Influence of Prestress on Axial Compressive Behavior of High-Strength Concrete-Filled FRP Tubes

Abstract

This paper presents an experimental investigation on the influence of prestress on axial compressive behavior of concrete-filled fiber reinforced polymer (FRP) tubes (CFFTs). A total of 12 aramid FRP- (AFRP) confined high-strength concrete (HSC) specimens with circular cross-sections were tested under monotonic axial compression. All specimens were cylinders with 152 mm diameter and 305 mm height and their unconfined concrete strengths were approximately 100 to 110 MPa. The influence of FRP prestress was examined by applying 3 different levels of lateral prestress ranging from 4.29 to 7.27 MPa. In addition to the prestressed specimens, companion specimens with no applied prestress were manufactured and tested to establish reference values. Results of the experimental study indicate that the influence of prestress on compressive strength is significant, with an increase in ultimate strength observed in all prestressed specimens compared to that of non-prestressed specimens. On the other hand, the influence of prestress on axial strain was found to be minimal, with prestressed specimens displaying a slight decrease in ultimate strain, compared to their non-prestressed counterparts. The results also indicate that prestressing the AFRP shell prevents the sudden drop in strength, typically observed in FRP-confined HSC specimens, that initiates at the transition point which connects the first and second branches of the stress-strain curves.