National annex

International standardisation runs into national facts: climates differ, seismicity differs, and — less visibly — accepted levels of safety and cost differ, as sovereign choices. The national annex is the container for those facts. The parent standard defines the method and marks the open slots; the annex of each adopting country fills them — the partial factors, the load maps, the choices among permitted alternatives — and may add non-contradictory guidance of its own. The Eurocodes are the canonical case, but the pattern recurs wherever an international standard is nationally adopted.

The operating rule is that the annex follows the structure: a bridge in one country is designed to the shared code with that country's annex, whoever designs it and wherever they sit. Multi-country portfolios therefore run one method with several parameter sets — the efficiency the system was built to deliver.

The failures are parameter failures: the home-market annex used abroad, values from two annexes mixed in one calculation, or an adoption so new that the annex does not yet exist, leaving the parameters to be chosen and justified case by case — a fact best discovered before the review, not during it.