The effect of fibres in UHPFRC beams with longitudinal steel reinforcement


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Title: The effect of fibres in UHPFRC beams with longitudinal steel reinforcement

Author(s): Norbert Randl; Tamás Mészöly

Publication: Special Publication

Volume: 310


Appears on pages(s): 181-192

Keywords: UHPC, UHPFRC, steel fibres, fibre reinforcement, cracking, high-grade steel reinforcement.

Date: 3/17/2017

In a research project funded by the Austrian Research Foundation (FFG), ultra-highperformance fibre-reinforced concrete (UHPFRC) mixtures were developed and optimized. Compression tests, uniaxial tension tests and several small-scale four-point bending tests were performed and the full constitutive law was derived. A series of 10 large-scale beams with a span of 3 m and an I-shaped cross-section was subsequently produced and tested in a fourpoint setup, where the reinforcement amount and the fibre content were varied. The tensile strength of the longitudinal reinforcement was 800-1100 MPa. Several circular openings were foreseen in order to facilitate potential installation crossings. In the tests with flexural failure at ultimate load level, a pronounced ductile behaviour was observed. Cracking and crack widths were controlled in a satisfying way by the longitudinal reinforcing bars and the fibres as well. Apart from the mostly observed bending failure mode, two beams with increased longitudinal reinforcement and 2% fibres exhibited diagonal tension failure in shear. Regarding the ultimate load, in the tests with shear failure the fibre contribution was much more significant than in the tests with bending failure.