A confinement model for FRP-confined normal and high-strength concrete in square and rectangular sections

The confinement of concrete with fiber reinforced polymer (FRP) composites can significantly enhance its strength and deformability. However, the effectiveness of FRP confinement on square and rectangular concrete sections, in which the concrete is non-uniformly confined, is much lower than the effective confinement of circular sections. To investigate the shape factors influencing the compressive behavior of FRP-confined concrete in square and rectangular sections, a database of existing test results was assembled. The database was then studied, together with a companion database consisting of the test results of FRP-confined concrete in circular sections, in order to capture the change in the effectiveness of confinement due to the change in the sectional shape. The combined database catalogued the compression test results of 1547 specimens with unconfined concrete strengths ranging from 6.2 to 169.7 MPa. It provided a significantly extended parameter space, thereby allowing clearer observations of the important factors influencing the compressive behavior of FRP-confined concrete in various sections. Based on the test database, a unified model for FRP-confined concrete in circular, square and rectangular sections was developed and presented in this paper.