Ultimate strain prediction of partially FRP confined concrete considering strain localization

This study experimentally and analytically investigated the compressive behaviour of partially FRP confined concrete, with emphasis on its strain localization phenomenon. An experimental programme was conducted first, in which both fully and partially FRP confined concrete specimens were tested under axial compression. The global deformation as well as the local deformation of the nonwrapped region were used to quantitively investigate the differences in the axial strains between the wrapped and nonwrapped regions. It was observed that significant strain localization occurred in the partially confined concrete specimens with either strain-hardening or strain-softening responses, and the arching action assumption could reasonably reflect the reduced confinement effectiveness due to the partial wrapping. Afterwards, an ultimate strain model that considers the strain localization behaviour was proposed. The proposed strain model was compared with other existing strain models based on a collected test database. It was found that the proposed strain model outperforms other strain models, and it is the only strain model that captures the strain localization behaviour.