Influence of overlap configuration on compressive behavior of CFRP-confined normal- and high-strength concrete

This paper presents the findings of an experimental investigation on the effect of overlap configuration on carbon fiber-reinforced polymer (CFRP)-confined normal- and high-strength concrete. A total of 33 specimens were prepared and tested under monotonic axial compression. All specimens were cylinders with 152 mm diameter and 305 mm height and confined by CFRP tubes. Two different concrete mixes were examined, with average compressive strengths of 52.0 and 84.7 MPa. The effect of overlap configuration was examined by manufacturing the specimens with different properties at the overlap region including overlap length, continuity and distribution. Axial and lateral behavior was recorded to observe the axial stress–strain relationship and hoop strain behavior for concentric compression. Ultimate axial and lateral conditions are tabulated and stress–strain curves have been provided. Detailed plots of hoop strain development and lateral confinement pressure at ultimate are presented. The results indicate that FRP overlap length has no significant influence on strain enhancement ratio (εcu/εco), but an increase in overlap length leads to a slight increase in strength enhancement ratio (f′cc/f′co), with these observations equally applicable to both continuously and discontinuously wrapped specimens. The results also indicate that continuity of the FRP sheet in the overlap region has some influence on the effectiveness of FRP confinement. Furthermore, it was observed that the distribution of FRP overlap regions for discontinuously wrapped specimens can influence the axial compressive behavior of these specimens in certain overlap configurations. Finally, it is found that the distribution of lateral confining pressure around specimen perimeter becomes less uniform for specimens with higher concrete strengths and those manufactured with overlap regions that are not evenly distributed.