Recent development on doubler or collar plate reinforced square hollow section joints under brace axial load

Tubular joints are crucial structural components in steel tubular truss structure. Doubler or collar plate reinforcement has gained popularity in strengthening square hollow section (SHS) joints on the chord. But the existing design rules for the reinforced tubular joints require improvement. This paper reviews literature on SHS joints strengthened by doubler or collar plate. Key geometrical parameters, structural behaviour and failure modes of reinforced SHS joints reported in literature were discussed. Design methods in specifications and literature were evaluated by comparing the design values with experimental results. It was shown that the approach using linear fitting coefficients obtained by key parameters is able to provide a more accurate prediction. The SHS joint strengthening process with doubler plate or collar plate is discussed, highlighting some construction restrains. Finally, the trend and development direction of this field are proposed.