Strengthening CHS T-joints subjected to brace axial compression using through-bolts

T-joints of circular hollow steel sections (CHS) with large brace-to-chord diameter ratios usually fail in an outward chord deformation (ovalization) mode when subjected to brace axial compression. In this paper, a new technique is presented for increasing the joint capacity using radial through-bolts to laterally brace the chord member and delay the joint failure. Strengthened CHS T-joint specimens were experimentally tested to scrutinize the effect of changing the number and spacing of the through-bolts on the gained strength and stiffness of the joint. This strengthening technique showed significant joint's strength enhancement even by using only one through-bolt where the joint capacity increased by at least 35%. Numerical analysis using the finite element method was carried out to examine the effect of a wider range of parameters such as the class of chord member section and the pattern/spacing of the through-bolts on the failure load of the joint. It is concluded that strengthening of CHS T-joints subjected to brace axial compression forces using through-bolts is an effective and practical strengthening technique. The investigation also revealed that increasing the number of closely spaced bolts increased the joint capacity; but, an odd number of the through bolts is recommended especially for large-spaced bolts. Based on the outcomes of the experimental and analytical investigation, a bolt spacing is proposed in order to get the maximum gain in strength and stiffness for CHS T-joints strengthened using transverse through bolts.