Size Effect on Nominal Strength of Circular Stirrup-Confined RC Columns under Axial Compression: Mesoscale Study

Abstract

Most previous studies have made great progress in the size effect of concrete materials and several classic size effect laws (SELs) have been proposed. However, there is a lack of size effect laws for RC components including beams, columns, and beam-column joints. The focus of this study is the size effect in RC columns confined by stirrups under axial compression. A three-dimensional mesoscale numerical method for the simulation of the failure of RC columns was established. The numerical results were found in good accordance with the available experimental ones, demonstrating the rationality of the simulation method. The simulation method was then extended to model the size effect of circular RC columns having larger sizes. The main parameter, stirrups ratio, which evaluates the size and interaction effects between the concrete and reinforcement, was examined and analyzed. Furthermore, the influence mechanisms of confinement effect generated by stirrups on the nominal compressive strength were explored. Finally, based on the available classic SEL for concrete materials, a predictive formula was built that can describe the quantitative influence of constraint generated by stirrups on size effect of RC columns under axial compression. For comparison, the validation of the predictive theorical formula with the available test data is presented.