Influence of fiber orientation and specimen end condition on axial' compressive behavior of FRP-confined concrete

This paper presents an experimental investigation on the effect of fiber angle and specimen end condition on axial compressive behavior of fiber reinforced polymer (FRP)-confined concrete. A total of 24 aramid FRP (AFRP)-confined concrete specimens with circular cross-sections were tested. 18 of these specimens were manufactured as concrete-filled FRP tubes (CFFTs), whereas the remaining 6 specimens were FRP-wrapped concrete cylinders. The specimens were manufactured using two different concrete mixes with average compressive strengths of 50 and 80 MPa. The influence of fiber orientation was examined through a group of CFFT specimens manufactured using an automated filament winding technique, with fibers aligned at 45, 60 or 75 degrees with respect to the longitudinal axis. Additional filament wound specimens with fibers aligned along the hoop direction were also prepared to allow a comparison between specimens with inclined fibers and hoop oriented fibers. The effect of specimen end condition was examined on both CFFTs and FRP-wrapped specimens. This parameter was selected to study the influence of loading the FRP jacket on the axial compressive behavior. The results of this experimental study indicate that specimen performance is optimized when fibers are aligned in the hoop direction and the performance diminishes with decreasing fiber angle. The results also indicate that the performance of FRP-wrapped specimens is similar to that of CFFT specimens and the influence of specimen end condition is negligible. (C) 2013 Elsevier Ltd. All rights reserved.