Title:
Tangential Strain Theory for Punching Failure of Flat Slabs
Author(s):
Carl Erik Broms
Publication:
Structural Journal
Volume:
113
Issue:
1
Appears on pages(s):
95-104
Keywords:
flat slab; mechanical model; punching failure
DOI:
10.14359/51687942
Date:
1/1/2016
Abstract:
A novel mechanical model for the punching failure at interior columns of flat slabs without shear reinforcement is presented. It is based on fundamental structural mechanics and the stress-strain relation of compressed concrete. The shear force is assumed to be transferred to the column by an inclined circumferential compression strut that squeezes the concrete within the column perimeter, and when the compression stress in this area approaches the yield level, an increasing part of the squeezing pressure is anchored back to the surrounding concrete. Ultimately, the compression zone outside the column is assumed to collapse due to the generation of radial tension strain. Validation against test results in the literature demonstrates that the proposed model can accurately predict the punching capacity and the concurrent ultimate slab rotation. Both concentric and eccentric punching can therefore be analyzed.
Related References:
1. Kinnunen, S., and Nylander, H., “Punching of Concrete Slabs without Shear Reinforcement,” Transactions of the Royal Institute of Technology, No. 158, Stockholm, Sweden, 1960, 112 pp.
2. Broms, C. E., “Punching of Flat Plates—A Question of Concrete Properties in Biaxial Compression and Size Effect,” ACI Structural Journal, V. 87, No. 3, May-June 1990, pp. 292-304.
3. Broms, C. E., “Concrete Flat Slabs and Footings—Design Method for Punching and Detailing for Ductility,” PhD thesis, Structural Design and Bridges, Royal Institute of Technology, Stockholm, Sweden, 2005, 114 pp.
4. Hallgren, M., “Punching Shear Capacity of Reinforced High Strength Concrete Slabs,” PhD thesis, Bulletin 23, Department of Structural Engineering, Royal Institute of Technology, Stockholm, Sweden, 1996, 206 pp.
5. Muttoni, A., “Punching Shear Strength of Reinforced Concrete Slabs without Transverse Reinforcement,” ACI Structural Journal, V. 105, No. 4, July-Aug. 2008, pp. 440-450.
6. Muttoni, A.; Ruiz, M. F.; Bentz, E.; Foster, S.; and Sigrist, V., “Background to fib Model Code 2010 Shear Provisions—Part II: Punching Shear,” Structural Concrete, V. 14, No. 3, 2013, pp. 204-214. doi: 10.1002/suco.201200064
7. Timoshenko, S., and Woinowsky-Krieger, S., Theory of Plates and Shells, International Student Edition, McGraw-Hill, New York, 1959, 580 pp.
8. Moe, J., “Shearing Strength of Reinforced Concrete Slabs and Footings under Concentrated Loads,” Development Department Bulletin d47, Portland Cement Association (PCA), Skokie, IL, 1961, 130 pp.
9. Tolf, P., “Influence of the Slab Thickness on the Punching Strength of Concrete Slabs—Tests with Circular Slabs,” Bulletin No. 146, Department of Structural Mechanics and Engineering, Royal Institute of Technology, Stockholm, Sweden, 1988, 64 pp. (in Swedish with a summary in English)
10. Eurocode 2, “Design of Concrete Structures—Part 1-1: General Rules and Rules for Buildings (EN 1992-1-1),” Comité Européen de Normalisation, Brussels, Belgium, 2004, 225 pp.
11. ACI Committee 318, “Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary,” American Concrete Institute, Farmington Hills, MI, 2008, 473 pp.