End Plate Connection Guide
End plates are steel plates welded to the end of a beam and bolted to the supporting member (usually a column flange or another beam). They are one of the most common connection types in UK steel construction. The type of end plate determines whether the connection transfers shear only (simple connection) or shear and moment (moment connection), which affects everything from the plate thickness to the bolt layout and weld specification.
Flush End Plates (Simple Connections)
A flush end plate sits within the depth of the beam, with the plate edge flush with the beam flange face. It is welded to the beam web (and sometimes the flanges) and bolted through the column flange. Flush end plates are classified as simple connections, meaning they transfer vertical shear but are assumed to have no significant moment resistance. This is the most common connection type in multi-storey braced frames and secondary beam connections.
Key Features
| Connection Type | Simple (pinned), shear only |
| Design Standard | BS EN 1993-1-8 |
| Standard Bolt Sizes | M20 or M24, Grade 8.8 |
| Typical Plate Grade | S275 |
| Standard Plate Width | 150mm |
| Bolt Gauge | 90mm |
| Vertical Bolt Pitch | 70mm |
Published Shear Capacities
The table below shows standard flush end plate configurations and their published shear capacities. These are based on non-preloaded bolts in clearance holes with standard geometry. Actual capacity in a specific connection depends on the beam web thickness, column flange thickness, and weld sizing, all of which must be verified by the structural engineer.
| Bolt Size | Bolt Rows | Plate (mm) | Weld (mm) | Shear Capacity (kN) | Notes |
|---|
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Extended End Plates (Moment Connections)
An extended end plate projects beyond the tension flange of the beam, allowing bolt rows to be placed above the flange. This means the bolts can resist tension from bending moment, making it a moment connection. Extended end plates are used wherever the connection needs to transfer moment as well as shear, most commonly at portal frame eaves, apex joints, and moment-resisting frames.
Key Features
| Connection Type | Moment-resisting (rigid or semi-rigid) |
| Design Standard | BS EN 1993-1-8 |
| Standard Bolt Sizes | M20 or M24, Grade 8.8 |
| Typical Plate Grades | S275 or S355 |
| Typical Plate Thickness | 15, 20, or 25mm |
| Plate Width | 200 or 250mm |
| Extension Above Flange | 75mm (typical) |
| Tension Flange Weld | Full penetration butt weld (standard practice) |
Indicative Moment Capacity Ranges
The ranges below are published indicative values showing the order of magnitude of moment capacity achievable for each beam serial size. The actual moment capacity of a specific connection depends on the column section, bolt layout, plate thickness, and stiffener arrangement, all determined by the connection designer using the equivalent T-stub method per BS EN 1993-1-8 clause 6.2.4.
| Beam Serial Size | Typical Bolt Size | Typical Plate Thickness (mm) | Indicative Moment Range (kNm) |
|---|
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Eaves & Apex End Plates
In portal frame construction, the two critical moment connections are at the eaves (where the column meets the rafter) and the apex (where two rafters meet at the ridge). Both use extended end plates, but with different demands.
Eaves Connection
| Location | Column-to-rafter junction |
| Moment | Highest in the frame, governed by wind and gravity combinations |
| Haunch | Almost always haunched to increase moment capacity at this point |
| Plate | Extended end plate, typically 20-25mm thick, S275 or S355 |
| Bolts | Typically M24 Grade 8.8, 6 or 8 bolt rows depending on frame size |
| Key Check | Column flange bending, often requires stiffeners opposite the tension bolts |
Apex Connection
| Location | Rafter-to-rafter junction at the ridge |
| Moment | Lower than eaves, but reverses under some load combinations |
| Haunch | Sometimes haunched for deeper beams, often un-haunched for lighter frames |
| Plate | Extended end plate, typically 15-20mm thick |
| Bolts | Typically M20 or M24 Grade 8.8, 4 or 6 bolt rows |
| Key Check | Moment reversal under wind uplift means both flanges can be in tension |
All eaves and apex end plate dimensions, bolt layouts, and weld specifications are determined by the structural engineer based on the specific frame analysis. The information above describes typical UK practice for portal frame connections.
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