• 한국공간구조학회논문집
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• 제15권2호
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• pp.69-77
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• 2015

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) has a outstanding tensile hardening behaviour after a crack develops, which gives ductility to structures. Existing shear strength model for fiber reinforced concrete is entirely based on crack opening behavior(mode I) which comes from flexural-shear failure, not considering shear-slip behavior(mode II). To find out the mode I and mode II behavior on a crack in UHPFRC simultaneously, maximum shear strength of cracked UHPFRC is investigated from twenty-four push-off test results. The shear stress on a crack is derived as variable of initial crack width and fiber volume ratio. Test results show that shear slippage is proportional to crack opening, which leads to relationship between shear transfer strength and crack width. Based on the test results a hypothesis is proposed for the physical mechanics of shear transfer in UHPFRC by tensile hardening behavior in stead of aggregate interlocking in reinforced concrete. Shear transfer strength based on tensile hardening behavior in UHPFRC is suggested and this suggestion was verified by comparing direct tensile test results and push-off test results.

• 한국안전학회지
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• 제23권3호
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• pp.42-50
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• 2008

This study, push-off tests for the initially uncracked specimens were conducted to investigate shear transfer mechanism in reinforce concrete elements. Experimental programs for shear transfer were undertaken to investigate the effect of the concrete compressive strength, the presence of steel stirrups as shear reinforcement and the amount of steel stirrups. As the shear plane is loaded, several cracks form in a direction inclined to the shear plane, creating compression struts in the concrete. For this stage, shear is being transferred through a truss-like action produced by the combination of the compressive force in the concrete struts and the tensile force that the steel reinforcement crossing the shear plane develops. In the normal strength concrete specimens with steel stirrups, ultimate failure occurred when the compression struts crushed in concrete. In the high strength concrete specimens, on the other hand, ultimate failure occurred when the steel stirrups developed their yield strength.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.585-590
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• 2001

Cracks in concrete can submit shear forces by virtue of the roughness of their interfaces. With regard to this roughness, the crack faces play an important role. By transmitting normal and shear stress across their faces, shear cracks contribute to shear resistance. This process is called shear transfer or more generally, shear friction. Both experimental and analytical program to investigate shear transfer mechanism in normal and high strength concrete were included in this study. The parameters investigated in push-off test included the concrete strength, the presence and amounts of steel stirrups, and aggregate size. Solution procedure based on the truss model was developed to analyze the shear transfer behavior. In general, it can be seen that the analytical results agree well with results of shear transfer test.

• Steel and Composite Structures
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• 제11권2호
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• pp.169-181
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• 2011

The behavior of connections between open sandwich slabs and double steel skin composite walls in steel plate-concrete(SC) structure is investigated by a series of experimental programs to identify the roles of components in the transfer of forces. Such connections are supposed to transfer shear by the action of friction on the interface between the steel surface and the concrete surface, as well as the shear resistance of the bottom steel plate attached to the wall. Experimental observation showed that shear transfer in slabs subjected to shear in short spans is explained by direct force transfer via diagonal struts and indirect force transfer via truss actions. Shear resistance at the interface is enhanced by the shear capacity of the shear plate as well as friction caused by the compressive force along the wall plate. Shear friction resistance along the wall plate was deduced from experimental observation. Finally, the appropriate design strength of the connection is proposed for a practical design purpose.

• Steel and Composite Structures
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• 제37권6호
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• pp.649-662
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• 2020

Although several types of rigid shear connectors have been developed particularly to increase load-carrying capacity, application is limited due to the complicated details of such connection. In this study, push-out tests were performed for specimens with hybrid shear connectors using headed studs and shear plates to identify the effects of each parameter on the structural performance of such shear connection. The test parameters included steel ratios of headed stud to shear plate, connection length, and embedded depth of shear plates. The peak strength and residual strength were estimated using various shear transfer mechanisms such as stud shear, concrete bearing, and shear friction. The hybrid shear connectors using shear plates and headed studs showed large load-carrying capacity and deformation capacity. The peak strength was predicted by the concrete bearing strength of the shear plates. The residual strength was sufficiently predicted by the stud shear strength of headed studs or by shear friction strength of dowel reinforcing bars. Further, the finite element analysis was performed to verify the shear transfer mechanism of the connection with hybrid shear connector.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.271-274
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• 2005

Existing strut-and-tie model cannot be applied to analysis of slender beams without shear reinforcement because shear transfer mechanism is not formed. In the present study, a new strut-and-tie model with rigid joint was developed. Basically, concrete strut is modeled as a frame element which can transfer shear force (or moment) as well as axial force. Employing Rankine failure criterion, failure strength due to shear-tension and shear-compression developed in compressive concrete strut was defined. For verification, various test specimens were analyzed and the results were compared with tests. The proposed strut-and-tie model predicted shear strength and failure displacement with reasonable precision, addressing the design parameters such as shear reinforcement, concrete compressive strength, and shear span ratio.

• Structural Engineering and Mechanics
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• 제37권1호
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• pp.39-59
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• 2011

Results of an experimental investigation on the behavior and ultimate shear capacity of 27 reinforced concrete Transfer (deep) beams are summarized. The main variables were percent longitudinal(tension) steel (0.28 to 0.60%), percent horizontal web steel (0.60 to 2.40%), percent vertical steel (0.50to 2.25%), percent orthogonal web steel, shear span-to-depth ratio (1.10 to 3.20) and cube concrete compressive strength (32 MPa to 48 MPa).The span of the beam has been kept constant at 1000 mm with100 mm overhang on either side of the supports. The result of this study shows that the load transfer capacity of transfer (deep) beam with distributed longitudinal reinforcement is increased significantly. Also, the vertical shear reinforcement is more effective than the horizontal reinforcement in increasing the shear capacity as well as to transform the brittle mode of failure in to the ductile mode of failure. It has been observed that the orthogonal web reinforcement is highly influencing parameter to generate the shear capacity of transfer beams as well as its failure modes. Moreover, the results from the experiments have been processed suitably and presented an analytical model for design of transfer beams in high-rise buildings for estimating the shear capacity of beams.

• 한국전산구조공학회논문집
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• 제31권6호
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• pp.315-329
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• 2018

최근 국내에서는 고층 벽식 아파트 건설 시, 하부 주차공간과 공용공간 확보를 위하여 RC 전이슬래브 시스템을 사용하는 경우가 증가하고 있다. 하지만 두께가 얇은 RC 무량판 슬래브를 위해 개발된 설계방법 및 구조성능평가 방법을 두께가 매우 두꺼운 전이슬래브 구조설계에 그대로 사용하고 있다는 문제점이 있다. 따라서 합리적인 전이슬래브의 구조설계를 위해서는 RC 전이슬래브 시스템의 2면 전단거동 양상에 대한 명확한 분석이 필요하다. 이에 따라 본 연구에서는 전이슬래브의 두께, 콘크리트 강도, 전단경간비, 철근비 등 다양한 설계변수에 따라 비선형 FEM을 이용하여 전이슬래브의 2면 전단거동을 분석하였다. 또한 비선형 FEM 해석결과와 기존의 2면 전단강도 평가식으로 예측한 전단강도를 비교분석하여 기존 평가식의 전이슬래브 2면 전단강도 평가 유효성을 검토하였다.

• 콘크리트학회논문집
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• 제27권3호
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• pp.299-309
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• 2015

강섬유 보강 초고성능 콘크리트(UHPFRC)는 뛰어난 압축 및 인장강도를 가지고 있는 재료이다. 일반 콘크리트는 균열 발생 후 균열에 수직으로 보강된 철근의 구속력을 수직항력으로, 구속력에 의해 발생하는 골재 맞물림 등에 의한 균열면의 거칠기를 마찰 계수로 표현하여 전단 마찰 강도를 정의하고 있다. UHPFRC는 골재 맞물림 현상은 없으나 강섬유의 부착응력에 의한 균열 후 인장력이 상당히 큰 특징이 있으며, 이러한 특징은 전단 마찰 강도에 반영되어야 함이 타당하다. 본 연구에서는 전단면에 횡철근이 보강된 24개의 직접 전단실험체를 제작하여 푸시 오프 실험을 수행하였다. 실험결과는 소성 이론에 의해 분석되었으며 이로부터 전단 마찰 계수와 유효 계수를 도출하였다. 소성 이론에 의한 전단 마찰 강도식은 기존 실험결과 및 기존 전단 마찰 강도식과 비교하여 타당성을 검증하였으며, 최종적으로 UHPFRC의 균열 후 인장강도를 고려한 일체식 구조체의 전단 마찰 강도식을 제안하였다.

• 콘크리트학회논문집
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• 제27권6호
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• pp.615-623
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• 2015

철근콘크리트 전단벽의 전단강도를 예측하기 위한 기존 연구자들의 스트럿-타이 모델(STM)들은 횡하중 및 상부의 축력에 대한 전단벽의 내부 힘의 흐름과 웨브의 전단철근에 의해 전달되는 전단력의 비율을 명확히 제시하고 있지 않다. 이를 개선하기 위해서, 이 연구에서는 콘크리트 파괴역학의 균열 띠 이론을 기반한 단순한 STM을 개발하였다. 응력이완 스트립을 동반하는 콘크리트 스트럿의 등가유효너비는 중립축 깊이와 콘크리트 유효압축강도 계수로 결정되었다. 균열 띠 확장영역의 전단 전달 메커니즘은 강성법에 의한 트러스 작용으로부터 산정되었다. 웨브 콘크리트 스트럿과 전단철근에 의한 전단 전달력은 응력이완 스트립과 균열 띠 이론을 기반한 에너지평형조건으로부터 유도되었다. 제시된 모델은 Siao와 Hwang et al.의 STM에 비해 150여개의 기존 실험결과의 경향을 잘 예측하였다. 또한, 제시된 STM은 각 변수에 따른 무차원된 전단강도의 경향을 잘 반영하고 있다.