Steel Column Cap Plate Details: Beam Sitting on Top of a Column

Rather than framing a beam into the side of a column with fin plates or web cleats, a cap plate allows the beam to sit directly on top of the column. This is often a simpler and faster site connection — especially for short columns where erection tolerances matter.

When Cap Plates Are Suitable

Cap plates are suitable for simple (pinned) connections that transfer vertical load only. They are not suitable for goalpost frames, where continuity between the column and the beam is required to maintain lateral stability. A goalpost frame requires a moment-resisting connection at the beam-column junction — a cap plate provides no such resistance.

SHS Columns: Single Beam

For SHS (square hollow section) columns carrying a single beam:

– The beam must be centred on the column — load applied eccentrically to an SHS column head induces bending in the column, which cap plate connections cannot accommodate
– The cap plate is sized based on the column dimensions and the applied load, per tables in the structural specification
– The beam is typically welded or bolted to the cap plate in the fabrication shop before delivery

UC or UB Columns: Single or Paired Beams

Universal column (UC) and universal beam (UB) sections have wider flanges and can accept paired beams at the cap plate:

– For a single beam, it is centred on the column as with an SHS column
– For a pair of beams (two beams sitting side by side on the same column head), each beam must be positioned no further than 100 mm from the column centreline. This limits eccentricity to an amount that the column can sustain
– The cap plate must be at least 20 mm thick when carrying a pair of beams — a thicker plate distributes the load from both beams into the column top without local bending of the plate

Connection Type

The cap plate connection is a shear-only connection. It transfers vertical load from the beam into the column. It does not transfer horizontal forces or bending moment. Where horizontal forces must be transferred — for example, from wind loads acting on a gable wall — a separate horizontal restraint connection is needed, and the cap plate design alone is insufficient.

Erection Advantages

Cap plate connections are often preferred on domestic projects with restricted access. The beam can be lowered vertically onto the column head from above, positioned, and then fixed — this is much simpler than inserting bolts horizontally into a fin plate connection through a narrow access gap.

Contact us if you have questions about column cap plate arrangements on your project, or to raise a Change Request if your design requires a modification to the specified connection.