Title: Fibre effect on shear behaviour of UHPC beams
Author(s): Randl, N.; Mészöly, T.
Publication: Symposium Paper
Appears on pages(s): 524-532
Keywords: UHPC, UHPFRC, fibre reinforcement, stirrups, shear load
The load bearing behaviour of fibre reinforced UHPC members in shear has not yet been
investigated sufficiently. Therefore, an experimental campaign was conducted, investigating
the behaviour of I-shaped beams made of Ultra-High Performance Concrete (UHPC)
subjected to shear loading. The height of the beams was 350 mm, and the single span length
3.00 m. The main parameters were the fibre content (up to 2% by volume) and the degree of
stirrup reinforcement (no stirrups or diameter 10 mm bars, spacing 125 to 300 mm).
A total of 20 tests were performed, all of them ending up in typical shear failure:
pronounced shear cracks formed along the web between support and load introduction at a
level of 60-70% of the ultimate load. The cracking process was monitored by a digital image
correlation (DIC) measurement system.
A decisive effect of the fibres was observed: the addition of 1% to 2% fibres by volume led
to a more distributed crack pattern as well as a significant increase of the ultimate load. The
enhancement of the shear load capacity was not proportional to the fibre content, but
corresponded quite well with the UHPFRC’s residual tensile strength in the post-cracking
stage. The interaction with varying degrees of stirrup reinforcement was assessed as well.