Fatigue performance of prestressed concrete beams using BFRP bars Taha Younes a,⇑ , Adil Al-Mayah a,b , Tim Topper a a Dept. of Civil and Env. Engineering, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada b Dept. of Mechanical and Mechatronics Engineering, University of Waterloo, 200 University Ave W, Waterloo, ON N2L 3G1, Canada highlights  Basalt bars were used in prestressing concrete beams subjected to fatigue loading.  There was little effect of prestressing on fatigue strength for low fatigue lives.  Enough prestress was retained to close cracks for fatigue lives above 100,000 cycles.  Prestressed beams failed by bar rupture after concrete crushing in monotonic tests. article info Article history: Received 7 September 2016 Received in revised form 14 June 2017 Accepted 15 September 2017 Keywords: BFRP bars Prestressed concrete Fatigue Flexural behaviour abstract Basalt fibers have recently been introduced as a promising addition to the existing fiber reinforced poly- mer (FRP) family. A limited amount of information is available on basalt FRP (BFRP) bars and their struc- tural concrete applications. This paper presents the flexural behaviour of sixteen prestressed concrete beams using BFRP bars under monotonic and fatigue loading. The investigated parameters were the level of prestress of the bars (0%, 20% and 40% of their static tension capacity) and the fatigue load ranges. The experimental findings showed that beams with the bars prestressed to 40% of the bar strength had a higher fatigue strength than those prestressed to 0% and 20%. For 40% and 20% prestressed beams, there is no improvement in fatigue performance for load ranges above 20% and 13% of the ultimate capacity of the beams a level at which calculations showed that the remaining prestress did not close cracks at the minimum load in the fatigue load cycle. When compared on the basis of load range versus cycles to fail- ure, the data for the three beam types fell onto a single curve at load levels where the remaining prestress after fatigue creep relaxation no longer closed the crack at the minimum load. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Structural elements can fail under either static or fatigue load- ing. Since concrete structures such as marine structures, parking garages and bridges are subjected to fatigue loading during their lives, it is important to understand their creep and fatigue beha- viour. In addition, the limit states (ultimate and serviceability) gov- erned by fatigue behaviour must be taken into account by designers. The primary variable in causing fatigue failure of both steel and composites is the range of applied stress. When a con- crete beam is prestressed, the range of stress in the reinforcement is small up to the load at which the concrete cracks. This is because the area of the uncracked concrete in the region of the reinforce- ment is much greater than that of the reinforcement, and most of the change in force required to balance an applied moment is supplied by a reduction in the compressive stress in the concrete. After cracking, however, the tensile forces required to balance additional moment are supplied by the reinforcement and the stress in the reinforcement increases rapidly and the beam stiff- ness is reduced. Glass and carbon fibers have a good resistance to creep; on the other hand, polymeric resins are more susceptible to creep; as a result, fiber type, volume fraction and fiber orientation and tem- peratures which lead to a decrease in resin strength play an impor- tant role in the creep performance of FRP reinforcing rebar. A study by Noël and Soudki [5] was conducted to investigate fatigue behaviour of GFRP, the results showed that GFRP bars embedded in concrete have shorter fatigue lives than similar bars tested in air by approximately a full order of magnitude. Preliminary fatigue test results carried out by El Refai [3] showed that the fatigue limit of BFRP bars was about 4% of their ultimate capacity. However, the fatigue limit of GFRP bars was about 3% of their ultimate capacity. Furthermore, the results https://doi.org/10.1016/j.conbuildmat.2017.09.086 0950-0618/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: tyounes@uwaterloo.ca (T. Younes). Construction and Building Materials 157 (2017) 313–321 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat