Title:
Effect of the Shear Reinforcement Anchorage and Detailing on the Punching Resistance of Flat Slabs
Author(s):
Guilherme S. Melo, Mauricio P. Ferreira, Henrique J. Lima, Manoel M. Pereira-Filho, Victor H. Oliveira, Joao P. Siqueira, and Rodolfo Palhares
Publication:
Symposium Paper
Volume:
357
Issue:
Appears on pages(s):
1-18
Keywords:
Closed stirrups, Experimental analysis, Flat slabs, Punching shear results, Prefabricated truss bars, Shear reinforcement, Shear reinforcement anchorage, Stud rail.
DOI:
10.14359/51738755
Date:
4/1/2023
Abstract:
Flat slabs with shear reinforcement not properly detailed and anchored as stated by ACI have been used in practice due to simplicity and the gained construction speed. This paper presents the results of 12 tests on slab-column connections with closed stirrups with anchorage variation and prefabricated truss bars as punching shear reinforcement. The behavior of the slabs, in terms of cracking pattern, displacements, and shear reinforcement strains, were analyzed, and ultimate loads were compared with estimations by ACI 318-19. Comparisons with the reference slabs without shear reinforcement showed that these two types of shear reinforcement effectively increased the load-carrying capacity of the tested slabs. For tests on slabs with closed stirrups, it was observed that if ACI detailing rules are followed, improvements in response and ductility of the slab-column connections should be expected. In the case of the slabs with prefabricated truss bars, it was observed that they were able to reach levels of punching shear resistance close to those of a reference slab with well-anchored stud rails. In both cases, further experimental research is needed. ACI 318-19 presented safe strength predictions for the different types of shear reinforcement tested, and in the case of the prefabricated truss bars, this was due to the conservative limitations imposed for calculating the crushing strength of the concrete strut close to the column.
Related References:
1. Einpaul, J., Brantschen, F., Ruiz, M. F., and Muttoni, A., 2016, "Performance of punching shear reinforcement under gravity loading: influence of type and detailing", ACI Structural Journal, 113, 827-838.
2. Hegger, J., Sherif, A.G., Kueres, D., and Siburg, C., 2017, "Efficiency of various punching shear reinforcement systems for flat slabs", ACI Structural Journal, 114, 631-642.
3. American Concrete Institute ACI 318, 2019. "Building code requirement for structural concrete (ACI 318-19)".
4. Caldentey, A. P., Lavaselli, P. P., Peiretti, H. C., and Fernández, F. A., 2013, "Influence of stirrup detailing on punching shear strength of flat slabs.", Engineering Structures, 49, 855-865.
5. Costa, M.G., 2021, "Stirrups detailing influence on punching shear resistance of reinforced concrete flat slabs", MSc Thesis, Federal University of Pará, Brazil. (In Portuguese)
6. Yamada, T., Nanni A., and Endo, K., 1992, "Punching shear resistance of flat slabs: influence of reinforcement type and ratio", ACI Structural Journal, 89, 555-563.
7. Regan, P. E., and Samadian, F., 2001, "Shear Reinforcement against punching in reinforced concrete flat slabs", The Structural Engineer, 79, 24-31.
8. Park, H. G., Kim, Y. N., Song, J. G., and Kang, S. M., 2007, "Lattice shear reinforcement for slab-column connections.", ACI Structural Journal, 104, 294-303.
9. Trautwein, L. M., Bittencourt, T. N., Gomes, R. B., and Bella, J. C. D., 2011, "Punching strength of flat slabs with unbraced shear reinforcement.", ACI Structural Journal, 108, 197-205.
10. Furche, J., Siburg, C., and Bauermeister, U., 2017, "Highly effective lattice punching shear reinforcement." ACI Special Publication, January, 138-148.
11. Ferreira, M. P., Barros, R. N. M., Pereira Filho, M. J. M., Tapajós, L. S., and Quaresma, F. S., 2016, "One-way shear resistance of RC members with unconnected stirrups.", Latin American Journal of Solids Structures, 13, 2670-2690.
12. Tapajos, L.S., 2017, "Shear in reinforced concrete members with unconnected stirrups", MSc Thesis, Federal University of Pará, Brazil. (In Portuguese)
13. Pinto, R.S., 2019, "Supplementary reinforcement influence on shear resistance of beams with prefabricated truss stirrups), MSc Thesis Federal, University of Pará, Brazil. (In Portuguese)
14. Lima, H. N., Palhares, R. A., Melo, G. S. S. A., and Oliveira, M. H., 2020, "Experimental analysis of punching shear in flat slabs with variation in the anchorage of shear reinforcement", Structural Concrete, 1-18.
15. Ferreira, M. P., Pereira Filho, M. J. M., Freitas, M. V. P., Lima Neto, A. F., and Melo, G. S. S. A., 2021, "Experimental resistance of slab-column connections with prefabricated truss bars as punching shear reinforcement", Engineering Structures, 233, 1-14.
16. ACI 421.1R, 2008, "Guide to Shear Reinforcement for Slabs", Reported by Joint ACI-ASCE Committee 421, American Concrete Institute (ACI).
17. Schmidt, P., Kueres, D., and Hegger, J., 2019, "Punching shear behavior of reinforced concrete flat slabs with a varying amount of shear reinforcement.". Structural Concrete, 20, 552-563.