• Structural Engineering and Mechanics
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• 제87권4호
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• pp.333-346
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• 2023

This paper presents findings from an experimental study that was focused on evaluating the use of Forta-Ferro (FF) and Polyvinyl Alcohol (PVA) fibers on the response of moderate and special ductility beams under load cycles. For this reason, eight full-scale specimens, identical in geometry, were subjected to gradual cyclic loading. The specimens included two plain concrete beams with medium and special ductility, three beams with medium ductility and stirrup spacing of one-quarter the effective depth (d/4) and three beams with special ductility, and stirrup spacing of one-half the effective depth (d/2), strengthened with FF and PVA fibers separately. The use of fibers was aimed at reducing the amount of shear reinforcement in flexural members. Here, the variation of parameters including the maximum strength, ultimate strength, stiffness, ductility, damage index, energy dissipation, and equivalent damping was studied. Utilizing FF and PVA fibers improved the performance in beams with moderate ductility when compared to those beams with special ductility. Therefore, in special ductility beams, fibers can be used instead of crossties and in moderate ductility beams, fibers can be added to reduce the ratio of shear reinforcement. Furthermore, increasing the stirrup spacing in the moderate ductility beams from d/4 to d/2 and adding 0.6% FF or 1.5% PVA fibers resulted in behavior similar to those of the moderate ductility beam.

• Earthquakes and Structures
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• 제18권5호
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• pp.581-598
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• 2020

This paper aims to investigate the seismic behavior and influence parameters of the large-scaled thin-walled reinforced concrete (RC) tubular columns in air-cooled supporting structures of thermal power plants (TPPs). Cyclic loading tests and finite element analysis were performed on 1/8-scaled specimens considering the influence of wall diameter ratio, axial compression ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio and adding steel diagonal braces (SDBs). The research results showed that the cracks mainly occurred on the lower half part of RC tubular columns during the cyclic loading test; the specimen with the minimum wall diameter ratio presented the earlier cracking and had the most cracks; the failure mode of RC tubular columns was large bias compression failure; increasing the axial compression ratio could increase the lateral bearing capacity and energy dissipation capacity, but also weaken the ductility and aggravate the lateral stiffness deterioration; increasing the longitudinal reinforcement ratio could efficiently enhance the seismic behavior; increasing the stirrup reinforcement ratio was favorable to the ductility; RC tubular columns with SDBs had a much higher bearing capacity and lateral stiffness than those without SDBs, and with the decrease of the angle between columns and SDBs, both bearing capacity and lateral stiffness increased significantly.

• Structural Engineering and Mechanics
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• 제23권5호
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• pp.579-597
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• 2006

The behaviour of reinforced concrete moment resisting frame structures in recent earthquakes all over the world has highlighted the consequences of poor performance of beam column joints. Large amount of research carried out to understand the complex mechanisms and safe behaviour of beam column joints has gone into code recommendations. This paper presents critical review of recommendations of well established codes regarding design and detailing aspects of beam column joints. The codes of practice considered are ACI 318M-02, NZS 3101: Part 1:1995 and the Eurocode 8 of EN 1998-1:2003. All three codes aim to satisfy the bond and shear requirements within the joint. It is observed that ACI 318M-02 requires smaller column depth as compared to the other two codes based on the anchorage conditions. NZS 3101:1995 and EN 1998-1:2003 consider the shear stress level to obtain the required stirrup reinforcement whereas ACI 318M-02 provides stirrup reinforcement to retain the axial load capacity of column by confinement. Significant factors influencing the design of beam-column joints are identified and the effect of their variations on design parameters is compared. The variation in the requirements of shear reinforcement is substantial among the three codes.

• Advances in concrete construction
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• 제11권3호
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• pp.193-206
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• 2021

Extensive research has been conducted on the basic mechanical property and structural applications of engineered cementitious composites (ECC). Despite the high tensile ductility and high toughness of ECC, transverse steel reinforcement is still necessary to confine ECC for high performance. However, limited research has examined performance of ECC confined with practical amount of transverse reinforcement. This paper presents the results of axial compression tests on 14 square ECC columns and 4 conventional concrete columns (used as control specimens) with transverse reinforcement. The test variables were spacing, configuration (square ties or square and diamond shape ties), and yield strength of stirrups. The test showed that ECC columns confined with steel stirrup had good compressive ductility, and the stirrup spacing had the greatest effect on the compressive performance. The self-confinement effect of ECC results in a more uniform but slower expansion of the whole column compared with CC ones. The test results are then compared against the predictions from a number of existing models for conventional confined concrete. It is indicated that these models fail to predict the axial strains at peak axial stress and the trend of the stress-strain curve of steel stirrups-confined ECC with sufficient accuracy. Several new equations are then proposed for the compressive properties of steel-confined ECC based on test results and potential approaches for future studies are proposed.

• 한국강구조학회 논문집
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• 제30권2호
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• pp.67-76
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• 2018

스터럽 보강 선설치 앵커의 동적 전단하중 하의 파열파괴강도를 평가하기 위한 실험 연구를 수행하였다. 전단 하중은 ACI 355.2 및 ETAG 001에 제시된 지진모의실험 방식으로 재하하였다. 시험체는 M36 앵커(연단거리 180mm)를 D10 스터럽(간격 100mm)으로 보강하였다. 이들 시험체는 거의 극한 파열파괴 강도에 도달한 후 앵커의 파단이 발생하였다. 이에 M42 앵커(연단거리 160mm)를 D6 스터럽(간격 100mm)으로 보강한 시험체에 대한 실험을 추가로 수행하였다. 실험 결과, 동적 전단강도는 정적 강도에 비해 낮은 값을 보이지 않았다. 또한, ACI 318 및 ETAG 001 기준은 스터럽 보강이 많을수록 파열파괴강도를 안전측으로 평가하는 것으로 나타났다.

• 콘크리트학회논문집
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• 제20권1호
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• pp.99-107
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• 2008

본 논문에서는 유효 스터럽 개념을 이용한 전단보강근의 강도 예측 방법을 제안하고 있다. 유효 스터럽 개념을 이용한 예측에서 가장 중요시 되는 부분인 전단 균열각 예측은 수정압축장이론 (modified compression field theory, MCFT)을 이용하여 수행하였다. 현 설계기준인 ACI 318-05와 기존 문헌에서 인용한 39개의 실제 실험 데이터를 이용하여 예측 방법의 유효성을 평가하였다. 평가시 고려한 영향인자로는 콘크리트 강도 그리고 전단보강근의 종류가 있었고, 추가로 2개의 full-scale의 보 실험을 수행하여 제안된 방법의 헤디드 바 사용 시험체의 확대 적용 가능성도 평가하였다.

• 한국강구조학회 논문집
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• 제26권1호
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• pp.21-30
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• 2014

본 연구에서는 헤어핀 보강 및 스트럽 보강 선설치앵커의 정적 및 동적 전단하중에 대한 저항강도 평가를 위한 실험을 수행하였다. 보강철근은 D6 이형철근을 사용하였으며 연단거리 120mm의 직경 20mm 앵커에 대해 정적 하중과 1Hz의 편진하중으로 각각 3개의 시험체에 대해 실험을 수행하였다. 헤어핀 보강 앵커는 헤어핀의 덮개가 강도에 직접 영향을 미치는 것으로 확인되었으며, 정적 대비 동적하중에서 강도의 저하는 없는 것으로 평가되었다. 스트럽 보강 앵커는 비보강 앵커에 비해 저항강도의 증가는 미소하였으며 동적하중에 의한 강도는 정적하중에 의한 강도와 거의 같은 값을 보였다.

• 한국구조물진단유지관리공학회 논문집
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• 제9권1호
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• pp.205-215
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• 2005

본 연구에서는 콘크리트 보의 전단거동에서 콘크리트 압축강도가 스터럽 유효성에 미치는 영향을 실험적으로 연구하였다. 전단파괴와 휨파괴가 동시에 일어나는 경계점은 대략 S=150mm부근으로 예상되며, 이때 전단철근비는 보통강도 콘크리트보에서는 $0.63{\rho}_{vmax}$ 이고, 고강도 콘크리트보에서는 $0.53{\rho}_{vmax}$로서 ACI 전단설계 산정식은 매우 안전측이라고 판단된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 춘계 학술논문 발표대회
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• pp.173-174
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• 2012

This study is concerned with the VSTUD shear reinforcement that it can be installed easily in filed as product at the factory and seismic performance can be achieved. The method of study is as follows. first, we researched constructability and economy of existing method. Secondly, we made specimen and were examined structural performance tests in order to verify the performance of the shear reinforcement. As a result, developed SL shear reinforcement increased in shear strength and stiffness of reinforcement, structural safety is judged to be increased.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.407-410
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• 2005

This paper describes an evaluation of reinforcement tension in RC beams using the variable truss models. The models were examined with the beam test results by Kim, Kim and White. Consequently, a fixed inclination $\theta$ at the support un-explains global state of internal force flow in cracked reinforced concrete beams subjected to shear and bending. Accordingly, we must introduce the arch factor for development of consistent model in reinforced concrete beams subjected to shear and bending