Replacing steel with FRP reinforcement has been practiced for many years but using basalt fiber reinforcement polymer tendons (BFRP) as a structural material is rather new. Tension strength of BFRP tendon is about twice the tension strength of steel reinforcement, but the elastic modulus is only 40-50 GPa while steel has 200 GPa.
Therefore, elastic lengthening of BFRP tendons is much more than of steel and strain in the tension zone of concrete structures will be over acceptable limits. To utilise the high-tension strength of BFRP and prevent cracking of concrete, the tendons could be prestressed.
In this research, four beams were concreted. Three of them were prestressed. The main findings were that the stiffness and bearing capacity of the beam increase relative to un-prestressed beam. Long-term relaxation of prestressed BFRP tendons is estimated close to 20%. New formula for shear resistance is derived from EC2.
Eythor Thorhalsson, Associated Professor Reykjavik University, Reykjavik, Iceland;
Bjorgvin Smari Jonsson, Research Assistant Reykjavik University, Reykjavik, Iceland.