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Structural behaviour of a 10-m pre-stressed slab made with basalt fibre reinforced polymer bars (BFRP) and fibre reinforced self-compacting concrete (FRSCC)

Author(s): Mohammed Sonebi, Bruno Dal Lago, Su Taylor, Peter Deegan, Liberato Ferrara, Philip Crosset, Andrea Pattarini
Paper category: Proceedings
Book title:4th International Symposium on Design, Performance and Use of Self-Consolidating Concrete
Editor(s): Caijun Shi & Zuhua Zhang, Hunan University, China
Kamal Henri Khayat, Hunan University, China
Missouri University of Science & Technology, USA
Publisher: RILEM Publications SARL
Publication year:2018
Total Pages:2
Language : English

Abstract: Basalt fibre reinforcing bars are proposed to be used as a pre-stressed reinforcement for precast concrete elements. Besides the enhanced resistance to aggressive agents of the bars, which are not subjected to corrosion, their low elastic modulus allows to limit the instantaneous and time-dependant losses and makes their application to pre-stressed precast concrete particularly promising. The design of a 10-m long steel-free precast fibre-reinforced concrete slab, pre-stressed with basalt-fibre reinforced polymer (BFRP) bars and shear-reinforced with glass-fibre reinforced polymer bars (GPRP) has been tested at Banagher precast concrete Ltd. The experiments are aimed at verifying the correct functioning of the pre-stressing system, typically employed for steel tendons, the time-dependant behaviour of the beam during
service loading and its resistance, allowing to obtain information about reliability and robustness of this technologic solution, even if the pre-stressing of the BFRP bars has been limited to half of their resistance, the traditional wedging anchorage system used for steel brought to the delayed failure of 25% of the bars due to the concentration of transversal loading in a short distance. A novel anchorage device is suggested to be developed, for instance with increased length for a better stress distribution. Despite positive preliminary testing, during element casting, traditional wedge anchorage systems, used for steel, caused some of the bars to fail, due to rupture of the outer fibres even though they were pre-stressed to about half of their strength. This is an issue to be considered for the application of this technology and the resin-based system that was developed for the laboratory tests should be used in future. The 3-point loading test showed a satisfactory performance of the member, with an efficient elastic performance of the pre-stressing reinforcement even at a load larger than the expected resistance, corresponding to mid-span deflections of more than 1/50 of the span, with small residual deflection and crack closing at unloading. Efficient elastic recovery with low residual deflection and crack closing were observed after unloading at up to 80% of the ultimate load. The crack pattern of the member showed a very good capacity of crack distribution and corresponding low mean crack opening, which is mainly attributable to the polypropylene fibres. Failure occurred due to the tensile rupture of the BFRP longitudinal bars. The shear-resisting truss made by GFRP non-bent bars inclined at 45° behaved satisfactorily even in the post-cracking phase and prevented a diagonal tension failure due to shear. An additional test on the damaged slab was carried out 9 months later to observe its failure mode, which has been, as predicted, dominated by flexure with tensile failure of the BFRP bars. The strength would have increased with pre-stressing in case failure would have occurred on the concrete side. The experimental results confirmed that the proposed technology, employing fully non-metallic reinforcement and relying on the toughening effect of the dispersed fibre reinforcement, is a viable and robust structural solution for durable low-carbon FRSCC pre-stressed beams or slabs.

Online publication : 2018
Publication type : full_text
Public price (Euros) : 0.00

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