Compressive Behavior of PET FRP-Confined Circular, Square, and Rectangular Concrete Columns

This paper presents the results of an experimental study on the compressive behavior of circular and noncircular concrete columns confined by polyethylene terephthalate (PET) fiber-reinforced polymer (FRP). The main objective of this study is to observe the compressive behavior of PET FRP-confined noncircular concrete columns, in which the cross-sectional geometry significantly influences the effectiveness of FRP confinement. For this purpose, 54 specimens were tested under monotonic axial compression. The parameters considered were the cross-sectional shape (i.e., circular, square, and rectangular), the corner radius in case of square and rectangular specimens, and the number of FRP layers. The results of this study showed that, unlike the bilinear stress-strain response of square and rectangular concrete columns confined by other FRP materials, PET FRP-confined square and rectangular concrete columns exhibit a distinct trilinear relationship. Owing to the large rupture strain (LRS) characteristics of PET FRP, all the confined specimens exhibit highly ductile behavior, and the knife action of sharp corners is efficiently resisted in noncircular columns. The results also indicate that the effectiveness of PET FRP confinement decreases with an increase in sectional aspect ratio and increases with an increase in corner radius. In addition, to evaluate the applicability of existing strength and strain models developed for other FRPs to PET FRP-confined concrete, the experimental results are compared with the predictions of five existing models. The results indicate that the average compressive strength of PET FRP-confined circular, square, and rectangular concrete columns is predicted well, but the average ultimate axial strain is highly underestimated by all the five models. (C) 2016 American Society of Civil Engineers.