The role of EN 1993-1-3

Where it sits in the system

Eurocode 3 covers steel structures. Within it:

• EN 1993-1-1: general rules and rules for buildings,
• EN 1993-1-3: supplementary rules for cold-formed members and sheeting,
• EN 1993-1-2: structural fire design,
• EN 1993-1-8: design of joints.

EN 1993-1-3 is therefore not a world of its own: it builds on the general rules and supplements them where the behaviour of thin sheet differs.

What it adds

Determination of the effective cross-section

The treatment of plate buckling and the calculation of effective widths for compressed and bent elements. The effective cross-section.

The treatment of distortional buckling

Modelling the flange–lip unit as an elastically restrained element. Distortional buckling.

Thin-sheet connections

Self-drilling screws, rivets and welds, where failure occurs in the sheet.

Accounting for the effects of cold forming

Limited use of the strength increase from work hardening at the corners, and the geometric treatment of rounded corners.

Design by testing as an alternative

Where calculation does not apply or is too conservative. Design by testing.

The generation change

The second generation of the Eurocodes is being introduced, and it affects EN 1993-1-3 too: the newer edition has been published while the earlier one is still in use.

A project must therefore record which edition the design was made to — years later that will be the question. The second-generation Eurocodes.

What to know about using it

• The text of the standard is paid-for, available through the national standardisation body.
• The national annex sets parameters that must be applied. The national annex.
• The design software has to be told which standard and which edition to work to — that is a setting, not an automatism.

The point

Thin-walled steel is not an unregulated area: it has its own part of the Eurocode with its own methodology. The question is not whether it can be designed, but who designs it and to which edition.