Fillet weld effective lengths in CHS X-connections. I: Experimentation

For the first time, an experimental test program was conducted to assess the strength of fillet welds in circular hollow section (CHS) connections. Six large-scale, fillet-welded CHS-to-CHS X-connections were designed with varied key parameters that affect the weld strength: branch-to-chord diameter ratio, chord wall slenderness, and branch inclination angle. By means of quasi-static tension applied to the branches, fracture of 12 test welds (two per connection) was obtained. Strain distributions measured adjacent to the welds indicated a weld effective length less than the total weld length, under pure axial load. Branch loads at rupture were also measured and used to determine the structural reliability of existing AWS provisions for weld effective lengths in CHS-to-CHS X-connections. For the range of parameters studied, the provisions are found to be very conservative. Hence, methods are assessed to accurately quantify the weld effective length. A parametric modelling study is presented in a companion paper to develop more liberal recommendations.