Flexural strength of hybrid steel I-beams based on slenderness

• We test six full scale beams subjected to uniform moment to verify numerical models.
• We conduct a parametric study for a wide range of slenderness ratios.
• A direct method to determine flexural strength of hybrid sections is proposed.
• Presented slenderness based method is to simplify the current design procedures.
• Result of comparative study shows a close agreement of current work with EC3.

This paper presents a new method to determine moment resistance of I-beams with hybrid and homogeneous sections based on a design procedure independent from the section classification, considering local and overall interaction instabilities of beams. Flexural tests on six full-scale I-shaped beams, three with hybrid sections and three with homogeneous sections, built up from high-strength steels (Q345 and Q460), subjected to constant moment about their major axis were carried out to verify numerical models. Three-dimensional nonlinear finite element models were established and verified with the experimental results accounting for material nonlinearity and manufacturing distortions. Stress–strain relationships obtained from tensile coupon tests were incorporated in the finite-element model. Close agreement was achieved between the test and finite element analysis results in terms of moment-rotation response and ultimate strength. A comprehensive parametric study was conducted for a wide range of local and overall slenderness ratios to investigate interactive effects of flange local buckling, web local buckling and lateral torsional buckling modes on flexural strength of steel beams. The main goal of this research is to simplify the current design procedure of steel members subjected to bending. Presented equation to determine flexural strength may also applicable for hybrid sections made of high strength steel grades. A comparative study was performed between the proposed method with EC3 and AISC. Results show a close agreement of current work with EC3.