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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 21 Abstracts search results
Document:
23-223
Date:
November 1, 2024
Author(s):
Basel H. Aljada, Amr El Ragaby, and Ehab F. El-Salakawy
Publication:
Structural Journal
Volume:
121
Issue:
6
Abstract:
Interface shear transfer is vital to maintain the structural integrity of concrete composite elements. Therefore, shear connectors are provided at the concrete joint interface to maintain such integrity. Due to its high tensile strength and non-corrodible nature, glass fiber-reinforced polymer (GFRP) reinforcement can be used as shear connectors in composite elements, particularly those in harsh environments. Fifteen pushoff specimens were constructed and tested to failure. The specimen consisted of two L-shaped concrete blocks cast at two stages to provide the cold joint interface. The test parameters were the type, shape, and ratio of shear-friction reinforcement and concrete strength. It was demonstrated that GFRP-reinforced concrete (RC) specimens with reinforcement ratios of 0.36% or more could resist the shear-friction stresses similarly to their steel-RC counterparts. Also, increasing the concrete strength increased the shear-friction capacity significantly. Moreover, the design model in the Canadian Highway Bridge Design Code resulted in very conservative predictions.
DOI:
10.14359/51740861
21-309
September 1, 2022
Paolo M. Calvi, Stephan Ahn, and Dawn Lehman
119
5
An experimental program involving 24 reinforced concrete (RC) pushoff specimens was conducted to investigate shear stress transfer across untreated and intentionally roughened cold joints. The variables were the number of bars crossing the joint interface, the reinforcement ratio, the yield strength of the reinforcing steel, and the joint surface roughness. During each experiment, shear and normal stresses across the main crack and joint interface opening and sliding were continuously monitored. The experimental results demonstrate that roughening the joint interface enhances the joint stiffness and peak strength, while the use of Grade 80 steel reinforcement did not result in any strength benefit, although the use of higher-strength steel can improve constructability. The test results were compared with predictions obtained using ACI and AASHTO provisions. Comparison of the measurements and predictions show that both ACI and AASHTO provide generally conservative, yet scattered, estimates of the experimental strengths. Thus, based on the findings of this study, a number of modifications to the current shear friction provisions were proposed to achieve higher strength prediction accuracy.
An experimental program involving 24 reinforced concrete (RC) pushoff specimens was conducted to investigate shear stress transfer across untreated and intentionally roughened cold joints. The variables were the number of bars crossing the joint interface, the reinforcement ratio, the yield strength of the reinforcing steel, and the joint surface roughness. During each experiment, shear and normal stresses across the main crack and joint interface opening and sliding were continuously monitored.
The experimental results demonstrate that roughening the joint interface enhances the joint stiffness and peak strength, while the use of Grade 80 steel reinforcement did not result in any strength benefit, although the use of higher-strength steel can improve constructability.
The test results were compared with predictions obtained using ACI and AASHTO provisions. Comparison of the measurements and predictions show that both ACI and AASHTO provide generally conservative, yet scattered, estimates of the experimental strengths. Thus, based on the findings of this study, a number of modifications to the current shear friction provisions were proposed to achieve higher strength prediction accuracy.
10.14359/51734667
21-225
July 1, 2022
Vasiliki Palieraki, Elizabeth Vintzileou, and John F. Silva
4
The shear behavior of reinforced concrete interfaces between new and existing concrete is known to be a key parameter for the effectiveness of strengthening and repair interventions in reinforced concrete structures subject to earthquakes. In this work, the mechanisms mobilizing the shear resistance of interfaces, both under monotonic and cyclic actions, are described. Constitutive relationships based on previous research are adopted for friction, for dowel action, and for their interaction. A simple algorithm is applied whereby for each value of imposed shear slip, the contributions of the two participating mechanisms are summed, as dictated by the adopted constitutive relationships. The algorithm is applied to experimental results as found in the literature and as obtained by tests conducted by the authors. The agreement of experimental and calculated load-displacement curves under monotonic and cyclic shear loading is quite satisfactory.
10.14359/51734521
19-437
May 1, 2022
3
Provisions for the calculation of interface shear strength have remained unchanged in ACI 318 since the 1980s. The shear friction concept, while simple to apply, does not address many of the most important influencing parameters for interface shear strength. It is silent on cyclic loading, intermediate levels of interface roughness, and the strength of interfaces reinforced with short dowels. To assess the approach included in ACI 318 and to enable the formulation of a new approach, a comprehensive database of test results has been assembled. The results of recent cyclic shear tests performed at the National Technical University of Athens (NTUA) have been combined with the results of investigations conducted worldwide between 1960 and 2020—a total of nearly 1240 tests—to provide a definitive basis for the development of a model for the accurate prediction of interface shear strength under both monotonic and cyclic displacements.
10.14359/51734519
17-333
September 1, 2018
Mahmoodreza Soltani, Brandon E. Ross, and Amin Khademi
115
Interface shear transfer (IST) theory describes the mechanisms by which shear force is transferred across concrete-to-concrete interfaces. Previous research has shown that current code-based IST models produce inconsistent levels of accuracy for different values of design parameters (that is, material strength, reinforcement density, and member size). Objectives for the current research were to identify parameters having the greatest impact on the IST capacity, and to create a model that produces consistent levels of accuracy. Using a database of experimental results, an artificial neural network model was created to estimate IST strength and to perform a sensitivity analysis of the parameters affecting capacity. The sensitivity analysis demonstrated that compressive strength of concrete is the most significant parameter affecting IST capacity. A multiple linear-regression analysis was also performed to aid in development of a new IST design model. Based on the results of the sensitivity analysis, and in contrast to current model codes, the proposed IST model directly accounts for compressive strength of concrete as one of the model parameters. The model is strongly correlated (R2 ≥ 0.88 and p-values << 0.01) with the experimental data, and relative to current codes, it produces more consistent levels of accuracy across ranges of design parameters.
10.14359/51702239
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