12 June 2026
Who designs the steel connections? Delegated design, explained
On most steel frames the engineer designs the members and someone else designs the joints. Here's how delegated connection design works, where responsibility sits, and why fabricators bring it in-house with their detailer.
On most structural steel projects in the UK and Ireland, the design engineer sizes the members — the beams and columns — and passes responsibility for the connections to the steelwork contractor. It's called delegated (or devolved) connection design, and it's the industry's standard answer to a practical problem: the people best placed to design a connection are the ones who know how it will be fabricated and erected.
How the hand-off works
The engineer's drawings state the design forces at each connection — or, on a well-run job, a complete force schedule — together with the design standards that apply. The steelwork contractor then has the connections designed to carry those forces, documented in calculations that the engineer reviews and accepts. The engineer keeps responsibility for the global design; the connection designer answers for every joint.
That split only works when the connection design actually gets done — and done by someone competent to do it. Fabricators traditionally bought this in from third-party consultants, adding a hand-off, a wait, and a coordination risk between the calculation pack and the workshop drawings.
Why we do it inside the detailing
OD3 designs connections in IDEA StatiCa, in the same workflow as the Tekla detailing — stress and strain, stiffness, member capacity, buckling and joint resistance checks, issued with full calculation reports and carried out under £2m professional indemnity insurance. Because the connection designer and the detailer share one model, the joint that gets checked is exactly the joint that gets fabricated. No translation between a consultant's sketch and the workshop drawing — and approvals come back faster because the package arrives complete.
What to look for
If you're a fabricator pricing a delegated-design job, the questions that matter are: who carries PI insurance for the connection design, which standards the calculations will reference (Eurocode 3 with the UK or Irish national annex), and whether the designer works from the engineer's force schedule or has to chase the forces down. Getting those three answers in writing before steel is ordered prevents most of the arguments that delegated design gets blamed for.