Rehabilitation of normal and self-compacted steel fiber reinforced concrete corbels via basalt fiber

Gulsan, Mehmet Eren,Al Jawahery, Mohammed S.,Alshawaf, Adnan H.,Hussein, Twana A.,Abdulhaleem, Khamees N.,Cevik, Abdulkadir Techno-Press 2018 Advances in concrete construction Vol.6 No.5

This paper investigates the behavior of normal and self-compacted steel fiber reinforced concrete (SCC-SFRC) corbels rehabilitated by Basalt Fiber Mesh (BFM) and Basalt Fiber Fabric (BFF) for the first time in literature. The research objective is to study the effectiveness of BFM and BFF in the rehabilitation of damaged reinforced concrete corbels with and without epoxy injection. The experimental program includes two types of concrete: normal concrete, and self-compacted concrete. For normal concrete, 12 corbels were rehabilitated by BFM without injection epoxy in cracks, with two values of compressive strength, three ratios of steel fiber (SF), and two values of shear span. For self-compacted concrete, 48 corbels were rehabilitated with different parameters where 12 corbels were rehabilitated by BFM with and without epoxy injection, 18 heated corbels with three different high-temperature level were rehabilitated by repairing cracks only by epoxy injection, and 18 heated corbels with three different high-temperature level were rehabilitated by repairing cracks by epoxy and wrapping by BFF. All 48 corbels have two values of compressive strength, three values volumetric ratios of SF, and two values of the shear span. Test results indicate that RC corbels rehabilitated by BFM only without injection did not show any increase in the ultimate load capacity. Moreover, For RC corbels that were repaired by epoxy without basalt wrapping, the ultimate load capacities showed an increase depending on the mode of failure of corbels before the rehabilitation. However, the rehabilitation with only crack repairing by epoxy injection is more effective on medium strength corbels as compared to high strength ones. Finally, it can be concluded that use of BFF is an effective and powerful technique for the strengthening of damaged RC corbels.

Strength Prediction of Corbels Using Strut-and-Tie Model Analysis

Wael Kassem 한국콘크리트학회 2015 International Journal of Concrete Structures and M Vol.9 No.2

A strut-and-tie based method intended for determining the load-carrying capacity of reinforced concrete (RC) corbels is presented in this paper. In addition to the normal strut-and-tie force equilibrium requirements, the proposed model is based on secant stiffness formulation, incorporating strain compatibility and constitutive laws of crackedRC.The proposed method evaluates the load-carrying capacity as limited by the failure modes associated with nodal crushing, yielding of the longitudinal principal reinforcement, as well as crushing or splitting of the diagonal strut. Load-carrying capacity predictions obtained fromthe proposed analysis method are in a better agreementwith corbel test results of a comprehensive database, comprising 455 test results, compiled from the available literature, than other existing models for corbels. This method is illustrated to provide more accurate estimates of behaviour and capacity than the shear-friction based approach implemented by the ACI 318-11, the strut-and-tie provisions in different codes (American, Australian, Canadian, Eurocode and New Zealand).

Behavior of reinforced concrete corbels

Wen-Yao Lu,Ing-Jaung Lin 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.2

Test results of thirteen reinforced concrete corbels with shear span-to-depth ratio greater than unity are reported. The main variables studied were compressive strength of concrete, shear span-todepth ratio and parameter of vertical stirrups. The test results indicate that the shear strengths of corbels increase with an increase in compressive strength of concrete and parameter of vertical stirrups. The shear strengths of corbels also increase with a decrease in shear span-to-depth ratio. The smaller the shear span-to-depth ratio of corbel, the larger the stiffness and the shear strength of corbel are. The higher the concrete strength of corbel, the higher the stiffness and the shear strength of corbel are. The larger the parameter of vertical stirrups, the larger the stiffness and the shear strength of corbel are. The softened strut-and-tie model for determining the shear strengths of reinforced concrete corbels is modified appropriately in this paper. The shear strengths predicted by the proposed model and the approach of ACI Code are compared with available test results. The comparison shows that the proposed model can predict more accurately the shear strengths of reinforced concrete corbels than the approach of ACI Code.

Behavior of reinforced concrete corbels

Lu, Wen-Yao,Lin, Ing-Jaung Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.3

Test results of thirteen reinforced concrete corbels with shear span-to-depth ratio greater than unity are reported. The main variables studied were compressive strength of concrete, shear span-to-depth ratio and parameter of vertical stirrups. The test results indicate that the shear strengths of corbels increase with an increase in compressive strength of concrete and parameter of vertical stirrups. The shear strengths of corbels also increase with a decrease in shear span-to-depth ratio. The smaller the shear span-to-depth ratio of corbel, the larger the stiffness and the shear strength of corbel are. The higher the concrete strength of corbel, the higher the stiffness and the shear strength of corbel are. The larger the parameter of vertical stirrups, the larger the stiffness and the shear strength of corbel are. The softened strut-and-tie model for determining the shear strengths of reinforced concrete corbels is modified appropriately in this paper. The shear strengths predicted by the proposed model and the approach of ACI Code are compared with available test results. The comparison shows that the proposed model can predict more accurately the shear strengths of reinforced concrete corbels than the approach of ACI Code.

강섬유 및 헤디드 바를 활용한 고강도 콘크리트 내민받침의 성능 향상

양준모(Jun-Mo Yang),이주하(Joo-Ha Lee),신현오(Hyun-Oh Shin),윤영수(Young-Soo Yoon) 한국콘크리트학회 2009 콘크리트학회논문집 Vol.21 No.6

Analysis of reinforced concrete corbel beams using Strut and Tie models

Jafarali Parol,Jamal Al-Qazweeni,Safaa Abdul Salam 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.1

Reinforced concrete corbel beams (span to depth ratio of a corbel is less than one) are designed with primary reinforcement bars to account for bending moment and with the secondary reinforcement placed parallel to the primary reinforcement (shear stirrups) to resist shear force. It is interesting to note that most of the available analytical procedures employ empirical formulas for the analysis of reinforced concrete corbels. In the present work, a generalized and a simple strut and tie models were employed for the analysis of reinforced corbel beams. The models were benchmarked against experimental results available in the literature. It was shown here that increase of shear stirrups increases the load carrying capacity of reinforced concrete corbel beams. The effect of horizontal load on the load carrying capacity of the corbel beams has also been examined in the present paper. It is observed from the strut and tie models that the resistance of the corbel beam subjected to combined horizontal and vertical load did not change with increase in shear stirrups if the failure of the corbel is limited by concrete crushing. In other words, the load carrying capacity was independent of the horizontal load when failure of the beam occurred due to concrete crushing.

Fiber reinforced concrete corbels: Modeling shear strength via symbolic regression

Ahmet E Kurtoglu,Mehmet E Gulsan,Hussein A Abdi,Mohammed A Kamil,Abdulkadir Cevik 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.20 No.1

In this study, a novel application of symbolic regression (SR) is employed for the prediction of ultimate shear strength of steel fiber reinforced (SFRC) and glass fiber reinforced (GFRC) corbels without stirrups, for the first time in the literature. A database is created using the test results (42 tests) conducted by the authors of current paper as well as the previous studies available in the literature. A symbolic regression based empirical formulation is proposed using this database. The formulation is unique in a way that it has the capability to predict the shear strength of both SFRC and GFRC corbels. The performance of proposed model is tested against randomly selected testing set. Additionally, a parametric study with a wide range of variables is carried out to test the effect of each parameter on the shear strength. The results confirm the high prediction capacity of proposed model.

전단마찰 및 스트럿-타이 모델을 이용한 철근콘크리트 코벨의 전단강도 예측

윤영묵(Yun Young Mook),김병헌(Kim Byung Hun),이원석(Lee Won Seok),정찬핵(Jeong Chan Haek) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.2A

철근콘크리트 코벨은 주로 보나 거더를 지지하기 위하여 프리캐스트 콘크리트 구조물의 건설에 널리 사용되고 있으며, 이러한 프리캐스트 콘크리트 구조물이 많이 보급됨에 따라 철근콘크리트 코벨의 설계는 점점 중요시되고 있다. 철근콘크리트 코벨은 주인장 철근의 항복에 의한 파괴, 콘크리트 스트럿의 압축에 의한 파괴, 하중의 기둥면을 따라서 발생하는 전단파괴, 그리고 하중판 아래의 지압파괴 등 여러 가지 형상의 파괴형태를 보이나, 이러한 파괴메카니즘을 예측하여 철근콘크리트 코벨을 설계하는 것은 쉽지 않다. 본 연구에서는 전단마찰 모델에 근거한 ACI 318-05 설계기준과 트러스 모델에 근거한 연화 및 비선형 스트럿-타이 모델 방법의 특정적인 사항을 소개하였고 이들 방법을 이용하여 파괴실험이 수행된 19개의 일반강도 및 고강도 철근콘크리트 코벨의 전단강도를 평가하였다. 또한 평가결과의 비교분석과 각 방법의 장단점 분석을 통하여 해석 및 실무설계 적용 시의 적합성을 검토하였다. The reinforced concrete corbels are used extensively in precast concrete constructions to support primary beams and girders. Because of the prevalence of precast concrete, the design of corbels has become increasingly important. The reinforced concrete corbels tend to fail in several modes. The most common of which are the yielding of main tensile reinforcement, the crushing or splitting of the compression strut, the shearing failure along the column face, and the localized bearing failure under the loading plate. Because of these various failure modes, the rational analysis and design of reinforced concrete corbels are difficult. In this study, the characteristic features of the currently used analysis and design methods of reinforced concrete corbels, i.e, the ACI 318-05 design code implementing the shear-friction model and the softened and nonlinear strut-tie model approaches implementing the truss model, are introduced. In addition, the appropriateness of each model is examined through the strength evaluation of 19 normal and high strength reinforced concrete corbels tested to failure.

철근콘크리트 내민받침 부재의 구조성능 평가 및 내력 추정

조승호,윤주영,김학진,박현수,정란 단국대 부설 리모델링연구소 2007 리모델링 연구소 논문집 Vol.5 No.1

In order to identify the exact behavior of corbel section, the horizontal force acting on corbel section should be considered as well as the vertical force. In this study, a new corbel section, which is economical and easy to construct, is developed by evaluating the exact strength of the section. Experiments were performed to verify the strengths of the proposed sections comparing with those of the currently used section. The summary of the experiment results are as follows: 1) In order to minimize the horizontal force effect, it was found that the use of pre-stressing was most effective, and that TB type corble section is a most efficient section in terms of economy and workability. 2) The experimentally obtained strength of corbel section matched well with that estimated using shear friction theory. Therefore, it is concluded that shear friction theory would be very useful if a precise crack angle in the corble section, which is pre-stressed by PS strings and threaded bolts, is available.

Stochastic finite element based reliability analysis of steel fiber reinforced concrete (SFRC) corbels

Mehmet Eren Gulsan,Abdulkadir Cevik,AhmetEminKurtoglu 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.2

In this study, reliability analyses of steel fiber reinforced concrete (SFRC) corbels based on stochastic finite element were performed for the first time in literature. Prior to stochastic finite element analysis, an experimental database of 84 sfrc corbels was gathered from literature. These sfrc corbels were modeled by a special finite element program. Results of experimental studies and finite element analysis were compared and found to be very close to each other. Furthermore experimental crack patterns of corbel were compared with finite element crack patterns and were observed to be quite similar. After verification of the finite element models, stochastic finite element analyses were implemented by a specialized finite element module. As a result of stochastic finite element analysis, appropriate probability distribution functions (PDF’s) were proposed. Finally, coefficient of variation, bias and strength reduction (resistance) factors were proposed for sfrc corbels as a consequence of stochastic based reliability analysis.