The design of longitudinal fillet welds in RFEM 6 is performed by activating the “Design of Longitudinal Fillet Welds” option in the ultimate configurations of the Steel Design add-on (see Image 1).
The correlation factor βw is determined by default according to EN 1993-1-8, Section 4.5.3.2 and Table 4.1. Alternatively, it can be set individually using the “User-defined correlation factor βw option.
Also, make sure that the weld thickness is specified correctly in the cross-section definition (see Image 2).
You can view the details of the recorded design checks by double-clicking on the relevant entry in the “Design Check Details” dialog box (see Image 3).