Axial compressive and seismic performance of GFRP wrapped square RC columns with different scales

The seismic and axial compressive behavior of columns wrapped with FRP sheets has been studied experimentally and theoretically over the last two decades. However, most tests and models focused on small-scale columns with/without steel reinforcement. To get a better understanding of this strengthening technique and to achieve reliable design approaches for practical applications, further studies should be carried out on full-scale columns with FRP wraps considering the influence of internal steel and column size. Due to such knowledge gaps, this study exhibits experimental results of 17 GFRP wrapped square RC column specimens with side lengths of 350 mm, 495 mm, and 700 mm tested under both monotonic axial compressive load and cyclic lateral load combined with constant axial compression. The results indicate that the FRP confinement effect is highly affected by column size in both axial compression and cyclic loading. Moreover, provisions of three design codes GB50367–2013, GB50608-2020, and ACI440.2R-17 on the axial loading capacity of FRP confined concrete columns are reviewed and verified with the test data. It is suggested that the influence of column size should be further considered in the codes to widen the application range of the present provisions.