Practical design equations of the axial compressive capacity of circular CFST stub columns based on finite element model analysis incorporating constitutive models for high-strength materials

Abstract

Step into the 21st century, high strength materials have been increasingly used in engineering practice. However, current design codes for concrete-filled steel tube (CFST) columns have limitations when applied to high strength materials. At the meantime, few studies have investigated in such topic which leads to an inadequate validity of existing design formulae. In this paper, in order to develop a finite element model suitable for CFST columns using high strength materials, the stress-strain relations applicable for high strength materials was proposed by recalibrating the parameters of the models for normal strength materials. Then, a finite element model (FE) was established by incorporating the proposed stress-strain relations into the constitutive models. The validity and accuracy of established FE model were verified by comparing the collected experimental database. Full-range analyses of the behavior of HSCFST columns under axial loading were then carried out using the verified FE model to investigate the composite interactions of different material matching at the limit state. Numerical results presented show that normal strength steel filled with normal strength concrete have the strongest confinement effect, while the normal strength steel filled with high strength concrete exhibited almost no confinement effect. Moreover, to extend the applications of high strength materials, a new design formula was proposed based on the superposition theory with incorporating the effects of high strength materials. It was found that the proposed design formula yields satisfactory predictions when compared with current major code formulae.

Keywords

• Concrete-filled steel tube stub (CFST) columns
• Constitutive relation
• Finite element analysis
• High strength materials
• Confinement effect