REQUIREMENTS FOR STEEL AND ALUMINIUM STRUCTURES

Design according:

EN 1993 (Eurocode 3: Design of steel structures)

EN 1999 (Eurocode 9: Design of aluminium structures)

Manufacturing according:

EN 1090-1: Requirements for conformity assessment for structural components

EN 1090-2: Technical requirements for the execution of steel structures

EN 1090-3: Technical requirements for the execution of aluminium structures

ISO 5817: Welding - Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded)

- Quality levels for imperfections ISO 10042: Welding -- Arc-welded joints in aluminium and its alloys -- Quality levels for imperfections

TECHNICAL REQUIREMENTS FOR STEEL STRUCTURES

SUMMARY

The extent of all inspection and quality requirements shall be specified. All welds or parts of welds that require

inspection shall be unequivocally defined or designated. Subjects in the specification are:

execution class EXC

depends on consequence class CC, service categories SC, production categories PC;

quality level according to EN ISO 5817;

extent of additional NDT.

All welds could perform welders, which are categorised in three groups:

International Welding Engineer (IWE);

International Welding Technologist (IWT);

International Welding Specialist (IWS).

EXECUTION CLASS

Execution classes may be applied to the whole structure, its part or selected elements.

The selection of a given execution class is conditioned by factors affecting its reliability. In general, while establishing

an execution class one should take into account as follows:

classes of consequences – characterising structural reliability,

application categories – characterising the risk related to the application of structure;

production categories – characterising the risk related to the execution of structure.

EN 1990 Table B.1

Consequence

classes

Description Examples of buildings and civil

engineering works

CC3

(>1000 people)

High consequence for loss of human life, or

economic, social or environmental very great

Grandstands, public buildings where

consequences of failure are high (e.g. a

concert hall)

CC2

(Standard)

Medium consequences for loss of human life,

economic, social or environmental consequences

considerable

Residential and office buildings, public

buildings where consequences of failure

are medium (e.g. an office building)

CC1 Low consequences for loss of human life, and

economic, social or environmental

consequences small or negligible

Agricultural buildings where people do not

normally enter(e.g. storage buildings),

greenhouses

Service Category- category that characterises a component in terms of the circumstances of its use.

EN 1090-2 Table B.1 — Suggested criteria for service categories

Categories Criteria

SC1 Structures and components designed for quasi static actions only (Example: Buildings)

Structures and components with their connections designed for seismic actions in regions with

low seismic activity and in DCL*

Structures and components designed for fatigue actions from cranes (class S0)**

SC2 Structures and components designed for fatigue actions according to EN 1993. (Examples: Road

and railway bridges, cranes (class S1 to S9)**, structures susceptible to vibrations induced by

wind, crowd or rotating machinery)

Structures and components with their connections designed for seismic actions in regions with

medium or high seismic activity and in DCM* and DCH*

* DCL, DCM, DCH: ductility classes according to EN 1998-1

** For classification of fatigue actions from cranes, see EN 1991-3 and EN 13001-1

A structure or part of a structure can contain components or structural details that belong to different service categories.

EN 1090-2 Table B.2 — Suggested criteria for production categories Categories Criteria

PC1 • Non welded components manufactured from any steel grade products

• Welded components manufactured from steel grade products below S355

PC2

≥S355

• Welded components manufactured from steel grade products from S355 and

above

• Components essential for structural integrity that are assembled by welding on

construction site

• Components with hot forming manufacturing or receiving thermic treatment during

manufacturing

• Components of CHS lattice girders requiring end profile cuts

A structure or part of a structure may contain components or structural details that belong to different production

categories.

EN 1090-2 Table B.3 — Recommended matrix for determination of execution classes

Consequence classes CC1 CC2 CC3

Service categories SC1 SC2 SC1 SC2 SC1 SC2

Production

categories

PC1 EXC1 EXC2 EXC2 EXC3 EXC3a EXC3a

PC2 EXC2 EXC2 EXC2 EXC3 EXC3a EXC4

a EXC4 should be applied to special structures or structures with extreme consequences of a structural failure as

required by national provisions.

QUALITY LEVEL

EN 1090-2 A.3 7.6

No. Structure Execution Level Quality Level (EN ISO 5817)

1 EXC1 D

2 EXC2 C

3 EXC3 B

4 EXC4 B+

The acceptance criteria for weld imperfections shall be as follows, with reference to EN ISO 5817, except "Incorrect

toe" (505) and "Micro lack of fusion" (401) which are not to be taken into account. Any additional requirements

specified for weld geometry and profile shall be taken into account.

EXC1 quality level D;

EXC2 generally quality level C except quality level D for "Undercut" (5011, 5012), "Overlap" (506), "Stray

arc" (601) and "End crater pipe" (2025);

EXC3 quality level B;

EXTENT OF NDT

EN 1090-2 12.4.2.2 Scope of inspection

All welds shall be visually inspected throughout their entire length. If surface imperfections are detected, surface

testing by penetrant testing or magnetic particle inspection shall be carried out on the inspected weld.

Unless otherwise specified no supplementary NDT is required for EXC1 welds. For EXC2, EXC3 and EXC4 welds

the extent of supplementary NDT is as specified below.

EN 1090-2 Table 24 — Extent of supplementary NDT

Type of weld Shop and site welds

EXC2 EXC3 EXC4

Transverse butt welds and partial penetration welds in butt joints subjected to

tensile stress:

U ≥ 0,5

10% 20% 100%

U < 0,5 0% 10% 50%

Transverse butt welds and partial penetration welds:

in cruciform joints

10% 20% 100%

in T joints 0% 10% 50%

Transverse fillet welds in tension or shear:

With a > 12 mm or t > 20 mm 5% 10% 20%

With a ≤ 12 mm and t ≤ 20 mm 0% 5% 10%

Longitudinal welds and welds to stiffeners 0% 5% 10% NOTE 1 Longitudinal welds are those made parallel to the component axis. All the others are considered as transverse welds. NOTE 2 U = Utilization grade for welds for quasi-static actions. U = Ed/Rd, where Ed is the largest action effect of the weld and Rd is the

resistance of the weld in the ultimate limit state. NOTE 3 Terms a and t refer respectively to the throat thickness and the thickest material being joined

EN 1090-2:2008 12.4.1

Generally ultrasonic testing or radiographic testing applies to butt welds and penetrant testing or magnetic particle

inspection applies to fillet welds.

TECHNICAL REQUIREMENTS FOR ALUMINIUM STRUCTURES

SUMMARY

The extent of all inspection and quality requirements shall be specified. All welds or parts of welds that require

inspection shall be unequivocally defined or designated. Subjects in the specification are:

execution class;

service category (significant fatigue SC2 or predominantly static SC1);

quality level according to EN ISO 10042;

additional and supplementary quality requirements e.g. according to this European Standard and NE 1999-1-3;

extent of additional NDT;

any additional tests and testing methods.

EXECUTION CLASS

Execution classes may be applied to the whole structure, its part or selected elements.

The selection of a given execution class is conditioned by factors affecting its reliability. In general, while establishing

an execution class one should take into account as follows:

classes of consequences – characterising structural reliability,

application categories – characterising the risk related to the application of structure;

production categories – characterising the risk related to the execution of structure.

EN 1990 Table B.1

Consequence

classes Description

Examples of buildings and civil

engineering works

CC3

High consequence for loss of human life, or

economic, social or environmental very great

Grandstands, public buildings where

consequences of failure are high (e.g. a

concert hall)

CC2

Medium consequences for loss of human life,

economic, social or environmental consequences

considerable

Residential and office buildings, public

buildings where consequences of failure

are medium (e.g. an office building)

CC1

Low consequences for loss of human life, and

economic, social or environmental

consequences small or negligible

Agricultural buildings where people do not

normally enter(e.g. storage buildings),

greenhouses

EN 1999-1-1 Table A.1 —Criteria for service categories

Categories Criteria

SC1 Structures subject to quasi static actions a

SC2 Structures subject to repeated actions of such intensity that the inspection regime specified for

components subject to fatigue is required b a Guidance is given in EN 1999-1-3 whether a component or structure may be regarded as subject to quasi static

actions and classified in category SC1. b Service category SC2 should be used for cases not covered by SC1.

EN 1999-1-1 Table A.2 — Criteria for production categories

Categories Criteria

PC1 Non welded components

PC2 Welded components

EN 1999-1-1 Table A.3 — Recommended matrix for determination of execution classes

Consequences Classes CC 1 CC 2 CC 3

Service Categories SC1 SC2 SC1 SC2 SC1 SC2

Production

Categories

PC 1 EXC 1 EXC 1 EXC 2 EXC 3 EXC 3a EXC 3a

PC2 EXC 1 EXC 2 EXC 2 EXC 3 EXC 3a EXC 4 a EXC 4 Should be applied to special structures or structures with extreme consequences of a structural failure also

in the indicated categories as required by national provision

QUALITY LEVEL

Utilization grades

Utilization grades are given in EN 1999-1-1 used to determine requirements to the amount of inspection and to the

acceptance criteria for welds, see EN 1090-3.The utilization grade U for structures and components subject to

predominantly static loading is defined by

Ek is the characteristic action effect

Rk is the characteristic resistance

For combined actions U is given by the interaction formula. The utilization grade for structures and components

subject to fatigue loads is defined in EN 1999-1-3.

EN 1090-3 specifies three ranges for the utilization grade, denoted UR1, UR2 and UR3, called utilization ranges, see

Table L.1.

Rules for determination of the utilization grade U are given in EN 1999-1-1.

Rules for determination of the utilization grade U are given in EN 1999-1-3.

EN 1090-3:2008 Table L.1 – Utilization ranges

Service

Category

Loading UR1 UR2 UR3

SC1 Tension and bending U

0,60 < U

Shear and compression U

0,80 < U

SC2 Fatigue U

0,60 < U

Fatigue U, if damage assessment DL

according

to EN 1999-1-3

U

0,70 < U

Provisions for welds

All welds shall be visually inspected throughout their entire length. If surface breaking planar defects are detected,

surface testing by liquid penetration testing shall be carried out on the inspected weld. For examples of how to present

these requirements on drawings, see Annex J. The minimum extent of inspection for welded joints shall be specified

as follows:

Table L.2 should be used for SC1 and Table L.3 should be used for SC2;

EN 1090-3:2008 Table 9 — Test methods to be applied for NDT

Execution class Butt welds Fillet welds

EXC1 RT or UT --

EXC2 RT or UT PT

EXC3 PT + RT or UT PT

EXC4 PT + RT or UT PT

RT Radiographic testing

UT Ultrasonic testing

PT Penetrant testing

Extent of additional NDT

Extent of NDT (%) for components/structures in service category SC1

The extent of NDT (in %) should be specified not less than according to the provisions of Table L.2.

EN 1090-3:2008 Extent of additional NDT (in %) for structures/components in service category SC1

Type of weld Utilization

ranges

EXC1 EXC2 EXC3 EXC4

Butt welds

under transverse

tension and

shear

UR3 5 10 20 To be specified

UR2 - 5 10 To be specified

All other welds UR3 - 5 10 To be specified

UR2 - - 5 To be specified

Extent of NDT (%) for components/structures in service category SC2

The extent of NDT (in %) should be specified not less than according to the provisions of Table L.3.

EN 1090-3:2008 Extent of additional NDT (in %) for structures/components in service category SC1

Type of weld Utilization

ranges

EXC1 EXC2 EXC3 EXC4

Butt welds (each QL) and fillet

welds QL Bb both under tensionc

or shear excl. DT 3.5 and 3.6 in EN

1999-1-3:2007, Table J3

UR3 - 20 50 100

UR2 - 10 20 50

Fillet welds under tension or

shear

UR3 - 10 20 50

UR2 - 5 10 20

All other welds UR3 - 5 10 10

UR2 - - 5 5

a Butt weld with partial penetration (see EN 1999-1-3 for the relevant detail type DT) are basically not allowed

for fatigue, see EN 1999-1-1.

b This concerns only fillet welds, where EN 1999-1-3 specifies quality level B for internal imperfections.

c Includes longitudinal welds that are subject to the strain of adjacent member.

Acceptance criteria for welds

Acceptance criteria for welds in service category SC1

If no special conditions are given, the quality level should be specified according to the provisions of Table L.4.

EN 1090-3:2008 Table L.4 — Quality level for welds for structures/components in service category SC1

Utilization ranges Quality level in accordance with EN ISO

10042:2005abc

UR1 D

UR2 D

UR3 C

a For the imperfections 2.7 and 2.9 according EN ISO 10042:2005, the requirements apply when the weld length

is more than 25 mm. For shorter weld lengths, these imperfections are not permitted.

b The requirements for the following imperfections according to EN ISO 10042:2005 do not apply: 1.4, 1.11,

1.12, 1.14, 1.15, 1.17, 2.2 and 2.5.

c Additional requirements to EN ISO 10042:2005 are given in table 10.

Acceptance criteria for welds in service category SC2

L.4.2.1 Detail types according to EN 1999-1-3

EN 1090-3:2008 Table L.5 — Quality level for welds for structures/components in service category SC2

Utilization

ranges

Quality level according to

EN ISO 10042:2005

Additional requirements to be

specified

Supplementarya requirements to be

specified

UR1 See recommendations for SC1 in Table L.4.

UR2 See EN 1999-1-

3:2007, Annex J

None See EN 1999-1-3:2007, Annex J

UR3 See EN 1999-1-

3:2007, Annex J

B+, C+ or D+ respectively,

depending on detail typeb

See EN 1999-1-3:2007, Annex J

a The supplementary requirements are defined for the concerned detail types in EN 1999-1-3:2007, Annex J.

b Guideline is given in Annex M.

DESIGNATION OF REQUIREMENTS TO WELDS ON DRAWINGS

GENERAL

This Annex gives guidelines on how to specify the requirements to welds and their testing in accordance with 12.4.3,

12.4.4.1 and 12.4.4.2. The information is normally given on drawings. The following information should be given on

the drawing(s), as relevant:

The execution class should be designated as EXC1, EXC2, EXC3 or EXC4;

The service category should be designated as SC1 (static) or SC2 (fatigue);

The extent of testing should be given in per cent and may be given in the following values: 5, 10, 20, 50

or100;

The quality levels should be given according to Annex L as D, C or B;

For cases where additional quality requirements to the quality levels D, C and B are required in Annex L and defined

in Tables 11, 12 and 13, these should be given as D+, C+ or B+;

For cases where supplementary requirements are given in EN 1999-1-3 (see also Table L.4), they should be specified

explicitly.

An overview for specifying the requirement for structures in SC2 is provided in Annex M.

GLOBAL SPECIFICATION

When the quality requirement can be specified globally, the following form of presentation of the quality requirements

may be given on the drawings:

Example Table

EN 1090-3 Table J.1

Quality and testing requirements:

Execution class EXC2

Service category SC1

Quality level acc. to EN ISO 10042:2005 C

Extent of NDT 10 %

NOTE This may often be the case for predominately static loaded structures.