Title:
Influence of Unbalanced Moment on Punching Shear Behavior of Footings
Author(s):
Jan Ungermann, Matthias Kalus, and Josef Hegger
Publication:
Symposium Paper
Volume:
357
Issue:
Appears on pages(s):
240-255
Keywords:
punching shear; spread footings; unbalanced moments; load eccentricities; design provisions; ACI 318-19; Eurocode 2; stable version of new Eurocode 2; innovative strain measurements
DOI:
10.14359/51738768
Date:
4/1/2023
Abstract:
While the punching shear behavior of centrically loaded footings has been investigated in the past, the influence of unbalanced moments has remained almost uninvestigated for footings. Nevertheless, unbalanced moments are also transferred into the column by shear stresses requiring consideration in punching shear design. Here, design approaches often use coefficients to increase the load on action side or to decrease the resistance. To fill the gap in test data necessary for validation of design approaches, tests of four centrically and fourteen eccentrically loaded footings without shear reinforcement were conducted. Here, innovative measurement techniques were used to determine the development of the compression ring at the column-footing connection. While the constriction of the concrete compression zone due to the multiaxial load transfer leads to the formation of a circumferential compression ring with multiaxial concrete strains for centrally loaded slabs, which enhances the punching shear resistance compared to one-way shear, this compression ring only develops to a reduced extent with increasing load eccentricity. Based on the test results, a new proposal for consideration of unbalanced moments is proposed and compared to existing design approaches according to ACI 318-19, Eurocode 2 and the stable version of new Eurocode 2.
Related References:
1. Mast, P. E., “Stresses in Flat Plates Near Columns,” ACI Journal, V. 67, No. 5, 1970, pp. 761–768.
2. Zaghlool, E. R. F., “Strength and behaviour of corner and edge column-slab connections in reinforced concrete flat plates,” PhD-Thesis, The University of Calgary, 1971.
3. Beukel, A. van den, “Punching Shear at Inner, Edge and Corner Columns,” HERON, V. 21, No. 3, 1976, pp. 1–30.
4. Gilbert, S. G., and Glass, C., “Punching failure of reinforced concrete flat slabs at edge columns,” The Structural Engineer, Volume 65B, No. 1, 1987, pp. 16–28.
5. Narasimhan, N., “Shear Reinforcement in RC Column Heads,” PhD-Thesis, University of London, London, Great Britain, 1971, 189 pp.
6. Sudarsana, I. K., “Punching shear in edge and corner column slab connections of flat plate structures,” PhDThesis, University of Ottawa, Ottawa, Canada, 2001, 259 pp.
7. Hegger, J., and Tuchlinski, D., “Zum Durchstanzen von Flachdecken - Einfluß der Momenten-Querkraft-Interaktion und der Vorspannung,” BuSt, V. 101, No. 10, 2006, 742–753.
8. Hegger, J., Ricker, M., Häusler, F., and Tuchlinski, D., “Versuche zum Durchstanzen im Bereich von Randstützen mit und ohne Durchstanzbewehrung,” Bauingenieur, V. 82, No. 6, 2007, pp. 270–278.
9. Richart, F. E., “Reinforced Concrete Wall and Column Footings: Part 1,” Journal of the American Concrete Institute, V. 45, No. 2, 1948, pp. 97–127.
10. Hallgren, M., Kinnunen, S., and Nylander, B., “Punching Shear Tests on Column Footings,” Nordic Concrete Research, V. 21, No. 1, 1998, pp. 1–22.
11. Siburg, C., and Hegger, J., “Experimental investigations on the punching behaviour of reinforced concrete footings with structural dimensions,” Structural Concrete, V. 15, No. 3, 2014, pp. 331–339.
12. Talbot, A. N., “Reinforced Concrete Wall Footings and Column Footings,” Bulletin No. 67, Urbana, Illinois, USA, 1913, 130 pp.
13. Simões, J. T., Bujnak, J., Fernández Ruiz, M., and Muttoni, A., “Punching shear tests on compact footings with uniform soil pressure,” Structural Concrete, V. 17, No. 4, 2016, pp. 603–617.
14. Hegger, J., Ricker, M., Ulke, B., and Ziegler, M., “Investigations on the punching behaviour of reinforced concrete footings,” Engineering Structures, V. 29, 2007, pp. 2233–2241.
15. Hegger, J., Ricker, M., and Sherif, A. G., “Punching Strength of Reinforced Concrete Footings,” ACI SJ, V. 106, No. 5, 2009, pp. 706–716.
16. Hegger, J., Sherif, A., and Ricker, M., “Experimental Investigations on Punching Behavior of Reinforced Concrete Footings,” ACI SJ, V. 103, No. 4, 2006, pp. 604–613.
17. Kordina, K., and Nölting, D., “Tragverhalten von ausmittig beanspruchten Einzelfundamenten aus Stahlbeton,” Abschlussbericht zum DFG - Forschungsvorhaben Ko 204/27 + 30, Braunschweig, Germany, 1981, 155 pp.
18. Zhang, W.-X., Li, B., Hwang, H.-J., Zhang, J.-Y., Xiao, L.-J., Yi, W.-J., and Park, H., “Punching shear strength of reinforced concrete column footings under eccentric compression: Experiment and analysis,” Engineering Structures, V. 198, 2019, p. 109509.
19. Kordina, K., and Nölting, D., “Tragfähigkeit durchstanzgefährdeter Stahlbetonplatten - Entwicklung von Bemessungsvorschlägen: DAfStb-Heft 371,” Ernst & Sohn, 1986.
20. Ungermann, J., Schmidt, P., and Hegger, J., “Einfluss exzentrischer Belastungen auf das Tragverhalten von Einzelfundamenten,” BuSt, V. 117, No. 1, 2021, pp. 24–36.
21. Ungermann, J., Schmidt, P., Classen, M., and Hegger, J., “Eccentric punching tests on column bases – new insights into the inner concrete strain development,” Engineering Structures, 2022.
22. Ungermann, J., Schmidt, P., Christou, G., and Hegger, J., “Eccentric punching tests on column bases – influence of column geometry,” Struct Concrete, 2022.
23. American Concrete Institute, 2019, Building Code Requirements for Structural Concrete and Commentary: Commentary on Building Code Requirements for Structural Concrete, American Concrete Institute, Farmington Hills, Mich., ACI 318-19/ ACI 318R-19.
24. European Standard, 2014, Eurocode 2: Design of concrete structures – Part 1-1: General rules and rules for buildings. Incl. Corrigendum 1: EN 1992-1-1:2004/AC:2008, incl. Corrigendum 2: EN 1992-1-1:2004/AC:2010, incl. Amendment 1: EN 1992-1-1:2004/A1:2014, EN 1992-1-1:2004/A1.
25. CEN/TC 250/SC 2/WG 1, 2021, prEN 1992-1-1/2021-09: Eurocode 2: Design of Concrete Structures - Part 1-1: General rules for buildings, bridges and civil engineering structures, stable version by Project Team SC2.T1.
26. International Federation for Structural Concrete, 2013, fib Model Code for Concrete Structures, Ernst & Sohn, Berlin, Model Code 2010.
27. Vocke, H., “Zum Durchstanzen von Flachdecken im Bereich von Rand- und Eckstützen,” Dissertation, Universität Stuttgart, Institut für Werkstoffe im Bauwesen, Stuttgart, 2002, 287 pp.
28. Elgabry, A. A., and Ghali, A., “Transfer of Moments between Columns and Slabs - Proposed Code Revisions,” ACI SJ, V. 93, No. 1, 1996, pp. 56–61.
29. Stasio, J. D., and Buren, M. P. V., “Transfer of Bending Moment Between Flat Plate Floor and Column,” Concrete International, V. 25, No. 7, 2003, pp. 57–72.
30. Megally, S., and Ghali, A., “Punching of Concrete Slabs Due to Column Moment Transfer,” J. Struct. Eng., V. 126, No. 2, 2000, pp. 180–189.
31. Schmidt, P., Kueres, D., and Hegger, J., “Punching shear behavior of reinforced concrete flat slabs with a varying amount of shear reinforcement,” Structural Concrete, V. 21, No. 1, 2020, pp. 235–246.
32. Kueres, D., Schmidt, P., and Hegger, J., “Punching shear behavior of reinforced concrete footings with a varying amount of shear reinforcement,” Structural Concrete, V. 20, No. 2, 2019, pp. 552–563.
33. Kueres, D., Ricker, M., and Hegger, J., “Improved Shear Reinforcement for Footings - Punching Strength inside Shear-Reinforced Zone,” ACI SJ, V. 114, No. 6, 2017, pp. 1445–1456.
34. Tassinari, M., “Poinçonnement symétrique des dalles en béton armé avec armature de poinçonnement,” PhDThesis, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 2011.