• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.68-71
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• 2004

In the shear strengthening with FRP sheets, beams are wrapped around the webs and tension face of critical shear span by fiber sheets. The shear strength of RC beam strengthened with FRP sheets must be calculated based on the effective strain that can be developed in the FRP sheets at ultimate stage because the final failure modes of beams are governed by premature debonding of FRP sheet due to the limitation of bonded length by beam depth. An experimental study is carried out to evaluate the shear strengthening effect of AFRP or GFRP sheets with respect to shear reinforcement ratio of rebar. From the test results, it was found that the additional shear strength provided by GFRP or AFRP can be estimated by $p_w{\cdot}f_w$ based on the maximum effective strain of FRP sheet $4,000m{\mu}$ proposed by ACI 440 committee.

• 대한기계학회논문집A
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• 제37권10호
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• pp.1239-1249
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• 2013

본 연구에서는 zircaloy-4 판재에 대해 바우싱거 효과를 고려한 경화거동 예측모델을 구축했다. 금속소재 가공에서 인장 후 압축 시 항복응력이 감소한다. 이에 스프링백 해석 시 바우싱거 효과를 반드시 고려해야 한다. Simple shear 시험에서 적정 시편크기 및 적정 조임토크에 대한 결정법을 제시했다. 5 가지 재료에 대한 simple shear 시험을 통해 응력-변형률 곡선을 구했다. 또한 유한요소해석을 활용해 simple shear 하중-변위 곡선으로부터 유효응력-변형률 곡선으로 변환과정을 소개했다. 등방/운동성 경화 조합모델을 활용해 simple shear 순/역방향 시험을 모사했다. 이때 각 경화계수에 따른 하중-변위 곡선 변화를 관찰하고, zircaloy-4에 대한 경화계수를 결정했다.

• Structural Engineering and Mechanics
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• 제58권3호
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• pp.475-514
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• 2016

Various models have been proposed by several researchers for predicting the exterior RC beam-column joint shear strength. Most of these models were calibrated and verified with some limited experimental database. From the models it has been identified that the joint shear strength majorly depends on ten governing parameters. In the present paper, detailed investigation of twelve analytical models for predicting shear strength of exterior beam-column joint has been carried out. The study shows the effect of each governing parameter on joint shear strength predicted by various models. It has been observed that the consensus on effect of few of the governing parameters amongst the considered analytical models has not been attained. Moreover, the predicted joint strength by different models varies significantly. Further, the prediction of joint shear strength by these analytical models has also been compared with a set of 200 experimental results from the literature. It has been observed that none of the twelve models are capable of predicting joint shear strength with sufficient accuracy for the complete range of experimental results. The research community has to reconsider the effect of each parameters based on larger set of test results and new improved analytical models should be proposed.

• 콘크리트학회논문집
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• 제14권6호
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• pp.910-921
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• 2002

철근콘크리트 보의 전단거동을 예측하기 위하여 휨모멘트가 고려된 변환각 트러스 모델(TATM)을 제안하였다. 제안된 TATM으로 구한 전단응력-전단변형률 관계는 본 연구에서 수행된 실험결과와 잘 일치하였다. 또한, TATM으로 구한 전단강도는 다양한 전단스팬비와 지점형태 및 단면형태를 가지는 총 170개 실험결과와 비교되었다. TATM에 의한 해석결과는 평균 0.96, 변동계수 11.9 %로서 기존의 트러스 모델에 의한 해석결과보다 실험결과를 더 잘 예측하였으며, 해석결과에 대한 실험결과의 비는 a/d와 η에 관계없이 거의 일정하였다.

• 대한건축학회논문집:구조계
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• 제36권2호
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• pp.117-126
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• 2020

The main objective of this experimental study is to investigate shear strength of reinforced concrete beams according to longitudinal reinforcement ratio (ρ) and size effect. In order to find out the shear strength according to the tensile reinforcement ratio, in particular, the main variables are 100%, 75% and 50% of ρ=0.01 which is widely used in construction field. A total of twelve RC beams were tested under 4-point loading conditions. In addition to the existing proposal equations, the theoretical values such as KBC and ACI equations are compared with the experimental data. Through this analysis, this study is designed to provide more reasonable equations for shear design of reinforced concrete beams. When shear reinforcement bar spacing of nine specimens (R^*-1, R^*-2, and R^*-3 series) fixed as d/s=2.0 and three specimens of R^*-4 series fixed as d/s=1.5 are compared, the shear strength of two groups showed similar values. As a result, the current standard of d/s=2.0 for shear reinforcement bar spacing may be somewhat alleviated.

• Earthquakes and Structures
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• 제23권3호
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• pp.297-313
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• 2022

Composite steel plate shear wall (CSPSW) is a relatively novel structural system proposed to improve the performance of steel plate shear walls by adding one or two layers of concrete walls to the infill plate. In addition, the buckling of the infill steel plate has a significant negative effect on the shear strength and energy dissipation capacity of the overall systems. Accordingly, in this study, using the finite element (FE) method, the performance and behavior of composite steel shear walls using T-shaped stiffeners to prevent buckling of the infill steel plate and increase the capacity of CSPSW systems have been investigated. In this paper, after modeling composite steel plate shear walls with and without steel plates with finite element methods and calibration the models with experimental results, effects of parameters such as several stiffeners, vertical, horizontal, diagonal, and a combination of T-shaped stiffeners located in the composite wall have been investigated on the ultimate capacity, web-plate buckling, von-Mises stress, and failure modes. The results showed that the arrangement of stiffeners has no significant effect on the capacity and performance of the CSPSW so that the use of vertical or horizontal stiffeners did not have a significant effect on the capacity and performance of the CSPSW. On the other hand, the use of diagonal hardeners has potentially affected the performance of CSPSWs, increasing the capacity of steel shear walls by up to 25%.

• KSBB Journal
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• 제11권1호
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• pp.52-57
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• 1996

평활근 세포에 대한 shear stress의 영향을 알아보기 위해 슬라이드 글라스위에 배양된 牛 대통맥의 평활근 세포를 120시간 동안 0~26 dyn/$cm^2$의 각기 다른 일정한 shear stress의 유체에 노출하였다. 실험 장치를 순환하는 배지의 lactate dehydrogen­a ase의 농도측정 결과, 본 연구에서 적용된 shear stress 범위에서는 유체의 흐름으로 인하여 세포가 슬라이드 글라스 표면으로부터 이탈되는 현상은 없었다. 표면 $cm^2$ 당 존재하는 세포의 수를 측정한 결과, 평활근 세포는 정체배양시 가장 빨리 성장하였다. 표변에서의 shear stress가 증가할수록 i영활근 세포의 성장은 늦었으며, shear stress가 17 dyn/$cm^2$ 이상에서는 세포의 성장이 관찰되지 않았다.

• Earthquakes and Structures
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• 제7권5호
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• pp.691-704
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• 2014

Reinforced concrete (RC) shear walls are commonly used for building structures to resist seismic loading. While the RC shear walls can have a high load-carrying capacity, they tend to fail in a brittle mode under shear, accompanied by forming large diagonal cracks and bond splitting between concrete and steel reinforcement. Improving seismic performance of shear walls has remained a challenge for researchers all over the world. Engineered Cementitious Composite (ECC), featuring incredible ductility under tension, can be a promising material to replace concrete in shear walls with improved performance. Currently, the application of ECC to large structures is limited due to the lack of the proper constitutive models especially under shear. In this paper, a new Cyclic Softening Membrane Model for reinforced ECC is proposed. The model was built upon the Cyclic Softening Membrane Model for reinforced concrete by (Hsu and Mo 2010). The model was then implemented in the OpenSees program to perform analysis on several cases of shear walls under seismic loading. The seismic response of reinforced ECC compared with RC shear walls under monotonic and cyclic loading, their difference in pinching effect and energy dissipation capacity were studied. The modeling results revealed that reinforced ECC shear walls can have superior seismic performance to traditional RC shear walls.

• 한국지진공학회논문집
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• 제25권1호
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• pp.1-9
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• 2021

Most commercial buildings among existing RC buildings in Korea have a multi-story wall-frame structure where RC shear wall is commonly used as its core at stairways or elevators. The members of the existing middle and low-rise wall-frame buildings are likely arranged in ordinary details considering building occupancy, and the importance and difficulty of member design. This is because there are few limitations, considerations, and financial burdens on the code for designing members with ordinary details. Compared with the intermediate or unique details, the ductility and overstrength are insufficient. Furthermore, the behavior of the member can be shear-dominated. Since shear failure in vertical members can cause a collapse of the entire structure, nonlinear characteristics such as shear strength and stiffness deterioration should be adequately reflected in the analysis model. With this background, an 8-story RC wall-frame building was designed as a building frame system with ordinary shear walls, and the effect of reflecting the shear failure mode of columns and walls on the collapse mechanism was investigated. As a result, the shear failure mode effect on the collapse mechanism was evident in walls, not columns. Consequently, it is recommended that the shear behavior characteristics of walls are explicitly considered in the analysis of wall-frame buildings with ordinary details.

• Structural Engineering and Mechanics
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• 제53권1호
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• pp.41-55
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• 2015

In this paper, a model for the evaluation of shear strength of fibre reinforced polymer (FRP)-reinforced concrete beams is given. The survey of literature indicates that the FRP reinforced beams tested with shear span to depth ratio less than or equal to 1.0 is limited. In this study, eight concrete beams reinforced with GFRP rebars without stirrups are cast and tested over shear span to depth ratio of 0.5 and 1.75. The concrete compressive strength is varied from 40.6 to 65.3 MPa. The longitudinal reinforcement ratio is varied from 1.16 to 1.75. The experimental shear strength and load-deflection response of the beams are determined and reported in this paper. A model is proposed for the prediction of shear strength of beams reinforced with FRP bars. The proposed model accounts for compressive strength of concrete, modulus of FRP rebar, longitudinal reinforcement ratio, shear span to depth ratio and size effect of beams. The shear strength of FRP reinforced concrete beams predicted using the proposed model is found to be in better agreement with the corresponding test data when compared with the shear strength predicted using the eleven models published in the literature. Design example of FRP reinforced concrete beam is also given in the appendix.