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

Abstract

Usually, 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.

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

“…The loading procedure was carried out in three phases: (i) loading up to 20 kN, (ii) unloading, and (iii) stepwise loading up to the failure [1].…”

“…Aluminium structures were mainly designed and built as temporary structures, but nowadays, when economic and environmental resources are very important, there is an evident need for their permanent usage and, consequently, their reliable design [1]. One of the most common applications of aluminium in civil engineering is a prefabricated hall, mostly designed as portal frames with or without a steel tie element.…”

“…In such joints, the transmission of forces is realized partially through bolts and partially through a complex contact mechanism between aluminium and the steel insert. Simple expressions for behaviour assessment of such joints do not exist, which makes laboratory tests necessary in order to check their reliability [1]. In the first stage of research, only steel joint inserts were tested.…”

Parametric Numerical Study of Welded Aluminium Beam-to-Column Joints

“…In typical portal frames (with or without steel tension tie elements), which are the subject of recent research studies [10][11][12][13], beam-to-column joints play a key role as their stiffness directly affects the behaviour of the frame systems. These are also the most common types of joints in metal structures.…”

Seismic Design of Aluminium Structures in the Second Generation of Eurocode 8

“…[3]. Therefore, aluminium alloys are the rational solution any time durable light weight constructions are of utmost importance and, consequently, reliable and ease-ofuse design methods are of great importance [3][4][5]. It is also worth noting that aluminium alloys have been largely used in seismic-resistant structures for dissipative fuses and/or hysteretic dampers [6][7][8].…”