TITLE 3. TECHNOLOGICAL PROPERTIES OF MATERIALS AND DURABILITY

CHAPTER VI. MATERIALS

Construction products may be used under this Code if they are manufactured or marketed lawfully in the Member States of the European Union and the signatory states to the Agreement Creating the European Economic Area, wherever such products comply with the legislation of any Member State of the European Union, and guarantee a level of safety equivalent to that required by this Code, in respect of their intended purpose.

This level of equivalence shall be justified in accordance with Article 4(2) or Article 16 of Directive 89/106/EEC of the Council of 21 December 1988 on the approximation of laws, regulations and administrative provisions of the Member States relating to construction products.

The preceding paragraphs shall also apply to construction products manufactured or marketed lawfully in states with customs association agreements with the European Union where such agreements treat such products in the same way as those manufactured or marketed in a Member State of the European Union. In such cases, the level of equivalence shall be confirmed by applying the procedures for that purpose stipulated in the aforementioned Directive.

Section 25. General

This Chapter prescribes the requirements that shall be met by materials that may be used in steel structures. Section 26 defines the chemical composition, mechanical and technological properties that they shall have, as well as testing methods for them. Sections 27 and 28, respectively, relate to types of steel and the various products (beams and plates) that may be used.

Section 29 specifies joints that may be used, and Section 30 relates to the necessary protection systems.

TITLE 3 page 1

Section 26. Steel properties

26.1. Chemical composition

The chemical composition of steel that may be used to manufacture beams and plates for steel structures shall be specified in the paragraph corresponding to the relevant type of steel in Section 27.

26.2. Mechanical properties

For the purposes of this Code, the basic properties used to define steel quality are as follows:

a) stress/strain diagram;

b) ultimate strength or tensile resistance (fu);

c) yield strength (fy);

d) ultimate strain (εmax);

e) elongation at failure (εu);

f) modulus of elasticity (E);

g) reduction of area (Z) expressed as a percentage;

h) notch impact value (KV);

i) fracture toughness;

The Manufacturers shall guarantee the properties listed under b), c), d), e), f) and h) as a minimum requirement.

26.3. Ductility requirements

The steel shall meet the following requirements in order to guarantee sufficient ductility:

fu/fy ≥ 1.10

εu ≥ 0.15

εmax ≥ 15 εy

where εu is the elongation at failure on a gauge length of 5.65 A where Ao is theo

original cross-section, εmax is the ultimate strain, and εy is the yield strain, given by εy = 0.002 + fy/E, where E is the steel’s modulus of elasticity, for which the conventional value of 210 000 N/mm2 may be used, unless otherwise dictated by the results of tests on the steel.

26.4. Technological properties

Weldability is the ability of steel to be welded using normal processes without any cold cracking occurring. This is a key technological property for the execution of the

TITLE 3 page 2

structure. According to ISO 581:80, “steel is considered weldable to a predetermined degree by means of a set procedure and for a specific purpose, where a suitable technique is used to make a continuous metal joint, in such a way that it fulfils the requirements laid down for its local properties and its impact on the construction of which it is”.

Resistance of steel to lamellar tearing is defined as resistance to the appearance of cracks in welded parts subjected to out-off plane tensile stresses. In order to avoid lamellar tearing, such stress shall be minimised using an adequate design for the relevant construction details and analysing whether it is necessary to use steel that is unlikely to develop this defect, such as steel with improved resistance to out-off plane deformation, as discussed in subsection 27.2.5.

Bendability is an indicator of the material’s ductility, and is defined by the presence or absence of cracks during the bending test. Bendability is an optional property that need only be verified if so required by the design’s Special Technical Specifications or the order contract.

26.5. Definition of steel properties

26.5.1. Chemical composition

With regard to the chemical composition of steel, the most important components are those of the elements that appear in the expression of the equivalent carbon value (defined in 26.5.5), as well as its phosphorus and sulphur content, which is restricted owing to the need to minimise it.

The chemical composition is determined using the methods specified in the relevant UNE standard for the steel type.

26.5.2. Tensile properties

Mechanical tensile properties (fu, fy, εmax, εu, E) are defined using the standardised tensile test in UNE-EN ISO 6892-1.

Reduction of area (Z) is defined using the straight, initial and fractured sections of A A

the test specimen submitted to the tensile test, using the expression: Z i u 100 .Ai

26.5.3. Notch impact value

Notch impact value is determined using the standardised Charpy shock bend test in UNE 7475-1.

26.5.4. Fracture toughness

Fracture toughness is determined rigorously, in special cases where so required, using specific fracture mechanics tests, which shall be conducted at specialist laboratories.

26.5.5. Weldability (equivalent carbon)

The basic parameter for steel, from the weldability perspective, is the carbon equivalent value (CE) stipulated for each type of steel.

TITLE 3 page 3

The carbon equivalent value is defined using the following expression, where the content of the chemical elements indicated is expressed as a percentage:

Mn Cr Mo V Ni CuCEV C

6 5 15

However, the weldability requirement shall be regarded as having been met if the steel has a carbon equivalent value exceeding the value stipulated for it in this Code, if its welding process is qualified in accordance with UNE-EN ISO 15614-1 (or UNE-EN ISO 15613 if it is necessary to use a non-standardised test coupon).

26.5.6. Bending properties

Bendability shall be determined by testing whether there is an absence of cracks during a simple bending test standardised by UNE-EN ISO 7438.

26.5.7. Resistance to lamellar tearing

The resistance of steel to lamellar tearing shall be checked by obtaining a reduction of area in the tensile test that meets the specifications in Table 27.2.5.

Section 27. Steel types

This Code considers the following types of steel, which may be used in profiles and plates for steel structures:

— non-alloyed, hot-rolled steel. This means non-alloyed steel that does not have any particular mechanical resistance properties or resistance to corrosion, but does have a normal ferrite-pearlite microstructure;

— steel with special properties. This includes the following types:

- weldable fine-grained steel in normalized condition;

- thermomechanical rolled, weldable fine-grained steel;

- steel with improved atmospheric corrosion resistance (weathering steel);

- steel of high yield strength, in quenched and tempered condition;

- steel with improved resistance to out-off-plane deformation.

For the purposes of this Code, steel that is standardised under the standards given in Table 27 are considered to be equivalent to the aforementioned steel types:

Table 27. Steel equivalent to the given steel types

STEEL TYPE UNE-EN STANDARD

non-alloyed, hot-rolled steel UNE-EN 10025-2

weldable fine-grained steel in normalized condition

UNE-EN 10025-3

TITLE 3 page 4

thermomechanical rolled, weldable fine­grained steel

UNE-EN 10025-4

steel with improved atmospheric corrosion resistance (weathering steel)

UNE-EN 10025-5

steel of high yield strength, in quenched and tempered condition

UNE-EN 10025-6:2007+A1

steel with improved resistance to out-off­plane deformation

UNE-EN 10164

UNE-EN 10025-1

Subsections 27.1 and 27.2 stipulate the characteristics and properties for the steel thus described on the basis of those given in the steel standards for hot-rolled products UNE-EN 10025-2, UNE-EN 10025-3, UNE-EN 10025-4, UNE-EN 10025-5 and UNE-EN 10025-6:2007+A1, and they are compatible with the steel types and mechanical properties of steel in standards UNE-EN 10210-1 and UNE-EN 10219-1 for hollow sections and UNE-EN 10162 for open sections.

The nominal value given in the relevant UNE-EN standard for the type of steel in question shall be used for the characteristic yield strength fyk, depending on the type and grade of steel and the nominal thickness of the product or, alternatively, where the steel has certain additional guarantees in accordance with Section 84, the nominal value stipulated in this Section for the type of steel in question. It shall also have the other characteristics and properties that appear in the other subsections of this Section.

27.1. Non-alloyed, hot-rolled steel

For the purposes of this Code, usable non-alloyed, hot-rolled steel corresponds to the types and grades listed in Table 27.1.a.

Table 27.1.a. Non-alloyed, hot-rolled steel

Grade Type

S 235 S 275 S 355

JR S 235 JR S 275 JR S 355 JR J0 S 235 J0 S 275 J0 S 355 J0 J2 S 235 J2 S 275 J2 S 355 J2 K2 - - S 355 K2

Deoxidation state FN is permitted for grades JR and J0 (rimmed steel is not permitted), and FF (killed steel) is permitted for grades J2 and K2.

The carbon equivalent value (CE) based on the cast analysis shall comply with Table 27.1.b.

Table 27.1.b. Maximum CE

Type Nominal product thickness t (mm)

≤ 30 30 < t ≤40 40 < t ≤150 150 < t ≤250 S 235 0.35 0.35 0.38 0.40 S 275 0.40 0.40 0.42 0.44 S 355 0.45 0.47 0.47 0.49

TITLE 3 page 5

The percentages of phosphorus and sulphur in the product analysis shall comply with Table 27.1.c.

Table 27.1.c. Maximum P and S content

Type P (max %) S (max %)

S235 JR, S275 JR, S355 JR 0.045 0.045

S235 J0, S275 J0, S355 J0 0.040 0.040

S235 J2, S275 J2, S355 J2, S355 K2 0.035 0.035

Table 27.1.d gives the relevant specifications for yield strength fy and ultimate tensile strength fu for the various types of steel.

Table 27.1.d. Minimum yield strength and ultimate tensile strength (N/mm2)

Type Nominal thickness t (mm) t ≤ 40 40 < t ≤80

fy fu fy fu

S 235 235 360<fu<510 215 360<fu<510 S 275 275 430<fu<580 255 410<fu<560 S 355 355 490<fu<680 335 470<fu<630

Table 27.1.e gives the notch impact value specifications for the different steel grades.

Table 27.1.e. Notch impact value (J), according to nominal product thickness t (mm)

Grade Test

temperature (ºC)

Notch impact value (J)

t ≤ 150 150< t ≤ 250 250< t ≤ 400

JR 20 27 27 -J0 0 27 27 -J2 -20 27 27 27 K2 -20 40 (*) 33 33

(*) Equivalent to resistance of 27J at –30 ºC.

UNE-EN 10025-1 applies to t ≤ 12 mm.

All the types and grades of steel given in Table 27.1.a are generally suitable for all types of welding process, where weldability increases from grade JR up to K2.

27.2. Steel with special properties

27.2.1. Weldable fine-grained steel in normalized condition

Weldable fine-grained steel in normalized condition that is usable for the purposes of this Code corresponds to the types and grades given in Table 27.2.1.a.

Table 27.2.1.a. Weldable fine-grained steel in normalized condition

Grade Type

S 275 S 355 S 420 S 460

N S 275 N S 355 N S 420 N S 460 N

NL S 275 NL S 355 NL S 420 NL S 460 NL

TITLE 3 page 6

The carbon equivalent value (CE) based on the cast analysis shall comply with Table 27.2.1.b.

Table 27.2.1.b. Maximum CE

Type Nominal thickness t (mm)

t ≤ 63 63 < t ≤100 100 < t ≤250

S 275 N/NL 0.40 0.40 0.42

S 355 N/NL 0.43 0.45 0.45

S 420 N/NL 0.48 0.50 0.52

S 460 N/NL 0.53 0.54 0.55

The percentages of phosphorus and sulphur in the product analysis shall comply with Table 27.2.1.c.

Table 27.2.1.c. Maximum P and S content

Type P (max %) S (max %)

S275 N, S355 N, S420 N, S460 N 0.035 0.030

S275 NL, S355 NL, S420 NL, S460 NL 0.030 0.025

Table 27.2.1.d gives the relevant specifications for yield strength fy and ultimate tensile strength fu for the various types of steel.

Table 27.2.1.d. Minimum yield strength and ultimate tensile strength (N/mm2)

Type Nominal thickness t (mm)

t ≤ 40 40 < t ≤80 fy fu fy fu

S 275 N/NL 275 370<fu<510 255 370<fu<510 S 355 N/NL 355 470 <fu<630 335 470<fu<630 S 420 N/NL 420 520<fu<680 390 520<fu<680 S 460 N/NL 460 540<fu<720 430 540<fu<720

Table 27.2.1.e gives the notch impact value specifications for the different steel grades.

Table 27.2.1.e. Notch impact value (J) according to the test direction, longitudinal (L) or transversal (T)

Grade Direction Test temperature (ºC)

20 0 -10 -20 -30 -40 -50

N L T

55 31

47 27

43 24

40(*) 20

--

--

--

NL L T

63 40

55 34

51 30

47 27

40 23

31 20

27 16

(*) Equivalent to resistance of 27J at –30 ºC.

The values in this table shall be verified using tests conducted on the longitudinal direction and at a temperature of –20 ºC or –50 ºC for grades N and NL respectively, unless otherwise stipulated in the Special Technical Specifications.

All the types and grades of steel in Table 27.2.1.a shall be suitable for welding using normal processes.

TITLE 3 page 7

27.2.2. Thermomechanical rolled, weldable fine-grained steel

Thermomechanical rolled, weldable fine-grained steel that is usable for the purposes of this Code corresponds to the types and grades given in Table 27.2.2.a.

Table 27.2.2.a. Thermomechanical rolled, weldable fine-grained steel

Grade Type

S 275 S 355 S 420 S 460

M S 275 M S 355 M S 420 M S 460 M

ML S 275 ML S 355 ML S 420 ML S 460 ML

The carbon equivalent value (CE) based on the cast analysis shall comply with Table 27.2.2.b.

Table 27.2.2.b. Maximum CE

Type Nominal thickness t (mm)

t ≤ 16 16 < t ≤40 40 < t ≤63 63 < t S 275 M/ML 0.34 0.34 0.35 0.38 S 355 M/ML 0.39 0.39 0.40 0.45 S 420 M/ML 0.43 0.45 0.46 0.47 S 460 M/ML 0.45 0.46 0.47 0.48

The percentages of phosphorus and sulphur in the product analysis shall comply with Table 27.2.2.c.

Table 27.2.2.c. Maximum P and S content

Type P (max %) S (max %)

S275 M, S355 M, S420 M, S460 M 0.035 0.030 S275 ML, S355 ML, S420 ML, S460 ML 0.030 0.025

Table 27.2.2.d gives the relevant specifications for yield strength fy and ultimate tensile strength fu for the various types of steel.

Table 27.2.2.d. Minimum yield strength and ultimate tensile strength (N/mm2)

Type Nominal thickness t (mm)

t ≤ 40 40 < t ≤80 fy fu fy fu

S 275 M/ML 275 370<fu<530 255 360<fu<520 S 355 M/ML 355 470<fu<630 335 450<fu<610 S 420 M/ML 420 520<fu<680 390 500<fu<660 S 460 M/ML 460 540<fu<720 430 530<fu<710

Table 27.2.2.e gives the notch impact value specifications for the different steel grades.

TITLE 3 page 8

Table 27.2.2.e: Notch impact value (J) according to the test direction, longitudinal (L) or transversal (T)

Grade Direction Test temperature (ºC)

20 0 -10 -20 -30 -40 -50

M L T

55 31

47 27

43 24

40(*) 20

--

--

--

ML L T

63 40

55 34

51 30

47 27

40 23

31 20

27 16

(*) Equivalent to resistance of 27 J at –30 ºC.

The values in this table shall be verified using tests conducted on the longitudinal direction and at a temperature of –20 ºC or –50 ºC for grades M and ML respectively, unless otherwise stipulated in the Special Technical Specifications.

All the types and grades of steel in Table 27.2.2.a shall be suitable for welding using normal processes.

27.2.3. Steel with improved atmospheric corrosion resistance (weathering steel)

Steel with improved atmospheric corrosion resistance (also called weathering steel or self-protecting steel) that is usable for the purposes of this Code corresponds to the types and grades given in Table 27.2.3.a.

Table 27.2.3.a. Steel with improved atmospheric corrosion resistance

Grade Type

S 235 S 355

J0 S 235 J0 W S 355 J0 W J2 S 235 J2 W S 355 J2 W K2 S 355 K2 W

The carbon equivalent value (CE) based on a cast analysis shall be less than or equal to 0.44 for type S235, and less than or equal to 0.52 for type S 355.

The percentages of phosphorus and sulphur in the product analysis shall comply with Table 27.2.3.b.

Table 27.2.3.b. Maximum P and S content

Type P (max %) S (max %) S235 J0 W, S355 J0 W 0.040 0.040

S235 J2 W 0.040 0.035 S355 J2 W, S355 K2 W 0.035 0.035

Table 27.2.3.c gives the relevant specifications for yield strength fy and ultimate tensile strength fu for the various types of steel.

TITLE 3 page 9

Table 27.2.3.c. Minimum yield strength and ultimate tensile strength (N/mm2)

Type Nominal thickness t (mm)

t ≤ 40 40 < t ≤80 fy fu fy fu

S 235 J0W S 235 J2W

235 360<fu<510 215 360<fu<510

S 355 J0W S 355 J2W S 355 K2W

355 490<fu<680 335 470<fu<630

Table 27.2.3.d gives the notch impact value specifications for the different steel grades.

Table 27.2.3.d. Notch impact value (J)

Grade Test temperature (ºC) Notch impact value (J) J0 0 27 J2 -20 27 K2 -20 40 (*)

(*) Equivalent to resistance of 27 J at –30ºC.

UNE-EN 10025-1 applies to t ≤ 12 mm.

All the steel types listed here may be welded, but their weldability is limited among various welding processes. The supplier shall therefore advise Project Management of the recommended processes for welding where necessary. In any case, the self-protective coating that forms in the area (less than 20 mm) near the edges of the joint shall be removed prior to welding. It shall be ensured that the weld is also resistant to atmospheric corrosion.

27.2.4. Steel of high yield strength, in quenched and tempered condition

Steel of high yield strength, in quenched and tempered condition that is usable for the purposes of this Code corresponds to the types and grades given in Table 27.2.4.a.

Table 27.2.4.a. Steel of high yield strength, in quenched and tempered condition

Type

S 460

Grade

Q S 460 Q QL S 460 QL

QL1 S 460 QL1

The percentages of phosphorus and sulphur in the product analysis shall comply with Table 27.2.4.b.

Table 27.2.4.b. Maximum P and S content

Type P (max %) S (max %)

S460 Q 0.030 0.017 S460 QL, S460 QL1 0.025 0.012

TITLE 3 page 10

Table 27.2.4.c gives the relevant specifications for minimum yield strength fy and ultimate tensile strength fu for these types of steel.

Table 27.2.4.c. Minimum yield strength and ultimate tensile strength (N/mm2)

Type Nominal thickness t (mm)

t ≤ 40 40 < t ≤80 fy fu fy fu

S 460 Q S 460 QL

S 460 QL1 460 550<fu<720 440 550<fu<720

Table 27.2.4.d gives the notch impact value specifications for the different steel grades.

Table 27.2.4.d. Notch impact value (J) according to the test direction, longitudinal (L) or transversal (T)

Grade Direction Test temperature (ºC)

0 -20 -40 -60

Q L T

40 30

30 27

--

--

QL L T

50 35

40 30

30 27

--

QL1 L T

60 40

50 35

40 30

30 27

The values in this table shall be verified using tests conducted on the longitudinal direction and at a temperature of –20 ºC, –40 ºC or –50 ºC for grades Q, QL and QL1 respectively, unless otherwise stipulated in the Special Technical Specifications.

Due to its chemical composition, and in order to ensure the steel's weldability, the supplier shall inform Project Management of the alloy elements that have been incorporated into the steel supplied, together with the recommended procedures for carrying out welding where necessary.

27.2.5. Steel with improved resistance to out-off-plane deformation

Steel with improved resistance to out-off-plane deformation that is usable for the purposes of this Code is steel that is classified under any of the subsections of this Section (Section 27) and which also fulfils the minimum values given for reduction of area in Table 27.2.5, obtained from a tensile test in the direction of thickness.

Table 27.2.5. Minimum grades and values for reduction of area

Grade Reduction of area (%)

Minimum mean value from 3 tests

Individual minimum value

Z 15 Z 25 Z 35

15 25 35

10 15 25

TITLE 3 page 11

Section 28. Steel products

Steel structures shall use only the profiles and plates mentioned in this Section, with the dimensions and tolerances given in each case.

Profiles and plates shall be prepared using the steel specified in Section 27.

28.1. Hot-rolled full-section profiles and plates

For the purposes of this Code, hot-rolled full-section profiles and plates are products obtained from the hot-rolling, with uniform and full cross-section and a thickness greater than or equal to 3 mm, used in the construction of structures or the manufacture of members made of structural steel.

It shall correspond to one of the series given in Table 28.1.

Table 28.1. Series of hot-rolled full-section profiles and plates

Series Product standard

Dimensions Tolerances

IPN sections UNE 36521 UNE-EN 10024

IPE sections UNE 36526 UNE-EN 10034

HEB sections (base) UNE 36524 UNE-EN 10034

HEA sections (light) UNE 36524 UNE-EN 10034

HEM sections (heavy) UNE 36524 UNE-EN 10034

Standard U sections (UPN) UNE 36522 UNE-EN 10279

UPE sections UNE 36523 UNE-EN 10279

Commercial U sections (U) UNE 36525 UNE-EN 10279

Equal leg angles (L) UNE-EN 10056-1 UNE-EN 10056-2

Unequal leg angles (L) UNE-EN 10056-1 UNE-EN 10056-2

T section UNE-EN 10055 UNE-EN 10055

Circular UNE-EN 10060 UNE-EN 10060

Square UNE-EN 10059 UNE-EN 10059

Rectangular UNE-EN 10058 UNE-EN 10058

Hexagonal UNE-EN 10061 UNE-EN 10061

Plate (*) UNE 36559 UNE 36559

(*) The plate is a flat, rolled product with a width larger than 600 mm, and mainly used as batch material for the manufacture of flat members. According to its thickness “t,” it is classified as medium plate (3 mm ≤ t ≤ 4.75 mm) or heavy plate (t > 4.75 mm).

28.2. Hot-finished hollow sections

According to this Code, hot-finished hollow sections are structural hollow sections of uniform cross-section and a thickness greater than or equal to 2 mm, either hot­formed with or without subsequent heat treatment, or cold-formed with subsequent heat treatment, and used in the construction of structures.

TITLE 3 page 12

It shall correspond to one of the series given in Table 28.2.

Table 28.2. Series of heat-finished hollow sections

Series Product standard

Dimensions Tolerances

Circular section

UNE-EN 10210-2 UNE-EN 10210-2 Square section

Rectangular section

Elliptical section

28.3. Cold-formed hollow sections

According to this Code, cold-formed hollow sections are welded structural hollow sections that are cold-formed without subsequent heat treatment and have a thickness larger than or equal to 2 mm and a uniform cross-section, and are used in the construction of structures.

It shall correspond to one of the series given in Table 28.3.

Table 28.3. Series of cold-shaped hollow sections

Series Product standard

Dimensions Tolerances

Circular section

UNE-EN 10219-2 UNE-EN 10219-2 Square section

Rectangular section

28.4. Cold-formed open sections

According to this Code, cold-formed open sections are profiles with a uniform cross-section, in various shapes, produced by cold-forming of flat, hot-rolled or cold­rolled plate, and used in the construction of structures.

They shall correspond to one of the following sections:

- L section;

- U section;

- C section;

- Z section;

- Ω section;

- tubular section with pointed edges.

TITLE 3 page 13

Standard UNE-EN 10162 sets out the dimensions and tolerances for cold-formed open sections.

28.5. Non-standardised profiles and plates

In addition to the profiles and plates considered in subsections 28.1 to 28.4, which correspond to standard series, non-standard profiles and plates may be used in the construction of structures, both special open shape ones, or variants of standardised series, that fulfil the following conditions:

– the profiles and plates shall be prepared using steel specified in Section 27;

– the manufacturer shall guarantee the dimensions and tolerances, both dimensional and cross-sectional, of the profiles and plates;

– the manufacturer shall supply the data values for the section that are necessary for design (area of the cross-section, second moment of area, resistance modulus, radius of gyration, centre of gravity, etc.).

Section 29. Fasteners

29.1. General

The fasteners discussed in this Code comprise bolts, nuts and washers for bolted joints, and the welding consumables.

29.2. Bolts, nuts and washers

According to this Code, bolts that may be used for joints in steel structures correspond to the grades in Table 29.2.a, with the specifications for yield strength fyb

and ultimate tensile strength fub given there.

Table 29.2.a. Minimum yield strength fyb and minimum ultimate tensile strength fub for bolts (N/mm2)

Type Standard bolts High-strength bolts

Grade 4.6 5.6 6.8 8.8 10.9

fyb 240 300 480 640 900

fub 400 500 600 800 1 000

Bolts of a grade lower than 4.6 or higher than 10.9 may not be used without documented experimental justification that such bolts are adequate for the joint for which they are intended.

Bolts that are standardised under the standards given in Table 29.2.b are considered to be usable for the purposes of this Code. For each standardised group of bolts, the table shows the standards relating to nuts and washers that may be used with them. The table applies to bolts, nuts and washers for assemblies that are not pre­loaded, in accordance with UNE-EN 15048.

TITLE 3 page 14

Table 29.2.b. Compatibility of use of bolts, nuts and washers

Standardised bolts Standardised hexagonal

nuts Standardised flat washers

UNE-EN ISO 4014 UNE-EN ISO 4016 UNE-EN ISO 4017 UNE-EN ISO 4018

UNE-EN ISO 4032 UNE-EN ISO 4033 UNE-EN ISO 4034

UNE-EN ISO 7089 UNE-EN ISO 7090 UNE-EN ISO 7091 UNE-EN ISO 7092

UNE-EN ISO 7093-1 UNE-EN ISO 7093-2 UNE-EN ISO 7094

Normal series washers are standardised by UNE-EN ISO 7089, 7090 and 7091; the small series is standardised by UNE-EN ISO 7092; the large series is standardised by UNE-EN ISO 7093-1 and 7093-2; and finally, the extra-large series is standardised by UNE-EN ISO 7094.

Only bolts of grades 8.8 and 10.9. that are standardised according to UNE-EN 14399-1 may be pre-loaded. In such case, the assemblies shall comply with the applicable parts of UNE-EN 14399: parts 3, 4, 7, 8 and 10 for bolts and nuts; parts 5 and 6 for washers.

29.3. Special types of bolt

This Code considers the use of bolts with countersunk heads, fit bolts and injection bolts as special types.

They shall be made of materials that fulfil the provisions of subsection 29.2. They shall be used as non-preloaded bolts, or as pre-loaded bolts (in the latter case, they shall satisfy the requirements stipulated for them in subsection 29.2).

29.3.1. Bolts with countersunk heads

These are bolts with the shape and dimensional tolerance that after installation shall remain nominally flush with the outer face of the outer ply.

29.3.2. Fit bolts

Fit bolts are installed in holes that, when reamed in situ, shall be pre-drilled using a drill or punch with a diameter at least 3 mm undersized than the final diameter. Where the bolt has to join several plies, they shall be welded firmly together during the reaming process.

Reaming shall be carried out with a fixed spindle device; no acidic lubricants may be used.

29.3.3. Injection bolts

Injection bolts feature a perforated head into which resin is injected to fill any gaps between the shank and the hole.

The head of an injection bolt shall have a hole with a minimum diameter of 3.2 mm, to which the needle of the injection device may be fitted. A special washer shall be used beneath the head of the bolt. The internal diameter of such a washer shall be at

TITLE 3 page 15

least 0.5 mm oversized than the actual diameter of the bolt, and it shall have a mechanised side. A special slotted washer shall be used underneath the nut.

Tightening of the bolts should be carried out before starting the injection procedure. This consists of a resin made of two components, the temperature of which shall fall between 15ºC and 25ºC. The joint shall be free of water at the time of injection.

29.4 Pins

Standard UNE-EN 10083-1 defines the quality of steel for pins that are usable in joints for steel structures, for the purposes of this Code, with the specifications of yield strength fyb and ultimate tensile strength fub given in Table 29.4 below.

Table 29.4. Minimum yield strength and ultimate tensile strength of steel that may be used for pins (N/mm2)

State Quenching and tempering Standardised d ≤ 16 mm 16 mm < d ≤

40 mm 40 mm < d ≤

100 mm d ≤ 16 mm 16 mm < d

≤ 100 mm Name fyb fub fyb fub fyb fub fyb fub fyb fub

C 22 340 500 to 650

290 470 to

620

-- -- 240 430 210 410

C 25 370 550 to 700

320 500 to

650

-- -- 260 470 230 440

C 30 400 600 to 750

350 550 to

700

300 (*) 500 to 550 (*)

280 510 250 480

C 35 430 630 to 780

380 600 to

750

320 550 to 700

300 550 270 520

C 40 460 650 to 800

400 630 to

780

350 600 to 750

320 580 290 550

C 45 490 700 to 850

430 650 to

800

370 630 to 780

340 620 305 580

C 50 520 750 to 900

460 700 to

850

400 650 to 800

355 650 320 610

C 55 550 800 to 950

490 750 to

900

420 700 to 850

370 680 330 640

C 60 580 852 to 1000

520 800 to

950

450 750 to 900

380 710 340 670

(*) Only applies up to d = 63 mm.

29.5 Welding consumables

Welding consumables that may be used to weld (wire, cables and electrodes) shall be appropriate for the welding process, considering the material that is to be welded and the welding process to be used; certain mechanical properties shall also be taken into consideration, in terms of yield strength, ultimate tensile strength, ultimate

TITLE 3 page 16

strain, and notch impact value, which shall not be less than those of the parent material of which the profiles or plates that will be welded are made.

For the welding of steel with improved atmospheric corrosion resistance, the welding consumables shall have resistance to corrosion at least equivalent to that of the parent metal, unless otherwise permitted by the design’s Special Technical Specifications.

Section 30. Protection systems

This Section mainly stipulates the paint types and systems that may be used to protect steel structures, as well as the technical provisions with which they shall comply according to the durability required by the protective paint system.

Other protection systems for steel construction that are proven to be effective and are widely used, such as “thermal spraying with zinc” or “hot-dip galvanization”, are discussed below and in subsections 79.3.1 and 79.3.2.

30.1. Paint types

The following types of paint may be used:

– air-drying paint;

– physical sealant paints;

- solvent-based paints;

- water-based paints;

– chemical sealant paints;

- epoxy paints of two components;

- polyurethane paints of two components;

- moisture sealant paints.

30.2. Paint systems

Paint systems shall consist of a number of coats of primer (1 or 2, as needed), and a number of finishing coats (between 1 and 4, as needed) with defined nominal dry-film thickness that, when applied to a steel surface that has been prepared to a predetermined extent, result in durability determined by the protective paint system.

The durability of a protective paint system depends on the type of system, the design of the structure, the state of the steel surface (which in turn depends on the prior condition of the surface and the extent to which it has been prepared), the quality of application, the conditions during application and the conditions to which it is exposed during service.

The degree of durability of a paint system is a useful technical concept for selecting the system to use in a given case and for defining the relevant maintenance

TITLE 3 page 17

programme, but it may not, under any circumstances, be understood as a warranty period.

Three grades of durability are stipulated for paint systems:

- low durability (L): from 2 to 5 years;

- medium durability (M): from 5 to 15 years;

- high durability (H): more than 15 years.

30.3. Specifications and tests for paint systems

Paint systems that are used for steel structures shall meet the specifications in Table 30.3.a, which sets the test duration, in hours, that the paint system shall withstand for each structural exposure class given in subsection 8.2.2, and the durability grade of the paint system. Table 30.3.b sets out the adherence specifications for paint systems applied to zinc-covered steel.

The tests referred to in the tables are the following:

– chemical resistance test according to UNE-EN ISO 2812-1;

– immersion test according to UNE-EN ISO 2812-2, in water (class Im1) or in an aqueous 5 % sodium chloride solution (classes Im2 and Im3);

– continuous water condensation test according to UNE-EN ISO 6270-1;

– neutral salt spray test according to UNE-EN ISO 9227.

Table 30.3.a. Specifications for paint systems applied to steel Exposure

class Durability

grade Chemical resistance

test (h) Immersion

test (h) Water condensation

test (h) Neutral salt spray test

(h) C2 Low

Medium High

---

---

48 48

120

---

C3 Low Medium

High

---

---

48 120 240

120 240 480

C4 Low Medium

High

---

---

120 240 480

240 480 720

C5-I Low Medium

High

168 168 168

---

240 480 720

480 720

1 440

C5-M Low Medium

High

---

---

240 480 720

480 720

1 440

Im1 Low Medium

High

---

-2 000 3 000

-720

1 440

---

Im2 Low Medium

High

---

-2 000 3 000

---

-720

1 440

Im3 Low Medium

High

---

-2 000 3 000

---

-720

1 440

TITLE 3 page 18

Table 30.3.b. Adherence specifications for paint systems applied to zinc-covered steel

Exposure class Durability grade Water condensation test

h

C2 Low

Medium High

240 240 240

C3 Low

Medium High

240 240 240

C4 Low

Medium High

240 240 480

C5-I Low

Medium High

240 480 720

C5-M Low

Medium High

240 480 720

The test specimens shall be made of the type of steel that will be used (and, where needed, with the zinc coating that will be used), and have a minimum size of 150 x 70 mm and thickness as dictated by the test but never less than 2 mm. Test specimens shall fulfil the preparation and surface state conditions stipulated in UNE-EN ISO 12944-6.

A test on a specimen is considered to fulfil the specifications of either Table 30.3.a or Table 30.3.b where:

– the specimen is classed as 0 or 1 before the test according to UNE-EN ISO 2409. Where the dry-film thickness of the painting system is greater than 250 μm, this requirement shall be replaced by a requirement to ensure that the paint substrate (A/B) does not blow during the adherence test according to UNE-EN ISO 4624, unless the tensile values are greater than or equal to 5 N/mm2;

– the specimen does not show any defects according to the evaluation methods given in UNE-EN ISO 4628-2 to UNE-EN ISO 4628-5 and it is of class 0 or 1 according to UNE-EN ISO 2409, after testing during the period given in Table 30.3.a or 30.3.b as relevant for the required exposure class and durability grade. Where the dry-film thickness of the painting system is greater than 250 μm, this requirement is also replaced in the same way as in the preceding point. The condition after the test according to UNE-EN ISO 2409 or according to the substitution test shall be evaluated after the specimen has been reconditioned for 24 hours.

The specimen shall be considered as having no defects according to the evaluation methods given in UNE-EN ISO 4628-2 to UNE-EN ISO 4628-5 when it satisfies the following requirements:

- according to UNE-EN ISO 4628-2: blistering 0 (S0);

- according to UNE-EN ISO 4628-3: Ri oxide 0;

- according to UNE-EN ISO 4628-4: cracking 0 (S0);

- according to UNE-EN ISO 4628-5: flakiness 0 (S0).

TITLE 3 page 19

In addition to these requirements, which are evaluated immediately, there shall also be no development of substrate corrosion greater than 1 mm from the incision, calculated according to UNE-EN ISO 12944-6, after the artificial ageing stipulated by UNE-EN ISO 9227.

Defects closer than 10 mm from the edges of the specimen should not be taken into account.

30.4.Specifications for protection systems using thermal spraying with zinc and hot-dip galvanizing

The minimum and maximum durations (in year) of zinc coating until its first maintenance is given in standard UNE-EN ISO 14713 for the various categories of corrosivity in standard ISO 9223.

So, for example, in the case of a hot-dip galvanised coating (carried out in accordance with UNE-EN ISO 1461) of 85 micro-metres in thickness (which is the minimum average thickness value required for a coating for structural steel members with a thickness greater than 6 mm), standard UNE-EN ISO 14713 gives the durations for protection (in years), which are 40/>100 (for environments in category C3), 20/40 (for C4 environments) and 10/20 (for C5 environments).

TITLE 3 page 20

CHAPTER VII. DURABILITY

Section 31. Durability of steel structures

31.1. General

The durability of a steel structure is its capacity to withstand the physical and chemical conditions to which it is exposed and which may cause it to deteriorate as a result of effects other than loads considered in the structural analysis, throughout the design working life.

A durable structure shall comply with a strategy that allows all possible deterioration factors to be considered and for each phase of the structure’s design, execution and use to be acted upon subsequently.

A proper durability strategy shall consider the fact that a structure may have different structural members that are subjected to different types of environment.

31.1.1. Consideration of durability in the design phase

The design for a steel structure shall include the necessary measures for the structure to achieve the predetermined working life, in accordance with the conditions relating to environmental aggressiveness and the type of structure. It shall therefore include a durability strategy in accordance with the criteria set out in subsection 31.2.

The environmental aggressiveness to which the structure is subjected shall be identified according to the type of environment, in accordance with subsection 8.2.1.

The report shall justify the selection of exposure classes considered for the structure. The drawings shall also show the environment type for which each member has been designed.

The design shall also define structural shapes and details that facilitate the water drainage and are effective in the light of possible steel corrosion.

Equipment members, such as supports, joins, drains, etc., may have a shorter working life than the structure itself, so the possibility of adopting design measures that facilitate the maintenance and replacement of such members during the use phase is to be examined as needed.

TITLE 3 page 21

31.1.2. Consideration of durability in the execution phase

High quality on-site work has a decisive influence on whether the structure is durable.

The durability specifications shall be complied with in full during the execution phase. Compensation for any effects resulting from failure to comply with any of the specifications is not permitted.

31.2. Durability strategy

31.2.1. General requirements

In order to satisfy the requirements of Section 5, it is necessary to follow a strategy that considers all possible mechanisms of deterioration, by adopting specific measures depending on the environmental aggressiveness to which each member will be subjected.

The durability strategy shall include at least the aspects mentioned in the following subsections:

– selection of suitable structural shapes, in accordance with subsection 31.2.2;

– selection of suitable protective treatment (painting, metallising, hot-dip galvanisation), taking account of the exposure class to which the member will be subjected and the state of the surface that is to be protected, in accordance with Section 79;

– configuration of special protective measures in the case of highly aggressive environments, in accordance with subsection 31.2.4;

– setting out a programme of inspections to be conducted during and after painting, in accordance with Chapter XXI;

– setting out a programme of maintenance that covers the whole working life of the structure, in accordance with Chapter XXIII.

31.2.2. Selection of structural shapes

The design shall define the structural layouts, geometric shapes and details compatible with ensuring suitable durability for the structure. The design shall facilitate the preparation of surfaces, painting, inspections and maintenance.

The use of structural designs that result in increased susceptibility to corrosion shall be avoided. It is therefore recommended that structural members be simple in shape, avoiding excessive complexity, and that the methods for executing the structure do not reduce the effectiveness of the protective systems used (by damage to the members during transportation and handling).

Direct contact between steel surfaces and water shall be minimised by avoiding the formation of water deposits, facilitating the rapid evacuation of water and preventing water from passing into joined areas. Precautions shall therefore be adopted, such as avoiding a configuration of horizontal surfaces that encourages water or dirt to accumulate, eliminating open sections in the upper part that facilitates such accumulation, filling cavities and holes where water could be retained, and configuring suitable systems on an oversized scale for the conduction and drainage of water.

TITLE 3 page 22

Where the structure has closed areas (accessible interior) or hollow members (inaccessible interior), it shall be ensured that they are protected effectively against corrosion. Water shall therefore be prevented from being trapped inside during the assembly of the structure, the necessary measures for ventilation and drainage (accessible interiors) shall be taken, and it shall be sealed effectively so that air and moisture cannot enter inaccessible interiors, by means of continuous welds.

Potential corrosion in narrow openings, blind cracks and overlap joints shall be avoided by means of an effective seal, which usually consists of continuous welds.

Special attention shall be paid to protection against corrosion of joints, both bolted (so that the bolts, nuts and washers have the same durability as the rest of the structure) and welded (ensuring that the surface of the weld is free of imperfections such as cracks, craters and projections that are difficult to cover effectively when they are subsequently painted over), and additionally, in the case of backing arrangements or the execution of notches (on webs, reinforcement, etc.), the need to allow the surface to be prepared and for the paint to be applied adequately shall be taken into account (by continuous welding of the intersection between the backing and the reinforced member, with a minimum radius of 50 mm for the notches and avoiding any water retention).

The appearance of galvanic coupling, which are produced when there is electrical continuity between two metals of different electro-chemical potential (such as stainless steel and carbon steel), shall be avoided by isolating the surfaces of both metals electrically by means of painting or other procedures.

31.2.2.1. Additional thickness on inaccessible surfaces

Surfaces of steel structures that are subjected to a risk of corrosion, and which are inaccessible for inspections and maintenance and not sealed adequately, shall initially have suitable protection for the design working life, and the thickness of the steel resulting strictly from the structural design shall also be increased by an additional thickness that compensates for the effect of corrosion during the working life.

In the absence of more detailed studies, the additional thickness (increase in nominal thickness) shall have the following minimum value, expressed in mm per inaccessible surface and for every 30 years of the working life planned for the structure:

– exposure classes C4 (high corrosive), C5-I and C5-M (very high corrosive): 1.5 mm;

– exposure class C3 (medium corrosive): 1 mm;

– exposure class C2 (low corrosive): 0.5 mm.

No additional thickness is required for exposure class C1 (very low corrosive).

The resulting thickness (nominal thickness plus additional thickness) for inaccessible bridge caissons shall not be less than 8 mm.

31.2.2.2. Use of steel with improved resistance to atmospheric corrosion

Steel with improved resistance to atmospheric corrosion may be used without protective painting on external surfaces, by increasing the nominal thickness obtained from the calculation by 1 mm for the surface exposed to the external environment. The

TITLE 3 page 23

provisions of subsection 31.2.2.1 (adequate protection system for the design working life, and additional steel thickness) shall apply to the internal surfaces of inaccessible closed sections.

The use of such steel in cases where its surface is supposed to be in contact with the ground or with water for long periods of time, permanently wet, or subject to a marine environment with moderate or high salinity, an industrial environment with high SO3 content, or the presence of deicing salt, requires a detailed examination of whether it is suitable. The surface of the steel shall be protected in such cases.

31.2.3. Construction details

The construction details described as inadequate in the following figures should be avoided, and construction details described as adequate be used. Adequate construction details are those that meet the general criteria given in subsection 31.2.2.

Dirt and water retained

Inadequate Suitable

Discontinuity

Figure 31.2.3.a. Prevention of the accumulation of water and dirt

painting

Difficult to prepare for blast cleaning and

prepare for Easier to

blast cleaning and painting

Figure 31.2.3.b. Welding

TITLE 3 page 24

Closed crack Continuous welds

Crack Inadequate (narrow crack that is difficult to protect)

Better

Suitable (solid, whole component)

Figure 31.2.3.c. Treatment of hollows

Protective paint systems Protective paint systems Protective paint systems

Steel Steel Steel

Acute edge Bevelled edge Rounded edge Inadequate Better Suitable

Figure 31.2.3.d. Elimination of acute edges

Insufficiently flat surface Paint protection systems Smooth welded surface

Irregularities Accumulated dirt

Inadequate Better Suitable

Figure 31.2.3.e. Elimination of imperfections on the welded surface

TITLE 3 page 25

Backing

Web

Notch Welds

Base flap

For notches, r ≥ 50 mm

Figure 31.2.3.f. Recommended backing design for protection against corrosion

31.2.4. Special protective measures

In cases of particularly harsh corrosion, where normal protective measures are inadequate, special protection systems may be used.

The design shall consider the working life of the additional protection, and stipulate an adequate maintenance programme for it.

31.3. Conditions for facilitating inspections and maintenance

Access shall be planned, wherever possible, to all the structure’s members, as well as to the supports, joints and drainage members, and it shall be examined whether it is worth having specific systems in place to facilitate inspection and maintenance during the service phase. Accordingly, and given that including access systems for maintenance in service that were not initially planned is a difficult task, the design shall stipulate the necessary access systems, which may include fixed walkways, motorised platforms or other auxiliary measures.

The fundamental accessibility criterion is that all the structure’s surfaces that are to be inspected and maintained shall be visible and within the reach of the maintenance worker, using a safe method. The worker shall be able to move throughout all parts of the structure that is to be maintained, and shall have sufficient space to work in those parts.

Particular attention shall be paid to the accessibility of closed areas of the structure, such as metal caissons. Access openings shall be of sufficient size to allow safe access, both for workers and for maintenance equipment. Minimum dimensions of 500 x 700 mm (width x height) are recommended for rectangular or oval access points, and a minimum diameter of 600 mm for circular ones. There shall also be suitable ventilation openings for the protection system used for maintenance work.

TITLE 3 page 26