Fin-plates are the most straightforward to fabricate and erect and use Through Bolts to make the connections. It's common practice to set out the vertical holes equal about the center of the beam while the fin-plate is welded to the column to suit as opposed to using open sections, which we'll look at later in this post.
Fig. 1 shows 3 options using hollow sections for both the column and beam.
Option A shows a typical Tee connection where the fin-plate is shop welded to the column and a Tee shop-welded to the beam end. The Tee may be either a standard hot-rolled profile and indicated in the structural tables, or a fabricated Tee made form plates.
Option B shows a through plate which is welded to the inside of the beam at a depth not less that the width of the beam. the beam end is then closed using closure plates welded against the through plate. On narrow beams it can sometimes be tricky to get access for the weld inside the profile - in such cases it might be worth looking at Option C
Option C indicates a tongue Plate replacing the through plate - in this case, a slot is cut into the beam allowing the tongue plate to fit, which is then shop-welded from the outside. This is a slightly more expensive option, but it is easier to fabricate.
The last option is shown in Fig. 2 where the fin-plate is fitted into a slot cut into the column. This is a much stronger connection as it does not rely on the weld to resist any rotational moments - but it is quite costly to produce and requires a high level of accuracy in the workshop.
It can be useful where there are adjacent beam connections which have different load patterns
Fig. 3 shows a typical beam to column connection using an open section beam. This is by far the most used connection of this type - it's straightforward to fabricate and erect and uses the minimum amount of material.
When setting out the vertical bolt pitch, it's usual practice to set out from the top of the beam, as opposed to the center of the beam as usual when using hollow section beams.
For more information on fin-plates go to Welded Fin-Plates