Discussion: Branch plate to reinforced HSS connections in tension and compression

Abstract

The authors contribute to the continued better understanding of the behaviour and design of HSS connections. Their work is of special value to engineers involved in the steel fabrication industry. These engineers must often reinforce columns, or chord members of trusses, when it is found that the wall thickness selected by the designer is of insufficient capacity to withstand forces from beams or web members framing into them. In order to increase the understanding of the paper, it would be helpful if the authors could comment on the following: 1. The thicknesses of the reinforcing plate has not been varied in the tension and compression series. Why were they not varied, and is it still expected that eq. [7] and [8] apply to all reinforcing plate thicknesses? 2. Figure 1 shows that the reinforcing plates were welded with 6 mm fillet welds across the ends. No size is given for the welds along the sides. While 6 mm would appear adequate along the sides of the compression series, it is probably inadequate for the tension series. What size of fillet welds was used in the tests? Furthermore, how can fillet welds (and therefore reinforcing plates) be justified when CSA (1989) Standard W59, Clause 4.1.3.3.2, states that fillet welds and partial joint penetration groove welds shall not be used when they are subjected to bending about the longitudinal axis of the weld of it produces tension at the root of the weld? 3. Equations [2], [3], [6], and [7] all imply that the thickness of the branch plate affects the strength of the connections. Do the data support this contention? If so, there may be a benefit by welding the branch plate with fillet welds, and substituting t i for (ti + 2 x fillet weld size). Fillet welds are also more economical to use than the full penetration groove welds used in the study. 4. Figure 8 shows the stress distribution across the branch plate for selected tensile tests. The distribution of stress strongly favours the ends of the plate, with compression indicated for the central part of the two wider plates. This uneven distribution of the stress indicates that arecommendation for welding to develop the full capacity of the branch appears justified. 5. A recommendation is made for the sidewall bearing capacity in eq. [8]. This expression would apply to X-joints. Is it the authors' suggestion that this formula should also apply to T-joints. If not, can a recommendation be made for T-joints on the basis of the results from this study?