Behaviour of Steel Tubular Knee Joint in Aluminium Frames with Tension-Tie Element

Federico M Mazzolani,Ivica Garašić,Davor Skejić,Ivan Čudina

doi:10.3390/app11010070

Federico M Mazzolani, Ivica Garašić + Show 2 more

Open Access

https://doi.org/10.3390/app11010070

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Abstract

Aluminium portal frames with a tension tie element are a commonly used type of aluminium structure. Due to the significant reduction in aluminium’s mechanical properties caused by welding, typical beam to column joints of such frames are formed using bolts and welded steel knee joints embedded in the structure. Expressions for the reliable assessment of the behaviour of such joints are lacking, thus limiting the use of aluminium portal frames. Although the behaviour of steel joints using hollow sections is well investigated, there are only a small number of studies regarding knee joints, none of which investigate the influence of the tie element on the joint behaviour. Therefore, the first stage of the research is focused on the flexural behaviour of steel knee joints with tension tie elements. Laboratory tests of three identical steel knee joints with a tension tie element were conducted as well as a parametric numerical study with variation of tie element stiffness. It was concluded that different stiffnesses of the tie element have little influence on moment–rotation behaviour of the knee joint, but greatly affect overall frame resistance to vertical loads. It was also concluded that different stiffnesses of the tie element can lead to different failure modes of the knee joint as well.

Highlights

Aluminium structures have mostly been used in cases where the lowest possible weight of the structure and the longest durability are essential [1,2]
The results show that compression force increases the rigidity of such joints
The overall behaviour of all specimens is characterised by the load–displacement curves given in Figure 7, where the steel joints are marked with S1–S3

Summary

Introduction

Aluminium structures have mostly been used in cases where the lowest possible weight of the structure and the longest durability are essential [1,2]. Prefabricated aluminium halls are mostly designed as portal frames with added high-grade steel tension tie elements, where larger spans are required. Since welding in some types of aluminium alloy causes a significant reduction in resistance [4], typical joints of such structures are formed using bolts in combination with steel reinforcement embedded inside hollow aluminium sections. Such joints transfer the load partially through bolts and partially through a complex contact between the steel insert and aluminium tubes [3]. Expressions for reliable assessment of the behaviour for such joints are lacking, inhibiting the usage of aluminium prefabricated halls

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