THE ROLE OF SECONDARY VARIABLES IN PUNCHING STRENGTH OF SLABS

Öz

Punching shear strength of reinforced concrete slabs exhibits size effect. Size effect on punching shear of reinforced concrete slabs has been being discussed since past decades and there has not been any consensus on the subject yet. Most of the discussions focus on the nonlinearity of the structures, of which deviates the size effect slope of the LEFM from -1/2 to milder slopes. But extrapolation of the practical sizes to very large sizes results in brittle behavior. Diminishing the secondary influencing parameters, makes linear elastic fracture mechanics available to apply. In this study it is intended to demonstrate the structural scaling phenomenon that the large structures behave more brittle and conical fracture surface of slab punch becomes more smooth.

Anahtar Kelimeler

• Size effect,Fracture surface,Asymptotic extrapolation,Concrete,Punching

ZIMBALAMA BOYUT ETKİSİNDE İKİNCİL DEĞİŞKENLERİN İŞLEVİ

Öz

Betonarme döşemelerin zımbalama kırılmalarında boyut etkisi gözlenir. Bu etkinin matematiksel ifadesi konusunda mühendisler arasında bir fikir birliği bulunmamaktadır. Tartışmalar yapısal elemanların doğrusal olmayan davranışlarının betonun kırılma yüzeyinin şeklini değiştirdiği ve böylece boyut etkisi asimptotik eğiminin -1/2’den saptığı konusunda yoğunlaşmıştır. Fakat normal boyuttaki betonarme yapıların asimptotik ekstrapolasyonu bizi lineer elastik kırılma mekaniğinin geçerli olduğu durumlara yaklaştırır. Bu çalışmada zımbalama etkisindeki elemanların boyutlarının artması ile lineerliği bozan ikincil parametrelerin etkilerinin azaldığı gösterilmiştir. Yapı elemanlarının boyutlarının artması ile daha gevrek davrandığı hipotezi üzerinde durulmuş olup bu durumun sonuçları üzerinde tartışılmıştır.

Anahtar Kelimeler

• Boyut etkisi,Kırılma yüzeyi,Asimptotik ekstrapolasyon,Beton,Zımbalama

Kaynakça

1. ACI 318. 2011. Building Code Requirements for Structural Concrete, American Concrete Institute, ACI Committee 318, Detroit, USA, 503.
2. Bazant, Z.P., 2005. Scaling of structural strength. Butterworth-Heinemann.
3. Bazant, Z.P., ve Planas, J., 1997. Fracture and size effect in concrete and other quasibrittle materials (Vol. 16). CRC press.
4. Bazant, Z.P., ve Cao, Z., 1987. Size effect in punching shear failure of slabs. ACI Structural Journal, 84(1), 44-53.
5. Bazant, Z.P., Yu, Q., Gerstle, W., Hanson, J., ve Ju, J.W., 2008. Justification of ACI 446 Proposal for Updating ACI Code Provisions for Shear Design of Reinforced Concrete Beams. ACI Structural Journal, 105(4), 507.
6. Birkle, G., ve Dilger, W.H., 2008. Influence of slab thickness on punching shear strength. ACI Structural Journal, 105(2), 180-188.
7. Broms, C.E., 2016. Tangential strain theory for punching failure of at slabs. ACI Structural Journal, 113(1), 95.
8. BS 8110, Structural Use of Concrete, Part 1: Code of Practice for Design and Construction, British Standards Institute, London, UK, 1997.

9. Caner, F.C., ve Bazant, Z.P., 2012. Microplane model M7 for plain concrete. I: Formulation. Journal of Engineering Mechanics, 139(12), 1714-1723.
10. CSA A23.3-04, Design of Concrete Structures, Canadian Standards Association, Rexdale, ON, Canada, 2004, 214 pp.
11. Dönmez, A., ve Bazant, Z.P., 2017. Size Effect on Punching Strength of Reinforced Concrete Slabs with and without Shear Reinforcement. ACI Structural Journal, 114(4), 875.
12. Eurocode 2. 2004. Design of Concrete Structures Part 1: General rules and rules for building. European Committee for Standardization, Brussels, 241
13. Gardner, N.J., 1996. Punching Shear Provisions for Reinforced and Prestressed Concrete Flat Slabs, Canadian Journal of Civil Engineering, V. 23, No. 2, Apr., pp. 502-510.
14. KCI (Korea Concrete Institute), 2012. KCI 2012: KCI Concrete Design Code 2012. Korea Concrete Institute, Korea, 548 pp.
15. Kueres, D., Siburg, C., Herbrand, M., Classen, M., ve Hegger, J., 2017. Uniform Design Method for punching shear in at slabs and column bases. Engineering Structures, 136, 149-164.
16. Lovrovich, J.S., ve McLean, D.I., 1990. Punching Shear Behavior of Slabs with Varying Span-Depth Ratios. Structural Journal, 87(5), 507-512.
17. Marsden, J.E., ve Hughes, T.J., 1994. Mathematical foundations of elasticity. Courier Corporation.
18. Marzouk, H., Emam, M., ve Hilal, M.S., 1998. Sensitivity of shear strength to fracture energy of high-strength concrete slabs. Canadian Journal of Civil Engineering, 25(1), 40-50.
19. Marzouk, H., ve Hussein, A., 1991. Experimental investigation on the behavior of high-strength concrete slabs. ACI Structural Journal, 88(6), 701-713.
20. Matthys, S., ve Taerwe, L., 2000. Concrete slabs reinforced with FRP grids. II: Punching resistance. Journal of Composites for Construction, 4(3), 154-161.
21. ModelCode 2010., 2010. Federation Internationale du Beton: Model Code 2010. Lausanne, 2010.
22. Muttoni, A., ve Schwartz, J., 1991. Behavior of beams and punching in slabs without shear reinforcement. In IABSE colloquium, 62, EPFL-CONF-111612, 703-708.
23. Muttoni, A., ve Ruiz, M.F., 2008. Shear strength of members without transverse reinforcement as function of critical shear crack width. ACI Structural Journal, 105(2), 163-172.
24. Neth, V.W., de Paiva, H.A.R., ve Long, A.E., 1981. Behavior of Models of a Reinforced Concrete Flat Plate Edge-Column Connection. In Journal Proceedings 78(4), s. 269-275.
25. Nguyen-Minh, L., ve Rovk, M., 2012. Punching shear resistance of interior GFRP reinforced slab-column connections. Journal of Composites for Construction, 17(1), 2-13.
26. Regan, P.E., 1981. Behaviour of reinforced concrete flat slabs. Construction Inudstry Research and Information Association.
27. Ruiz, M.F., ve Muttoni, A., 2017. Size Effect on Punching Shear Strength: Differences and Analogies with Shear in One-way Slabs. ACI Special Publication, 315, 59-72.
28. Shehata, I.A., ve Regan, P.E., 1989. Punching in RC slabs. Journal of Structural Engineering, 115(7), 1726-1740.
29. Sigrist, V., Bentz, E., Ruiz, M.F., Foster, S., ve Muttoni, A., 2013. Background to the fib Model Code 2010 shear provisions, part I: beams and slabs. Structural Concrete, 14(3), 195-203.
30. Subcommittee on English Version of Standard Specifications for Concrete Structures (2007). JSCE Guidelines for Concrete No. 15: Design. Japan Society of Civil Engineering.
31. Theodorakopoulos, D.D., ve Swamy, R.N., 2008. A design model for punching shear of FRP-reinforced slab-column connections. Cement and Concrete Composites, 30(6), 544-555.
32. TS 500, 2000. Betonarme Yapıların Tasarım ve Yapım Kuralları, Madde 11-Betonarme Döşeme Sistemleri, 52-60.
33. Uçar, T., Merter, O. 2012. Narinlik Oranının Yanal Ötelenmeli Betonarme Çerçevelerin Göçme Davranışına Etkisinin Doğrusal Olmayan ve Enerji Esaslı Yöntemlerle Araştırılması. Mühendislik Bilimleri ve Tasarım Dergisi, 2 (1), 13-25.