Size Effect of Concrete Short Columns Confined with Aramid FRP Jackets

Most previous studies on concrete short columns confined with fiber-reinforced polymer (FRP) composites were based on small-scale testing, and size effect of the columns still has not been studied thoroughly. In this study, 99 confined concrete short columns wrapped with aramid FRP (AFRP) jackets and 36 unconfined concrete short columns with circular and square cross sections were tested under axial compressive loading. The circular specimens were divided into six groups, and the square specimens were divided into five groups, with each group containing different levels of the AFRP’s confinement. In each group, the specimens were geometrically similar to one another and had three different scaling dimensions. Statistical analyses were used to evaluate the size and interaction effects between the specimen size and the AFRP’s confinement, and a size-dependent model for predicting the strength of the columns was developed by modifying Bazănt’s size-effect law. The experimental results showed that the size of a specimen had a significant effect on the strength of AFRP-confined concrete short columns, lesser effect on the axial stress-strain curves, and slight effect on the failure modes. The modified Bazănt model was in good agreement with the experimental data.