Load-Strain Model for Steel-Concrete-FRP-Concrete Columns in Axial Compression

AbstractA load-strain model for a steel-concrete-FRP-concrete (SCFC) hybrid column section in compression is proposed. The section layout has a square steel tube as the outer layer and a circular fiber-reinforced polymer (FRP) tube as the inner layer, and concrete is filled between these two layers and inside the FRP tube. Thus the section can be regarded as a concrete-filled steel tube (CFST) with a FRP-confined concrete core (FCCC), in which the FCCC is essentially a concrete-filled FRP tube (CFFT) in sectional configuration. However, the mechanical behavior of a SCFC is superior to the simple superposition of CFST and CFFT without consideration of the interaction mechanisms among the different materials. The load-strain behavior of a SCFC differs from that of a CFST or CFFT in that it includes an initial parabola portion, a second linear portion, and a postpeak portion. The model is established by superposing four load-strain models of the constituent layers and attempting to reveal the mechanical resp...