Static strengths of cold-formed steel elliptical hollow section X-joints: Fid-Bau Portal

Static strengths of cold-formed steel elliptical hollow section X-joints

Chen, Man-Tai / Chen, Yangyu / Young, Ben

Abstract The newly emerged elliptical hollow section (EHS) has a vast of structural and architectural merits and is favorable for engineers and designers. This paper presents an experimental investigation concerning the structural behavior of cold-formed steel EHS X-joints. Thirty elliptical hollow section X-joints with three different brace-chord orientations were carefully designed, fabricated by robotic gas metal arc welding and tested with the braces axially compressed. The width ratio between brace and chord ( $β$ ) ranged from 0.29 to 1. The brace-to-chord thickness ratio ( $τ$ ) ranged from 0.58 to 1.83 and the chord width-to-thickness ratio (2 $γ$ ) ranged from 10.1 to 52.6. The static strengths, failure modes and load-deformation responses are discussed. The current codified design provisions do not cover the design of cold-formed steel elliptical hollow section X-joints investigated in this study. As the performance of EHS lies between the circular and rectangular hollow sections, the feasibility of the design provisions initially calibrated for conventional X-joints as specified in the CIDECT and Eurocode 3 with incorporation of equivalent section methods as well as the design recommendations previously proposed for hot-rolled steel elliptical joints was evaluated. In general, these design methods provide accurate strength predictions for cold-formed steel elliptical hollow section X-joints. Nevertheless, the scattering of predictions is still a concern and the design method shall be further improved.

Highlights • Structural behavior of cold-formed steel elliptical hollow section X-joints with braces in compression was investigated. • The test program contained 30 elliptical hollow section X-joint tests with three different brace-chord orientations. • The static strengths, failure modes and load-deformation responses were discussed. • Predictions by the existing design approaches were compared with the test results. • The design predictions are generally accurate.