Parametric analysis on dilation and confinement of axially loaded circular concrete-filled steel tubes using mesoscale modeling approach

Abstract

Mesoscale modeling can more realistically describe concrete heterogeneity and phase interaction than macroscopic homogeneous simulation. A mesoscale model was developed in this study to investigate the dilation and confinement behavior of circular concrete-filled steel tube (CFST) columns. The validity of the model was demonstrated by comparing it with experimental stress-strain curves and dilation ratio curves. Parametric analysis revealed that the dilation was non-uniformly distributed along the circumference and the height of the specimen, while an increase in confinement factor inhibited dilation development and promoted confining pressure growth. Based on the parametric analysis, a law for hoop-axial strain relationship and confining pressure versus hoop strain curve were proposed. Additionally, an investigation into the behavior at peak load showed that the dilation ratio of circular CFST at peak load was approximately 0.92. The hoop stress ratio of steel tube decreased from 0.29 to 0.19 as the confinement factor varied from 0.2 to 1.5, while the axial stress showed an opposite growth trend. With increasing confinement factor, confining pressure nonlinearly increased, whereas the load-sharing ratio of between steel tube and concrete showed a linear growth trend. Finally, corresponding formulas were proposed.