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Abstract
The research is devoted to the shear of slender concrete beams without transverse reinforcement flexurally reinforced with two types of bars: steel and composite (glass fiber reinforced polymer - GFRP). The motivation to undertake research pro-gram was desire to determine an effect of the low elasticity modulus of the longitudinal GFRP bars and their anisotropic structure on the failure mechanism and shear capacity. The main purpose of the work was to analyse the failure mechanism with the flexural GFRP or steel reinforcement without transverse reinforcement and to compare the shear capacity and deformability of the beams. The remaining objectives included: the influence of the following variable parameters on the ultimate loads and failure modes: degree of the longitudinal reinforcement (1.0%, 1.4% and 1.8%), number of bar levels (one, two), number and diameter of bars selected for specified reinforcement ratio and the thickness of the concrete cover (15 mm, 35 mm). To analyse the cracking pattern of the beams, the digital image correlation system Aramis was used, what allowed a detailed registration of the failure mechanism the flexural cracking, through crack development until to the fail-ure. Using the kinetic shear model, the process of beams' failure was precisely described, with the indication of differences regarding to the location and inclination of the diagonal critical cracks in the all beams. The research program included thirty three single-span, simply supported T-section beams (beff = 400 mm, bw = 150 mm, hf = 60 mm, htot = 400 mm) with the axis span of 1800 mm without transverse reinforcement. The three point loaded beams (with the load located at a dis-tance of 1100 mm from the support) had the shear span to depth ratio a/d in the range of 2.9-3.0 referring to the slender beams. Research revealed two failure modes. The first, shear - tension occurred in most of the beams (all RC elements and parts of the GFRP reinforced elements) and the second one relating to the bond loss between GFRP reinforcement and concrete, which occurred in three beams of the II series, reinforced with GFRP rods. The research confirmed the influence of a type of the longitudinal reinforcement on the behaviour of beams without transverse reinforcement. The four times lower modulus of elasticity of the GFRP reinforcement revealed a gentle, progressive shear - tension failure mode, opposite to the to the abrupt failure mode of the RC beams. The difference in the elasticity modulus of both types of reinforcement resulted in increase in the shear capacity of the RC beams in the range between 30% and 66% comparing to the shear ca-pacity of the GFRP reinforced beams with the same reinforcement ratio. The increase in a the longitudinal reinforcement ratio reduced cracking pattern, the crack width, increased of beams stiffness and shear capacity. The two-layer reinforce-ment levels occurred more beneficial only for the GFRP reinforced beams. The influence of the diameter change was more pronounced in the beams with the low reinforcement ratio (about 1%). The influence of the concrete cover thickness was quite small, which confirmed a negligible effect of the dowel action in the elements without transverse reinforcement.
References
Cavagnis, F., Fernández Ruiz, M. i Muttoni, A. (2015) „Shear failures in reinforced concrete members without transverse reinforcement: An analysis of the critical shear crack development on the basis of test results”, Engineering Struc-tures, 103, ss. 157–173. doi: 10.1016/j.engstruct.2015.09.015.
CEN (2017) CEN/TC 250/SC 2/WG 1/TG 1 N 110 Draft Reinforcing With FRP.
Cladera, A. i in. (2015) „Predicting the shear-flexural strength of slender reinforced concrete T and I shaped beams”, Engineering Structures, 101, ss. 386–398. doi: 10.1016/j.engstruct.2015.07.025.
Cladera, A. i in. (2016) „The compression chord capacity model for the shear design and assessment of reinforced and prestressed concrete beams”, Structural Concrete, 17(6), ss. 1017–1032. doi: 10.1002/suco.201500214.
DIN EN 10002-1 (2001) Metallic materials - Tensile testing - Part 1: Method of testing at ambient temperature.
International Organization for Standardization (ISO) (2015) „10406-1. Fibre-reinforced polymer (FRP) reinforcement of concrete Test methods Part 1: FRP bars and grids”.
Kotynia, R., Szczech, D. i Kaszubska, M. (2017) „Bond Behavior of GRFP Bars to Concrete in Beam Test”, Procedia En-gineering, 193, ss. 401–408. doi: 10.1016/j.proeng.2017.06.230.
Kowalewski, Z. i in. (2016) „Nowoczesne systemy optyczne w badaniach mechanicznych – budowa, działanie, zastosowa-nia”, w XXII Seminarium Nieniszczące badania materiałów. Zakopane.
Krawczyk, Ł., Gołdyn, M. i Urban, T. (2017) „O niedokładnościach systemów cyfrowej korelacji obrazu”, Journal of Civil Engineering, Enviroment and Architecture, XXXIV(64), ss. 259–270.
Leonhardt, F. i Walther, R. (1962a) „Schubversuche an einfeldigrn Stahlbetonbalken mit und ohne Schubbewehrung”, DAfSt.
Leonhardt, F. i Walther, R. (1962b) „Shear Tests on Beams With and Without Shear Reinforcement”, Deutscher Ausschuss für Stahlbeton, 151(151), s. 83.
Marí, A. i in. (2014) „Shear design of FRP reinforced concrete beams without transverse reinforcement”, Composites Part B: Engineering, 57, ss. 228–241. doi: 10.1016/j.compositesb.2013.10.005.
Mazaheripour, H. i in. (2013) „Experimental study on bond performance of GFRP bars in self-compacting steel fiber rein-forced concrete”, Composite Structures, 95, ss. 202–212. doi: 10.1016/j.compstruct.2012.07.009.
Muttoni, A. i Ruiz, M. F. (2008) „Shear strength of members without transverse reinforcement as function of critical shear
crack width”, ACI Structural Journal, 105(2), ss. 163–172. doi: 10.1139/l96-004. Perry, C. C. (1989) „Data-Reduction Algorithms for Strain Gage Rosette Measurements”, Experimental Techniques,
ss. 13-18. PN-EN 1992-1-1 (2008) Eurokod 2. Projektowanie konstrukcji z betonu. Część 1-1: Reguły ogólne i reguły dla budynków. PN-EN 206-1 (2003) Beton. Cz.1: Wymagania, właściwości, produkcja i zgodność. PN-EN ISO 6892-1 (2016) Metale - Próba rozciągania - Część 1: Metoda badania w temperaturze pokojowej, Pn-En Iso. Dostępne na: http://sklep.pkn.pl/pn-en-iso-6892-1-2016-09e.html.
Szczech, D. i Kotynia, R. (2017) „Beam bond test of GFRP and steel reinforcement to concrete”, Archieves of Civil Engi-neering.
Taylor, H. P. J. (1969) Investigation of the dowel shear forces carried by tensile steel in reinforced concrete beams. Cement and Concrete Association, Technical Report no. TRA 431, London (UK). London.
Taylor, H. P. J. (1970) Investigation of the forces carried across cracks in reinforced concrete beams in shear by interlock of aggregate. Cement and Concrete Association, Technical Report No. 42.77, London (UK). Londyn.
Yang, Y. (2014) Shear behaviour of reinforced concrete members without shear reinforcement, a new look at an old prob-lem. PhD thesis. Delft University of Technology.