Eurocode 1 — Actions on Structures (EN 1991) Interactive Overview

Quickly explore the main Eurocode 1 actions, partial factors and combination rules. Use the interactive helper to build basic load combinations for buildings according to EN 1990/EN 1991 concepts.

EN 1991 Actions on structures Load combinations Structural design

EC1 Load Combination Helper (Conceptual)

This helper illustrates how Eurocode 1 actions are combined at the ultimate limit state (ULS) for a simple building. It is for educational use only and does not replace the official standards or National Annexes.

Includes self-weight of structure and finishes.

Example: imposed floor load from EN 1991‑1‑1.

From EN 1991‑1‑3 (snow on roof or ground).

Resultant wind pressure/suction from EN 1991‑1‑4.

What is Eurocode 1 (EN 1991)?

Eurocode 1 (EN 1991) is the European standard that defines actions on structures. It provides characteristic values, models and combination rules for:

  • Permanent actions (self‑weight, fixed equipment, earth pressure).
  • Variable actions (imposed loads on floors and roofs, snow, wind, temperature).
  • Accidental actions (impact, explosions, fire, vehicle collision, etc.).
  • Traffic loads on bridges, silos and tanks, and actions during execution.

EN 1991 is used together with EN 1990 (Basis of structural design) and the material Eurocodes (EN 1992–EN 1999) to design safe and reliable structures across Europe and many other countries.

Main parts of Eurocode 1

EN 1991 is divided into several parts. The most commonly used for building design are:

  • EN 1991‑1‑1 – General actions: densities, self‑weight and imposed loads for buildings.
  • EN 1991‑1‑3 – Snow loads.
  • EN 1991‑1‑4 – Wind actions.
  • EN 1991‑1‑5 – Thermal actions.
  • EN 1991‑1‑6 – Actions during execution.
  • EN 1991‑1‑7 – Accidental actions (impact and explosions).

Other parts cover traffic loads on bridges, crane loads, silos and tanks, etc.

Basic notation and action types

Eurocode 1 uses a consistent notation:

  • G – Permanent actions (e.g. self‑weight).
  • Q – Variable actions (e.g. imposed loads, snow, wind).
  • A – Accidental actions.
  • ψ – Combination, frequent and quasi‑permanent factors for variable actions.
  • γ – Partial safety factors for actions.
Characteristic vs design values
Characteristic action: Fk
Design value of action: Fd = γF · Fk

Ultimate limit state (ULS) combinations

For persistent and transient design situations, the basic ULS combination according to EN 1990 / EN 1991 is:

Ed = γG · Gk + γQ,1 · Qk,1 + Σ γQ,i · ψ0,i · Qk,i
  • Gk – characteristic permanent action.
  • Qk,1 – leading variable action.
  • Qk,i – accompanying variable actions.
  • γG, γQ – partial factors (from National Annex).
  • ψ0,i – combination factors for accompanying variable actions.

Different variable actions are considered as leading in turn (imposed load, snow, wind, etc.) and the most unfavourable effect is used for design.

Serviceability limit state (SLS) combinations

For serviceability checks, Eurocode 1 and EN 1990 define three main combinations:

  • Characteristic combination – for rare events (e.g. crack width checks).
  • Frequent combination – for reversible phenomena (e.g. vibrations).
  • Quasi‑permanent combination – for long‑term effects (e.g. creep, long‑term deflection).
Example: quasi‑permanent combination
Eqp = Gk + Σ ψ2,i · Qk,i

Typical partial and combination factors (illustrative)

The table below shows illustrative values often seen in literature. Always use the values from the relevant National Annex.

Action type γG / γQ ψ0 ψ1 ψ2
Permanent (unfavourable) γG ≈ 1.35 – – –
Imposed load (residential) γQ ≈ 1.50 0.7 0.5 0.3
Snow γQ ≈ 1.50 0.7 0.2 0.0–0.2
Wind γQ ≈ 1.50 0.6 0.2 0.0

Values above are indicative only and may differ in each country’s National Annex.

Workflow for applying Eurocode 1 in design

  1. Identify the relevant EN 1991 parts for the structure and location.
  2. Obtain characteristic actions (Gk, Qk, etc.) from geometry, densities and code tables.
  3. Determine design situations (persistent, transient, accidental, seismic).
  4. Apply partial factors γ and ψ factors from EN 1990 and the National Annex.
  5. Build ULS and SLS combinations and analyse the structure.
  6. Check material‑specific requirements in EN 1992–EN 1999.

Eurocode 1 – frequently asked questions

Is Eurocode 1 mandatory?

In the EU and many other countries, Eurocodes are adopted as national standards and referenced by building regulations. Whether they are legally mandatory depends on the jurisdiction, but they are widely regarded as the default basis for structural design.

How do National Annexes affect Eurocode 1?

Each country publishes a National Annex that sets nationally determined parameters (NDPs), such as snow maps, basic wind velocities, partial factors and ψ factors. When designing in a specific country, you must always use that country’s National Annex in addition to the main EN 1991 text.

Can I use this tool for final design?

No. The interactive helper on this page is intended for education, quick checks and communication. It simplifies many aspects of Eurocode 1 and does not cover all actions or design situations. For any real project, you must perform a full structural analysis using the official standards, National Annexes and appropriate engineering judgement.