ABSTRACT
A Diamond Bird-Beak T-joint (DBB T-joint) is a new type of welded joints made of Square Hollow Section (SHS) members, different from a conventional SHS T-joint for rotating both chord and brace by 45°. This paper presents a series of research on fatigue behavior of DBB T-joints. Static hot spot stress testing was firstly carried out on a set of DBB T-joints under brace loading. Compared with conventional SHS T-joints, DBB T-joints have much lower SCFs. FE analysis on SCFs was then performed for further parametric study, so that SCF formulae were obtained by multiple regressive analyses. Fatigue tests were conducted to explore crack patterns, failure modes and fatigue lives of DBB T-joints. For the need of fatigue design, new fatigue design curves (S-N curves) in terms of hot spot stress ranges were recommended. It is concluded that DBB T-joints have longer fatigue lives than conventional SHS T-joints.
