Axial compressive behavior and design-oriented model for large-rupture-strain (LRS) FRP-confined concrete in rectangular columns

Polyethylene terephthalate (PET) fiber-reinforced polymer (FRP) composites, which is a kind of low-carbon production and have a large rupture strain, may have prosperous application outlooks. PET FRP wrap has been explored as confining reinforcement for concrete, and the majority of investigations are limited to PET FRP-confined concrete in circular and square columns, whereas PET FRP-confined rectangular columns have barely been touched. To fill this research gap and gain a fundamental understanding of the confinement mechanism, comprehensive compressive tests on 36 columns were conducted in this study, in which the confinement thickness, cross-section aspect ratio, and specimen size were the focal points. All specimens exhibited a three-segment behavior (i.e., strain hardening-softening-hardening response). In addition, it is demonstrated that specimen size had an insignificant effect on the axial stress-strain response of small and medium columns with a height less than 400 mm, provided that their confinement levels were the same (or similar). Furthermore, the minimum effective confinement stiffness for PET FRP-confined rectangular columns to achieve sufficient confinement was 0.004, which was extracted from all available test results. A design-oriented model with improved performance was proposed and the simulated full axial stress-strain showed close agreements with the test results.

Automated summary

This study investigated the confinement mechanism of PET FRP-confined columns by conducting comprehensive compression tests on 36 specimens. The results showed a three-segment behavior (strain hardening-softening-hardening response) in all specimens. The size of the specimens had an insignificant effect on the axial stress-strain response of small and medium columns with a height less than 400 mm. A design-oriented model with improved performance was proposed and showed close agreements with the test results.