A UNIFIED FIBER ELEMENT MODEL FOR SOLID AND HOLLOW CONCRETE-FILLED STEEL TUBE

Fiber element method is an efficient method for structural integrity analysis． There are some calculation methods for fiber element model of solid concrete-filled steel tubes ( CFST) ，but rare for hollow CFST． This paper provides a unified fiber element model for CFST columns which is applicable for all solid，hollow，circular and polygon members，based on a unified formula of bearing capacity for CFST． The proposed model is intended to be used as a numerical approach for integrity analysis of CFST structures． The hysteretic constitutive model of confined concrete and some key parameters are also presented with considering effects of shapes of the sections and hollow ratio． The suitability of the material-based fiber element model is verified by comparing the results of axial load tests of long and short columns with different section shapes，to those of pushover tests and cyclic tests．