Large-rupture-strain (LRS) FRP-confined concrete in square stub columns: Effects of specimen size and assessments of existing models

•Effects of specimen size of PET FRP-confined concrete in square stub columns are first ever studied.•Existing models on PET FRP-confined concrete in square stub columns are first ever assessed.•The minimum confinement stiffness ratio for a sufficient confinement is 0.0036.•Increasing PET FRP thickness and corner radius ratio shorten transition segment and enhance ultimate stress.•Specimen size has insignificant effect for small- and medium-sized stub columns with similar confinement level. As an environmental-friendly material with high rupture strain capacity, polyethylene terephthalate (PET) fiber reinforced polymer (FRP) has promising industry applications. Previous studies mainly focused on the application of PET FRP-confined concrete in circular columns, while investigations on PET FRP-confined concrete in square columns are rather limited. The purpose of this study is to fundamentally understand the confinement mechanism of PET FRP-confinede concrete in square stub columns by conducting axial compression tests. Particularly, the influences of confinement thickness, corner radius and specimen size were investigated. Test results reveal that the specimen size is not significant for small- and medium-sized stub columns with a similar confinement level. The minimum confinement stiffness ratio and modified confinement ratio for achieving a sufficient confinement are 0.0036 and 0.13 respectively. Additionally, assessments of existing confinement models for PET FRP-confined concrete are conducted.