Behaviour of Over-reinforced High-Strength Concrete Beams Confined with Post-Tensioned Steel Straps: an experimental investigation

This study examines the flexural behaviour of High-Strength Concrete (HSC) beams confined using an innovative Steel Strapping Tensioning Technique (SSTT) able to provide active confinement. Twelve overreinforced HSC beams (fc=50 or 80 MPa) were designed to fail prematurely by concrete crushing at midspan. The midspan of eight of such beams was confined externally using the SSTT with different steel strap confinement ratios, which aimed to delay concrete crushing. The test results are discussed in terms of the failure modes, load-deflection response, and observed concrete and tensile reinforcement strains. Whilst unconfined beams failed in a brittle manner with no post-peak deflection, the steel straps were very effective at enhancing the post-peak deformation of the SSTT-confined beams by up to 126%. Moreover, for the beams tested in this study, the use of the SSTT led to failures after yielding of the tensile reinforcement. The proposed SSTT can be used to confine HSC elements where ductility is required.