INVESTIGATION OF THE SIZE EFFECT IN SHEAR OF STEEL FIBER REINFORCED CONCRETE (SFRC) SLENDER BEAMS

Author(s): M. Zarrinpour, J.-S. Cho and S.-H. Chao
Book Title: Seventh International RILEM Conference on High Performance Fiber Reinforced Cement Composites (HPFRCC7)
Editor: H.W. Reinhardt, G.J. Parra-Montesinos, H. Garrecht
ISBN: 978-2-35158-145-2
e-ISBN: 978-2-35158-146-9
Publisher: RILEM Publications SARL
Publication year: 2015
Pages: 375-382
Total Pages: 8
Language: English

Abstract: Significant shear strength reduction with the increase of the height of slender plain concrete beams with no web reinforcement is a well-known phenomenon called size effect. The American Concrete Institute’s ACI 318 Building Code allows steel fiber reinforced concrete (SFRC) to replace conventional minimum shear reinforcement in slender beams; however, the beam’s height is limited to 610 mm (24 in.) This is due to the fact that, except for a very few tests, the majority of test results on shear behavior of SFRC beams has been evaluated on specimens with an effective depth of 178 mm (7 in.) to 572 mm (22.5 in.). The object of this research was to investigate the size effect of SFRC beams in shear as well as the long-term shear performance (up to 33 months after casting) of SFRC beams by experimentally testing four pairs of SFRC slender beams with an extended observance time after casting. These beams had total heights of 457 mm (18 in.), 610 mm (24 in.), 915 mm (36 in.), and 1220 mm (48 in.), and one pair of beams was 457 mm (18 in.) high companion beams made of plain concrete. The only variable parameter was the overall depth, while the remaining key factors were held constant including shear span to effective depth ratio of 3.5, longitudinal reinforcement ratio (approximately 2.7%), compressive strength of concrete (targeted at 42 MPa), steel fiber volume fraction (0.75%), and types of steel fiber (hooked-end fibers conformed to ACI requirements). Test results indicate that the normalized shear stress at failure is substantially increased for all SFRC specimens as a result of fiber inclusion. In spite of the various effective depths of the specimens, the discrepancy in normalized shear strengths was relatively marginal. Also, even though the specimens were tested at a quite high age ranging from 502 to 1005 days and exposed to weather, no degradation was observed in terms of their shear behavior.

Online publication: 2015
Publication Type: full_text
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