Size effect on axial behavior of concrete-filled box columns

Abstract

The use of concrete-filled box columns could provide an economical alternative to building and bridge construction. Past experimental results showed that current building codes provided an adequate accuracy in determining axial capacity of such composite members. However, the sizes of the previously studied test specimens were mostly smaller than those for practical applications. As the column size increases, the size effect may become significant. Therefore, the applicability of extrapolating those test results to larger concrete-filled box columns needs to be justified. This study was devoted to investigating the potential size effect on axial behavior of concrete-filled box columns. Six short square concrete-filled box columns, with cross-sectional dimensions ranging from 300 to 750 mm, were tested under axial loading. Comparisons between experimental and analytical results were presented. It was observed that the size effect was prominent for the concrete-filled box columns studied herein. The results of this study showed that current design codes overestimated the axial capacity of the test columns with a dimension of 750 mm. In addition, finite element simulations of the axially loaded specimens were conducted to investigate the stress–strain behaviors of the concrete enclosed in different sizes of steel box columns. Results from the finite element analysis suggested that the larger steel box columns were less effective in enhancing the compressive strength of the enclosed concrete than smaller steel box columns.