Eurocode 1: Actions on Structures - Traffic Loads on Bridges - Track-Bridge Interaction

This Technical Report reviews current practice with regard to designing, constructing and maintaining the parts of bridges and tracks where railway rails are installed across discontinuities in supporting structures. Current Standards and Codes of Practice are examined and some particular case histories are reviewed. The Technical Report gives guidance with respect to current best practice and makes recommendations for future standards development and also identifies areas in which further research and development is needed.

Eurocode 1: Einwirkungen auf Tragwerke - Verkehrslasten auf Brücken - Gleis-Brücken Interaktion

Dieses Dokument überprüft die gegenwärtige Praxis in Bezug auf Bemessung, Bau und Instandhaltung Brückenbauteilen und Gleisen in Bereichen, in denen die Eisenbahnschienen über Unstetigkeitsstellen der gleistragenden Strukturen hinweg verlegt sind. Gegenwärtige Normen und Leitfäden für die Praxis werden untersucht und einige spezielle Fälle hinsichtlich ihrer historischen Entwicklung überprüft.
Das Dokument dient als Leitfaden in Bezug auf die gegenwärtige bewährte Vorgehensweise und gibt Empfehlungen für die Erarbeitung zukünftiger Normen und es identifiziert Bereiche, in denen weiterführende Forschung und Entwicklung nötig sind.

Eurocode 1 : Actions sur les structures - Actions sur les ponts, dues au trafic - Interaction voie-pont

Evrokod 1: Vplivi na konstrukcije - Prometna obtežba mostov - Medsebojni vpliv tračnice-most

To tehnično poročilo podaja pregled trenutne prakse, povezane s projektiranjem, postavitvijo ter vzdrževanjem delov mostov in tračnic, pri čemer so tračnice nameščene na nehomogenih podpornih konstrukcijah. Preverjeni so trenutni standardi in pravila ravnanja ter pregledanih je nekaj posebnih preteklih primerov. Tehnično poročilo podaja navodila v zvezi s trenutno najboljšo prakso in priporočila za prihodnje razvojne standarde ter določa področja, za katera so potrebne nadaljnje raziskave in razvoj.

General Information

Status
Published
Publication Date
31-Jul-2018
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
04-Dec-2017

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SLOVENSKI STANDARD
SIST-TP CEN/TR 17231:2018
01-oktober-2018
(YURNRG9SOLYLQDNRQVWUXNFLMH3URPHWQDREWHåEDPRVWRY0HGVHERMQLYSOLY
WUDþQLFHPRVW

Eurocode 1: Actions on Structures - Traffic Loads on Bridges - Track-Bridge Interaction

Eurocode 1: Einwirkungen auf Tragwerke - Verkehrslasten auf Brücken - Gleis-Brücken

Interaktion

Eurocode 1 : Actions sur les structures - Actions sur les ponts, dues au trafic - Interaction

voie-pont
Ta slovenski standard je istoveten z: CEN/TR 17231:2018
ICS:
45.080 7UDþQLFHLQåHOH]QLãNLGHOL Rails and railway
components
91.010.30 7HKQLþQLYLGLNL Technical aspects
93.040 Gradnja mostov Bridge construction
SIST-TP CEN/TR 17231:2018 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN/TR 17231:2018
CEN/TR 17231
TECHNICAL REPORT
RAPPORT TECHNIQUE
August 2018
TECHNISCHER BERICHT
ICS 91.010.30; 93.040
English Version
Eurocode 1: Actions on Structures - Traffic Loads on
Bridges - Track-Bridge Interaction

Eurocode 1 : Actions sur les structures - Actions sur les Eurocode 1: Einwirkungen auf Tragwerke -

ponts, dues au trafic - Interaction voie-pont Verkehrslasten auf Brücken - Gleis-Brücken

Interaktion

This Technical Report was approved by CEN on 16 April 2018. It has been drawn up by the Technical Committee CEN/TC 250.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 17231:2018 E

worldwide for CEN national Members.
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Contents Page

European foreword ....................................................................................................................................................... 5

Introduction .................................................................................................................................................................... 6

1 Scope .................................................................................................................................................................... 7

2 Normative references .................................................................................................................................... 7

3 Terms and definitions ................................................................................................................................... 7

4 Symbols and abbreviations ......................................................................................................................... 9

5 Description of the Technical Issue ......................................................................................................... 10

5.1 General ............................................................................................................................................................. 10

5.2 Axial effects .................................................................................................................................................... 11

5.2.1 Origin of axial forces and displacements ............................................................................................. 11

5.2.2 Force transfer between track and deck ends ..................................................................................... 11

5.2.3 Rail stresses ................................................................................................................................................... 11

5.2.4 Forces acting on the fixed point (e.g. Bearing forces) ..................................................................... 14

5.2.5 Interaction with sub-structure ................................................................................................................ 14

5.3 Vertical effects ............................................................................................................................................... 15

5.3.1 Effect of vertical forces and displacements ........................................................................................ 15

5.3.2 Bridge deck end rotation ........................................................................................................................... 15

5.4 Limits to the need for detailed calculations ....................................................................................... 16

5.5 Calculation of multiple loading conditions ......................................................................................... 17

5.6 Effect of bridge deformations .................................................................................................................. 17

5.6.1 Effect on track geometry ........................................................................................................................... 17

5.6.2 Effect on stability of ballasted track ...................................................................................................... 18

5.6.3 Effect of ballast degradation over structural joints. ........................................................................ 18

5.7 Effects on track construction and maintenance activities ............................................................ 18

6 History and background ............................................................................................................................ 19

6.1 Existing codes and standards .................................................................................................................. 19

6.2 Differences between national rules....................................................................................................... 21

7 Case studies .................................................................................................................................................... 21

7.1 Scheldt River Bridge (Belgium) .............................................................................................................. 21

7.2 Dedicated high speed lines in France and Spain ............................................................................... 21

7.3 Olifants River Bridge (South Africa)...................................................................................................... 21

7.4 Bridges on Denver RTD (USA) ................................................................................................................. 21

7.5 Historic bridges in central Europe ......................................................................................................... 22

7.6 Semi-integral bridges on German high speed lines ......................................................................... 22

8 Design considerations for track. ............................................................................................................. 23

8.1 Representation of axial behaviour of track. ....................................................................................... 23

8.2 Understanding of ballast behaviour ...................................................................................................... 24

8.2.1 Ballast properties......................................................................................................................................... 24

8.2.2 Importance of effective ballast retention ............................................................................................ 24

8.3 Description/ limitations of available track devices for mitigation of effects ......................... 24

8.3.1 Principles ........................................................................................................................................................ 24

8.3.2 Practical solutions ....................................................................................................................................... 26

8.4 Description/ limitations of bridge design for mitigation of effects ........................................... 31

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8.4.1 General ............................................................................................................................................................. 31

8.4.2 "Steering bars” and virtual fixed points. .............................................................................................. 31

8.4.3 Damper Systems ............................................................................................................................................ 32

8.5 Effects of track curvature and switches and crossings ................................................................... 32

9 Design criteria ............................................................................................................................................... 33

9.1 General ............................................................................................................................................................. 33

9.1.1 Rail stress ........................................................................................................................................................ 33

9.1.2 Rail break containment .............................................................................................................................. 33

9.2 Displacement limits ..................................................................................................................................... 33

9.3 Differentiation between ultimate- and service-loading ................................................................. 35

9.4 Safety factors .................................................................................................................................................. 35

9.5 Differences between ballasted and ballastless tracks .................................................................... 35

9.6 Calculations for configurations with rail expansion devices ........................................................ 36

10 Calculation methods .................................................................................................................................... 36

10.1 Methods in EN 1991-2:2003 ..................................................................................................................... 36

10.1.1 General ............................................................................................................................................................. 36

10.1.2 Software based on UIC 774-3R ................................................................................................................. 38

10.1.3 Linear analysis with manual intervention (LAMI) ........................................................................... 38

10.2 Load configurations ..................................................................................................................................... 40

10.3 Sensitivity analysis ....................................................................................................................................... 40

10.4 Numerical comparisons of calculation methods ............................................................................... 41

11 Information and process management ................................................................................................. 46

12 GUIDANCE – Current best practice ......................................................................................................... 47

12.1 Bridge design principles ............................................................................................................................ 47

12.2 Track design principles .............................................................................................................................. 47

12.2.1 Ballasted track ............................................................................................................................................... 47

12.2.2 Ballastless track ............................................................................................................................................ 47

12.2.3 Special rail fastening systems .................................................................................................................. 48

12.2.4 Rail expansion devices ................................................................................................................................ 48

12.2.5 Derivation of the behaviour ...................................................................................................................... 48

13 Recommendations for future standards development ................................................................... 49

14 Recommendations for future research and development ............................................................. 49

14.1 General ............................................................................................................................................................. 49

14.2 Improved input data for existing calculation methods................................................................... 49

14.3 Extension of existing models to include other track configurations ......................................... 50

14.4 Collecting data for better verification of analytical models .......................................................... 50

14.5 Providing a basis for developing new, more rigorous, models .................................................... 50

Annex A (informative) Calculation of rail break gap .................................................................................... 51

A.1 Rail break gap for track with conventional fastenings (not on a bridge) ................................ 51

A.2 Rail break gap for track on a bridge, with conventional fastenings ........................................... 52

A.3 Rail break gap for track with sliding (ZLR) fastenings ................................................................... 54

A.4 Limiting values of rail break gap ............................................................................................................ 54

Annex B (informative) Algebraic studies of longitudinal track characteristics ................................. 55

B.1 Algebraic representations of behaviour .............................................................................................. 55

B.1.1 Sliding action .................................................................................................................................................. 55

B.1.2 The k-function ................................................................................................................................................ 56

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B.1.3 Temperature change ................................................................................................................................... 57

B.1.4 Temperature gradients .............................................................................................................................. 67

B.1.5 Track springs ................................................................................................................................................. 67

B.1.6 Joint movements ........................................................................................................................................... 71

B.1.7 Track forces resulting from joint movements ................................................................................... 73

B.2 The Two Spreadsheet Method ................................................................................................................. 77

B.2.1 General ............................................................................................................................................................. 77

B.2.2 The Temperature Stress Spreadsheet (TSS) ...................................................................................... 77

B.2.3 The Additional Stress Spreadsheet (ASS) ............................................................................................ 80

Annex C (informative) Examples of Track-Bridge Interaction calculations ........................................ 83

C.1 Introduction to calculation methods .................................................................................................... 83

C.2 Example 1: Simply supported deck with no rail expansion device ............................................ 83

C.3 Example 2: Series of continuous decks with no rail expansion device ..................................... 85

C.4 Continuous deck with a rail expansion device .................................................................................. 88

Annex D (informative) Alternative method for determining the combined response of a

structure and track to variable actions ................................................................................................ 91

Annex E (informative) Proposed revision of EN 1991-2:2003, 6.5.4 ...................................................... 92

E.1 General ............................................................................................................................................................. 92

E.2 Combined response of structure and track to variable actions .................................................. 92

E.2.1 General principles ........................................................................................................................................ 92

E.2.2 Parameters affecting the combined response of the structure and track ............................... 92

E.2.3 Actions to be considered ........................................................................................................................... 95

E.2.4 Modelling and calculation of the combined track/structure system ........................................ 95

E.2.5 Design criteria ............................................................................................................................................... 98

E.2.6 Calculation methods .................................................................................................................................. 100

Bibliography ............................................................................................................................................................... 104

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European foreword

This document (CEN/TR 17231:2018) has been prepared by Technical Committee CEN/TC 250

“Structural Eurocodes”, the secretariat of which is held by BSI.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

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Introduction

The subject of Track-Bridge Interaction has become particularly important with respect to longer span

bridges and viaducts supporting tracks, especially for those carrying high speed trains. However,

investigations which have been undertaken in order to address that specific issue have raised points

which are relevant to all types of railway bridge. Consequently, the content of this Technical Report is

intended to be applicable to all types of railway bridge, for both ballasted and ballastless track, and for all

types of railway (e.g. conventional railways, metro and light rail systems, and high speed railways).

It is also clear that the increased availability of computational methods of analysis, since the basis for

existing codes was laid down in the 1990s, has made it possible to consider approaches to calculation of

Track-Bridge Interaction effects which could not be expected to be used in routine procedures in the past.

There are three principal 'outputs' set out in the final sections of this Technical Report. They are as

follows:

1) Guidance for designers and maintainers of railway track and structures to assist them in adopting

current best practice in taking Track-Bridge Interaction effects into account (Clause 12 of this

report).

2) Recommendations for future development of standards, especially the revision of the relevant

section of the Eurocode EN 1991-2:2003 6.5.4 (Clause 13 and Annex E of this report).

3) Identification of areas in which new research and development is needed to make further

improvements in approaches to Track-Bridge Interaction (Clause 14 of this report).

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1 Scope

This document reviews current practice with regard to designing, constructing and maintaining the parts

of bridges and tracks where railway rails are installed across discontinuities in supporting structures.

Current Standards and Codes of Practice are examined and some particular case histories are reviewed.

The document gives guidance with respect to current best practice and makes recommendations for

future standards development and also identifies areas in which further research and development is

needed.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
track-bridge interaction

conditions under which forces and/or displacements in a railway track and its supporting bridge

structure are influenced by the fact that rails span discontinuities in a bridge structure e.g. structural

movement joints or bridge deck ends
3.2
additional load

load in an element of the track, (e.g. rail and rail fixing) on a bridge compared with what is expected in

that element if the same track system were to be installed with the same loading actions away from any

bridge

Note 1 to entry The word 'additional' is used in the same sense to describe additional stresses, additional forces

and additional deformations.
3.3
thermal fixed point

point in the structure of the bridge, without the track, which is assumed not to be displaced when there

is a change in temperature. (Otherwise known as the “centre of thermal displacement” or “thermal

centre”)
3.4
deck length
distance between structural movement joints in the bridge deck
3.5
span length
distance between vertical supports, e.g. piers and abutments
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3.6
expansion length, L of a deck
distance between the thermal fixed point and the free end of the deck

Note 1 to entry: For bridge designs in which the thermal fixed point is neither at one end nor at the mid-point of

the deck, the distance from the thermal fixed point to the further free end is taken to be L . (See Figure1.)

3.7
effective expansion length, L at a joint

total of the distances from the joint to the thermal fixed point for the two bridge decks adjacent to the

joint
Note 1 to entry: See Figure 1.
Key
△ represents a 'fixed' support
○ represents a 'free' support
Figure 1 — Examples of expansion lengths L and L
J T
3.8
support stiffness
longitudinal stiffness of a single pier given by
δδ++δ
phϕ

Note 1 to entry: Depending on the type of bearings used, the tolerance of the bearing and the shear stiffness may

have to be considered by calculating the longitudinal stiffness.
Note 2 to entry: For the case represented in Figure 2 as an example.
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Key
(1) bending of the pier
(2) rotation of the foundation
(3) displacement of the foundation
(4) total displacement of the pier head

Figure 2 — Example of the determination of equivalent longitudinal stiffness at bearings

4 Symbols and abbreviations

For the purposes of this document, the following symbols and abbreviations apply.

E elastic (“Young's”) modulus. For rails, it is assumed that E = 210 GN/m.
F longitudinal force
K longitudinal stiffness at a single pier (see Clause 3 definition 7)
L deck length (see Clause 3 definition 4)
L effective expansion length at a joint (see Clause 3 definition 6)
L span length (see Clause 3 definition 5)
L expansion length (see Clause 3 definition 4)

SFT Stress Free Temperature. (Temperature at which the axial stress in the rail is zero for

unloaded track)
SLS Serviceabiity Limit State (see definition in EN 1990:2002 , 1.5.2.14)
ULS Ultimate Limit State (see definition in EN 1990:2002 , 1.5.2.13)
th −5 -1

α, 𝛼𝛼 coefficient of thermal expansion. For rails, it is assumed that α = 1,2 × 10 K

δ axial displacement of the bridge deck due to traction or braking forces

δ longitudinal displacement due to rigid body translation of the pier (see Figure 2)

δ longitudinal displacement due to bending of the pier (see Figure 2)
As impacted by EN 1990:2002/A1:2005 and EN 1990:2002/A1:2005/AC:2010.
As impacted by EN 1990:2002/A1:2005 and EN 1990:2002/A1:2005/AC:2010.
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δ axial displacement of the bridge deck due to vertical loading
δ δ displacements due to rotation of the free end of the deck
θD, θR

δ longitudinal displacement due to rotation of the foundation of the pier (see Figure 2)

λ ratio of span length (L ) to depth of bridge deck structure

θ angle of rotation of the free end of the bridge deck due to temperature difference

5 Description of the Technical Issue
5.1 General

Interaction between the track structure and a bridge structure (i.e. the consequences of the behaviour of

one of those structures on the other) occurs because there is a physical connection between them,

whether the rails are directly fixed or there is a ballast bed in between the track and the bridge. The

interaction results in forces being applied to the track (rails, fastenings and ballast) and the bridge

substructure (foundations, piers, abutments, bearings). These forces are in addition to those which would

be expected if the track and bridge were analysed separately.

If these additional forces are too high this may lead to failure modes including tensile failure of the rail,

lateral buckling of the track, shear failure of bridge bearings, longitudinal failure of the bridge

substructure or uplift of track elements. These forces shall be taken into account in assessing both

serviceability limit state (SLS) and ultimate limit state (ULS) conditions of the structure, although only

SLS conditions should be taken into account for calculating stresses in the track (see 9.3 and 9.4),

As a general principle, track engineers prefer to have bridges which are designed to reduce the influence

of the bridge on the track to a minimum. Existing and proposed standards and codes set maximum

limiting values of stresses, forces and deformations. For specific projects the preferred practice at the

design stage may be to aim to achieve values well below those limits.

However, historically the problem of Track-Bridge Interaction has been solved by installing rail

expansion devices close to structure movement joints on longer bridges. Rail expansion devices are

expensive to install and to maintain, especially on high speed lines where impact forces arising from

imperfect joints in the rail cause deterioration of the track and the supporting structure. On many urban

railways there is a need to reduce the number of rail expansion devices to remove a source of noise, even

if the train speeds are lower.

The resolution of this apparent conflict between the interests of bridge designers and track designers

shall be based on an understanding of the economic implications of different solutions. At the simplest

level, this requires an understanding of the relative construction and maintenance costs of, for example,

installing rail expansion devices compared to modifying the bridge design (e.g. longitudinal stiffness of

sub-structures) and/or accepting higher operational stresses in the rails. However, even more significant

economic benefits may accrue from chan
...

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