Creep Buckling Analysis of Concrete-Filled Steel Tubular Columns

In order to investigate the influence of concrete creep on the long-term stability of concrete-filled steel tubular (CFST) columns under axial load, based on the energy method and age-adjusted effective modulus method, the long-term stability equations for the critical force of CFST columns with different boundary conditions considering creep and pre-buckling deformation were deduced using an instability criterion. The influence of the critical force and strength of the core concrete were studied. In addition, the value of the current standard and critical loads were compared. The results show that the critical load for creep stability of CFST columns is related to the creep coefficient; CFST columns with the same calculated length but different boundary conditions have the same long-term critical load. The influence of creep on the stability of the column decreased with increasing core concrete strength. When designing CFST columns with low-strength concrete using the current code for the design of concrete structures, additional attention should be paid to the influence of creep buckling. The long-term stability of the critical forces of CFST column was reduced obviously reduced in the first 60 days, which accounts approximately for 80% of the total decline. The bearing capacity of the steel tube tends to be stabilize after 100 days.