• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.878-883
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• 2003

To modify some problems of ACI shear provisions, ultimate shear strength equation considering size effect and arch action to compute shear strength in high-strength concrete beams without stirrups is presented in this research. Three basic equations, namely size reduction factor, rho factor, and arch action factor, are derived from crack band model of fracture mechanics, analysis of previous some shear equations for longitudinal reinforcement ratio, and concrete strut described as linear function in deep beams. Constants of basic equations are determined using statistical analysis of previous shear testing data. To verify proposed shear equation for each variable, namely d, , ρ, f/sub c/' and aid, about 250 experimental data are used and proposed shear equation is compared with ACI 318-99 code, CEB-FIP Model code, Kim & Park's equation and Zsutty's equation. While proposed shear equation is simpler than other shear equations, it is shown to be economical predictions and reasonable safety margin. Hence proposed shear strength equation is expected to be applied to practice shear design.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.443-446
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• 2005

The shear strength equations of the joint with RC column and steel beam are used the proposed equations of ASCE, Kanno and AIJ but there are not applied variable joint details. Until now the variable experimental studies are practiced but the studies of predicted shear strength equation are not integrated and only the applicable equations to each case are proposed. The purpose of this study is statistical analysis for the proposed equations applied existing experiments. The proposed equations are ASCE, Kanno, M-Kanno, AIJ and M-AIJ. The 47 of shear failure experiments are used in this study The consequence is that the Kanno's equation is very analogized with the experimental result but ASCE equation underestimates about 42$\%$. AIJ and M-AIJ are not proper equations for estimating the shear strength of RCS joint.

• Structural Monitoring and Maintenance
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• 제9권4호
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• pp.337-357
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• 2022

The objective of this study is to present a data-driven machine learning (ML) framework for predicting ultimate shear strength and failure modes of reinforced concrete ledge beams. Experimental tests were collected on these beams with different loading, geometric and material properties. The database was analyzed using different ML algorithms including decision trees, discriminant analysis, support vector machine, logistic regression, nearest neighbors, naïve bayes, ensemble and artificial neural networks to identify the governing and critical parameters of reinforced concrete ledge beams. The results showed that ML framework can effectively identify the failure mode of these beams either web shear failure, flexural failure or ledge failure. ML framework can also derive equations for predicting the ultimate shear strength for each failure mode. A comparison of the ultimate shear strength of ledge failure was conducted between the experimental results and the results from the proposed equations and the design equations used by international codes. These comparisons indicated that the proposed ML equations predict the ultimate shear strength of reinforced concrete ledge beams better than the design equations of AASHTO LRFD-2020 or PCI-2020.

• Computers and Concrete
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• 제27권5호
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• pp.473-487
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• 2021

The review of the literature and design guidelines indicates a lack of design codes governing the shear strength of reinforced concrete (RC) beams strengthened with ultrahigh-performance fiber-reinforced concrete (UHPFRC). This study uses the results of a 3D finite element model constructed previously by the authors and verified against an experimental programme to gain a clear understanding of the shear strength of RC beams strengthened with UHPFRC by using different schemes. Experimental results found in the literature along with the numerical results for shear capacities of normal-strength RC and UHPFRC beams without stirrups are compared with available code design guidelines and empirical models found in the literature. The results show variance between the empirical models and the experimental results. Accordingly, proposed equations derived based on empirical models found in the literature were set to estimate the shear capacity of normal-strength RC beams without stirrups. In addition, the term 'shear span-to-depth ratio' is not considered in the equations for design guidelines found in the literature regarding the shear capacity of UHPFRC beams without stirrups. Consequently, a formula estimating the shear strength of UHPFRC and RC beams strengthened with UHPFRC plates and considering the effect of shear span-to-depth ratio is proposed and validated against an experimental programme previously conducted by the authors.

• 콘크리트학회논문집
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• 제20권2호
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• pp.257-267
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• 2008

본 연구에서는 강섬유보강 콘크리트 휨부재에 적용할 수 있는 휨강도 산정식과 전단강도 제안식을 분석하였으며, 보다 정확성과 안전성이 향상된 전단강도 산정식이 필요한 것으로 판단되어 새로운 전단강도 제안식을 도출하였다. 휨강도 산정식은 휨파괴한 36개의 실험체를 대상으로 검토해본 결과 기존의 콘크리트보에서 무시되는 콘크리트의 인장강도를 고려하는 것이 타당한 것으로 나타났으며, 제안된 휨강도 약산식은 실험 결과와 공칭휨강도 산정식과 비교할 때 양호한 수준의 강도 예측이 가능하다고 사료된다. 또한 본 연구에서 제안한 전단강도 산정식과 기존 연구자의 전단강도 제안식을 전단파괴한 실험체의 최대강도와 비교, 검토한 결과에 의하면, 본 연구의 제안식이 정확성과 안전성을 모두 확보하면서 전단강도를 예측하는 것으로 평가되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 봄 학술발표회 논문집
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• pp.51-56
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• 1990

Investigations on the behavior of steel fiber reinforced high strength concrete beams subjected to predominant shear are accomplished to determine their diagonal shear strength including ultimate shear strength. The parameters varied were the volume fraction(Vf) of the fibers, shear span depth ratio(a/d). The test result show that diagonal shear strength and ultimate shear strength are increased siginificantly due to crack arrest mechanism. Predictive equations are suggested for evaluating the diagonal cracking strength and ultimate shear strength of the fiber reinforced high strength concrete beams.

• 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.

• Computers and Concrete
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• 제17권6호
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• pp.739-760
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• 2016

This paper reports on punching shear behavior of reinforced concrete panels, investigated experimentally and through finite element simulation. The aim of the study was to examine the punching shear of high strength concrete panels incorporating different types of aggregate and silica fume, in order to assess the validity of the existing code models with respect to the role of compressive and tensile strength of high strength concrete. The variables in concrete mix design include three types of coarse aggregates and three water-cementitious ratios, and ten-percent replacement of silica fume. The experimental results were compared with the results produced by empirical prediction equations of a number of widely used codes of practice. The prediction of the punching shear capacity of high strength concrete using the equations listed in this study, pointed to a potential unsafe design in some of them. This may be a reflection of the overestimation of the contribution of compressive strength and the negligence of the role of flexural reinforcement. The overall findings clearly indicated that the extrapolation of the relationships that were developed for normal strength concrete are not valid for high strength concrete within the scope of this study and that finite element simulation can provide a better alternative to empirical code Equations.

• International Journal of Concrete Structures and Materials
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• 제10권4호
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• pp.451-460
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• 2016

An anchorage system is necessary in most reinforced concrete structures for connecting attachments. It is very important to predict the strength of the anchor to safely maintain the attachments to the structures. However, according to experimental results, the existing design codes are not appropriate for large anchors because they offer prediction equations only for small size anchors with diameters under 50 mm. In this paper, a new prediction model for breakout shear strength is suggested from experimental results considering the characteristics of large anchors, such as the prying effect and size effect. The proposed equations by regression analysis of the derived model equations based on the prying effect and size effect can reasonably be used to predict the breakout shear strength of not only ordinary small size anchors but also large size anchors.

• 콘크리트학회논문집
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• 제15권6호
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• pp.820-828
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• 2003

최근의 연구를 통해서, ACI 전단 규준은 크기가 크고 인장철근비가 낮은 보에서 비보수적 예측을 보이는 반면 깊은 보에 대해서는 보수적 예측을 보임을 알 수 있다. 이러한 ACI 전단 규준이 가지고 있는 문제점을 수정하기 위해, 본 연구에서는 스터럽이 없는 고강도 철근 콘크리트 보의 전단강도 계산시 크기효과와 아치작용을 고려한 극한 전단강도 예측식을 제안하였다. ACI 전단 규준의 수정을 위해 포함될 항은 과학적 이론 및 분석에 근거한 $f_{sr}$ (dr), $f_{si}$ (${\rho}$)와 $f_{aa}$ (a/d)항이며, 선형 및 비선형 회귀분석을 통해 도출되었다. 기존의 실험 데이터 약 300여 개를 이용하여 각각의 변수에 대한 제안식의 검증 및 제안식과 ACI 318-99 code, CEB-FIP model code, Kim &Park 식 및 Zsutty 식과의 비교를 수행하였다. 제안식은 간단한 형태를 지니고 있지만, 경제적이면서도 합리적인 안전율을 확보할 수 있는 전단강도를 예측한다. 따라서 제안식은 실무에서 콘크리트 구조물의 전단설계에 적용 가능할 것으로 판단된다.