Shear Mechanism and Size Effect of RC Deep Beams without Stirrups Based on Crack Kinematics in Tests
Publication: Journal of Structural Engineering
Volume 149, Issue 11
Abstract
Based on the experimental results, this paper investigates the shear mechanism of reinforced concrete deep beams without stirrups. By analyzing the kinematics of the critical shear crack, it can be found that the compression of concrete above the critical shear crack causes the crack sliding and that the combined action of the elongation of longitudinal reinforcement and the compression of concrete above the critical shear crack causes the crack opening. Based on the new-found crack kinematics and test data, the aggregate interlock force is calculated by two methods. The dowel action is also calculated. The results reveal that the shear forces transmitted by the aggregate interlock and the dowel action are relatively small, ranging from 0.5% to 9.2%. The uncracked concrete in the compression zone provides the primary resistance. Both the aggregate interlock and the uncracked concrete in the compression zone can cause a size effect. But because of the small proportion of the aggregate interlock, the size effect of shear strength is mainly caused by the size effect of uncracked concrete in the compression zone. A modified strut-and-tie model (STM) is established based on the shear mechanism found in the test. It considers the size effect using the modified size effect law. The modified STM is evaluated by comparing the calculation results with the experimental results of 194 beams. It is shown that the prediction of the modified STM is more accurate than those of the other five models, with a mean value of of 1.01 and a coefficient of variation value of 0.22. The proposed model well captures the effect of the shear span-to-effective depth ratio and the size effect on the shear strength. The modified STM reflects the actual shear transfer mechanism of deep beams without stirrups and has the advantages of simple calculation and accurate prediction.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China (Nos. 51878260 and 52078201) and the Hunan Provincial Innovation Foundation for Postgraduate No. 541109080046 (CX2017B121). The findings and opinions expressed in this paper are those of the authors and do not necessarily reflect those of the sponsor.
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Journal of Structural Engineering
Volume 149 • Issue 11 • November 2023
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© 2023 American Society of Civil Engineers.
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Received: Jan 4, 2023
Accepted: Jul 19, 2023
Published online: Sep 13, 2023
Published in print: Nov 1, 2023
Discussion open until: Feb 13, 2024
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