Abstract
The chord length is an essential geometric property that must be defined in the analysis of isolated joints composed of hollow steel sections, as well as the boundary conditions of the test. The analysis of these parameters’ effect on the behavior of joints has been addressed by other studies, mostly with joints between circular hollow sections with compact or semi-compact cross-sections. Recent research about tubular joints has addressed cases with slender sections, where the design of joints containing these sections is still in development. In this context, this study aimed to evaluate the effect of the chord length in the behavior of T-joints between circular hollow section braces and slender rectangular hollow section chords through experimental tests and a numerical study considering the application of axial compression at the braces. The joint behavior was examined through the load-strain and load-deformation curves and the von Mises stress distribution, which allowed the failure mode's determination and the joint resistance value. Chord face failure was observed in the prototypes. It was concluded that a minimum chord length of 0.6m would be the adequate value for the study of the T-joints containing the geometric properties used in this study, which would be equivalent to a chord length five times higher than the width of the cross-section (5b0).
Highlights
The design of joints between tubular sections is currently contemplated in several design guides and normative prescriptions, such as ISO 14346 (ISO, 2013), EN 19931-8 (CEN, 2005), NBR 16239 (ABNT, 2013), and CIDECT Design Guide (Packer et al, 2009)
In the analysis of isolated joints, a minimum chord length must be considered to avoid its influence on the joint ultimate bearing capacity, as well as the proper boundary conditions
The condition with central support enabled the analysis of the chord length influence in the joint resistance, since bending moments were not acting in the joint region
Summary
The design of joints between tubular sections is currently contemplated in several design guides and normative prescriptions, such as ISO 14346 (ISO, 2013), EN 19931-8 (CEN, 2005), NBR 16239 (ABNT, 2013), and CIDECT Design Guide (Packer et al, 2009). The design equations do not contemplate joints containing chords with slender cross-sections and were mainly originated from studies of isolated joints, in which the proper boundary conditions must be considered to accurately analyze the joint behavior (Vegte; Makino, 2010). In the analysis of isolated joints, a minimum chord length must be considered to avoid its influence on the joint ultimate bearing capacity, as well as the proper boundary conditions. Vegte (1995), in the analysis of X-joints with circular hollow sections (CHS), concluded that, for chord sections with slenderness values equal to 25.4, a minimum chord length of 6 times its diameter (d0) should be used. In CHS T-joints under axial brace loading, Vegte and Makino (2006) developed finite element (FE) models varying the chord length (from 48cm to 114cm), the slenderness of the chord section (from 25.4 to 63.5), and the brace-to-chord ratio (from 0.25 to 0.98); the same parameters were varied in CHS X-joints in the study of Vegte and Makino (2010)
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