Behaviour of Steel Tube Knee Joint Inserts used in Aluminium Portal Frames

Abstract

AbstractUsually, prefabricated aluminium halls use portal frame structures with a high strength steel tension tie element. Due to the high reduction of aluminium strength induced by welding, aluminium joints of prefabricated halls are almost exclusively formed using bolts in combination with steel reinforcements. The most convenient type of reinforcement is a steel tube knee joint insert. In these joints, the transmission of forces is realized partially through bolts and partially through a complex contact mechanism between aluminium members and the steel tube knee joint insert. Detailed overview of the behaviour of such joints is still unknown and simple expressions for the assessment of their behaviour are lacking. With that in mind, as a first phase of the research, laboratory tests of steel tube welded knee joints with bolted tie element were performed under the application of static loading. Numerical simulations in ANSYS were performed to enable a deeper insight into the complex interaction of different joint components. Due to the limitations of laboratory equipment and the fact that only a ‘rigid’ tie element (circular tube) was utilized in tests, numerical simulations were also applied to extend experimental results and include different, more realistic, levels of axial stiffness of the tie element. Obtained structural properties of the tested joint type are provided and discussed regarding the advancement of understanding underlying behaviour parameters and outlining further research phases.