The line of shear transfer in fin plate connections is not exactly known. The most conservative and safe approach is to design the bolt group and the welds for the combination of shear and moment from the eccentricity of the shear force, as shown in case a), Fig. 1, for the welds design and as shown in case b), Fig. 1, for the bolt group design.
In case a) the shear acts along the centre of the bolt group as the rotation of the bolted part is larger than the rotation of the plate at the support. The welds must be designed for a shear force and a bending moment. Bolts are loaded only by a shear force.
Case b) (Fig. 1) shows the situation where the support is more flexible and the hinge line is identified at the face of the column. Welds are now only loaded by a shear force and the bolt group transfers a shear force and a bending moment.
Results from a series of tests on fin plate connections concluded that the line of shear transfer moves towards the support as the shear force is increased. It was recommended to design both bolts and welds for combined effects of direct shear and a moment equal to the shear multiplied by the eccentricity.
It is worth noting that The Steel Solutions Center states that it is generally safe to assume the line of shear transfer at the face of the supporting member and this is consistent with common design practices in the USA.