Size effect prediction on axial compression strength of circular CFST columns

Based on size effect law of plain concrete, a size-dependent analytical model for axially loaded CFST column was developed by considering the influence of confinement on size effect. The proposed model can make a similar forecasting precision for CFST specimens in different size ranges, and it was efficient to predict the size effect of axial compression strength, therefore it was used here to conduct the parametric analysis on size effect of CFST column. The analysis results indicated that the size effect of axial compression strength was connected with the confinement level apart from the specimen size. As the steel ratio of the specimen or yield strength of steel tube increased, size effect of axial compression strength tended to become less obvious. Conversely, the size effect was more obvious as the concrete strength increased. Based on parametric analysis, a formula was developed to predict the size effect of axial compression strength for CFST specimens by considering the specimen size and the influence of confinement factor.