Shear Behavior of Thick Slabs

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Title: Shear Behavior of Thick Slabs

Author(s): Michael P. Collins, Phillip T. Quach, and Evan C. Bentz

Publication: Structural Journal

Volume: 117

Issue: 4

Appears on pages(s): 115-125

Keywords: aggregate interlock; cracking; design equations; safety; shear; size effect; stirrups; test/experiment; thick slabs

DOI: 10.14359/51724666

Date: 7/1/2020

Abstract:
Thick reinforced concrete members not containing shear reinforcement can fail at shear stresses significantly lower than those specified by the 2014 ACI Code. This is because the traditional ACI shear provisions were based on tests of small specimens, and do not account for the size effect in shear. This paper focuses on an experimental program in which a 4000 mm (13 ft) thick slab strip specimen and a 300 mm (12 in.) deep companion specimen were constructed and tested to failure. These tests extend the range of a series of 17 such slab strip experiments previously tested at the University of Toronto. The results show that the 2014 ACI Code can give dangerously high estimates of shear capacity for very thick slabs not containing shear reinforcement. The research also shows that minimum shear reinforcement greatly increases both the strength and deformability of thick slabs.

Related References:

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8. Collins, M. P.; Bentz, E. C.; Quach, P. T.; and Proestos, G. T., “The Challenge of Predicting the Shear Strength of Very Thick Slabs,” Concrete International, V. 37, No. 11, Nov. 2015, pp. 29-37. (CI)

9. Reineck, K.-H.; Bentz, E.; Fitik, B.; Kuchma, D. A.; and Bayrak, O., “ACI-DAfStb Databases for Shear Tests on Slender Reinforced Concrete Beams with Stirrups,” ACI Structural Journal, V. 111, No. 5, Sept.-Oct. 2014, pp. 1147-1156. doi: 10.14359/51686819

10. Quach, P. T., Understanding and Safely Predicting the Shear Response of Large-Scale Reinforced Concrete Structures, University of Toronto, Toronto, ON, Canada, 2016, 305 pp.

11. Bentz, E. C., “Empirical Modeling of Cracking in Reinforced Concrete,” ACI Structural Journal, V. 116, No. 3, May 2019, pp. 233-242. doi: 10.14359/51714476

12. Calvi, P. M.; Bentz, E. C.; and Collins, M. P., “Reversed Cyclic Experiments on Shear Stress Transfer across Cracks in Reinforced Concrete Elements,” ACI Structural Journal, V. 113, No. 4, July-Aug. 2016, pp. 851-859. doi: 10.14359/51688926

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16. Sherwood, E. G.; Bentz, E. C.; and Collins, M. P., “Effect of Aggregate Size on Beam-Shear Strength of Thick Slabs,” ACI Structural Journal, V. 104, No. 2, Mar.-Apr. 2007, pp. 180-190.

17. Joint ACI-ASCE Committee 326, “Shear and Diagonal Tension,” ACI Journal Proceedings, V. 59, No. 1, 2, and 3, Jan., Feb., and Mar., 1962, pp. 1-30, 277-334, and 352-396 and Disc. and Clos., Oct. 1962, pp. 1323-1349.

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20. Bentz, E. C., and Collins, M. P., “Updating the ACI Shear Design Provisions,” Concrete International, V. 39, No. 9, Sept. 2017, pp. 33-38.

21. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19),” American Concrete Institute, Farmington Hills, MI, 2019, 624 pp.

22. Mihaylov, B. I.; Bentz, E. C.; and Collins, M. P., “Two-Parameter Kinematic Theory for Shear Behavior of Deep Beams,” ACI Structural Journal, V. 110, No. 3, May-June 2013, pp. 447-456.

23. Bentz, E. C., and Collins, M. P., “The Toronto Size Effect Series,” Shear in Structural Concrete, SP-328, American Concrete Institute, Farmington Hills, MI, 2018, 12 pp.


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