# Eurocodes Overview ## Table of Contents - [[#Overview]] - [[#The Eurocode Suite EN 1990 to EN 1999]] - [[#Eurocode 0 Basis of Structural Design EN 1990]] - [[#Eurocode 1 Actions on Structures EN 1991]] - [[#Eurocode 2 Concrete EN 1992]] - [[#Eurocode 3 Steel EN 1993]] - [[#Eurocode 4 Composite Steel and Concrete EN 1994]] - [[#Eurocode 5 Timber EN 1995]] - [[#Eurocode 6 Masonry EN 1996]] - [[#Eurocode 7 Geotechnical Design EN 1997]] - [[#Eurocode 8 Seismic Design EN 1998]] - [[#Eurocode 9 Aluminium EN 1999]] - [[#National Annexes]] - [[#Partial Safety Factors and Limit States]] - [[#Practical Application for Architects]] - [[#References and Standards]] --- ## Overview The Eurocodes are a set of ten European standards (EN 1990 to EN 1999) providing a common approach to the structural design of buildings and civil engineering works. Developed by the European Committee for Standardization (CEN), they are mandatory for structural design in all EU and EEA member states and are increasingly adopted or referenced worldwide. The Eurocodes establish the principles and rules for structural safety, serviceability, and durability, using a unified framework of partial safety factors and limit state design. They replace national structural codes in adopting countries while allowing national calibration through National Annexes. --- ## The Eurocode Suite EN 1990 to EN 1999 | Eurocode | EN Number | Title | |----------|-----------|------------------------------------------| | EC0 | EN 1990 | Basis of Structural Design | | EC1 | EN 1991 | Actions on Structures | | EC2 | EN 1992 | Design of Concrete Structures | | EC3 | EN 1993 | Design of Steel Structures | | EC4 | EN 1994 | Design of Composite Steel and Concrete | | EC5 | EN 1995 | Design of Timber Structures | | EC6 | EN 1996 | Design of Masonry Structures | | EC7 | EN 1997 | Geotechnical Design | | EC8 | EN 1998 | Design of Structures for Earthquake Resistance | | EC9 | EN 1999 | Design of Aluminium Structures | Each Eurocode contains multiple parts addressing specific aspects (e.g., EN 1992-1-1 for general concrete rules, EN 1992-1-2 for fire design of concrete structures). --- ## Eurocode 0 Basis of Structural Design EN 1990 EC0 is the overarching Eurocode establishing the principles applicable to all structural design: - **Reliability framework**: Defines target reliability indices (β) for different consequence classes. - **Limit states**: Distinguishes between Ultimate Limit States (ULS) and Serviceability Limit States (SLS). - **Action combinations**: Provides combination rules for permanent, variable, and accidental actions. - **Design working life**: Defines the assumed period of structural use. - **Consequence classes**: CC1 (low), CC2 (medium), CC3 (high), linked to reliability classes RC1–RC3. See [[Eurocode Structural Design]] for detailed treatment of partial factors and combination rules. --- ## Eurocode 1 Actions on Structures EN 1991 EC1 defines the loads (actions) to be considered in design: | Part | Subject | |----------|----------------------------------------| | 1-1 | Densities, self-weight, imposed loads | | 1-2 | Actions on structures exposed to fire | | 1-3 | Snow loads | | 1-4 | Wind actions | | 1-5 | Thermal actions | | 1-6 | Actions during execution | | 1-7 | Accidental actions (impact, explosion) | | 2 | Traffic loads on bridges | | 3 | Actions induced by cranes and machinery | | 4 | Actions in silos and tanks | **Key imposed loads for buildings (EN 1991-1-1)**: | Category | Use | qk (kN/m²) | Qk (kN) | |----------|---------------------------|-------------|-----------| | A | Residential/domestic | 1.5–2.0 | 2.0–3.0 | | B | Office | 2.0–3.0 | 1.5–4.5 | | C | Assembly (congregation) | 2.5–5.0 | 3.0–7.0 | | D | Shopping/retail | 4.0–5.0 | 3.5–7.0 | | E | Storage | 6.0–7.5 | 7.0 | Exact values are nationally determined through the National Annex. --- ## Eurocode 2 Concrete EN 1992 Covers the design of reinforced and prestressed concrete structures: - **EN 1992-1-1**: General rules and rules for buildings. - **EN 1992-1-2**: Structural fire design. - **EN 1992-2**: Concrete bridges. - **EN 1992-3**: Liquid retaining and containment structures. Key concepts: stress-strain relationships for concrete and reinforcement, bending, shear, torsion, punching shear, deflection control, crack width limits, anchorage and lap lengths, and durability (exposure classes XC, XD, XS, XA, XF). --- ## Eurocode 3 Steel EN 1993 Covers the design of structural steelwork: - **EN 1993-1-1**: General rules and rules for buildings. - **EN 1993-1-2**: Fire design. - **EN 1993-1-3**: Cold-formed sections. - **EN 1993-1-8**: Design of joints. Key concepts: cross-section classification (Class 1–4), resistance of cross-sections (bending, shear, axial), buckling resistance (flexural, lateral-torsional, plate), connection design (bolted and welded), and fatigue. --- ## Eurocode 4 Composite Steel and Concrete EN 1994 Addresses structures combining steel sections with concrete: - Composite beams (steel beam with concrete slab acting together via shear connectors). - Composite columns (steel section encased in or filled with concrete). - Composite slabs (profiled steel decking as permanent formwork and tensile reinforcement). --- ## Eurocode 5 Timber EN 1995 Covers the design of timber and wood-based structures: - **EN 1995-1-1**: General rules and rules for buildings. - **EN 1995-1-2**: Fire design. Key concepts: strength classes (C14–C50 for solid timber, GL24–GL36 for glulam), load duration classes, service classes (moisture content), modification factors (kmod), member design in bending, compression, tension, and connections (dowel-type fasteners, nailed, bolted, screwed). --- ## Eurocode 6 Masonry EN 1996 Covers structural masonry design: - **EN 1996-1-1**: General rules for reinforced and unreinforced masonry. - **EN 1996-1-2**: Fire design. - **EN 1996-2**: Design considerations, selection of materials, and execution. Key concepts: characteristic compressive strength (fk), compressive resistance of walls under vertical loading, eccentricity and slenderness effects, lateral load resistance, and movement joint spacing. --- ## Eurocode 7 Geotechnical Design EN 1997 Covers foundation and geotechnical design: - **EN 1997-1**: General rules. - **EN 1997-2**: Ground investigation and testing. Three Design Approaches (DA1, DA2, DA3) apply partial factors differently to actions, soil parameters, and resistances. The National Annex specifies which approach(es) are permitted. Key topics: spread foundations, pile foundations, retaining structures, slopes, embankments, ground improvement, and hydraulic failure. --- ## Eurocode 8 Seismic Design EN 1998 Covers earthquake-resistant design: - **EN 1998-1**: General rules, seismic actions, and rules for buildings. - **EN 1998-2**: Bridges. - **EN 1998-3**: Assessment and retrofitting of buildings. Key concepts: seismic hazard zones (PGA mapping), importance classes, ground types (A–E), response spectra, behaviour factors (q), ductility classes (DCL, DCM, DCH), capacity design principles, and second-order effects. --- ## Eurocode 9 Aluminium EN 1999 Covers structural aluminium design: - **EN 1999-1-1**: General structural rules. - **EN 1999-1-2**: Fire design. - **EN 1999-1-3**: Fatigue. - **EN 1999-1-4**: Cold-formed structural sheeting. Primarily relevant for curtain walling, glazing support systems, and lightweight structures. --- ## National Annexes Each EU member state publishes a National Annex (NA) for each Eurocode part, specifying: - **Nationally Determined Parameters (NDPs)**: Values for partial factors, climatic loads (wind, snow, thermal), and seismic parameters specific to the country. - **National choice**: Selection among alternative methods where the Eurocode permits options (e.g., Geotechnical Design Approach). - **Non-contradictory complementary information (NCCI)**: Additional guidance documents (e.g., PD 6687 in the UK for concrete, SCI publications for steel). Architects must always use the Eurocode together with the relevant National Annex for the country of the project. The Eurocode alone is insufficient for design. --- ## Partial Safety Factors and Limit States The Eurocodes use a semi-probabilistic partial factor method to ensure structural reliability: ### Ultimate Limit States (ULS) - **STR**: Internal failure or excessive deformation of the structure. - **GEO**: Failure or excessive deformation of the ground. - **EQU**: Loss of static equilibrium. - **FAT**: Fatigue failure. ### Serviceability Limit States (SLS) - Deflection limits, crack width limits, vibration limits. ### Key partial factors (recommended values per EN 1990): | Symbol | Factor on | ULS (Persistent/Transient) | |--------|-------------------|----------------------------| | γG | Permanent actions | 1.35 (unfavourable), 1.00 (favourable) | | γQ | Variable actions | 1.50 (unfavourable), 0.00 (favourable) | | γA | Accidental actions | 1.00 | Material partial factors are specified in each material Eurocode (e.g., γc = 1.5 for concrete, γs = 1.15 for reinforcement). See [[Eurocode Structural Design]] for detailed action combination expressions. --- ## Practical Application for Architects - **Structural coordination**: Architects are not expected to perform structural calculations but must understand the Eurocode framework to coordinate effectively with structural engineers. - **Load awareness**: Know the imposed load categories for the spaces being designed (Category A for residential, B for offices, C for assembly, etc.) to anticipate structural depth requirements. - **Fire resistance**: Eurocode fire parts (e.g., EN 1992-1-2, EN 1993-1-2) work alongside [[Fire Safety Building Regulations]] to define structural fire resistance periods. - **Seismic design**: In seismic zones, building form, regularity, and joint detailing significantly affect structural behaviour. Irregular plan forms (L, T, U shapes) attract seismic penalties. - **Material selection**: The choice between concrete (EC2), steel (EC3), timber (EC5), or masonry (EC6) affects not only structure but also fire resistance, acoustic performance, and embodied carbon (see [[Operational vs Embodied Carbon]]). - **Specification**: Reference the correct Eurocode part and National Annex in project specifications and structural calculations. - **Second-generation Eurocodes**: CEN is developing updated Eurocodes (expected publication from 2025–2028) with enhanced provisions for sustainability, robustness, and existing structures. --- ## References and Standards - EN 1990:2002+A1: Eurocode 0 — Basis of Structural Design - EN 1991 series: Eurocode 1 — Actions on Structures - EN 1992–EN 1999: Material-specific Eurocodes - BSI, National Annexes to BS EN 1990–1999 - [[Eurocode Structural Design]] - [[Fire Safety Building Regulations]] - [[International Building Code IBC]] - [[Operational vs Embodied Carbon]] --- #codes #eurocodes #structural #EN1990 #partialfactors #limitstates