Non-linear creep modelling on circular concrete-filled steel tubular columns

Abstract The particularity of the non-linear creep behavior of the circular concrete-filled steel tubes (CFST) is 1) the concrete core will not exchange moisture with the surrounding environment as sealed inside the steel tube, and 2) confinement effects will restrain the development of microcracking and prevent creep failure. In this context, the available creep model and analysis method will not be applicable in the prediction of the non-linear creep responses of circular CFST columns. In this paper, a non-linear creep model was proposed for circular CFST columns. This model was benchmarked against available experimental data. Extensive parametric study was performed to investigate the non-linear creep effects on the static responses of circular CFST columns. Finally, the applicability of different algebraic methods in calculating the non-linear creep responses of circular CFST columns was evaluated against the results obtained from refined analysis procedure. Investigation results have shown that non-linear creep could lead up to a 90% increase in the creep coefficient and, if not well accounted, would make the steel tube yield in the service life. The long-term responses of the circular CFST columns can be well depicted by introducing an ‘amplification factor’ into the Eurocode 2. The Age-Adjusted Effective Modulus method was recommended for simple design calculations.