Concrete-filled VHS-to-steel fabricated section stub columns subjected to axial compression

• Fabricated square and triangular section stub columns with concrete infill are studied.
• Experimental load-deformation curves of the fabricated columns are presented.
• A finite element model is developed to simulate axial load-deformation curves.
• A design model for the ultimate compressive strength is proposed.

The use of very high strength materials is currently being researched as a way to reduce material use and improve sustainability. In this investigation a total of 32 specimens were fabricated using very high strength (VHS) steel tubes and plates to form stub columns. The VHS-plate fabricated stub columns were tested under axial compression. The specimens comprised 20 fabricated square sections and 12 fabricated triangular sections. The VHS steel tubes used have a nominal yield stress of 1350 MPa and a nominal ultimate tensile strength of 1500 MPa. Mild steel plates and high strength steel plates were used to connect the VHS tubes at the vertices thereby forming square and triangular cross sections. Normal strength concrete with a standard concrete strength grade of 32 MPa was used as concrete in-fill. Finite element models are developed to simulate the behaviour of the VHS-plate stub columns. The finite element models predicted the load–deformation behaviour of the fabricated columns well with the peak strength and post-peak behaviour similar to the experimental results. A parametric study was also carried out to determine the effect of concrete strength, facet plate yield strength and facet plate width to wall thickness ratio. The parametric study shows that there is benefit in concrete confinement through the use of higher strength steel facet plates. This paper also proposes a method for determining the axial compression capacity of fabricated VHS-plate stub columns. The predicted peak strength from the proposed design method is in good agreement with the test results.