• Structural Engineering and Mechanics
• /
• 제24권1호
• /
• pp.107-136
• /
• 2006

The present paper proposes a semi-empirical analytical expression that is capable of determining the shear strength of reinforced concrete beams with longitudinal bars, in the presence of reinforcing fibers and transverse stirrups. The expression is based on an evaluation of the strength contribution of beam and arch actions and it makes it possible to take their interaction with the fibers into account. For the strength contribution of stirrups, the effective stress reached at beam failure was considered by introducing an effectiveness function. This function shows the share of beam action strength contribution on the global strength of the beam calculated including the effect of fibers. The expression is calibrated on the basis of experimental data available in literature referring to fibrous reinforced concrete beams with steel fibers and recently obtained by the authors. It can also include the following variables in the strength previsions: - geometrical ratio of longitudinal bars in tension; - shear span to depth ratio; - strength of materials and fiber characteristics; - size effects. Finally, some of the more recent analytical expressions that are capable of predicting the shear strength of fibrous concrete beams, also in the presence of stirrups, are mentioned and a comparison is made with experimental data and with the results obtained by the authors.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.53-56
• /
• 2005

This paper investigates the effect of ductile deformation behavior of high performance hybrid fiber-reinforced cement composites (HPHFRCCs) on the shear behavior of coupling beams to lateral load reversals. The matrix ductility and the reinforcement layout were the main variables of the tests. Three short coupling beams with two different reinforcement arrangements and matrixes were tested. They were subjected to cyclic loading by a suitable experimental setup. All specimens were characterized by a shear span-depth ratio of 1.0. The reinforcement layouts consisted of a classical scheme and diagonal scheme without confining ties. The effects of matrix ductility on deflections, strains, crack widths, crack patterns, failure modes, and ultimate shear load of coupling beams have been examined. The combination of a ductile cementitious matrix and steel reinforcement is found to result in improved energy dissipation capacity, simplification of reinforcement details, and damage-tolerant inelastic deformation behavior. Test results showed that the HPFRCC coupling beams behaved better than normal reinforced concrete control beams. These results were produced by HPHFRCC's tensile deformation capacity, damage tolerance and tensile strength.

• Steel and Composite Structures
• /
• 제30권4호
• /
• pp.365-382
• /
• 2019

In steel frame-tube structures (SFTSs) the application of flexural beam is not suitable for the beam with span-to-depth ratio lower than five because the plastic hinges at beam-ends can not be developed properly. This can lead to lower ductility and energy dissipation capacity of the SFTS. To address this problem, a replaceable shear link, acting as a ductile fuse at the mid length of deep beams, is proposed. SFTS with replaceable shear links (SFTS-RSLs) dissipate seismic energy through shear deformation of the link. In order to evaluate this proposal, buildings were designed to compare the seismic performance of SFTS-RSLs and SFTSs. Several sub-structures were selected from the design buildings and finite element models (FEMs) were established to study their hysteretic behavior. Static pushover and dynamic analyses were undertaken in comparing seismic performance of the FEMs for each building. The results indicated that the SFTS-RSL and SFTS had similar initial lateral stiffness. Compared with SFTS, SFTS-RSL had lower yield strength and maximum strength, but higher ductility and energy dissipation capacity. During earthquakes, SFTS-RSL had lower interstory drift, maximum base shear force and story shear force compared with the SFTS. Placing a shear link at the beam mid-span did not increase shear lag effects for the structure. The SFTS-RSL concentrates plasticity on the shear link. Other structural components remain elastic during seismic loading. It is expected that the SFTS-RSL will be a reliable dual resistant system. It offers the benefit of being able to repair the structure by replacing damaged shear links after earthquakes.

• Advances in concrete construction
• /
• 제13권3호
• /
• pp.243-254
• /
• 2022

Reinforced concrete (RC) deep beams are critical structural elements used in offshore pile caps, rectangular cross-section water tanks, silo structures, transfer beams in high-rise buildings, and bent caps. As a result of the low shear span ratio to effective depth (a/d) in deep beams, arch action occurs, which leads to shear failure. Several studies have been carried out to improve the shear resistance of RC deep beams and avoid brittle fracture behavior in recent years. This study was performed to investigate the behavior of RC deep beams numerically and experimentally with different reinforcement arrangements. Deep beams with four different reinforcement arrangements were produced and tested under monotonic static loading in the study's scope. The horizontal and vertical shear reinforcement members were changed in the test specimens to obtain the effects of different reinforcement arrangements. However, the rebars used for tension and the vertical shear reinforcement ratio were constant. In addition, the behavior of each deep beam was obtained numerically with commercial finite element analysis (FEA) software ABAQUS, and the findings were compared with the experimental results. The results showed that the reinforcements placed diagonally significantly increased the load-carrying and energy absorption capacities of RC deep beams. Moreover, an apparent plastic plateau was seen in the load-displacement curves of these test specimens in question (DE-2 and DE-3). This finding also indicated that diagonally located reinforcements improve displacement ductility. Also, the numerical results showed that the FEM method could be used to accurately predict RC deep beams'behavior with different reinforcement arrangements.

• 콘크리트학회논문집
• /
• 제25권2호
• /
• pp.175-185
• /
• 2013

최근 다른 압축강도로 타설된 프리캐스트 콘크리트(PC)와 현장타설 콘크리트(CIP)의 복합 부재의 사용이 증가하고 있지만 현행 기준에는 서로 다른 강도로 복합화된 부재의 전단강도에 대한 설계 기준이 없다. 그래서 이번 연구에서 서로 다른 압축강도(24 MPa, 60 MPa)로 분리 타설된 보의 전단강도 실험을 수행하여 복합 부재의 전단강도에 대해 알아보았다. 변수로는 단면형상, 휨철근비, 그리고 전단경간비를 고려하였다. 실험 결과 값과 현행 전단 기준식과 단면적비로 계산한 유효 콘크리트 강도를 이용한 예측 값을 비교하였다. 실험 결과를 분석해보면 철근비가 낮고 압축대에 60 MPa가 사용된 실험체들에 대해 설계 기준식을 과대평가하였다. 실험 결과를 기준으로 PC와 CIP 복합부재의 전단설계 기준을 제안하였다.

• International Journal of Concrete Structures and Materials
• /
• 제10권1호
• /
• pp.99-112
• /
• 2016

During earthquake, reinforced concrete walls show complicated post-yield behavior varying with shear span-to-depth ratio, re-bar detail, and loading condition. In the present study, a macro-model for the nonlinear analysis of multi-story wall structures was developed. To conveniently describe the coupled flexure-compression and shear responses, a reinforced concrete wall was idealized with longitudinal and diagonal uniaxial elements. Simplified cyclic material models were used to describe the cyclic behavior of concrete and re-bars. For verification, the proposed method was applied to various existing test specimens of isolated and coupled walls. The results showed that the predictions agreed well with the test results including the load-carrying capacity, deformation capacity, and failure mode. Further the proposed model was applied to an existing wall structure tested on a shaking table. Three-dimensional nonlinear time history analyses using the proposed model were performed for the test specimen. The time history responses of the proposed method agreed with the test results including the lateral displacements and base shear.

• Structural Engineering and Mechanics
• /
• 제26권4호
• /
• pp.427-439
• /
• 2007

The exploitation of fibre reinforced polymer composites, as external reinforcement is an evergreen and well-known technique for improving the structural performance of reinforced concrete structures. The demand to use FRP composites in the civil engineering industry is mainly due to its high strength, light weight, and stiffness. This paper exemplifies the shear strength of partially precracked reinforced concrete rectangular beams repaired with externally bonded Bi-Directional Carbon Fibre Reinforced Polymer (CFRP) Fabrics strips. All specimens were cast in the laboratory environment without any internal shear reinforcement. The test parameters were longitudinal tensile reinforcement, shear span to effective depth ratio, spacing of CFRP strips, and orientation of CFRP reinforcement. It mainly focuses on the shear capacity and modes of failure of the CFRP strengthened shear beams. Results have shown that the CFRP repaired beams attained a shear enhancement of 32% and 107.64% greater than the control beams. This study underscores that the CFRP strip technique significantly enhanced the shear capacity of precracked reinforced concrete rectangular beams without any internal shear reinforcement.

• 대한토목학회논문집
• /
• 제13권1호
• /
• pp.75-87
• /
• 1993

본 논문은 강섬유보강콘크리트 deep beam의 전단특성을 규명하고 균열전단강도와 극한전단강도를 예측하기 위한 것으로 섬유로 보강된 16개의 보를 포함한 총 20개의 보를 4 series로 나누어 실험을 수행하였다. 실험의 변수는 콘크리트의 강도, 섬유혼입률, 전단지간 등이며, 실험 과정을 통해 파괴형상, 처짐, 변형률, 전단강도 등을 측정 하였다. 실험결과로 부터 섬유의 혼입량이 많아지고, 콘크리트의 강도가 커질 수록, 그리고 전단지간이 짧아질수록 섬유보강콘크리트 deep beam의 균열 및 극한전단강도가 증가됨을 밝혔다. 또한, 실험성과를 회귀분석하여 균열전단강도와 극한전단강도 추정식을 제안 하였다. 제안된 추정식에 의한 계산값과 실험성과를 비교 검토하여 그 상관성을 확인하였다.

• 대한토목학회논문집
• /
• 제13권3호
• /
• pp.1-12
• /
• 1993

본 논문은 전단철근을 갖지 않는 강섬유보강콘크리트 보의 전단특성을 규명하고 균열전단강도와 극한전단강도를 예측하기 위한 것으로 섬유로 보강된 21개의 보를 포함한 총 36개의 보를 4 series로 나누어 실험을 수행하였다. 실험의 변수는 콘크리트의 강도, 섬유혼입율, 전단지간, 인장철근량 등이며, 실험과정을 통해 파괴형상, 처짐, 전단강도 등을 측정하였다. 실험결과로부터 섬유의 혼입량이 많아지고, 콘크리트의 강도가 커질수록, 그리고 전단지간이 짧아질수록 섬유보강콘크리트 보의 균열 및 극한전단강도가 증가됨을 밝혔다. 또한, 실험결과를 회귀분석하여 균열전단강도와 극한전단강도 추정식을 제안하였다. 제안된 추정식에 의한 계산값과 실험결과를 비교 검토하여 그 상관성을 확인하였다.

• 콘크리트학회논문집
• /
• 제27권3호
• /
• pp.215-227
• /
• 2015

본 연구에서는 순환골재를 사용한 강섬유보강 콘크리트보의 전단거동을 알아보기 위하여 순환골재 치환율은 30 %로 고정하고, 전단경간비(a/d = 2, 3, 4), 인장철근비(${\rho}=0.8$, 1.27 %) 및 강섬유 혼입율($V_f=0$, 0.5, 0.75, 1%)을 변수로 한 총 24개의 강섬유보강 콘크리트보를 만들어 실험하였다. 또한 순환골재를 사용한 강섬유보강 콘크리트보의 전단강도를 여러 연구자들의 제안식과 비교 분석하였다. 즉, 순환골재를 사용한 강섬유보강 콘크리트보의 전단거동에 따른 전단내력을 분석하고, 강섬유보강 전단강도 제안식과 실험값을 비교하여 순환골재를 사용한 강섬유보강 콘크리트보의 사용가능성을 평가하고자 하였다. 대부분의 실험값이 제안식에 의한 이론값보다 높게 나타나 순환골재를 사용한 강섬유보강 콘크리트보를 구조부재로 사용하여도 무방하다고 판단된다.