This was the joint second place winning presentation from the Young Researchers Conference 2020.
The most economically competitive composite materials for internal reinforcement are glass FRP (GFRP) and basalt FRP (BFRP). Their main limitation for flexural elements is the higher deformability in comparison with steel, due to relatively low Young modulus.
Corresponding RC structural elements experience significant deflections at stages of loading well below the ultimate strength of the materials. This forces the designers to use design procedures where the governing limit state is serviceability, which results in inclusion of significant amount of reinforcement to mitigate the deflections.
A much more effective and economical approach is prestressing of the reinforcement. Previous research in this area by Thorhallsson and Jonasson (2012), Crossett et al. (2015) and Mirshekari et al. (2016) indicates that the prestressing of FRP reinforcement could be a viable way for utilising their high strength and to achieve reduced deformability of flexural RC elements without the use of an excessive amount of reinforcement.
For further effective use of this approach the detailed information about long-term behaviour of FRP reinforcing bars and related reduction of initially generated stresses with the time, i.e. losses of prestress, need further investigation.
Hence, this research project aims to investigate the long-term behaviour of pretensioned BFRP reinforced beams, focusing on both short and longterm losses. The goal is to obtain information about the range of prestress losses, through experimental research complemented by finite element modelling (FEM).
Prestress losses of pretensioned BFRP reinforced concrete beams