Size effect of axially-loaded CFRP ring-confined circular concrete columns: 3D mesoscale simulation

Most of the available experimental research on Fiber reinforced polymer (FRP) confined concrete columns focus on the fully-confined and small-sized ones, while there are few studies on the axial compression behavior and size effect of FRP ring-confined concrete columns. In this study, a three-dimensional mesoscopic numerical model of Carbon Fiber Reinforced Polymer (CFRP) ring-confined concrete in a circular column was established, taking into account the heterogeneity of concrete and the interaction between CFRP and concrete. Based on the meso-scale simulation method, the failure of a total of 36 columns with different structural sizes (the maximum crosssectional width is 1000 mm) were simulated, and the influences of FRP volumetric ratio and vertical confinement effectiveness coefficient on axial compression behavior and size effect was explored. Moreover, considering the influence of FRP volumetric ratio and vertical confinement effectiveness coefficient, a semi-empirical and semi-theoretical formula for describing the size effect on compressive strength was established by modifying Baz?ant's size effect law for concrete materials, and it is suitable for fully-confined and partially-confined concrete columns. The accuracy and applicability of the proposed formula was verified by comparing with the test results and the predicted results.