Analytical behavior of concrete-encased CFST columns under cyclic lateral loading

• We develop a 3-D FEA model on concrete-encased CFST columns under cyclic loading.
• We discuss analytical behavior of concrete-encased CFST columns under cyclic loading.
• We propose a moment–curvature hysteretic model for concrete-encased CFST columns.

The analytical behavior of concrete-encased CFST (concrete-filled steel tube) columns under cyclic lateral loading is reported in this paper. A finite element analysis (FEA) model is developed to investigate the cyclic behavior of such composite column. Comparisons are made between measured and predicted results on failure modes, load versus displacement relationships and ultimate strength. It is found that the proposed FEA model can reproduce the experimental results with good accuracy. The full-range load–displacement relationships, the contact stress between steel tube and concrete and the axial load distribution among different components are analyzed using the verified FEA model. The cyclic behavior of concrete-encased CFST is compared with that of conventional CFST and reinforced concrete (RC) columns. The parametric analysis is conducted to investigate influences of various parameters on the moment–curvature (Μ − ϕ) envelope curves. The parameters include the material strength, the steel ratio of inner CFST, the longitudinal reinforcement ratio, the stirrup characteristic value, the tube diameter to cross-sectional width ratio (D/B) and the axial load level. Finally, a simplified hysteretic model for the Μ − ϕ relationship of concrete-encased CFST column is proposed.