Investigating the behavior of circular concrete filled PVC tube columns under concentric and eccentric load using FEM

The purpose of this research is to investigate the response of concrete-filled composite tube column under concentric and eccentric loads. To evaluate the influence of PVC pipe on the behavior of concrete-filled composite tubes, concrete-filled PVC pipe (CFPT) were modeled by ABAQUS software. The results demonstrate that the presence of the PVC pipe makes the concrete column more ductile and have a significant effect on the stress–strain curve of the CFPT after the peak strength, in a way that the confinement increased by raising the thickness of PVC pipe, but the confinement effect of the PVC pipe decreased by the increment of the column diameter and compressive strength of the concrete core. The existence of gaps at two ends of the CFPT column does not significantly influence the initial slope of the axial stress-axial strain curve but increases the column’s load capacity and ductility. Peak strength of columns with gaps at two ends is lower than columns without gaps at two ends. Increasing the thickness of the PVC pipe in columns without gaps, with compressive concrete strength of more than 60 MPa, results in an earlier failure. When the eccentric load was applied to this type of column, it did not experience any increase in its initial peak, and columns with gaps at two ends experienced a failure with lower peak strength than the columns without gaps. These types of columns maintain about 50% of their strength under loads with eccentricity up to 20% of column’s diameter.