• KCI Concrete Journal
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• 제11권3호
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• pp.5-17
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• 1999

In recent years. the concept of the modified compression field theory (MCFT) was develped and applied to the analysis of reinforced concrete beams subjected to shear, moment, and axial load. Although too complex for regular use in the shear design or beams. the procedure has value in its ability to provide a rational method of anlysis and design for reinforced concrete members. The objective of this paper is to review the MCFT and apply it for the prediction of the response and shear strength of reinforced concrete beams A Parametric analysis was Performed on a reinforced T-section concrete beam to evaluate and compare the effects of concrete strength. longitudinal reinforcement ratio shear reinforcement ratio, and shear span to depth ratio in two different approaches the MCFT and the ACI code. The analytical study showed that the concrete contribution to shear strength by the MCFT was higher than the one by the ACI code in beams without stirrups, while it was lower with stirrups. On the other hand. shear reinforcement contribution predicted by the MCFT was much higher than the one by the ACI code. This is because the inclination angle of shear crack is much smaller than 45$^{\circ}$assumed in the ACI code.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.201-206
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• 1993

Four reinforced concrete beams without shear reinforcement were tested statically up to failure to investigate the arch action in reinforced concrete beams. Major variable was the shear span to depth ratio varied from 2 to 4. Due to the reduction of internal moment arm length by the development of arch action, the measured steel tension was higher than the calculated steel tension.

• 한국가시화정보학회지
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• 제11권2호
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• pp.46-54
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• 2013

Study of the wave structure and shear layer in the vicinity of a wall mounted cavity is done by time averaged colour schlieren and time resolved instantaneous shadowgraph technique in an M=1.7 flowfield. Effect of change of cavity width on flow structure is investigated by using constant length to depth (L/D) ratio cavity models with varying length to width (L/W) ratio of 0.83 to 4. The time averaged shock wave structure was observed to change with change in cavity width. Dependence of the shock angle at the leading edge on the shear layer width is also evident from the images obtained. Unsteadiness in the flow field in terms of shear layer dynamics and quasi steady nature of shock waves was evident from the images obtained during instantaneous shadowgraph experiments. Apart from the leading and trailing edge shocks, several other waves and flow features were observed. These flow features and the associated physical phenomena are discussed in details and presented in the paper.

• KCI Concrete Journal
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• 제14권1호
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• pp.51-60
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• 2002

Strengthening of existing concrete structures is a major concern in recent years as the number of degraded structures increases. The purpose of this paper is to investigate the static and fatigue behavior of reinforced concrete (RC) beams strengthened with steel plates. To this end, a comprehensive test program has been set up and many series of strengthened beams have been tested. The major test variables include the plate thickness, adhesive thickness, and the shear-span to depth ratio. The test results indicate that the separation of plates is the dominant failure mechanism even for the full-span-length strengthened beams with steel plate. The theoretical ultimate load capacities for strengthened beams based on the full composite action of concrete beam and steel plate are found to be larger than the actual measured load capacities. The strengthened beams exhibit more dominant shear cracking as the shear-span to depth ratio decreases. The ultimate capacity of strengthened beams increases slightly with the increase of adhesive thickness, which may be caused by the late initiation of plate separation in the beams with thicker adhesive. A realistic concept of ductility for plate-strengthened beams is proposed in this study. It is seen that the strengthened beams show relatively low ductility compared with unstrengthened beams. The present study indicates that the strengthened beams exhibit much higher fatigue resistance than the unstrengthened beams. The increase of deflections of strengthened beams according to the number of load cycles is much smaller than that of unstrengthened beams. The present study provides very useful results for the realistic application of plate-strengthening method in reinforced concrete structures.

• Steel and Composite Structures
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• 제21권2호
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• pp.289-302
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• 2016

A new kind of partially precast or prefabricated castellated steel reinforced concrete beam, which is abbreviated here as CPSRC beam, was presented and introduced in this paper. This kind of CPSRC beam is composed of a precast outer-part and a cast-in-place inner-part. The precast outer-part is composed of an encased castellated steel shape, reinforcement bars and high performance concrete. The cast-in-place inner-part is made of common strength concrete, and is casted with the floor slabs simultaneously. In order to investigate the shear performance of the CPSRC beam, experiments of six CPSRC T-beam specimens, together with experiments of one cast-in-place SRC control T-beam specimen were conducted. All the specimens were subjected to sagging bending moment (or positive moment). In the tests, the influence of casting different strength of concrete in the cross section on the shear performance of the PPSRC beam was firstly emphasized, and the effect of the shear span-to-depth ratio on that were also especially taken into account too. During the tests, the shear force-deflection curves were recorded, while the strains of concrete, the steel shapes as well as the reinforcement stirrups at the shear zone of the specimens were also measured, and the crack propagation pattern together with the failure pattern was as well observed in detail. Based on the test results, the shear failure mechanism was clearly revealed, and the effect of the concrete strength and shear span-to-depth ratios were investigated. The shear capacity of such kind of CPSRC was furthermore discussed, and the influences of the holes on the steel shape on the shear performance were particularly analyzed.

• 콘크리트학회지
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• 제7권5호
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• pp.179-188
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• 1995

강섬유보강콘크리트는 콘크리트의 취성을 극복하고 콘크리트 내의 강섬유의 구속작용과 균열제어메카니즘, pull-out저항 등에 의하여 강도가 증진되며 이러한 작용에 의하여 전단하중하에서도 강도와 연성의 증대를 가져온다. 강섬유보강콘크리트의 2차적인 보강효과는 휨보다는 전단거동에 대하여 더 효율적인 것으로 보고되고 있다. 따라서 시멘트계 재료에 훅트강섬유를 혼입함으로써 전단하중 하에서 훅트강섬유보강 철근콘크리트보(RHSFCB)의 전단저항력이 증가되고 결과적으로 보의 구조적 거동과 전단강도가 향상된다. 본 연구에서는 RHSFCB의 전단거동에 영향을 미치는 주요 변수들에 대한 각 영향을 실험적으로 고찰하였으며, 본 연구에서 고찰한 주요변수는 섬유혼입율, 전단-스팬비, 스터럽의 간격등이다. 이론적 고찰은 문헌에 보고된 각 전단강도 예측식들에 본 실험에서 전단파괴한 9개 시험체와 문헌에 나타난 86개의 전단파괴시험체를 적용하여 각 예측식들의 전단강도를 비교하였으며, 그 결과치를 통계분석하여전단강도예측식의 정확성을 고찰하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 가을 학술발표회 논문집
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• pp.337-344
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• 1996

Reinforced concrete deep beams with conpressive strengths in the range of 500kg/$\textrm{cm}^3$~750kg/$\textrm{cm}^3$ were tested under two-point loding. All the beams were singly reinforced with main steel percent $\rho$=1.29% and with nominal percentage of vertical shear reinflrcements $\rho_v$=0.26%. According to shear-span to depth ratio a/d. The beams were tested for four horizontal shear reinforcement ratio $\rho_h$, ranging from$\rho_h$=0.0 to $\rho_h$=0.53. The results indicate that the horizontal shear reinforcements of beams have an effect on failure load and on ductile behavior of deep beams. The test results are compared with predictions based on the current ACI Building Code. The computated reports in the paper will have designers assured for design of high strength concrete deep beam. Though ACI Code is relatively conservative and tend to non-economical, ACI Code has the merit that is easy to use.

• 한국지진공학회논문집
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• 제13권6호
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• pp.1-9
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• 2009

본 연구는 아라미드 섬유 보강 폴리머(Aramid Fiber Reinforced Polymers, 이하 AFRP)rebar로 보강된 콘크리트 깊은보의 전단강도를 평가하기 위하여 전단경간비, 보강비, 유효깊이, 주근을 변수로 총 8본의 시험체에 대한 전단 실험을 수행하였다. ACI 318-08의 스트럿-타이 모델(이하 STM)을 이용한 전단강도와 아치작용을 고려한 제안식에 의한 전단강도를 비교-평가하였으며, 그 결과 AFRP rebar로 보강한 경우, Steel rebar로 보강한 경우보다 전단강도가 증가하는 것으로 나타났다. 전단강도 산정에 있어 ACI 318-08 STM을 이용한 해석이 상대적으로 정확했으며, 실험결과를 토대로 스트럿의 크기효과를 고려한 유효압축강도 산정 모델을 제안하였다. 이를 본 실험에 적용시킨 결과 기존 기준 및 제안식을 이용한 전단강도 산정방법보다 합리적인 결과를 얻을 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.50-53
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• 2006

An experimental investigation on the behavior of reinforced concrete coupling beams is presented. The test variables are the span-to-depth ratio, the ratio of flexural reinforcement and the ratio of shear rebar. The distribution of arch action and truss action which compose the mechanism of shear resistance is discussed. This study proposes the deformation model for reinforced concrete coupling beams considering the bond slip of flexural reinforcement. The yielding of flexural reinforcements determines yielding states and the ultimate states of reinforced concrete coupling beam are defined as the ultimate compressive strain of struts and the degradation of compressive strength due to principal tensile strain of struts. It is expected that this model can be applied to displacement-based design methods.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.233-240
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• 2006

An experimental investigation on the behavior of reinforced concrete coupling beams is presented. The test variables are the span-to-depth ratio, the ratio of flexural reinforcement and the ratio of shear rebar. The distribution of arch action and truss action which compose the mechanism of shear resistance is discussed. This study proposes the deformation model for reinforced concrete coupling beams considering the bond slip of flexural reinforcement. The yielding of flexural reinforcements determines yielding states and the ultimate states of reinforced concrete coupling beam are defined as the ultimate compressive strain of struts and the degradation of compressive strength due to principal tensile strain of struts. It is expected that this model can be applied to displacement-based design methods.