Hello!
I would say your primary concern with the wide beam-column joint should be the shear transfer as well as the torsion of the beams you are anchoring your girders into. A good starting point would be to consult ACI 352R-02. There is another useful post that you may take a look at...
EN74 prescribes 50Nm torque for tightening the couplers' bolts. With this value you could calculate the tension force induced in the bolt (based on the NASA Fastener Design Manual - see attached images)). I think you could find the a.m. manual on the web.
Once you calculate the tension force in...