Steel Connection Design
Design bolted and welded steel connections to Eurocode 3 (EN 1993-1-8). Choose a connection type below - each opens an interactive 3D calculator that verifies every failure mode (bolt group, plate, member, weld) with step-by-step derivations and a clear PASS/FAIL. Fin plate (shear) connections are available now; end plate, hollow-section and bracing connections are being added.
Free online calculator with step-by-step working and one-click Excel (.xlsx) and PDF export.
Choosing the right steel connection tool
What this page is for
Steel connection design to EN 1993-1-8 splits into distinct connection types, each with its own failure modes and its own dedicated calculator. This page is the starting point: it explains which tool applies to which detail, so you land on the right one rather than forcing a check that does not fit.
Every connection tool on the site verifies all the relevant modes and reports the governing one, because a connection is only as strong as its weakest path - and which path that is varies far more between connection types than people expect.
Which tool for which detail
- Fin plate (shear tab)
- Beam to column or beam to beam, nominally pinned - bolt group usually governs
- End plate
- Partial or full depth, shear or moment - the T-stub tension zone usually governs
- Hollow section connection
- Beam to CHS/SHS/RHS column - chord face plastification usually governs
- Bracing connection
- Gusset plate for an axial brace - net section usually governs
- Beam splice
- Joining two beam lengths - slip governs a preloaded splice
- Column splice
- Joining two column lengths - the minimum-resistance rule usually governs
- Weld strength
- A fillet, butt or weld group in isolation, EC3 / AISC / TCVN
- Bolt data
- Individual bolt resistances and detailing dimensions
- Anchor bolt
- Baseplate anchorage into concrete, EN 1992-4
The three load paths
Every bolted or welded connection transfers load through some combination of three paths: the fasteners (bolts or welds), the connected plates, and the members themselves. A complete check covers all three, and the governing mode is often not the one a designer expects.
The recurring lesson across the tools is that the fastener is rarely the weak link. Bearing on the plate beats bolt shear on a thin plate; the tube wall beats the fin plate by an order of magnitude on a hollow section; net section beats gross section on a gusset. Upgrading bolt grade is the intuitive move and is usually the wrong one - plate thickness, edge distance and member geometry are what shift the governing number.
Simple versus moment connections
A simple connection is designed to transmit shear while rotating freely, so the frame analysis can treat it as a pin. A moment connection transmits moment and must be stiff enough that the assumed rotational restraint is real. The distinction is a modelling decision that has to be matched by the detailing.
The failure mode of a mismatch is subtle rather than dramatic: a connection detailed as simple but stiffer than assumed attracts moment it was never designed for, while a nominally rigid connection that is too flexible leaves the frame with more sway than the analysis predicted. EN 1993-1-8 provides classification by stiffness and by strength to keep the two consistent.
Assumptions and limits
The connection tools check connections, not members and not frames. A connection can be entirely adequate while the beam it joins fails in bending, or the column fails in web panel shear - those are separate checks in EN 1993-1-1 and EN 1993-1-8 respectively.
All the tools assume a static persistent design situation with non-preloaded bolts in normal clearance holes unless the specific tool says otherwise. Fatigue, fire resistance and seismic detailing - where capacity design changes the whole basis - are outside the scope of every one of them.