Research
Research
Prog
Prog
ramme
ramme
Engineering
Engineering
Design of railway structures
Design of railway structures
to the structural Eurocodes
to the structural Eurocodes
Part 1
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Development for permission. Any additional queries can be directed to [email protected]@rssb.co.uk.. This publication can be accessed via the RSSB website:
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Disclaimer
This document has been prepared for the titled project or named part thereof and should not be relied This document has been prepared for the titled project or named part thereof and should not be relied upon or used for any other project without an independent check
upon or used for any other project without an independent check being carried out as to its suitability andbeing carried out as to its suitability and prior written authority of Mott MacDonald being obtained.
prior written authority of Mott MacDonald being obtained. Mott MacDonald accepts no responsibility orMott MacDonald accepts no responsibility or liability for the consequence of this document being used for
liability for the consequence of this document being used for a purpose other than the purpa purpose other than the purp oses for whichoses for which it was commissioned.
it was commissioned. Any person using or relying on the document for such other purpose agrees, andAny person using or relying on the document for such other purpose agrees, and will by such use or reliance be taken to confirm his agreement to indemnify Mott MacDonald for all loss will by such use or reliance be taken to confirm his agreement to indemnify Mott MacDonald for all loss or damage resulting therefrom.
or damage resulting therefrom. Mott MacDonald accepts no responsibility or liabiliMott MacDonald accepts no responsibility or liability for this documentty for this document to any party other than the person by whom it was commissioned.
to any party other than the person by whom it was commissioned. To the extent that this report
To the extent that this report is based on information supplied by other is based on information supplied by other parties, Mott MacDonald acceptsparties, Mott MacDonald accepts no liability for any loss or damage suffered by the client, whether contractual or tortious,
no liability for any loss or damage suffered by the client, whether contractual or tortious, stemming fromstemming from
any conclusions based on data supplied by parties other than Mott MacDonald and used by Mott any conclusions based on data supplied by parties other than Mott MacDonald and used by Mott Mac-Donald in preparing this report.
Copyright
Copyright
© RAIL S
© RAIL SAFETY AFETY AND STANDAND STANDARDS BOARD ARDS BOARD LTD. 20LTD. 2009 ALL 09 ALL RIGHTS RIGHTS RESERVERESERVEDD This publication may be reproduced free of charge
This publication may be reproduced free of charge for research, private study or for internalfor research, private study or for internal circulation within an organisation. This is subject to it being reproduced
circulation within an organisation. This is subject to it being reproduced and referencedand referenced accurately and not being used in a misleading context. The material must be acknowledged as accurately and not being used in a misleading context. The material must be acknowledged as the copyright of Rail Safety and Standards Board and the
the copyright of Rail Safety and Standards Board and the title of the publication specifiedtitle of the publication specified accordingly. For any other use of the material please apply
accordingly. For any other use of the material please apply to RSSB's Head of Research andto RSSB's Head of Research and Development for permission. Any additional queries can be directed to
Development for permission. Any additional queries can be directed to [email protected]@rssb.co.uk.. This publication can be accessed via the RSSB website:
This publication can be accessed via the RSSB website: www.rssb.co.ukwww.rssb.co.uk..
Disclaimer
Disclaimer
This document has been prepared for the titled project or named part thereof and should not be relied This document has been prepared for the titled project or named part thereof and should not be relied upon or used for any other project without an independent check
upon or used for any other project without an independent check being carried out as to its suitability andbeing carried out as to its suitability and prior written authority of Mott MacDonald being obtained.
prior written authority of Mott MacDonald being obtained. Mott MacDonald accepts no responsibility orMott MacDonald accepts no responsibility or liability for the consequence of this document being used for
liability for the consequence of this document being used for a purpose other than the purpa purpose other than the purp oses for whichoses for which it was commissioned.
it was commissioned. Any person using or relying on the document for such other purpose agrees, andAny person using or relying on the document for such other purpose agrees, and will by such use or reliance be taken to confirm his agreement to indemnify Mott MacDonald for all loss will by such use or reliance be taken to confirm his agreement to indemnify Mott MacDonald for all loss or damage resulting therefrom.
or damage resulting therefrom. Mott MacDonald accepts no responsibility or liabiliMott MacDonald accepts no responsibility or liability for this documentty for this document to any party other than the person by whom it was commissioned.
to any party other than the person by whom it was commissioned. To the extent that this report
To the extent that this report is based on information supplied by other is based on information supplied by other parties, Mott MacDonald acceptsparties, Mott MacDonald accepts no liability for any loss or damage suffered by the client, whether contractual or tortious,
no liability for any loss or damage suffered by the client, whether contractual or tortious, stemming fromstemming from
any conclusions based on data supplied by parties other than Mott MacDonald and used by Mott any conclusions based on data supplied by parties other than Mott MacDonald and used by Mott Mac-Donald in preparing this report.
1 1
Applicable British Standards, Eurocodes, National Annexes and Other Referenced Publications Applicable British Standards, Eurocodes, National Annexes and Other Referenced Publications Glossary
Glossary Summary
Summary S-1S-1
Chapters and Appendices Chapters and Appendices 1
1 Recommended Recommended Values Values where where National National Choice Choice is is Allowed Allowed in in BS BS EN EN 1990:2002. 1990:2002. 2424 2
2 Recommended Values where National Choice is Allowed in Recommended Values where National Choice is Allowed in Eurocodes, other than BS ENEurocodes, other than BS EN 1990:2002
1990:2002 + + A1:2005. A1:2005. 3333
3
3 Part Part 1 1 - - Enhancement Enhancement of of Previous Previous Studies Studies 4242
3.1
3.1 Load Load Comparison Comparison Factor Factor 4242
4
4 Comparison Comparison of of Design Design Load Load Effects Effects 4343
4.1
4.1 Partial Partial and and Combination Combination Factors Factors 4343
4.1.1
4.1.1 Eurocodes Eurocodes 4343
4.1.2
4.1.2 British British Standards Standards 4444
4.1.3
4.1.3 Deck Deck Types Types 4545
4.2
4.2 Variation of Load Classification Factor,Variation of Load Classification Factor, αα. . 4646 4.3
4.3 Variation of Dynamic Load Factor, Ф.Variation of Dynamic Load Factor, Ф. 5050 5
5 Live Live Load Load Surcharge Surcharge on on Substructures Substructures 5353
5.1
5.1 Differences Differences in in Applied Applied Actions Actions 5353
6
6 Longitudinal Longitudinal Actions Actions 5555
6.1
6.1 Traction Traction 5555
6.2
6.2 Braking Braking 5858
7
7 Accidental Accidental Actions Actions 6161
7.1
7.1 Derailment Derailment Effects Effects 6161
7.2
7.2 Collision Collision Effects Effects 6464
8
8 Vertical Vertical Deformation Deformation and and Rotation Rotation 6666
9
9 Wind Wind Effects Effects 6969
9.1
9.1 Wind Wind - - Ultimate Ultimate Limit Limit State State 7272
9.1.1
9.1.1 Summary Summary of of ULS ULS Wind Wind Combination Combination Results Results 7373 9.2
9.2 Wind Wind - - Serviceability Serviceability Limit Limit State State 7474
9.2.1
9.3
9.3 Discussion Discussion 7676
9.3.1
9.3.1 Wind Wind Only Only 7676
9.3.2
9.3.2 Wind Wind (Leading) (Leading) and and Railway Railway Traffic Traffic 7676
9.3.3
9.3.3 Railway Railway Traffic Traffic (Leading) (Leading) and and Wind Wind 7777
10
10 Temperature Temperature Effects Effects 7878
10.1
10.1 Ultimate Ultimate Limit Limit State State Actions Actions 7878
10.2
10.2 Serviceability Serviceability Limit Limit State State Actions Actions 7979
10.3
10.3 Global Global Temperature Temperature Effects Effects 8080
10.4
10.4 Discussion Discussion 8181
10.5
10.5 Thermal Thermal Gradient Gradient Effects Effects 8282
10.5.1
10.5.1 Temperature Temperature Only Only 8282
10.5.2
10.5.2 Temperature Coexistent with Railway Loading, Temperature Leading ActionTemperature Coexistent with Railway Loading, Temperature Leading Action 82
82 10.5.3
10.5.3 Temperature Coexistent with Railway Loading, Railway Loading LeadingTemperature Coexistent with Railway Loading, Railway Loading Leading Action 83
Action 83 10.5.4
10.5.4 Conclusion Conclusion 8383
11
11 Groups Groups of of Loads Loads 8484
List of Figures List of Figures
Figure 1: ULS Moments in Very
Figure 1: ULS Moments in Very Light Bridge Main Girder for Variation of Light Bridge Main Girder for Variation of α (Alpha)α (Alpha) 4747 Figure 2
Figure 2: ULS Moments in Medium Weight Bridge Main Girder for Variation of α : ULS Moments in Medium Weight Bridge Main Girder for Variation of α (Alpha)(Alpha) 4747 Figure 3:
Figure 3: ULS Moments ULS Moments in Very Heavin Very Heavy Bridge Mainy Bridge Main Girder for Variation of α (Alpha)Girder for Variation of α (Alpha) 4848 Figure 4: ULS Shear in Very Light Bridge Main
Figure 4: ULS Shear in Very Light Bridge Main Girder for Variation of α (Alpha)Girder for Variation of α (Alpha) 4949 Figure 5: ULS Shear in Medium Weight Bridge Main Girder for Variation
Figure 5: ULS Shear in Medium Weight Bridge Main Girder for Variation of α (Alpha)of α (Alpha) 4949 Figure 6: ULS Shear in Very Heavy Bridge Main
Figure 6: ULS Shear in Very Heavy Bridge Main Girder for Variation of α (Alpha)Girder for Variation of α (Alpha) 5050 Figure 7: ULS Shear in Medium Weight Bridge Main Girder for Variation
Figure 7: ULS Shear in Medium Weight Bridge Main Girder for Variation of Φof Φ 5252
Figure 8: ULS Shear in Very Heavy Bridge Main
Figure 8: ULS Shear in Very Heavy Bridge Main Girder for Variation of ΦGirder for Variation of Φ 5252 Figure
Figure 9: 9: Comparison Comparison between between Characteristic Characteristic (Nominal) (Nominal) Traction Traction Forces Forces 5757 Figure
Figure 10: 10: Comparison Comparison between between ULS ULS Traction Traction Forces Forces 5757
Figure
Figure 11: 11: Comparison Comparison between between Characteristic Characteristic (Nominal) (Nominal) Braking Braking Forces Forces 5959 Figure
Figure 12: 12: Comparison Comparison between between ULS ULS Braking Braking Forces Forces 6060
Figure
Figure 13: 13: Comparison Comparison between between Characteristic Characteristic (Nominal) (Nominal) & ULS & ULS Longitudinal Longitudinal Train Train Forces Forces 6060 Figure
Figure 14: 14: Design Design Moments Moments due due to to Derailment Derailment Effects Effects 6262 Figure
Figure 15: 15: Design Design Shears Shears due due to to Derailment Derailment Effects Effects 6363 Figure
Figure 16: 16: BS BS EN EN 1991-2 1991-2 Table Table 6.11 6.11 Groups Groups of of Loads Loads 8484
List of Tables List of Tables Table
Table 1: 1: Documents Documents and and Standards Standards Referenced Referenced Throughout Throughout the the Study Study 77 Table
Table 2: 2: Recommended Recommended Values Values in in BS BS EN EN 1991-1-1 1991-1-1 3333
Table
Table 3: 3: Recommended Recommended Values Values in in BS BS EN EN 1991-2 1991-2 3535
Table
Table 4: 4: Alternative Alternative Values Values for for Traction Traction and and Braking Braking BS BS EN EN 1991-2 1991-2 3636 Table
Table 5: 5: Recommended Recommended Values Values in in BS BS EN EN 1992-2 1992-2 3737
Table
Table 6: 6: Recommended Recommended Values Values in in BS BS EN EN 1993-2 1993-2 3939
Table
Table 7: 7: Recommended Recommended Values Values in in BS BS EN EN 1994-2 1994-2 4040
Table 8: Eurocode SLS Partial
Table 8: Eurocode SLS Partial and Combination Factors used for Investigatingand Combination Factors used for Investigatingα and Φα and Φ 4343 Table 9: Eurocode ULS Partial
Table 9: Eurocode ULS Partial and Combination Factors used for Investigatingand Combination Factors used for Investigating α and Φα and Φ 4444 Table 10: Eurocode ACC Partial and
Table 10: Eurocode ACC Partial and Combination Factors used for InvestigatingCombination Factors used for Investigating α and Φα and Φ 4444 Table 11: British Standards SLS Partial
3
Table 15: Range of Factor Φ Considered i n Study 51
Table 16: British Standards Live Load Surcharge Values and Partial Factors 53
Table 17: Eurocode Live Load Surcharge Values and Partial Factors 53
Table 18: Comparison of the Live Load Surcharge Effects on Typical Retaining Structures 54
Table 19: Comparison between Traction Forces 56
Table 20: Comparison between Braking Forces 58
Table 21: Derailment Loads 62
Table 22: Eurocode Collision Loading (Class A Structures) 64
Table 23: GC/RC5510 Collision Loading 65
Table 24: Comparison of Design Criteria for a Typical Pier in the Hazard Zone 65
Table 25: Comparison of Deflections for the Typical Decks Studied 66
Table 26: Summary of Deck Type 5 (Pre-stressed Concrete Beams) Deflections 66
Table 27: Eurocode ULS Partial and Combination Factors used for Wind Study 72
Table 28: British Standards ULS Partial and Combination Factors used for Wind Study 72
Table 29: Summary of ULS Wind Combination Results 73
Table 30: Eurocodes SLS Partial and Combination Factors used for Wind Study 74
Table 31: British Standards SLS Partial and Combination Factors used for Wind Study 74
Table 32: Summary of SLS Wind Combination Results 75
Table 33: Eurocode ULS Partial and Combination Factors used for Temperature Study 78
Table 34: British Standards ULS Partial and Combination Factors used for Temperature Study 79
Table 35: Eurocode SLS Partial and Combination Factors used for Temperature Study 79
Table 36: British Standards SLS Partial and Combination Factors used for Temperature Study 80
Table 37: Summary of Expansion and Contraction with T0Specified (+/- 10°C) 80
Applicable British Standards, Eurocodes, National Annexes and Other
Referenced Publications
Standard or Report Reference Title Date Published
BS 5400-1:1998 Incorporating Amendment No. 1
Steel, concrete and composite bridges — Part 1: General statement
12 March 2003
BS 5400-2:2006 Steel, Concrete and Composite
Bridge Part 2: Specification for Loads
September 2006
BS 5400-3:2000 Incorporating Corrigendum No. 1
Steel, concrete and composite bridges – Part3: Code of practice for design of steel bridges
May 2001
BS 5400-4:1990 Steel, concrete and
composite bridges —
Part 4: Code of practice for design of concrete bridges June 1990 BS 5400-5:1979 Reprinted, incorporating Amendment No. 1
Steel, concrete and
composite bridges —
Part 5: Code of practice for design of
composite bridges
May 1982
BS 5400-10:1980:1980
Incorporating Amendment No. I
Steel, concrete and composite bridges
-Part 10: Code of practice for fatigue
March 1999
BS 7608:1993 Incorporating Amendment No. 1
Code of practice for Fatigue design and assessment of steel structures
April 1993
BS 8002:1994 Code of practice for earth
retaining structures
April 1994
GC/RT5110 Design Requirements for
Structures
August 2000
GC/RT5112 Loading Requirements for the
Design of Bridges
May 1997
GC/RC5510 Recommendations for the
Design of Bridges
August 2000
NR/GN/CIV/025 The Structural Assessment of
Underbridges
June 2006
BS EN 1990:2002 Eurocode — Basis of Structural
Design
April 2002 DRAFT National Annex to BS
EN 1990:2002
UK National Annex to
Eurocode – Basis of Structural Design
2006
BS EN 1991-1-1:2002 Eurocode 1: Actions on
Structures – Part 1-1: General Actions – Densities, Self-weight, Imposed Loads for Buildings
5
BS EN 1991-1-3:2003 Eurocode 1 — Actions on
structures — Part 1-3: General
actions — Snow loads
July 2003
BS EN 1991-1-4:2005 Eurocode 1: Actions on
structures - Part 1-4: General actions - Wind actions
April 2005
DRAFT National Annex to BS EN 1991-1-4:2005
UK National Annex to
Eurocode 1 - Part 1-4: General actions - Wind actions
June 2005
BS EN 1991-1-5:2003 Eurocode 1: Actions on
structures — Part 1-5: General
actions — Thermal actions
March 2004
National Annex to BS EN 1991-1-5:2003
UK National Annex to
Eurocode 1 — Part 1-5: General
actions — Thermal actions
April 2007
BS EN 1991-1-7:2005 Eurocode 1: Actions on
structures — Part 1-7: General
actions — Accidental
actions
September 2006
DRAFT National Annex to BS EN 1991-2:2003
UK National Annex to Eurocode 1: Actions on Structures – Part2: Traffic Loads on Bridges Draft, dated 07/08/03. National Annex to BS EN 1991-1-3:2003 UK National Annex to Eurocode 1: Actions on structures —
Part 1-3: General actions —
Snow loads
December 2005
DRAFT National Annex to BS EN 1991-1-4:2005
UK National Annex to Eurocode 1: Actions on structures - Part 1-4: General actions - Wind actions
June 2005 National Annex to BS EN 1991-1-5:2003 UK National Annex to Eurocode 1: Actions on structures –
Part 1-5: General actions – Thermal actions
April 2007
BS EN 1992-1-1:2004 Eurocode 2: Design of Concrete
Structures Part 1-1: General Rules and Rules for Buildings
December 2004
National Annex to BS EN 1992-1-1:2004
UK National Annex to
Eurocode 2: Design of Concrete Structures Part 1-1: General Rules and Rules for Buildings
December 2005
BS EN 1992-2:2005 Eurocode 2: Design of Concrete
Structures Part 2: Concrete Bridges Design and Detailing Rules
National Annex to BS EN 1992-2:2005
UK National Annex to
Eurocode 2: Design of concrete structures. Concrete bridges -Design and detailing rules
December 2007
BS EN 1993-1-1:2005 Eurocode 3: Design of Steel
Structures - Part 1-1: General Rules and Rules for Buildings
May 2005
DRAFT National Annex 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
Undated Draft.
BS EN 1993-1-5:2006 Eurocode 3: Design of Steel
Structures - Part 1-5: Plated Structural Elements
October 2006
BS EN 1993-1-8:2005 Eurocode 3: Design of Steel
Structures - Part 1-8: Design of Joints
May 2005
BS EN 1993-1-9:2005 Eurocode 3: Design of Steel
Structures - Part 1-9: Fatigue
May 2005 DRAFT National Annex to BS
EN 1993-1-9:2005
UK National Annex to Eurocode 3: Design of Steel Structures Part 1-9: Fatigue
July 2007
BS EN 1993-2:2006 Eurocode 3: Design of Steel
Structures - Part 2: Steel Bridges
October 2006
DRAFT National Annex to BS EN 1993-2:2006
UK National Annex to Eurocode 3: Design of Steel Structures Part 2: Steel Bridges
May 2007
BS EN 1994-1-1:2004 Eurocode 4: Design of
composite steel and concrete structures — Part 1-1: General rules and rules for buildings
February 2005
BS EN 1994-2:2005 Eurocode 4 — Design of
composite steel and concrete structures — Part 2: General rules and rules for bridges
December 2005
National Annex to BS EN 1994-2:2005
UK National Annex to Eurocode 4: Design of composite steel and concrete structures – Part 2: General Rules and rules for bridges
December 2007
BS EN 1997-1:2004 Eurocode 7: Geotechnical
Design Part 1: General Rules
December 2004
BS EN 1997-2:2007 Eurocode 7: Geotechnical
Design Part 2: Ground Investigation and Testing
April 2007
ISBN No. 978-0-7277-3160-9 Designer‘s Guide toBS 1993-2
– C.R. Hendy and C.J.Murphy,
Series Editor Haig Gulvanessian
7
Bridges – C.R. Hendy and D.A.
Smith, Series Editor Haig Gulvanessian
NETWORK RAIL REPORT Appraisal of Eurocode for
Railway Loading (by Scott Wilson for Network Rail)
July 2003
T696 Appraisal of Eurocodes for
Railway Loading
January 2008 RSSB REPORT
13410/R01 Rev B
EN 1992 Design Criteria for railway (by Gifford for RSSB)
May 2007
ERRI D216/RP1 ERRI Fatigue of Railway
Bridges, State of the Art Report
September 1999
96/48/EC Council Directive 96/48/EC on
the interoperability of the trans European high-speed rail system
(referenced throughout this
document as the High Speed TSI)
July 1996
2001/16/EC Directive 2001/16/EC of the
European Parliament and of the Council on the interoperability on the conventional rail system (referenced throughout this document as the Conventional RailTSI)
March 2001
UIC776-3 1st Edition Deformation of Bridges January 1989
UIC776-1 5th Edition Loads to be considered in
railway bridge design
August 2006
Glossary
Terms
Term Document Item
ACC BS EN 1990:2002 Accidental design situation
British Standards Not Applicable The current British Standards
used in bridge design that include the BS5400 suite of standards and Network Rail and Railway Group Standards
BS Not Applicable British Standard
EN Not Applicable Euronorm (Eurocode)
EQU BS EN 1990:2002 Limit state for loss of static
equilibrium of the structure or any part of it considered as a rigid body, where:
minor variations in the value or the spatial distribution of actions from a single source are significant, and
the strengths of construction
materials or ground are
generally not governing.
FAT BS EN 1990:2002 Limit state for fatigue failure of
the structure or structural members
GEO BS EN 1990:2002 Limit state for the failure or
excessive deformation of the ground where the strengths of soil or rock are significant in providing resistance.
Mott MacDonald Not Applicable Mott MacDonald
NA Not Applicable National Annex
Nom Not Applicable Nominal (equivalent to
characteristic in BS )
RSSB Not Applicable Railway Safety and Standards
Board
Seismic BS EN 1990:2002 Seismic design situation
SLS Not Applicable Serviceability Limit State
STR BS EN 1990:2002 Limit state for internal failure or
excessive deformation of the structure or structural members, including footings, piles,
basement walls etc, where the strength of construction
materials of the structure governs.
TSI Not Applicable Technical Specification for
Interoperability (mandatory)
UIC Not Applicable International Union of Railways
9
γfL BS 5400-2:2006 Partial factor for a load
γf3 BS 5400-3:2000
BS 5400-4:1990 BS 5400-5:1979
A factor that takes account of inaccurate assessment of the effects of loading, unforeseen stress distribution in the structure, and variations in dimensional accuracy achieved in construction.
γm BS 5400-3:2000
BS 5400-4:1990 BS 5400-5:1979
Partial factor for a material property, also accounting for model uncertainties and dimensional variations
τl BS 5400-3:2000 Limiting shear strength of web
τy BS 5400-3:2000 Shear strength
φ BS 5400-3:2000 Aspect ratio of a web panel
mfw BS 5400-3:2000 Factor used in determining
limiting shear strength
MR BS 5400-3:2000 Limiting moment of resistance
MULT BS 5400-3:2000 Moment of resistance if lateral
torsional buckling is prevented
G BS EN 1990:2002 Partial factor for permanent
actions.
P BS EN 1990:2002 Partial factor for Pre-stressing
actions
Q BS EN 1990:2002 Partial factor for variable
actions
BS EN 1990:2002 Partial factor for the
combination of actions
α BS EN 1991-2:2003 Load classification factor
applied to characteristic loading for railway lines carrying rail traffic which is heavier or lighter than normal rail traffic.
Φ BS EN 1991-2:2003 Dynamic factor which enhances
the static load effects under Load Models 71, SW/0 & SW/2
Qvk BS EN 1991-2:2003 Value of Vertical point loads in
Load Models
qvk BS EN 1991-2:2003 Value of Vertical uniformly
distributed loads in Load Models
γM BS EN 1992 (all)
BS EN 1993 (all) BS EN 1994 (all)
Partial factor for a material property, also accounting for model uncertainties and dimensional variations
Mcr BS EN 1993-1-1:2005 Elastic Critical Moment.
d0 BS EN 1993-1-8:2005 the hole diameter for a bolt
f ub BS EN 1993-1-8:2005 ultimate tensile strength for bolt
f u BS EN 1993-1-8:2005 ultimate tensile strength
e1 BS EN 1993-1-8:2005 the end distance from the centre
end of any part, measured in the direction of load transfer
p1 BS EN 1993-1-8:2005 the spacing between centres of
fasteners in a line in the direction of load transfer
η BS EN 1994-1-1:2004 Degree of shear connection;
11
Eurocodes and the current British Standards was awarded by RSSB to Mott MacDonald in August
2007. This report summarises Mott MacDonald‘s findings and experiences in using the Eurocodes.
Headline results are included in this summary section, along with outline details of the methodology used in achieving the objectives set out below. The main text of the report provides more details of the study and the principal outcomes. The appendices give a detailed breakdown of the work undertaken including graphs and a comprehensive results summary. Calculations supporting the results and conclusions reported were supplied to RSSB and may be available upon request. However, caution must be used as many of the standards and national annexes have been revised since the draft versions used in this study.
Objectives
The objectives of study T741, the design of railway structures to the Structural Eurocodes, are summarised below:
Recommend values where national choice is permitted in BS EN 1990:2002.
Confirm the appropriateness of the recommended values in the Eurocodes, other than BS EN 1990, where national choice is permitted.
Complete and update earlier studies into the differences in actions (by other parties for Network Rail and RSSB).
Compare the margin of capacity (utilisation) between the design of typical railway structural elements to current British Standards and the Eurocodes.
Discuss significant differences between the current British Standards and the Eurocodes. Provide a commentary on the lessons learned from using the Eurocodes.
Methodology
In achieving the majority of the study‘s objectives, the detailed design of selected details for a number of typical railway bridges was undertaken. This enabled Mott MacDonald to determine a comparison between the margin of capacity (utilisation) for a variety of bridge components and to identify issues arising from design using the Eurocodes. The designs, to both the current British Standards and the Structural Eurocodes, were augmented by a series of stand alone studies that included:
Investigating the sensitivity of varying the line classification factor, α, a factor for non -standard railway loads.
Investigating the sensitivity of varying the dynamic factor, Φ, for railway loads in determining shear effects.
Consideration of ‗Groups of Loads‘
Consideration of load effects not critical in designing the selected elements of the typical structures (for example wind and temperature).
Design of Railway Structures to the Structural Eurocodes
12 Summary of Study
The principal findings of the study are summarised in the table below. The results of design comparisons between the British Standards and the Eurocodes are described and discussed in more detail in the main text. The number of typical structures considered was limited to six superstructures and a generic substructure. Only the factors encountered during the design of the selected elements have been varied.
Description of Investigation Relevant Standards (refer to list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Recommending values where national choice is permitted in BS EN 1990:2002
BS EN 1990:2002 + A1:2005 (Annex A2)
Draft National Annex to BS EN 1990:2002 + A1:2005 (Annex A2)
The values in the draft National Annex are recommended with the following exceptions:
Table A2.4 (STR/GEO) (Set B) & (Set C), γQ,Supfor wind. Draft National Annex value = 1,70. Recommended value = 1,50 to avoid over-design of wind-sensitive elements. Table A2.4 (STR/GEO) (Set B), γG,Supfor superimposed loads. Draft National Annex value = 1,20. Recommended value = 1,35 for ballast to ensure equivalent load effects as current British Standards.
Confirming the appropriateness of the recommended values in the Eurocodes other than BS EN 1990 where national choice is permitted.
Note only the factors c onsidered in the design of typical elements agreed with RSSB have been considered.
BS EN 1991-1-1:2002
National Annex to BS EN 1991-1-1:2002
The values in the National Annex are recommended with the following exception: cl. 5.2.3 (1), the lower characteristic value of the density of ballast. National Annex value = 17kN/m3. Recommended value = 18kN/m3for design of structural elements. Note that dynamic effects were not considered in this study and the recommended value is generally taken as 17kN/m3for dynamic analyses.
Typical bridge designs BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The values in the draft National Annex are recommended.
Design of Railway Structures to the Structural Eurocodes
Description of Investigation Relevant Standards (refer to list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Typical bridge designs BS EN 1992-2:2005
National Annex BS EN 1992-2:2005 dated 31/12/2007
The values in the draft National Annex are recommended.
Typical bridge designs BS EN 1993-2:2006
Draft National Annex BS EN 1993-2:2006 dated 02/05/2007
The values in the draft National Annex are recommended.
Typical bridge designs BS EN 1994-2:2005
National Annex not available
The values in the Eurocode are recommended.
Investigating the sensitivity of varying the line classification factor, α
BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The use of α = 1,1 will be mandatory for the design of new railway structures following the implementation of the Technical Specifications for Interoperability (Conventional Rail and High Speed Infrastructure TSI). ULS assessment is comparable with British Standards. SLS assessment will be more onerous but is unlikely to result in significant changes in section sizes, quantities of reinforcement or numbers of connectors. Uncertainty surrounding the validity of simple FAT
assessment: BS EN 1991-2:2003 states simple FAT assessment not valid if α > 1,0 (see Error! Reference source not found. ).
Investigating the sensitivity of varying the dynamic factor, Φ
BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The use of Φ3for calculating shear effects due to transient load is recommended. The increased shear force due to the use of Φ3combined with α = 1,1 will lead to higher shear forces calculated in accordance with the Eurocodes compared with the current British Standards. The increase is unlikely to result in significant changes in section sizes or connection details.
13 publication)
Typical bridge designs BS EN 1992-2:2005
National Annex BS EN 1992-2:2005 dated 31/12/2007
The values in the draft National Annex are recommended.
Typical bridge designs BS EN 1993-2:2006
Draft National Annex BS EN 1993-2:2006 dated 02/05/2007
The values in the draft National Annex are recommended.
Typical bridge designs BS EN 1994-2:2005
National Annex not available
The values in the Eurocode are recommended.
Investigating the sensitivity of varying the line classification factor, α
BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The use of α = 1,1 will be mandatory for the design of new railway structures following the implementation of the Technical Specifications for Interoperability (Conventional Rail and High Speed Infrastructure TSI). ULS assessment is comparable with British Standards. SLS assessment will be more onerous but is unlikely to result in significant changes in section sizes, quantities of reinforcement or numbers of connectors. Uncertainty surrounding the validity of simple FAT
assessment: BS EN 1991-2:2003 states simple FAT assessment not valid if α > 1,0 (see Error! Reference source not found. ).
Investigating the sensitivity of varying the dynamic factor, Φ
BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The use of Φ3for calculating shear effects due to transient load is recommended. The increased shear force due to the use of Φ3combined with α = 1,1 will lead to higher shear forces calculated in accordance with the Eurocodes compared with the current British Standards. The increase is unlikely to result in significant changes in section sizes or connection details.
Design of Railway Structures to the Structural Eurocodes
14 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Braking BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS5400-2:2006
The values in the current British Standard are recommended in the National Annex. The characteristic braking forces in the BS are greater than the Eurocode values. A maximum braking force of 6000kN is specified in the Eurocode. No such cut off exists in the current British Standards. At ULS the differences are less and for loaded lengths above 305m the Eurocode values are greater, until the maximum value is achieved. Design to the current Eurocode values for loaded lengths <300m, will make the design of substructures within the allowable horizontal movement limits, the design of bearings resisting longitudinal forces and, e nsuring lateral stability of substructures, will be less onerous. Note that traction will govern the design of short and medium spans (up to 30m using the current British Standard and, up to 45m using Eurocode). Traction BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The values in the current British Standard are recommended in the National Annex. The characteristic traction forces in the BS are greater than the Eurocode values for spans less than 14.7m. Above 14.7m the Eurocode characteristic values are greater. The maximum characteristic traction force in the BS is 750kN compared with 1000kN specified in the Eurocode. The differences in the ULS values are similar. Design to the current Eurocode will make the design of, bearings resisting longitudinal forces, ensuring lateral stability of substructures and, meeting the allowable horizontal movement limits for substructures, less onerous for short spans (<15m) but more onerous for medium spans (15m to 50m). Above 50m braking governs the design. Derailment BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The study indicates that Eurocode derailment loadings are more onerous than those from current British Standards and that elements designed specifically to resist derailment loading may require increased capacity. The study did not cover the local effects of derailment loading and the associated effects on member sizes. However, for the design of the typical bridges considered, member sizes were dictated by load combinations for the Permanent/Transient design situations rather than from derailment loading (Accidental design situation).
Design of Railway Structures to the Structural Eurocodes
14 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Braking BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS5400-2:2006
The values in the current British Standard are recommended in the National Annex. The characteristic braking forces in the BS are greater than the Eurocode values. A maximum braking force of 6000kN is specified in the Eurocode. No such cut off exists in the current British Standards. At ULS the differences are less and for loaded lengths above 305m the Eurocode values are greater, until the maximum value is achieved. Design to the current Eurocode values for loaded lengths <300m, will make the design of substructures within the allowable horizontal movement limits, the design of bearings resisting longitudinal forces and, e nsuring lateral stability of substructures, will be less onerous. Note that traction will govern the design of short and medium spans (up to 30m using the current British Standard and, up to 45m using Eurocode). Traction BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The values in the current British Standard are recommended in the National Annex. The characteristic traction forces in the BS are greater than the Eurocode values for spans less than 14.7m. Above 14.7m the Eurocode characteristic values are greater. The maximum characteristic traction force in the BS is 750kN compared with 1000kN specified in the Eurocode. The differences in the ULS values are similar. Design to the current Eurocode will make the design of, bearings resisting longitudinal forces, ensuring lateral stability of substructures and, meeting the allowable horizontal movement limits for substructures, less onerous for short spans (<15m) but more onerous for medium spans (15m to 50m). Above 50m braking governs the design. Derailment BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003
The study indicates that Eurocode derailment loadings are more onerous than those from current British Standards and that elements designed specifically to resist derailment loading may require increased capacity. The study did not cover the local effects of derailment loading and the associated effects on member sizes. However, for the design of the typical bridges considered, member sizes were dictated by load combinations for the Permanent/Transient design situations rather than from derailment loading (Accidental design situation).
Design of Railway Structures to the Structural Eurocodes
Description of Investigation Relevant Standards (refer to list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Collision with substructures BS EN 1991-2:2003 referring to BS EN 1991-1-7:2006
There are potentially significant differences between the BSs and the EC, which will be addressed by the National Annex to BS EN 1991-1-7 (Published December 2008). The differences include the magnitude of the collision load, classification of structures and hazard zones, and the rules of application.
The most significant differences arise from consideration of the appropriate impact class, when impact shall be considered and, the magnitude of the equivalent impact force.
Deformation under transient railway actions
BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 UIC 776-3
GC/RT5110 GC/RC5510
The differences in the deformations of the steel structures studied were minimal and attributed to the different partial factors on the actions.
The differences encountered were greater for the reinforced concrete structure. The comparison factor was 1,15 for the vertical deformation and 1,12 for the rotation. This is attributed to the difference in the short term modulus of elasticity specified in the codes (for f cu= 50MPa, E = 34kN/mm2in current British Standards compared with 37kN/mm2in the Eurocodes), the different partial factors on the actions and, increased effective, cracked section properties permitted by the Eurocode.
The comparison for the composite concrete and steel structure was 0,89 for the vertical deformation and 1,041 for the rotation. This is attributed to the differences in the modulus of elasticity specified in the codes (as above) and the different partial factors on the actions.
Although there are differences, they should not result in any significant changes in design or construction of railway structures.
15 publication)
Collision with substructures BS EN 1991-2:2003 referring to BS EN 1991-1-7:2006
There are potentially significant differences between the BSs and the EC, which will be addressed by the National Annex to BS EN 1991-1-7 (Published December 2008). The differences include the magnitude of the collision load, classification of structures and hazard zones, and the rules of application.
The most significant differences arise from consideration of the appropriate impact class, when impact shall be considered and, the magnitude of the equivalent impact force.
Deformation under transient railway actions
BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 UIC 776-3
GC/RT5110 GC/RC5510
The differences in the deformations of the steel structures studied were minimal and attributed to the different partial factors on the actions.
The differences encountered were greater for the reinforced concrete structure. The comparison factor was 1,15 for the vertical deformation and 1,12 for the rotation. This is attributed to the difference in the short term modulus of elasticity specified in the codes (for f cu= 50MPa, E = 34kN/mm2in current British Standards compared with 37kN/mm2in the Eurocodes), the different partial factors on the actions and, increased effective, cracked section properties permitted by the Eurocode.
The comparison for the composite concrete and steel structure was 0,89 for the vertical deformation and 1,041 for the rotation. This is attributed to the differences in the modulus of elasticity specified in the codes (as above) and the different partial factors on the actions.
Although there are differences, they should not result in any significant changes in design or construction of railway structures.
Design of Railway Structures to the Structural Eurocodes
16 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Wind effects BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS EN 1991-1-4:2005 Draft National Annex BS EN 1991-1-4:2005
BS 5400-2:2006
The Eurocode basic wind velocity is lower than the current British Standard. The environmental factors are similar resulting in a wind pressure that is marginally higher than the Eurocode.
Wind only BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS EN 1991-1-4:2005 Draft National Annex BS EN 1991-1-4:2005
BS 5400-2:2006
The wind force coefficients and ULS partial factors are larger when calculated in accordance with the Eurocode. The resulting wind force is therefore marginally greater calculated in accordance with the Eurocode. Little change to the size and detailing for elements designed primarily to resist wind actions is likely.
Design of Railway Structures to the Structural Eurocodes
16 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Wind effects BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS EN 1991-1-4:2005 Draft National Annex BS EN 1991-1-4:2005
BS 5400-2:2006
The Eurocode basic wind velocity is lower than the current British Standard. The environmental factors are similar resulting in a wind pressure that is marginally higher than the Eurocode.
Wind only BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS EN 1991-1-4:2005 Draft National Annex BS EN 1991-1-4:2005
BS 5400-2:2006
The wind force coefficients and ULS partial factors are larger when calculated in accordance with the Eurocode. The resulting wind force is therefore marginally greater calculated in accordance with the Eurocode. Little change to the size and detailing for elements designed primarily to resist wind actions is likely.
Design of Railway Structures to the Structural Eurocodes
Description of Investigation Relevant Standards (refer to list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Wind coexistent with live load BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS EN 1991-1-4:2005 Draft National Annex BS EN 1991-1-4:2005
BS 5400-2:2006
The wind force coefficients, the wind area and the ULS partial factors are larger when calculated in accordance with the Eurocode. The resulting wind force is greater calculated in accordance with the Eurocode. The Eurocode includes a load
combination comprising maximum railway traffic actions plus wind. This may lead to larger section sizes for elements primarily resisting traffic actions but that are
vulnerable to wind forces.
It is recommended that the partial factor γQis 1,50 rather than the suggested 1,70 value in the draft National Annex to avoid potential increased conservatism. (Note that since the completion of this study, the UK national Annex recommends the value of partial factor γQis 1,70 if the characteristic value of wind actions which corresponds to 50 year return is used, or 1,45 if the characteristic value of wind actions for the required
return is c alculated). Global Temperature Effects BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS EN 1991-1-5:2003 Published National Annex BS EN 1991-1-5:2003
BS 5400-2:2006
Values of the coefficient of thermal expansion (CTE) for concrete a nd composite structures are different. There are also differences in the partial safety factors applied for the limit states, where the Eurocode is marginally more conservative for an equivalent temperature range.
In accordance with the Eurocode, where an installation temperature is not specified for bearings and expansion joints, the temperature range should be modified by adding up to a further 20 C to the range. Therefore the calculated Eurocode expansions and contractions calculated are greater than those calculated in accordance with British Standard, which is based on an assumed value of temperature at time zero.
Where temperatures are not modified in accordance with the Eurocode, the re sulting movements were similar to the current British Standard values.
It is recommended that the partial factors remain as the recommended values but that the 20 C adjustment need not necessarily be made to the temperature range where accurate consideration of the season when construction will take place has been made. (Note that since the completion of this study, the UK national Annex recommends the value of partial factor γQis 1,55).
17 publication)
Wind coexistent with live load BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS EN 1991-1-4:2005 Draft National Annex BS EN 1991-1-4:2005
BS 5400-2:2006
The wind force coefficients, the wind area and the ULS partial factors are larger when calculated in accordance with the Eurocode. The resulting wind force is greater calculated in accordance with the Eurocode. The Eurocode includes a load
combination comprising maximum railway traffic actions plus wind. This may lead to larger section sizes for elements primarily resisting traffic actions but that are
vulnerable to wind forces.
It is recommended that the partial factor γQis 1,50 rather than the suggested 1,70 value in the draft National Annex to avoid potential increased conservatism. (Note that since the completion of this study, the UK national Annex recommends the value of partial factor γQis 1,70 if the characteristic value of wind actions which corresponds to 50 year return is used, or 1,45 if the characteristic value of wind actions for the required
return is c alculated). Global Temperature Effects BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS EN 1991-1-5:2003 Published National Annex BS EN 1991-1-5:2003
BS 5400-2:2006
Values of the coefficient of thermal expansion (CTE) for concrete a nd composite structures are different. There are also differences in the partial safety factors applied for the limit states, where the Eurocode is marginally more conservative for an equivalent temperature range.
In accordance with the Eurocode, where an installation temperature is not specified for bearings and expansion joints, the temperature range should be modified by adding up to a further 20 C to the range. Therefore the calculated Eurocode expansions and contractions calculated are greater than those calculated in accordance with British Standard, which is based on an assumed value of temperature at time zero.
Where temperatures are not modified in accordance with the Eurocode, the re sulting movements were similar to the current British Standard values.
It is recommended that the partial factors remain as the recommended values but that the 20 C adjustment need not necessarily be made to the temperature range where accurate consideration of the season when construction will take place has been made. (Note that since the completion of this study, the UK national Annex recommends the value of partial factor γQis 1,55).
Design of Railway Structures to the Structural Eurocodes
18 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Effect of temperature gradient BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS 5400-2:2006
The temperature gradients through the sections are the same in accordance with the current British Standard and the Eurocode. However, the Eurocode is more conservative as the applied partial factors on the thermal effects are greater than the current British Standard.
The design situation involving coexistent railway load is similar at ULS but the Eurocode is more conservative at SLS.
Although the effects of temperature gradients rarely govern the design of continuous bridges at ULS, they often contribute significant components of stress that must be accounted for at SLS. When combined with the greater stress from the coexistent railway load, this will lead to changes in design of structural elements and connections compared to the current British Standard and a more c onservative design.
The Eurocode allows temperature effects to be combined with the railway traffic live load and wind. No equivalent combination exists in the current British Standard. This could lead to increases in element sizes for continuous bridges or integral (e.g. portal frame) structures which are primarily designed to resist traffic actions but which are vulnerable to wind and thermal actions.
Groups of loads BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003
BS 5400-2:2006
The Eurocode combines individual components of railway traffic actions into Groups of loads that can then be combined with appropriate other actions. Using specified groups of loads as a single (multi-directional) action as an alternative to determining the critical railway traffic actions individually may be more convenient to use and will not result in any difference in details or margin of c apacity for typical superstructures. No advantage in using the groups of loads approach in design could be determined when used with the factors in the UK National Annex to the Eurocode.
Design of Railway Structures to the Structural Eurocodes
18 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Effect of temperature gradient BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003 dated 07/08/2003 BS 5400-2:2006
The temperature gradients through the sections are the same in accordance with the current British Standard and the Eurocode. However, the Eurocode is more conservative as the applied partial factors on the thermal effects are greater than the current British Standard.
The design situation involving coexistent railway load is similar at ULS but the Eurocode is more conservative at SLS.
Although the effects of temperature gradients rarely govern the design of continuous bridges at ULS, they often contribute significant components of stress that must be accounted for at SLS. When combined with the greater stress from the coexistent railway load, this will lead to changes in design of structural elements and connections compared to the current British Standard and a more c onservative design.
The Eurocode allows temperature effects to be combined with the railway traffic live load and wind. No equivalent combination exists in the current British Standard. This could lead to increases in element sizes for continuous bridges or integral (e.g. portal frame) structures which are primarily designed to resist traffic actions but which are vulnerable to wind and thermal actions.
Groups of loads BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003
BS 5400-2:2006
The Eurocode combines individual components of railway traffic actions into Groups of loads that can then be combined with appropriate other actions. Using specified groups of loads as a single (multi-directional) action as an alternative to determining the critical railway traffic actions individually may be more convenient to use and will not result in any difference in details or margin of c apacity for typical superstructures. No advantage in using the groups of loads approach in design could be determined when used with the factors in the UK National Annex to the Eurocode.
Design of Railway Structures to the Structural Eurocodes
Description of Investigation Relevant Standards (refer to list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Comparison of the margin of capacity (utilisation) for the design of typical railway structural elements to current British Standards and the Eurocodes
BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003
BS 5400-2:2006
The summary is based on the study of the typical railway structures agreed with RSSB. Only the differences between the design of the agreed details are summarised in the following sections.
Steel plate girder structures BS EN 1993-2:2006
National Annex BS EN 1993-2
The results of the study indicate that designing details at SLS and ULS will be similar whether designed in accordance with the Eurocode or British Standards. Designs in accordance with the Eurocodes are generally less efficient (lower utilisation) than the current British Standards . The Eurocode design of connections subject to HSFG bolt shear tended to be more efficient (higher utilisation) than the British Standards but the conclusions for HSFG bolt slip and bearing were less conclusive.
The calculation of buckling capacity of beams with partially effective lateral restraint at ULS in accordance with the Eurocodes using non linear finite element buckling analysis could, in theory, result in a marginally smaller section being adopted. Designing sections subject to shear in accordance with the Eurocode will result in a marginally smaller section size being required except when the effects of shear buckling are considered.
Designing connections to satisfy the ULS and SLS (using HSFG bolts) requirements with the Eurocodes may require a greater number of bolts or greater bolt spacing, and hence larger connection plates and c onnection areas.
The assessment of fatigue susceptible details using the simple approach (no damage) in the current British Standards and Eurocodes shows similar results for all but the web shear fatigue assessment although fatigue is unlikely to govern the design of shear resisting details. It is therefore concluded that the design details to resist fatigue would be similar for most railway bridges designed to either the current British Standards or
19 publication)
Comparison of the margin of capacity (utilisation) for the design of typical railway structural elements to current British Standards and the Eurocodes
BS EN 1991-2:2003
Draft National Annex BS EN 1991-2:2003
BS 5400-2:2006
The summary is based on the study of the typical railway structures agreed with RSSB. Only the differences between the design of the agreed details are summarised in the following sections.
Steel plate girder structures BS EN 1993-2:2006
National Annex BS EN 1993-2
The results of the study indicate that designing details at SLS and ULS will be similar whether designed in accordance with the Eurocode or British Standards. Designs in accordance with the Eurocodes are generally less efficient (lower utilisation) than the current British Standards . The Eurocode design of connections subject to HSFG bolt shear tended to be more efficient (higher utilisation) than the British Standards but the conclusions for HSFG bolt slip and bearing were less conclusive.
The calculation of buckling capacity of beams with partially effective lateral restraint at ULS in accordance with the Eurocodes using non linear finite element buckling analysis could, in theory, result in a marginally smaller section being adopted. Designing sections subject to shear in accordance with the Eurocode will result in a marginally smaller section size being required except when the effects of shear buckling are considered.
Designing connections to satisfy the ULS and SLS (using HSFG bolts) requirements with the Eurocodes may require a greater number of bolts or greater bolt spacing, and hence larger connection plates and c onnection areas.
The assessment of fatigue susceptible details using the simple approach (no damage) in the current British Standards and Eurocodes shows similar results for all but the web shear fatigue assessment although fatigue is unlikely to govern the design of shear resisting details. It is therefore concluded that the design details to resist fatigue would be similar for most railway bridges designed to either the current British Standards or
Design of Railway Structures to the Structural Eurocodes
20 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
the Eurocodes with little change in the margin of capacity for the majority of details but an increase where fatigue of welds governs.
Calculating damage using the Miner sum approach shows the current British Standards to be more conservative because of the sensitivity of calculating damage with SN curves. Consideration of further detail types beyond the range studied is recommended before conclusions can be made with regard to the Miner sum fatigue assessment methods.
Changing the recommended partial factor values is not recommended.
Steel box girder structures BS EN 1993-2:2006
National Annex BS EN 1993-2
The calculation for the bending capacity of boxes at ULS in accordance with the Eurocodes is more efficient. The differences are small and it is unlikely that section sizes would change.
Designing sections subject to shear in ac cordance with the Eurocode will result in a smaller section at ULS.
Designing connections to satisfy the ULS and SLS (using HSFG bolts) requirements may require a greater number of bolts or greater bolt spacing, and hence larger connection plates and connection areas.
Design of Railway Structures to the Structural Eurocodes
20 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
the Eurocodes with little change in the margin of capacity for the majority of details but an increase where fatigue of welds governs.
Calculating damage using the Miner sum approach shows the current British Standards to be more conservative because of the sensitivity of calculating damage with SN curves. Consideration of further detail types beyond the range studied is recommended before conclusions can be made with regard to the Miner sum fatigue assessment methods.
Changing the recommended partial factor values is not recommended.
Steel box girder structures BS EN 1993-2:2006
National Annex BS EN 1993-2
The calculation for the bending capacity of boxes at ULS in accordance with the Eurocodes is more efficient. The differences are small and it is unlikely that section sizes would change.
Designing sections subject to shear in ac cordance with the Eurocode will result in a smaller section at ULS.
Designing connections to satisfy the ULS and SLS (using HSFG bolts) requirements may require a greater number of bolts or greater bolt spacing, and hence larger connection plates and connection areas.
Changing the proposed partial factor values is not recommended.
Design of Railway Structures to the Structural Eurocodes
Description of Investigation Relevant Standards (refer to list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Composite steel and concrete structures
BS EN 1994-1-1:2004, BS EN 1994-2:2005, National Annex BS EN 1994-2:2005.
The calculation of the bending capacity of beams with fully effective lateral restraint at ULS in accordance with the Eurocodes could result in a marginally larger section and hence some increase in the margin of capacity.
Designing sections subject to shear in ac cordance with the Eurocode is unlikely to result in a change of section or reduced margin of capacity at ULS.
Designing shear (stud) connections in accordance with the Eurocode may result in a reduction in the number of shear connectors.
The design of reinforced concrete slabs spanning between longitudinal girders in accordance with the Eurocodes is more onerous at ULS. Section sizes will have to increase, stronger concrete be specified, and larger bars or more reinforcing bars be used. The margin of capacity will be greater than designing to the current British Standards.
Changing the proposed partial factor values is not recommended. Pre-stressed concrete structures BS EN 1992-1-1:2004, BS EN
1992-2:2005, National Annex BS EN 1992-2:2005.
The Eurocodes are generally more efficient (higher utilisation) than the British Codes although this is dependent on the exposure condition of the bridge: if the bridge is exposed to chlorides, both the Eurocodes a nd British Standards were found to produce similar results.
If the bridge is not exposed to chlorides, the Eurocode provided more efficient results with savings of approximately 10% in the number of tendons required.
Changing the proposed partial factor values is not recommended. Composite steel and concrete
structures – Filler Decks
BS EN 1994-1-1:2004, BS EN 1994-2:2005, National Annex BS EN 1994-2:2005.
Designing filler beam decks in accordance with the British Standards resulted in a more efficient design (higher utilisation) at ULS and for fatigue. However, the differences were small and unlikely to result in any change in section size of any member.
21 publication)
Composite steel and concrete structures
BS EN 1994-1-1:2004, BS EN 1994-2:2005, National Annex BS EN 1994-2:2005.
The calculation of the bending capacity of beams with fully effective lateral restraint at ULS in accordance with the Eurocodes could result in a marginally larger section and hence some increase in the margin of capacity.
Designing sections subject to shear in ac cordance with the Eurocode is unlikely to result in a change of section or reduced margin of capacity at ULS.
Designing shear (stud) connections in accordance with the Eurocode may result in a reduction in the number of shear connectors.
The design of reinforced concrete slabs spanning between longitudinal girders in accordance with the Eurocodes is more onerous at ULS. Section sizes will have to increase, stronger concrete be specified, and larger bars or more reinforcing bars be used. The margin of capacity will be greater than designing to the current British Standards.
Changing the proposed partial factor values is not recommended. Pre-stressed concrete structures BS EN 1992-1-1:2004, BS EN
1992-2:2005, National Annex BS EN 1992-2:2005.
The Eurocodes are generally more efficient (higher utilisation) than the British Codes although this is dependent on the exposure condition of the bridge: if the bridge is exposed to chlorides, both the Eurocodes a nd British Standards were found to produce similar results.
If the bridge is not exposed to chlorides, the Eurocode provided more efficient results with savings of approximately 10% in the number of tendons required.
Changing the proposed partial factor values is not recommended. Composite steel and concrete
structures – Filler Decks
BS EN 1994-1-1:2004, BS EN 1994-2:2005, National Annex BS EN 1994-2:2005.
Designing filler beam decks in accordance with the British Standards resulted in a more efficient design (higher utilisation) at ULS and for fatigue. However, the differences were small and unlikely to result in any change in section size of any member.
Design of Railway Structures to the Structural Eurocodes
22 Description of Investigation Relevant Standards (refer to
list of references for dates of publication)
Summary of Recommended Values, New Studies and Commentary
Substructures BS EN 1997-1:2004 and National Annex BS EN 1997-1:2004
The Eurocodes are generally more onerous for design action DA1-1, but equivalent to BS 8002:1994 for design action DA1-2. DA1-1 load combination applies a factor to the permanent and variable actions, whilst DA1-2 applies factors to the materials and a reduced factor to the variable actions. It is not anticipated that the change from British codes to Eurocodes will have a significant impact upon the overall dimensions of retaining walls.
Note that the design of piers in the impact zone may be more substantial in accordance with the Eurocode where piers are supporting ‗Class A‘ structures and the impact forces are greater than those in the British Standards
Differences in the approach to fatigue assessment BS EN 1992-1-1:2004 BS EN 1992-2:2005 BS EN 1993-1-1:2005 BS EN 1993-1-9:2005 BS EN 1993-2:2006 BS EN 1994-1-1:2004 BS EN 1994-2:2005
There are significant differences in the detail classes / categories, most notably where fatigue failure across the throat of a weld is considered. In BS 5400-10:1980 the detail is class W and the equivalent allowable stress for 2x106cycles is 43MPa whereas the BS EN 1993-1-9 detail category is 36. This will lead to larger weld details.
The current, draft National Annex to BS EN 1993-1-9 limits the number of detail categories to the equivalent BS 5400-10:1980 classes to ensure the current margins of safety are maintained. The margin of capacity may reduce in where designs are undertaken in accordance with the Eurocodes.
There are significant differences in the S-N curves: The current British Standard is bi-linear with no cut off limits (except where all stresses are below the non-propagating level) whereas the Eurocodes are tri-linear with cut off limits. This leads to significant differences in the calculated number of cycles to failure or damage.
The train types and mixes are not the same in the current British Standards and the Eurocodes. It is recommended that the relevance of the Eurocode train types and traffic mixes to the UK railway network is established from further studies. Such a study should consider the design of fatigue s usceptible details for typical railway bridge structures subject to real trains, together with the application of the British