Application of high strength and ultra-high strength steel tubes in long hybrid compressive members: Experimental and numerical investigation

• Static compressive tests on innovative high strength long columns were conducted.
• Quantitative study was done on strength and ductility advances of these sections.
• Numerical model with simplified damage was developed to predict overall behavior.
• Considering HAZ properties in FE model reduces Ultra-high strength capacity by 23%.
• The benefit of these sections is demonstrated through an analytical comparison.

With the increasing application of high strength steel material in industries, there is a high potentiality for taking advantage of the exceptional load-bearing capacities of this material in construction practice. In the present study, an innovative application for high and ultra-high strength steel material is proposed which enhances the overall behavior of structural elements. The high strength and ultra-high strength steel with nominal tensile strengths of 750 MPa and 1250 MPa, respectively, are proposed to be utilized as tube elements welded to corners of mild steel plates shaping an innovative hybrid section. This section takes advantage of the combined material properties of the two constituting elements in terms of strength, local buckling behavior and ductility. Large-scale tests and numerical analysis have been conducted to compare the behavior of the proposed sections against conventional welded sections. The effect of heat on the material properties of the hybrid section has also been considered. These effects are included in the finite element modeling of innovative columns where numerical outputs have been verified accordingly.