Material properties and residual stresses of octagonal high strength steel hollow sections

This paper presents an experimental investigation to quantify the variation of material properties and residual stresses in the octagonal high strength steel hollow sections from different fabrication routes involving welding or combinations of welding and press-braking. Tensile coupon tests were conducted on the specimens extracted from different locations of the hollow sections with different fabrication routes and static mechanical properties and stress-strain relationship for the specimens were measured. The influence of welding on the material properties was found to be insignificant while strength enhancement was observed for the material at corners formed by press-braking. A stress-strain curve model was proposed for the material across octagonal high strength steel hollow sections. The magnitudes and distributions of longitudinal residual stresses of the octagonal high strength steel hollow sections with different fabrication routes were also measured using the sectioning method and were also found to be dependent on the fabrication route. Based on the measured residual stress results, residual stress models were developed for the hollow sections from different fabrication routes. The obtained variation of material properties and longitudinal residual stresses can be employed to accurately analyse the performance of octagonal high strength steel hollow section structural members for efficient structural designs.