bs.na.en.1993.1.1.2005

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BS NA EN 1993-1-1 (2005) (English): UK NationalAnnex to Eurocode 3. Design of steel structures.General rules and rules for buildings

NA to BS EN 1993-1-1:2005

UK National Annex to Eurocode 3: Design of steel structures Part 1-1 : General rules and rules for buildings

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NA to BS EN 1993-1-1:2005 BRITISH STANDARD

Publishing and copyright information

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© BSI2008

ISBN 978058054960 1

ICS 91.080.10

The following BSI references relate to the work on this standard: Committee reference B/525/31 Draft for comment 07/30128092 DC

Publication history

First published December 2008

Amendments issued since publication

Amd. No. Date Text affected

BRITISH STANDARD

Contents Introduction 1 NA.1 Scope 1

NA to BS EN 1993-1-1 :2005

NA.2 Nationally Determined Parameters 1 NA.3 Decisions on the status of informative annexes 7 NA.4 References to non-contradictory complementary information 7

Bibliography 8

Summary of pages This document comprises a front cover, an inside front cover, pages i to ii, pages 1 to 8, an inside back cover and a back cover.

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BRITISH STANDARD

NA.1

NA to BS EN 1993-1-1 :2005

National Annex (informative) to BS EN 1993-1-1:2005, Eurocode 3: Design of steel structures - Part 1-1: General rules and rules for buildings

Introduction This National Annex has been prepared by BSI Subcommittee B/525/31, Structural use of steel. It is to be used in conjunction with BS EN 1993-1-1:2005.

Scope This National Annex gives:

a) the decisions for the National Determined Parameters described in the following subclauses of BS EN 1993-1-1 :2005:

• 2.3.1(1) • 5.3.2(3) • 6.3.2.4(2)B

• 3.1(2) • 5.3.2(11) • 6.3.3(5)

• 3.2.1(1) • 5.3.4(3) • 6.3.4(1)

• 3.2.2(1) • 6.1 (1) • 7.2.1(1)B

• 3.2.3(1) • 6.1(1)B • 7.2.2(1)B • 3.2.3(3)B • 6.3.2.2(2) • 7.2.3(1)B

• 3.2.4(1)B • 6.3.2.3(1) • BB.1.3(3)B • 5.2.1(3) • 6.3.2.3(2)

• 5.2.2(8) • 6.3.2.4(1)B

b) Decisions on the status of BS EN 1993-1-1 :2005 informative annexes; and

c) References to non-contradictory complementary information.

NA.2 Nationally Determined Parameters

NA.2.1 General Decisions for the Nationally Determined Parameters decided in BS EN 1993-1-1 :2005 are given in clauses NA.2.2 to NA.2.26.

NA.2.2 Actions and environmental influences [BS EN 1993-1-1:2005,2.3.1(1)]

There are no additional regional, climatic or accidental situations to consider.

NA.2.3 Other Steel material and products [BS EN 1993-1-1 :2005, 3.1 (2)]

If other steels are used, due allowance should be made for variations in properties, including ductility and weldability. Further information on the ductility requirements for steel is given in BS EN 1993-1-1:2005,3.2.2(1),

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NA to BS EN 1993-1-1 :2005 BRITISH STANDARD

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Steel castings and forgings may be used for components in bearings, junctions and other similar parts. Castings should conform to BS EN 10293 and forgings should conform to BS EN 10250-2. Further guidance on steel castings is given in reference [1].

For higher strength steels see BS EN 1993-1-12.

NA.2.4 Material properties [BS EN 1993-1-1:2005, 3.2.1(1)] The nominal values of the yield strength fy and the ultimate strength fu for structural steel should be those obtained from the product standard. The ultimate strength fu should be taken as the lowest value of the range given for Rm in the product standard. Further information on the yield and ultimate strength for structural steel is also given in NA.4.

NA.2.S Ductility requirements [BS EN 1993-1-1 :2005, 3.2.2(1)] a) Elastic global analysis

The limiting values for the ratio fJfy, the elongation at failure and the ultimate strain Cu for elastic global analysis are given below.

fJfy, ~ 1.10;

Elongation at failure not less than 15%;

Cu ~ 1S€y.

b) Plastic global analysis

Plastic global analysis should not be used for bridges. For buildings the limiting values for the ratio fjfy, the elongation at failure and the ultimate strain Cu for plastic global analysis are given below.

fJfy ~ 1.15;

Elongation at failure not less than 15%;

Cu ~ 20cy•

NA.2.6 Fracture toughness [BS EN 1993-1-1:2005, 3.2.3(1)] For buildings and other quasi-statically loaded structures the lowest service temperature in the steel should be taken as the lowest air temperature which may be taken as -5°C for internal steelwork and -15°C for external steelwork.

For bridges the lowest service temperature in the steel should be determined according to the NA to BS EN 1991-1-5 for the bridge location. For structures susceptible to fatigue it is recommended that the requirements for bridges should be applied.

In other cases (e.g. the internal steelwork in cold stores) the lowest service temperature in the steel should be taken as the lowest air temperature expected to occur within the intended design life of the structure.

NA.2.7 Toughness properties for members in compression [BS EN 1993-1-1 :2005, 3.2.3(3)B] The recommendations given in the NA to BS EN 1993-1-10 should be used.

BRITISH STANDARD NA to BS EN 1993-1-1:2005

NA.2.8 Through-thickness properties [BS EN 1993-1-1:2005, 3.2.4(1)B] The recommendations given in the NA to BS EN 1993-1-10 should be used.

NA.2.9 Effects of deformed geometry of the structure [BS EN 1993-1-1 :2005, 5.2.1 (3)] For plastic analysis of clad structures provided that the stiffening effects of masonry infill wall panels or diaphragms of profiled steel sheeting are not taken into account:

U cr ~ 10

For plastic analysis of portal frames subject to gravity loads only with -frame imperfections:

provided the following conditions are satisfied:

a) The span, L, does not exceed 5 times the mean height of the columns

b) hr satisfies the criterion:

(h/sa)2 + (h/sbF ::::;; 0.5

in which sa and sb are the horizontal distances from the apex to the columns.

NOTE For a symmetrical frame this expression simplifies to hr ::::;; 0.2SL.

NA.2.10 Structural stability of frames [BS EN 1993-1-1:2005, 5.2.2(8)] This method should only be used for frames that comply with 5.2.2(6). In such cases the sway moments in the beams and beam-to-column connections should be multiplied by kr unless a smaller value is shown to be adequate by analysis. kr may be evaluated using the following expression provided that Ucr ~ 3.0:

k =_1_ r 1

NA.2.11 Design values of initial local bow imperfection [BS EN 1993-1-1 :2005, 5.3.2(3)] For elastic analysis of the cross-section, the initial imperfections for an individual section about a particular axis should be back-calculated from the formula for the buckling curves given in BS EN 1993-1-1:2005, 6.3 using the elastic section modulus.

For plastic analysis of the cross-section, the initial imperfections for an individual section about a particular axis should be back-calculated from the formula for the buckling curves given in BS EN 1993-1-1:2005, 6.3 using the full plastic section modulus.

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NA.2.12 Amplitude of imperfections [BS EN 1993-1-1:2005, 5.3.2(11)] The method given in BS EN 1993-1-1 :2005, 5.3.2(11} should not be used for buildings.

NA.2.13 Imperfections for lateral-torsional bucking in bending [BS EN 1993-1-1 :2005, 5.3.4(3)] The value of k should be taken as 1.0.

NA.2.14 Partial factors for structures not covered by BS EN 1993 Part 2 to Part 6 [BS EN 1993-1-1:2005,6.1(1)] For structures not covered by BS EN 1993 Part 2 to Part 6, the partial factors should be appropriate for the structure and agreed with the client.

NA.2.1S Partial safety factors for buildings [BS EN 1993-1 .. 1 :2005, 6.1(1)] For buildings the following partial factors should be used:

YMO = 1.00

YM1 = 1.00

YM2 = 1.10

NA.2.16 Imperfection factors for lateral torsional buckling [BS EN 1993-1-1 :2005, 6.3.2.2(2)] The recommended values given in BS EN 1993-1-1 :2005, Table 6.3 and Table 6.4 should be used.

NA.2.17 Lateral torsional buckling for rolled sections or equivalent welded sections [BS EN 1993-1-1 :2005, 6.3.2.3(1)] For buildings and bridges the following values of AlT,O and ~ should be used:

a} For rolled sections and hot-finished and cold-formed hollow sections:

ALT;o = 0.4

~ = 0.75

b} For welded sections:

ALT,o = 0.2

~ = 1.00

BRITISH STANDARD

Cross-section

NAto BS EN 1993-1-1:2005

BS EN 1993-1-1:2005, Table 6.5 should be replaced with the following table:

limits Buckling curve

Rolled doubly symmetric I and H sections and hot-finished h/b ~ 2 b hollow sections 2.0 < h/b ~ 3. 1 c

h/b> 3.1 d

Angles (for moments in the major principal plane) d

All other hot-rolled sections. d

Welded doubly symmetric sections and cold-formed h/b ~ 2 c hollow sections 2.0 ~ h/b < 3. 1 d

NA.2.18 Modification factor, f [BS EN 1993-1-1 :2005, 6.3.2.3(2)] The recommended expression for f should be used in which ke is given by:

where:

( Mer for the actual bending moment diagram

1 Mer for a uniform bending moment diagram

values of (1 are given in the references listed in NA.4.

NA.2.19 The slenderness limit Aco [BS EN 1993 .. 1-1:2005, 6.3.2.4(1)B]

For I, H, channel and box sections used in buildings the value of Aeo should be taken as 0.4.

NA.2.20 Modification factor, kfl [BS EN 1993 .. 1-1 :2005, 6.3.2.4(2)B] The value of the modification factor kfl should be taken as:

kfl = 1.0 for hot rolled I-sections;

kfl =1.0 for welded I-sections with h/b ~ 2;

kfl = 0.9 for other sections.

NA.2.21 Interactions factors kyy, kyz, kzyand kzz [BS EN 1993-1-1 :2005, 6.3.3(5)] The interaction factors kyy, kyz' kzy, kzz for doubly symmetric sections may be determined using either alternative Method 1 (given in BS EN 1993-1-1 :2005, Annex A) or alternative Method 2 (given in BS EN 1993-1-1 :2005, Annex B). Alternative Method 2 (given in BS EN 1993-1-1:2005, Annex B) may also be used for sections that are not doubly symmetric when modified in accordance with NA.3.2.

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Vertical deflection

Cantilevers

NA.2.22 General method for lateral and lateral torsional buckling of structural components [BS EN 1993-1-1 :2005, 6.3.4(1)] This method is only valid for nominally straight components subject to in-plane monoaxial bending and/or compression.

In this method Xop should be taken as the minimum value of X and XLT' Where X is determined in accordance with BS EN 1993-1-1 :2005, 6.3.1 for lateral buckling and XLT is determined in accordance with BS EN 1993-1-1 :2005, 6.3.2 for lateral torsional buckling

NA.2.23 Vertical deflections [BS EN 1993-1-1:2005, 7.2.1(1)B] The following table gives suggested limits for calculated vertical deflections of certain members under the characteristic load combination due to variable loads and should not include permanent loads. Circumstances may arise where greater or lesser values would be more appropriate. Other members may also need deflection limits.

On low pitch and flat roofs the possibility of ponding should be investigated.

Beams carrying plaster or other brittle finish

Other beams (except purlins and sheeting rails)

Purlins and sheeting rails

Length/180

Span/360

Span/200

To suit the characteristics of particular cladding

Horizontal deflection

NA.2.24 Horizontal deflections [BS EN 1993-1-1:2005, 7.2.2(1)B] The following table gives suggested limits for calculated horizontal deflections of certain members under the characteristic load combination due to variable load. Circumstances may arise where greater or lesser values would be more appropriate. Other members may also need deflection limits.

Tops of columns in single-storey buildings except portal frames

Heightl300

Columns in portal frame buildings, not supporting crane runways

In each storey of a building with more than one storey

To suit the characteristics of the particular cladding

Height of that storey/300

NA.2.2S Dynamic effects [BS EN 1993-1-1:2005, 7.2.3(1)B]

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Reference should be made to specialist literature as appropriate. For floor vibrations see NA.4.

BRITISH STANDARD NA to BS EN 1993-1-1:2005

NA.2.26 Hollow section buckling lengths in lattice girders [BS EN 1993-1-1 :2005, BB.1.3(3)B] The recommended values may be used and further information is given in NA.4.

NA.3 Decisions on the status of informative annexes

NA.3.1 BS EN 1993-1-1:2005, Annex A BS EN 1993-1-1 :2005, Annex A may be used. The scope of Method 1 given in Annex A should be limited to doubly symmetric sections.

NA.3.2 BS EN 1993-1-1:2005, Annex B BS EN 1993-1-1 :2005, Annex B may be used.

Where applied to sections that are not doubly symmetric Xz and Xz should be taken as the values of X and X from the highest value of \ to BS EN 1993-1-1, 6.3.1.3 or X to BS EN 1993-1-1, 6.3.1.4.

Where the sections are not I, H or hollow sections Class 1 and Class 2 sections should be designed as Class 3 sections.

NA.3.3 BS EN 1993-1-1:2005, Annex AB BS EN 1993-1-1:2005, Annex AB may be used.

NA.3.4 BS EN 1993 .. 1-1:2005, Annex BB BS EN 1993-1-1 :2005, Annex BB may be used.

NA.4 References to non-contradictory complementary information References cited in this National Annex to non-contradictory, complementary information can be found at www.steel-ncci.co.uk. Whilst this material is likely to be technically authoritative, not all of it has been reviewed by the UK national committee, and users should satisfy themselves of its fitness for their particular purpose. In particular, they should be aware that material indicated as not having been endorsed by the committee might contain elements that are in conflict with the Eurocode.

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BRITISH STANDARD

Bibliography

Standards publications For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

NA to BS EN 1991-1-5, UK National Annex to Eurocode 3: Design of steel structures - Part 1-5: Plated structural elements

BS EN 1993 {Parts 2 to 6}, Eurocode 3 - Design of steel structures

NA to BS EN 1993-1-101), UK National Annex to Eurocode 3: Design of steel structures - Part 1-10: Material toughness and through-thickness properties

BS EN 1993-1-12, Eurocode 3: Design of steel structures - Part 1-12: Supplementary rules for high strength steels

BS EN 10025-2:2004, Hot rolled products of structural steels - Part 2: Technical delivery conditions for non-al/oy structural steels

BS EN 10250-2, Open steel die forgings for general engineering purposes Part 2: Non-alloy quality and special steels

BS EN 10293, Steel castings for general engineering uses

Other publications [1] Castings in steel construction, SCI publication P 172, The Steel

Construction Institute, Silwood Park, Ascot, Berkshire SLS 70N.

1) In preparation.

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