Performance of concrete-encased CFST box members under bending

This paper described a series of tests and finite element analysis (FEA) on large-scale concrete-encased concrete-filled steel tube (CFST) box members under bending. Eight full-scale specimens, including six concrete-encased CFST box and two corresponding reinforced concrete (RC) box members were tested to investigate the influence of variations in diameter of steel tube (from 74.9mm to 102.2mm) and sectional height (from 840mm to 1260mm) on the performance of concrete-encased CFST box members under bending. The failure modes and performance of concrete-encased CFST box members under bending were investigated and compared with those of corresponding RC box members. A finite element analysis (FEA) model was developed to analyse the flexural performance of concrete-encased CFST box members, including full-range analysis of moment–curvature relation, loading transfer and effect of shear-span-to-depth ratio. Finally, a parametric study was carried out based on the FEA modelling, and a simplified model was proposed for predicting the flexural capacity of concrete-encased CFST box members.