Steel Connection Design (EN 1993-1-8)

An overview of how steel connections are designed to Eurocode 3 (EN 1993-1-8): the difference between simple (pinned), moment-resisting and semi-rigid joints, the main bolted and welded connection types (fin plate, end plate, base plate, hollow-section and bracing connections), and the design philosophy of verifying every failure mode in the bolts, plates, members and welds. Each connection type has its own interactive 3D calculator.

A steel connection transfers forces between members - beams, columns, braces - through bolts, welds and plates. Eurocode 3 (EN 1993-1-8) governs their design and requires that every credible failure mode is verified. This page is an overview of the connection types covered by these tools and how they differ; each type has its own interactive 3D calculator.

Joint classification

EN 1993-1-8 §5.2 classifies joints by stiffness as nominally pinned, rigid or semi-rigid, and by strength as nominally pinned, full-strength or partial-strength. A simple (pinned) joint transfers only shear and a small nominal moment; a moment connection transfers shear plus a design moment to the supporting structure. The classification must match the assumptions of the global analysis.

Connection types

• Fin plate (shear tab) - a plate welded to the support and bolted to the beam web. The most common simple shear connection. Available now.
• End plate - a plate welded to the beam end and bolted to the support; can be a flexible shear connection or, when extended, a moment connection using T-stub flange theory.
• Base plate - a steel column welded to a plate held down by anchors cast into concrete; the plate spreads the load over an effective bearing area and the anchors resist tension and shear (EN 1992-4).
• Hollow-section connections - I-beams to CHS / RHS columns, where the chord face, punching shear and CIDECT rules govern.
• Bracing / gusset - gusset plates and rod-to-plate connections transferring axial brace forces, checked for weld, block tear-out and gusset capacity.

The design philosophy

Whatever the type, the method is the same: identify every load path through the connection - the bolts (shear, bearing, tension), the plates (shear, bending, block tearing, buckling), the connected members (web/flange) and the welds - and verify that each design resistance is at least the design action. The governing mode is rarely obvious in advance, which is why a connection calculator checks them all and reports the lowest margin.

Frequently asked questions

Pick a connection type and run the full EN 1993-1-8 verification in 3D, with step-by-step derivations for every check.