Analysis and design of rectangular concrete-filled steel tubular members by considering size effect

Abstract

The aim of this research was to develop an accurate and versatile FE model for rectangular CFST members by considering the size effect. The developed FE model could then be used to generate numerical data for developing accurate design equations to predict the ultimate strengths of rectangular CFST members. For this purpose, only reliable test data of composite stub columns tested in a displacement-controlled mode were used for calibrating the key parameters of the refined concrete model used in the FE analysis. It was found that the refined FE model could provide reasonable predictions about these specimens in terms of the initial stiffness, ultimate strength and post-peak behaviour. An extensive parametric analysis was then conducted using the refined FE model to generate a numerical database of short columns covering a wide range of geometric and material parameters. The revised design equations incorporating the size effect were suitable for use in the design of rectangular CFST stub columns, which was verified by both numerical and test data. The prediction errors were normally within 10% for both the small and the large columns. Reliability analysis was further performed for rectangular CFST stub columns, indicating that the revised design equations significantly improved the design reliability of large columns. Reliability analysis was further performed for rectangular CFST stub columns, indicating that the revised design equations significantly improved the design reliability of large columns. A parametric analysis was further conducted for slender CFST columns with slenderness ratios varying from 10 to 200. Meanwhile, the geometric and material parameters were also varied in the same ranges as in the previous analyses of stub columns. It was found that the ultimate moment of a CFST beam should be defined on the basis of the curvature instead of extreme fibre strains or deflection at mid-span. After evaluation, the EC4 equations were modified to improve the prediction accuracy of the ultimate strengths of RCFST beams and short beam-columns by incorporating the size effect and/or the local buckling effect. Finally, the proposed equations were used to predict the ultimate strengths of slender beam-columns. A significant improvement in prediction accuracy over that of the existing EC4 approach was also found, and the prediction errors were normally within the 10% discrepancy limit.

Date of Award	2023
Original language	English