Strengthening T-joints of rectangular hollow steel sections against web buckling under brace axial compression using through-wall bolts

The effectiveness of through-wall bolts is examined for strengthening T-joints of rectangular hollow steel sections. This is accomplished by controlling the web outward buckling of the chord under the brace axial load. The study examined the effect of the number and pattern of bolts, as well as the web height-to-wall thickness (h/t) ratio of the chord, on strengthening effectiveness. Rectangular 203×76×(3.09, 4.5, and 5.92) mm chord members were tested. The number of 8 mm diameter steel bolts varied from a single bolt to 15 bolts of various distributions. Holes were first drilled in the vertical walls of the chord member, and then bolts were inserted through one wall and anchored at the other wall. The joint strength increased by 29% for chords with (h/t) of 65. As (h/t) ratio reduced to 45 and 35, the gains were only 6.2% and 3.1%, respectively. The number and distribution of bolts had little effect on their effectiveness.

► Rectangular hollow steel sections for chord members are vulnerable to local instability at T-joints in the vicinity of brace or column.
► Through-wall bolts technique is explored to strengthen T-joint.
► Study addresses the effects of web slenderness (h/t) ratio of chord and bolts number and distribution.
► Strength increased by 29% for h/t=65, but strength gain reduced as h/t reduced.
► Number and distribution of bolts had little effect on maximum gain in strength.