purpose of this study is to investigate the shear strength of reinforced concrete beam according to beam section size and shear reinforcement ratio. A total of nine specimens were tested and designed concrete compressive strength is 24 MPa. The main variables are shear reinforcement ratio and beam section size fixed with shear span to depth ratio (a/d = 2.5), the tensile reinforcement ratio (${\rho}=0.013$) and width to depth ratio (h/b = 1.5). The test specimens were divided into three series of S1 ($225{\times}338mm$), S2 ($270{\times}405mm$) and S3 ($315{\times}473mm$), respectively. The experimental results show that all specimens represent diagonal tensile failure. For $S^*-1$ specimens (d/s=0), the shear strength decreased by 33% and 46% with increasing the beam effective depth, 26% and 33% for $S^*-2$ specimens (d/s=1.5) and 16% and 20% for $S^*-3$ specimens (d/s=2.0) respectively. As the shear reinforcement ratio increases, the decrease range in shear strength decreases. In other words, this means that as the shear reinforcement ratio increases, the size effect of concrete decreases. In the S1 series, the shear strength increased by 39% and 41% as the shear reinforcement ratio increased, 54% and 76% in the S2 series and 66% and 100% in the S3 series, respectively. As the effective depth of beam increases, the increase range of shear strength increases. This means that the effect of shear reinforcement increases as the beam effective depth increases. As a result of comparing experimental values with theoretical values by standard equation and proposed equation, the ratio by Zsutty and Bazant's equation is 1.30 ~ 1.36 and the ratio by KBC1 and KBC2 is 1.55~.163, respectively. Therefore, Zsutty and Bazant's proposed equation is more likely to reflect the experimental data. The current standard for shear reinforcement ratio (i.e., $S_{max}=d/2$) is expected to be somewhat relaxed because the ratio of experimental values to theoretical values was found to be 1.01 ~ 1.44 for most specimens.

• Computational Structural Engineering : An International Journal
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• 제1권2호
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• pp.117-130
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• 2001

Investigations of low-rice unbounded reinforced concrete shear walls with or without openings are performed with comparison of analytical and experimental results. Theoretical analysis is based on nonlinear finite element algorithm, which incorporates concrete failure criterion and nonlinear constitutive relationships. Studios focus on the effects of height-to-length ratio of shear walls, opening ratio, horizontal and vertical reinforcement radios, and diagonal reinforcement. Analytical solutions conform well with experimental results. Equations for cracking, yielding and ultimate loads with corresponding lateral displacements are derived by regression using analytical results and experimental data. Also, failure modes of low-rise unbounded shear walls are theoretically investigated. An explanation of change in failure mode is ascertained by comparing analytical results and ACI code equations. Shear-flexural failure can be obtained with additional flexural reinforcement to increase a wall's capacity. This concept leads to a design method of reducing flexural reinforcement in low-rise bounded solid shear wall's. Avoidance of shear failure as well as less reinforcement congestion leer these walls is expected.

• Steel and Composite Structures
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• 제24권1호
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• pp.1-13
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• 2017

In order to improve the deformation capacity of the high-strength concrete shear wall, five high-strength concrete shear wall specimens confined with high-strength rectangular spiral reinforcement (HRSR) possessing different parameters, were designed in this paper. One specimen was only adopted high-strength rectangular spiral hoops in embedded columns, the rest of the four specimens were used high-strength rectangular spiral hoops in embedded columns, and high-strength spiral horizontal distribution reinforcement were used in the wall body. Pseudo-static test were carried out on high-strength concrete shear wall specimens confined with HRSR, to study the influence of the factors of longitudinal reinforcement ratio, hoop reinforcement form and the spiral stirrups outer the wall on the failure modes, failure mechanism, ductility, hysteresis characteristics, stiffness degradation and energy dissipation capacity of the shear wall. Results showed that using HRSR as hoops and transverse reinforcements could restrain concrete, slow load carrying capacity degeneration, improve the load carrying capacity and ductility of shear walls; under the vertical force, seismic performance of the RC shear wall with high axial compression ratio can be significantly improved through plastic hinge area or the whole body of the shear wall equipped with outer HRSR.

• 토지주택연구
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• 제4권4호
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• pp.371-382
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• 2013

불균형 모멘트가 작용하는 무량판 슬래브 내부접합부를 대상으로 폐쇄형 전단보강근으로 보강한 1개 실험체와 밴드형 전단보강근으로 전단보강한 2개의 실험체를 제작하여 구조성능을 평가하였다. 구조성능평가 결과, 구조설계기준(KBC 2009)으로 평가한 불균형모멘트는 실험결과의 95%로 매우 잘 일치하나, 개정 구조설계기준(KCI 2012)으로 산정한 불균형모멘트는 실험결과의 약 60%에 불과하여, 내부접합부의 불균형모멘트를 과대평가하는 것으로 나타났다. 밴드형 전단보강근은 기존 전단보강근과 비교하여 유사한 구조성능을 가지며, 시공성이 우수한 것으로 나타나 중진지역의 무량판구조물 설계 시 적용할 수 있는 것으로 평가되었다.

• 대한건축학회논문집:구조계
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• 제36권2호
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• pp.117-126
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• 2020

The main objective of this experimental study is to investigate shear strength of reinforced concrete beams according to longitudinal reinforcement ratio (ρ) and size effect. In order to find out the shear strength according to the tensile reinforcement ratio, in particular, the main variables are 100%, 75% and 50% of ρ=0.01 which is widely used in construction field. A total of twelve RC beams were tested under 4-point loading conditions. In addition to the existing proposal equations, the theoretical values such as KBC and ACI equations are compared with the experimental data. Through this analysis, this study is designed to provide more reasonable equations for shear design of reinforced concrete beams. When shear reinforcement bar spacing of nine specimens (R^*-1, R^*-2, and R^*-3 series) fixed as d/s=2.0 and three specimens of R^*-4 series fixed as d/s=1.5 are compared, the shear strength of two groups showed similar values. As a result, the current standard of d/s=2.0 for shear reinforcement bar spacing may be somewhat alleviated.