Pullout behaviour of bars in concrete confined with post-tensioned steel straps

Abstract

This paper presents the experimental results of bond and anchorage behaviours under Steel Strap Tensioning Technique (SSTT) confined high-strength concrete (HSC). The experimental tests consisted of pull-out test with short bond length and pull-out test with long bond length were performed to determine the bonding and anchorage capacity of SSTT-confined HSC. A total 36 specimens with short bond length and 16 specimens with long bond length were tested in this study. Three batches of concrete with compressive strength of 30 MPa, 60 MPa and 90 MPa were tested. Other parameter in this study was rebar diameter of 12 mm and 16 mm and different SSTT confinement ratios ranging from 0 to 0.2. To determine the effects of confinement on development bond and anchorage, an analytical expression was developed based on the parameters tested in this study. The equation is then verified with the bond strength proposed by the existing bond equations. The results from conducted tests indicated that the application of SSTT as an external confinement can increase the bond strength of confined concrete by up to 50%.