• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.683-691
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• 2013

Failure behaviour of deep beams is largely depend on shear span to effective depth ratio(a/d). For deep beams with $a/d{\leq}1.0$, the diagonal splitting of the web and local crushing of concrete near applied loads or supports is the most common failure mode. If the beam contains sufficient web reinforcement, area of local crushing will be increased while area of diagonal splitting is decreased. When web reinforcement above purpose, web should be reinforced both in the horizontal and vertical directions or be reinforced in perpendicular direction to diagonal cracks. For deep beams with 1.0${\leq}2.5$, the increment of shear strength by the horizontal web reinforcement are hardly expected unless amount of main bars very small that the main bars should be reached yielding state when shear failure occurs. In contrast, the vertical web reinforcement prevent the beam from being transferred to tied arch mechanism, and as a result th shear strength of beam increase. In this study, formulas based on upper bound theorem of plastic theory are proposed to predict the shear strength of reinforced concrete deep beams with $a/d{\leq}1.0$. Comparisons with other experiment results are performed, and good agreement between measured and predicted value by proposed formulas is obtained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6542-6549
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• 2013

In highly elevated piers and long span beams, a hollow section is often used to reduce the self-weight and increase the flexural rigidity of members. Numerical analysis was conducted to obtain the moment-curvature curves and curvature ductility factor for the RC hollow section beams under a range of hollow portion sizes and reinforcement conditions in the upper flange and web. The curvature ductility factor was constantly maintained until the hollow portion size($b_i/b_o/h_i/h_o$) was less than or equal to 0.5. The curvature ductility factor decreased sharply if ($b_i/b_o/h_i/h_o$) was 0.7 or more. The curvature ductility factor of the beam decreased if reinforcement was provided in the web of the RC hollow section beam. To obtain the same level of the ductility factor as the singly reinforced section, the reinforcement should be provided in the upper flange as much as the web reinforcement.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.59-68
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• 2010

In the present study, the deformation capacity of slender shear walls with thin web subject to inelastic deformation after flexural yielding was studied. Web-crushing and rebar-fracture were considered as the governing failure mechanisms of walls. To address the effect of the longitudinal elongation on web-crushing and rebar-fracture, the longitudinal elongation was predicted by using truss model analysis. The failure criteria by web-crushing and rebar-fracture were defined as a function of the longitudinal elongation. The proposed method was applied to 17 shear wall specimens with boundary columns, and the prediction results were compared with the test results. The results showed that proposed method predicted the maximum deformations and failure modes of the wall specimens with reasonable precision.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.1001-1009
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• 2002

The objective of this study is to determine the range of confinement (or the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The range of confinement for transverse reinforcement is related to the location of neutral axis and determined by the magnitude and distribution of compressive strain. The compressive strain depends on the ratio of wall cross sectional area to the floor-plan area, the aspect ratio, configuration, the axial load, and the reinforcement ratios. By affection of flange, the neutral axis appears different depending on positive and negative forces and because of this reason, when web and flange are subjected to compressive stress, the range of confinement for the transverse reinforcement of T-shaped walls would shows different result. Therefore this experimental research focused on the structural characteristics of T-shaped walls and suggested the neutral axis depth through comparing the results of this study with sectional analysis.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.233-240
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• 1998

A rational expression, developed to predict the shear strength of reinforced concrete beams, is derived from the relationship between shear and the rate of change of bending moment along a beam coupled with experimental findings for the arch action. The proposed ultimate shear strength equation, arising from analytical premises and then calibrated with experimental data, is a similar form to the ACI 318 equation derived mainly from empirical approach. The proposed equation depends on the concrete compressive strength, amount of longitudinal steel content, and the shear span-to-depth ratio, and rationally reflects the shear resistance mechanism of combined beam action and arch action in reinforced concrete beams. The proposed equation applied to existing test data and the results were compared with those predicted by the ACI 318 equation and the Zsutty's equation.

• Magazine of the Korea Concrete Institute
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• v.5 no.2
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• pp.151-161
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• 1993

본 논문은 전단철근을 갖지 않는 비교적 짧은 지간의 철근콘크리트 보에서 전단특성을 규명하고 균열전단강도와 극한전단강도를 예측하기 위한 것으로 총30개의 보를 4 series로 나누어 실험을 수행하였다. 실험의 변수는 콘크리트의 강도, 전단지간-유효높이의 비, 인장철근량등이며, 실험과정을 통해 파괴형상, 처짐, 전단강도등을 측정하였다. 실험결과로부터 콘크리트의 강도가 커지고 철근량이 많아질수록, 그리고 전단지간이 짧아질수록 철근콘크리트 보의 균열 및 극한전단강도가 증가됨을 밝혔다. 또한, 실험성과를 회귀분석하여 균열전단강도와 극한전단강도 추정식을 제안하였다. 제안된 추정식에 의한 계산값과 실험성과를 비교 검토하여 그 상관성을 확인하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.85-92
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• 2015

It is well known that axial tension decreases the shear strength of RC & PSC beams without transverse reinforcement, and axial compression increases the shear resistance. What is perhaps not very well understood is how much the shear resistance capacity is influenced by axial load. RC beams without shear reinforcement subjected to large axial compression and shear may fail in a very brittle manner at the instance of first diagonal cracking. As a result, a conservative approach should be used for such members. According to the ACI Code, the shear strength in web is calculated by effect of axial force and the vertical force in the stirrups calculated by $45^{\circ}$ truss model. This study was performed to examine the effect of axial force in reinforced concrete beams by nonlinear FEM program (ATENA-2D).

• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.819-825
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• 2006

The objective of the present study is to verify the validity of a new truss model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. The new truss model is based on the relationship between shear and bending moment in a beam subjected to combined shear and bending. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. On the basis of the analytical results, the contribution by the web to shear resistance can be constant and have an excellent linear correlation with the web reinforcement ratio. The present decoupling approach may provide a simple way for the assessment of the role of each parameter or mechanism that affects the ultimate shear behavior of reinforced concrete beams.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.839-842
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• 2008

The ACI 318-05 code requires the maximum amount of shear reinforcement in reinforced concrete (RC) beams to prevent possible sudden shear failure due to over reinforcement. The design equations of the maximum amount of shear reinforcement provided by the current four design codes, ACI 318-05, CSA-04, EC2-02, and JCI-99, differ substantially from one another. The ACI 318-05, CSA-04, and EC2-02 codes provide an expression for the maximum amount of shear reinforcement ratio as a function of the concrete compressive strength, but Japanese code does not take into account the influence of the concrete compressive strength. For high strength concrete, the maximum amount of shear reinforcement calculated by the EC2-02 and CSA-04 is much greater than that calculated by the ACI 318-05. This paper presents the effects of shear reinforcement ratio and compressive strength of concrete on the maximum shear reinforcement in reinforced concrete beams. Ten RC beams having various shear reinforcement ratio were tested. Although the test beams were designed to have much more amount of shear reinforcement than that required in the ACI 318-05 code, all beams failed due to web concrete crushing after the stirrups reached the yield strain.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.665-673
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• 2008

The composite structures of steel and reinforced concrete, which have been widely used in large-scale concrete structures, werestudied to investigate the cause of unexpected cracks and to verify the composite actions between the two materials. Vertical stiffeners between flanges, studs and dowel bars, stirrups, and concrete strength were chosen as experimental variables in afour-point loading test. The results showed that the vertical stiffener prevented not only the local web buckling, but also bond failures between steel and concrete. It increased the flexural resistance (fracture loads) due to the composite action of two materials, compared withthose of any experimental variable. However, the composite behavior of steel reinforced concrete beam was not affected seriously by additional studs, dowel bars, stirrups, and concrete strength.