capacity assessment of underbridges...t hr ci 12008 st capacity assessment of underbridges version...

Capacity Assessment of Underbridges

T HR CI 12008 ST

Standard

Version 2.0

Issue date: 25 June 2018

© State of NSW through Transport for NSW 2018

T HR CI 12008 ST Capacity Assessment of Underbridges

Version 2.0 Issue date: 25 June 2018

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Standard governance

Owner: Lead Civil Engineer, Asset Standards Authority

Authoriser: Chief Engineer, Asset Standards Authority

Approver: Executive Director, Asset Standards Authority on behalf of the ASA Configuration Control Board

Document history

Version Summary of changes

1.0 First issued 21 October 2015

2.0 Second issue. The changes from the previous issue include the following: • incorporation of the contents of technical note TN 006: 2016 • adjustment of technical content following the publication of AS 5100:2017 Bridge design (all

parts) • removal of the requirements for assessment for earthquake loading • title change

© State of NSW through Transport for NSW 2018 of 31



Preface

The Asset Standards Authority (ASA) is a key strategic branch of Transport for NSW (TfNSW).

As the network design and standards authority for NSW Transport Assets, as specified in the

ASA Charter, the ASA identifies, selects, develops, publishes, maintains and controls a suite of

requirements documents on behalf of TfNSW, the asset owner.

The ASA deploys TfNSW requirements for asset and safety assurance by creating and

managing TfNSW's governance models, documents and processes. To achieve this, the ASA

focuses on four primary tasks:

• publishing and managing TfNSW's process and requirements documents including TfNSW

plans, standards, manuals and guides

• deploying TfNSW's Authorised Engineering Organisation (AEO) framework

• continuously improving TfNSW’s Asset Management Framework

• collaborating with the Transport cluster and industry through open engagement

The AEO framework authorises engineering organisations to supply and provide asset related

products and services to TfNSW. It works to assure the safety, quality and fitness for purpose of

those products and services over the asset's whole-of-life. AEOs are expected to demonstrate

how they have applied the requirements of ASA documents, including TfNSW plans, standards

and guides, when delivering assets and related services for TfNSW.

Compliance with ASA requirements by itself is not sufficient to ensure satisfactory outcomes for

NSW Transport Assets. The ASA expects that professional judgement be used by competent

personnel when using ASA requirements to produce those outcomes.

About this document

This standard specifies the technical requirements for live load capacity assessment (that is,

load rating) and fatigue assessment performed on underbridges on the TfNSW heavy rail

network.

This document was previously issued as T HR CI 12008 ST Load Rating of Underbridges,

version 1.0 in October 2015 and is now updated and issued under a new title as

T HR CI 12008 ST Capacity Assessment of Underbridges, version 2.0.

This is a second issue.

This document is revised to incorporate the contents of TN 006: 2016, modify the contents

following the publication of AS 5100: 2017 Bridge Design and remove the requirements for

assessment of earthquake loading.




Table of contents 1. Introduction .............................................................................................................................................. 6

2. Purpose .................................................................................................................................................... 6 2.1. Scope ..................................................................................................................................................... 6 2.2. Application ............................................................................................................................................. 7

3. Reference documents ............................................................................................................................. 7

4. Terms and definitions ............................................................................................................................. 8

5. General requirements ............................................................................................................................. 8 5.1. Matters for resolution ............................................................................................................................. 9 5.2. Asset information records .................................................................................................................... 10

6. Condition assessment .......................................................................................................................... 11 6.1. Bridge examination .............................................................................................................................. 11 6.2. Section loss and deterioration ............................................................................................................. 11

7. Structural capacity ................................................................................................................................ 12 7.1. Historical bridge types not considered in AS 5100 .............................................................................. 12 7.2. Wind and sway bracing ........................................................................................................................ 13

8. Loads ...................................................................................................................................................... 13 8.1. Rail traffic load ..................................................................................................................................... 13 8.2. Dynamic load allowance ...................................................................................................................... 16 8.3. Wind load ............................................................................................................................................. 16

9. Load factors and combinations ........................................................................................................... 16 9.1. Load factors ......................................................................................................................................... 17 9.2. Load combinations ............................................................................................................................... 17

10. Fatigue assessment .............................................................................................................................. 17 10.1. Load history ..................................................................................................................................... 17 10.2. Rivets ............................................................................................................................................... 18 10.3. Fatigue life ....................................................................................................................................... 18

11. Substructure .......................................................................................................................................... 18 11.1. Stability analysis .............................................................................................................................. 18

12. Load rating factor .................................................................................................................................. 19 12.1. Combined actions ............................................................................................................................ 19 12.2. Bridges with rating factor less than 1.0 ............................................................................................ 20

13. Capacity deficient and fatigue life expired bridges ........................................................................... 20

14. Bridge capacity assessment report requirements ............................................................................. 21

Appendix A Operating consist axle diagram ....................................................................................... 22

Appendix B Historical design loads ..................................................................................................... 23

Appendix C Bridge load rating executive summary table - sample layout ....................................... 26

Appendix D Bridge load rating assessment summary table – sample layout .................................. 27

Appendix E Bridge capacity assessment report information ............................................................ 28 © State of NSW through Transport for NSW 2018 of 31



1. Introduction An underbridge is a bridge that supports a railway track or tracks that pass over roadways,

pathways, flood plains, waterways and other railway tracks. Underbridges include viaducts,

flyovers, dives, culvert structures and pedestrian subways.

Bridges have a typical service life of more than 100 years and the load carrying capacity of a

bridge can vary over time as outlined in AS 5100.7:2017 Bridge design Part 7: Bridge

assessment.

An underbridge may carry different loading across the life cycle as new rolling stock and

changes in line usage are introduced to the network. Repeated loading on bridge components

can induce cumulative damage, which may reduce remaining serviceable fatigue life.

The theoretical load rating of an underbridge can change due to changes to standards over the

life of the asset and changes in asset condition.

The need to undertake a bridge capacity assessment can arise from a requirement under a

technical maintenance plan (TMP) for a 30-year engineering assessment as specified in

TMC 301 Structures Examination.

The primary reference document for capacity assessment of underbridges is AS 5100.7 and this

document should be read in conjunction with AS 5100.7: 2017.

2. Purpose This standard specifies the technical requirements for live load capacity assessment (that is,

load rating) and fatigue assessment performed on underbridges on the TfNSW heavy rail

network.

2.1. Scope This standard supplements the requirements of AS 5100.7.

In addition to the requirements stated in AS 5100.7, this document includes the requirements for

management of capacity deficient bridges.

The requirements in this standard relate to calculated assessments only. Earthquake

assessment, load testing, structural health monitoring and other test methods are excluded from

this standard and are specified in AS 5100.7:2017. The need for these additional activities is

determined by the rail infrastructure manager (RIM).




2.2. Application This standard applies to all Authorised Engineering Organisations (AEOs) that undertake

underbridge capacity assessments on TfNSW heavy rail network.

If the intent of the standard is not clear, when using the standard, then a clarification should be

sought from the ASA.

3. Reference documents The following documents are cited in the text. For dated references, only the cited edition

applies. For undated references, the latest edition of the referenced document applies.

International standards

I.S. EN 1993-1-9 Eurocode 3: Design of steel structures -Part 1-9: Fatigue

Australian standards

AS 5100 Bridge design (all series)

AS 5100.7:2017 Bridge design – Part 7: Bridge assessment

AS ISO 13822 Basis for design of structures – Assessment of existing structures

(ISO 13822:2001, MOD)

Transport for NSW standards

ESC 200 Track System

ESC 300 Structures System

ESC 310 Underbridges

TMC 301 Structures Examination

TMC 305 Structures Assessment

T HR CI 12005 PR Underwater Examination of Structures

T HR RS 00100 ST RSU 100 series - Minimum Operating Standards for Rolling Stock

T MU AM 01001 ST Life Cycle Costing

Other reference documents

CIRIA C656 Masonry arch bridges: condition appraisal and remedial treatment

Design Manual for Roads and Bridges, Volume 3, BA 16/97 - The Assessment of Highway

Bridges and Structures

Design Manual for Roads and Bridges, Volume 3, BD 21/01 - The Assessment of Highway

Bridges and Structures




Design Manual for Roads and Bridges, Volume 3, BD 61/10 – The Assessment of Composite

Highways Bridges and Structures

Network Rail NR/GN/CIV/025/ Guidance Note - The Structural Assessment of Underbridges

4. Terms and definitions The following terms and definitions apply in this document:

AEO Authorised Engineering Organisation

ASA Asset Standards Authority

DLA dynamic load allowance

filler (encased) beam deck rolled or built-up steel or iron sections that act in conjunction with a

concrete slab and which are contained within the slab or with slab surfaces flush with one or

both flanges

jack arch deck rolled or built-up steel or iron sections separated by concrete, stone or brick

arches supported by the lower flanges, generally with loose fill or concrete fill above

RF load rating factor

RIM rail infrastructure manager (as defined in the Rail Safety National Law 2012 (NSW), in

relation to rail infrastructure of a railway, means the person who has effective control and

management of the rail infrastructure, whether or not the person–

(a) owns the rail infrastructure; or

(b) has a statutory or contractual right to use the rail infrastructure or to control, or provide,

access to it

TfNSW Transport for NSW

ULS ultimate limit state

SLS serviceability limit state

5. General requirements Load rating and fatigue assessment of underbridges shall be carried out in accordance with

AS 5100.7:2017 and the requirements of this standard. The ultimate limit state (ULS) and the

serviceability limit state (SLS) shall be used as necessary in the analysis load combinations to

determine the rating factors.

Where conflict exists between the requirements of AS 5100.7:2017 and this standard, this

standard shall take precedence.

All existing underbridges shall be assigned ‘as-new’ and ‘as-is’ load ratings.




The ‘as-new’ load rating shall be based on an inspection to confirm as-built information and

determination of load carrying capacity based on the constituent components of the bridge

being in new condition.

The ‘as-is’ load rating shall be based on an examination and determination of load carrying

capacity of a structure based on the existing condition of the components of the bridge.

Load ratings shall be carried out for the rating design load and the rating operating consist as

defined in Section 8.

Clause 6 of AS 5100.7:2017 shall be specifically referred to for conditions and events which

may initiate a load capacity assessment.

The bridge components shall be named in accordance with ESC 300 Structures System.

Clause 9 and Figure 9 of AS 5100.7:2017 provide a step-by-step process for bridge assessment

and load rating. The steps in the process that are discussed in this standard include the

following:

• Step 2 – condition assessment

• Step 4 – load effects and load factors

• Step 5 – capacity assessment

• Step 6 – fatigue assessment

• Step 7 – rating factor

5.1. Matters for resolution Clause 5 of AS 5100.7:2017 identifies matters for resolution that shall be confirmed and

accepted by the relevant authority before commencing the relevant assessment process.

Table 1 identifies the relevant responses sections for the associated list of matters for

resolution.

Table 1 - Matters for resolution

Item number (Clause 5 of AS 5100.7:2017) Relevant section (in this standard)

1 13

2 11, 12

4 7.1, 7.1.1, 10.2, 13

5 5, 11.1

10 7.1, 7.1.1

11 14

15 8.2




Item number (Clause 5 of AS 5100.7:2017) Relevant section (in this standard)

19 8.1

20 8.1

21 8.1

22 8.3

If other matters for resolution that are not listed in Table 1 are of concern, then the assessor

shall seek advice from the Lead Civil Engineer, ASA.

5.2. Asset information records The RIM shall have an asset information system that records current and past capacity

information for each underbridge as follows:

a. ‘design’ load rating value

b. ‘as-new’ load rating value

c. ‘as-is’ load rating value

d. source document identification and date for each of the three load rating values ('design',

'as-new' and 'as-is')

Examples include drawing numbers, report title and reference number, author and date of

issue

e. critical governing bridge components for ‘as-new’ load rating and applicable dynamic load

allowance (DLA) value

f. critical governing bridge components for ‘as-is’ load rating and applicable DLA value

g. ‘as-is’ speed restrictions for any applicable operating consist where applicable

h. other relevant load rating remarks for the underbridge

i. fatigue assessment values such as remaining life, expiry year, source document and date

assessed

Recorded load rating values for bridges assessed before 2004 may be based on the design

load that was current at the date of the design or assessment such as 300-A-12, M270, E60

and so on.

Recorded load rating values for bridges assessed after 2004 shall be based on 'LA'

configuration as specified in AS 5100.2.




6. Condition assessment Clause 10.3 of AS 5100.7:2017 requires the condition of the bridge to be assessed in

accordance with Level 2 inspection or Level 3 inspection. Load rating shall not be valid until the

examination and condition assessment has been undertaken.

Level 2 and Level 3 bridge inspections are defined in AS 5100.7.

6.1. Bridge examination A detailed bridge examination and assessment in accordance with the following standards shall

be undertaken prior to load rating:

• TMC 301 Structures Examination Manual

• TMC 305 Structures Assessment

• T HR CI 12005 PR Underwater Examination of Structures

Detailed bridge examinations and assessment in accordance with these TfNSW standards are

deemed to be equivalent to Level 2 inspection and Level 3 inspection as referenced in

AS 5100.7:2017 for capacity assessment purposes.

In addition to the requirements of Clause 10.3 of AS 5100.7:2017, the examination shall include

the position of the track or tracks relative to the structure and loss of structural section.

6.2. Section loss and deterioration Measurements of actual section loss and member deterioration shall be undertaken where

feasible. The extent and location of section loss and deterioration shall be quantified to permit

accurate determination of member capacity.

Where this is not feasible, assumptions of section loss based on qualitative defect descriptions

from inspection reports may be made for steel, wrought-iron and cast-iron structures and the

losses may be assumed as stated in Table 2.

The AEO shall identify the components of the bridge undergoing capacity assessment where it

is not feasible to measure thickness loss.

Table 2 – Assumed loss of structural section

Loss level Losses as a percentage of thickness

Minor Not more than 10% loss

Moderate Not more than 20% loss

Heavy Not more than 40% loss

Severe More than 40% loss




In using values from Table 2, the ‘as-is’ section properties shall be calculated assuming the

percentage thickness loss of the member elements, such as bottom flange thickness or web

thickness, and not calculated as a percentage reduction of global section property.

7. Structural capacity The capacity of underbridges shall be determined in accordance with AS 5100:2017.

Bridges and components that are not within the scope of AS 5100 shall have their capacities

calculated using alternative methods and procedures as outlined in this standard.

Bridges and components that are not within the scope of AS 5100 or this standard shall be

referred to the Lead Civil Engineer, ASA for discussion on appropriate assessment methods.

7.1. Historical bridge types not considered in AS 5100 TfNSW has many historical bridge structures which are not specifically provided for in AS 5100.

These structures include the following:

• jack arch decks with masonry or concrete vaults

• filler beam (steel RSJs embedded in concrete) decks without shear connectors

• concrete decks with old rail reinforcement (Table A6 of AS 5100.7:2017 sets out properties

for rail)

• cast iron beam decks

Reference to specialist literature is required to assess these types of structures. The following

references are provided for the capacity assessment of structures of these types:

• the structural capacity for jack arch, filler (encased) beam, and composite bridge decks

without shear interface connectors may be established in accordance with the following:

o Network Rail NR/GN/CIV/025/ Guidance Note The Structural Assessment of

Underbridges

o Design Manual for Roads and Bridges, Volume 3, BD 21/01 – The Assessment of

Highway Bridges and Structures

o Design Manual for Roads and Bridges, Volume 3, BA 16/97 – The Assessment of

Highway Bridges and Structures

o Design Manual for Roads and Bridges, Volume 3, BD 61/10 – The Assessment of

Composite Highway Bridges and Structures

• cast iron bridge components may be assessed using the working stress methods in Design

Manual for Roads and Bridges, Volume 3, BD 21/01 – The Assessment of Highway

Bridges and Structures and NR/GN/CIV/025




Other methods and standards may be used subject to the approval of Lead Civil Engineer, ASA.

7.1.1. Masonry arch bridges AS 5100.7:2017 provides detailed requirements for the assessment of masonry arch bridges

and makes specific reference to Design Manual for Roads and Bridges, Volume 3, BA 16/97 –

The Assessment of Highway Bridges and Structures, and NR/GN/CIV/025.

Additional guidance on masonry strength and bridge assessment can be found in BD 21/01 and

CIRIA C656 Masonry arch bridges: condition appraisal and remedial treatment.

7.2. Wind and sway bracing Bottom chord or flange wind and sway bracing on older generation steel bridges is generally

comprised of light weight angles and flat bars. This light weight bracing is generally found to

have insufficient calculated theoretical capacity as compression elements and should be

considered as ‘tension only’, as appropriate for the structure. In many cases there is no

evidence from the inspection that the bracing has been overloaded.

Bracing at the top chord or flange is usually more substantial, acting as axial tension or

compression. The limiting rating factor for a bridge may be found to be a bracing member in

compression. In such cases, the effects of the member omitted (that is, assumed buckled) with

horizontal forces redistributed through the bridge to tension members shall be assessed so that

the rating factor for the primary structural elements of the bridge can be determined without the

influence of the sway bracing.

8. Loads The loads for underbridge capacity assessment shall be in accordance with AS 5100 except as

modified in Section 8.1 to Section 8.3 of this standard.

The applicable ‘rating design load’ and ‘rating operating consist’ to be used depends on the

location of the underbridge within the TfNSW rail network track classification system.

The operating classes of main lines, yards and sidings within the TfNSW rail network are

defined in ESC 200 Track System.

8.1. Rail traffic load The provisions of Section 8.1.1 to Section 8.1.4 replace or supplement the requirements in

Clause 11.4.1 of AS 5100.7:2017.




8.1.1. Rating design load

Underbridge load ratings shall be calculated in terms of the current design loads.

The rating design load shall be based on the 300LA design loading as described in AS 5100

and adjusted for the line operating classification as shown in Table 3. The applicable reference

design load in Table 3 shall be used for load rating.

Table 3 – Rating design load

Line operating classification Rating design load

Passenger main line and light line 200LA plus DLA

Mixed passenger freight main line 300LA plus DLA

Freight line 300LA plus DLA

Heavy freight line 350LA plus DLA

General yard siding 300LA plus 0.5 x DLA

Passenger operations or maintenance siding 200LA

8.1.2. Historical bridge design loads Historical design loads for rail bridges on main lines in New South Wales (NSW) are listed in

Table 4. The exact timeframe for the introduction of E60 design load is uncertain.

These design loads are provided for a basis of comparison with the load rated capacity. Refer to

section 5.6 in Appendix E for further information.

Table 4 – Historical railway bridge design loads

Year Design load Standard

1922 E50 NSW GR (1)

1940 (circa) E60 NSW GR (1)

1974 M250 / M270 ANZRC (2)

1996 300-A-12 ABDC (3)

2004 + 300LA AS5100

Notes:

(1) New South Wales Government Railways and Tramways Standard Rules and

Formulas for Design

(2) Australia and New Zealand Railway Conference (A.N.Z.R.C.) Railway Bridge

Design Manual. ANZRC has M250 loading, M270 (approx. E60) had been adopted

(3) Australian Bridge Design Code - 1996 (Australian Standard HB 77.8-1996)

Load diagrams for E50, E60, M270 and 300-A-12 are provided in Appendix B.




8.1.3. Rating operating train consist

Underbridge load ratings shall also be calculated in terms of train consists currently operating

on the TfNSW heavy rail network.

The following list defines train consists operating on the TfNSW heavy rail network:

• Heavy coal (HC) – based on 5/165 tonne locomotives hauling 120 tonne coal wagons

• Main line freight (MF) – based on 5/132 tonne locomotives hauling 100 tonne coal wagons

• XPT/Explorer (XP)

• Waratah electric (WE)

For HC and MF load arrangements, the locomotives shall be distributed along the train consist

to produce the worst load effects. For example, one or more of the locomotives is allowed to be

positioned between loaded wagons if that arrangement produces the worst load effect under

consideration.

Sufficient number of wagons shall be included in the train consist to ensure that the wagons

alone fully load the bridge length under consideration. This will enable determination of whether

the locos, wagons or the combined effect of both the loco and wagons, results in the governing

load position on the bridge.

The rating operating consist based on line classification is nominated in Table 5. Appendix A

contains a diagrammatic representation of the listed train consists.

Table 5 – Rating operating consist

Line operating classification Rating operating train consist

Passenger main line and light line WE plus DLA

Mixed passenger freight main line MF plus DLA & WE plus DLA

Freight line MF plus DLA

Heavy freight line HC plus DLA & MF plus DLA

General yard siding MF plus 0.5 x DLA

Passenger operations or maintenance siding WE

The East Hills Line between the Illawarra Line junction and the Main South Line junction shall

also be assessed for ‘MF + DLA’ loading.

HC train consist loading assessment shall be carried out on those underbridges on the Main

North Line between Woodville Junction and Vales Point Junction.




8.1.4. Other rating train consists

The RIM may also nominate other rail traffic for capacity assessment such as the following:

• heritage steam locomotives and carriages

• specific locomotives and wagons

• track laying machine (TLM) (Refer to Appendix A for details)

• track maintenance machines

8.2. Dynamic load allowance The dynamic load allowance (α) for railway traffic for unrestricted operational speed shall be

calculated in accordance with AS 5100.2 Bridge design Part 2: Design loads.

The ‘α’ value may be adjusted in accordance with Clause 11.4.3 of AS 5100.7:2017 for rail line

speed at the bridge.

Clause 9.5.3 of AS 5100.2 2017 has a requirement that where a transition approach to a bridge

abutment is not provided, ‘α’ shall be increased by not less than 50%. This requirement shall not

be applied where the bridge end is in good condition.

Good condition is described as being free from defects affecting structural performance,

integrity and durability, negligible settlement, lateral or rotational movement of approaches.

The ‘α’ value for TLM load in operating mode shall be 0.1.

For steam locomotives, ‘α’ value shall be increased by 20% in accordance with Clause 9.5.3 of

AS 5100.2.

8.3. Wind load Wind loads are not usually considered in load rating calculations; however, for steel bridges with

wind and sway bracing, wind load on the bridge and on the train, shall be included. Two

separate load cases for wind are required; wind speed of 35m/s in accordance with

Clause 23.3 of AS 5100.2: 2017 and a wind speed of 20m/s.

9. Load factors and combinations Section 9.1 and Section 9.2 specifies the requirements for the load factors and load

combinations.




9.1. Load factors Load factors shall be determined in accordance with Clause 12 of AS 5100.7:2017.

The rating design load such as 300LA shall be adopted as ‘Traffic load (general rail freight

traffic) in Table 12.2(B) of AS 5100.7: 2017.

The operating consists described in Table 5 of this standard shall be adopted as ‘Traffic Load

(specific rail freight traffic)’ in Table 12.2(B) of AS 5100.7:2017. The ultimate live load factor (γQ)

shall also be adopted as 1.4 for other specific rail traffic listed in Section 8.1.4.

The requirements of note 2 and note 4 in Table 12.2(B) of AS 5100.7:2017 are deemed

satisfied by the requirements in T HR RS 00100 ST RSU 100 series - Minimum Operating

Standards for Rolling Stock.

9.2. Load combinations Load combinations shall be in accordance with AS 5100.2.

Wind load on the bridge and train, where included, shall be in combination with ultimate vertical

and horizontal traffic load.

The ULS and SLS limit state load combination (permanent effects + wind + traffic loads) shall

be included in accordance with Clause 23.3 of AS 5100.2 for ULS and Clause 23.4 of

AS 5100.2 for SLS.

10. Fatigue assessment Fatigue assessment, if requested by the RIM, shall be performed in accordance with the

requirements of AS 5100.7:2017. The cumulative fatigue damage and remaining fatigue life of

all critical structural components shall be calculated as part of this assessment.

10.1. Load history Historical loading data shall be obtained from reliable sources. Past working timetables for

passenger and freight trains may be available and the Australian Railway Historical Society can

be helpful in compiling load history data for the bridge.

Future fatigue loading shall be based on the assumption that current passenger and freight

timetable arrangements are maintained, or future predicted operations as advised by the RIM or

TfNSW. Future operating train consists shall be in accordance with Table 5 unless otherwise

advised by TfNSW.




10.2. Rivets Clause 13.2 of AS 5100.7:2017 provides requirements for the fatigue assessment of rivets and

bolts. Fatigue analysis of the rivets based on I.S. EN 1993-1-9 Eurocode 3: Design of steel

structures - Part 1-9: Fatigue (Including Irish National Annex) shall be used for estimating the

remaining fatigue life of rivets for comparison purposes with AS 5100.7:2017. A discussion and

comparison of the results of the two methods shall be included in the report.

The AEO shall recommend the method to be adopted.

10.3. Fatigue life If an underbridge is shown to have reached the end of its theoretical fatigue life, an additional

higher tier detailed analysis incorporating strain-gauge measurement and finite element analysis

or other instrumentation and monitoring shall be undertaken in consultation with the RIM in

order to obtain a more accurate fatigue assessment.

Visual examination on site shall be undertaken to look for supporting evidence of fatigue

damage.

Recommendations for interim actions should be made if evidence of fatigue damage is found.

11. Substructure Substructure shall be load rated in accordance with AS 5100.7:2017. This shall include a

stability analysis (sliding and overturning).

Most existing underbridges have heavy piers and abutments which have been performing

satisfactorily. Substructures which are in good condition, that is, free from defects affecting

structural performance, integrity and durability, negligible settlement, lateral or rotational

movement of the substructure, do not need to be load rated if the design loading is known from

existing drawing records and the design load is sufficient for operating train consists.

11.1. Stability analysis Many TfNSW bridges have masonry piers and abutments with unknown thickness, footing

depth, backfill and foundation material. If design drawings are not available and as directed by

the RIM, core holes shall be taken through the substructure to determine the relevant

parameters for load rating and stability assessment. If core holes are not taken, then all

assumptions related to the material properties and dimensions shall be stated and

substantiated.

Older substructures may be found to be unstable if assessed as free standing and require the

superstructure to provide propping for stability. Stability analysis with and without propping from




the superstructure shall be undertaken. The AEO shall assess whether the bridge has adequate

mechanisms to resist the propping actions.

If settlement has not occurred, and foundation loads have not significantly increased over the

original design load over 10%, then the geotechnical strength of the founding material may be

assumed to be adequate for the foundation bearing pressure. Additional requirements are

specified in Clause 10.6.1 of AS 5100.7:2017.

The results of the stability analysis shall be presented in terms of equivalent LA rating factor and

as a factor of safety against sliding and overturning for both the design rating load and operating

consist.

12. Load rating factor The load rating factor (RF) shall be calculated in accordance with Clause 14 of AS 5100.7:2017.

In the absence of any previous load rating, the initial ‘as-new’ load rating may be adopted as the

design load stated on the approved design drawings if the bridge is in good condition and

conforms to the design and ‘as-built’ drawings.

For subsequent capacity assessments, an ‘as-new’ and ‘as-is’ RF shall be calculated and

records updated.

12.1. Combined actions Clause 14.3 of AS 5100.7 deals with combined load effects; however, it does not provide clear

guidance on the use of the interaction equations for use with the rating factor (RF).

Where the value of the interaction equation from AS 5100.5, AS 5100.6 and AS 5100.9 is

calculated as less than 1.0, the live load factor, γQ, shall be increased until the value of the

combined action equation is equal to 1.

The modified γQ resulting in RF =1, divided by the original (AS 5100.7) value of γQ, will

represent the RF for that live load.

For example, if a MF operating consist with a value of γQ = 1.4 results in a combined load effect

equation value of 0.8, then γQ is increased until the value of the combined load effect equation

is equal to 1.0, say γQ = 1.5 for this example. Therefore the RF is equal to 1.5 / 1.4 = 1.07. The

load rating is 1.07MF.

Where the value of the combined load effects equation is greater than 1, the RF is calculated in

a similar manner, but decreasing the value of γQ.




12.2. Bridges with rating factor less than 1.0 Where the RF for a component or connection is assessed as less than 1.0 for an operating train

consist load, the following shall also be calculated:

• The reduced live load factor γQ based on an RF = 1.0 with full value of α (for example, if RF

= 0.9 for γQ = 1.4, then γQ may reduce to say 1.26 for RF = 1.0).

• The reduced load rating based on an ‘α’ value of zero and full design γQ (for example, if LR

= 273LA for full value of ‘α’ = 0.23, then LR may increase to 335LA for ‘α’ = 0).

• The permitted track speed based on a reduced α which results in a RF = 1.0 using full

design live load factor γQ (for example, if RF = 0.9 for 80 kph, the required speed may

reduce to say 40 kph for RF = 1.0).

• For RF = 1.0, it may be required that the value for ‘α’ is less than the 0.2 lower limit in

Eqn 9.5.3 of AS 5100.2. The actual calculated value of α shall be reported. The AEO shall

make comments and recommendations in the report.

For bridges with wind or sway bracing members in tension or compression governing the load

rating, a revised assessment with the governing bracing member(s) omitted (assumed buckled)

shall be undertaken. A revised RF for the bridges shall be calculated. The AEO shall compare

results and recommend the RF to be adopted.

For jack arch and filler beam deck bridges which have been assessed under the provisions of

BD 61/10 or other approved methods, a RF with and without composite action shall be

calculated. The AEO shall recommend the RF rating to be adopted.

For a bridge which is assessed as less than the required capacity for the nominated operating

train consist, that is, RF <1, consideration should be given to using higher tier assessment

methods as nominated in AS 5100.7:2017.

13. Capacity deficient and fatigue life expired bridges Many of the underbridges in the TfNSW heavy rail network have been designed for loads which

are below current design loads stated in AS 5100 and ESC 310 Underbridges. The RF for

current design loads for these bridges may be less than 1.0.

The RF for the operating consists may also be less than 1.0 and these bridges are of particular

concern for the safe operation of the TfNSW heavy rail network.

AS ISO 13822 Basis for design of structures – Assessment of existing structures (ISO

13822:2001, MOD) may be applied in accordance with Clause 10.6.1 of AS 5100.7:2017 to

demonstrate that a bridge is safe, subject to satisfying the required conditions.

The RIM shall have a process in place for the safe management of capacity deficient bridges

and bridges which are assessed to be fatigue life expired.




These bridges may require strengthening or replacement. Asset decisions shall take into

account the life cycle cost considerations specified in T MU AM 01001 ST Life Cycle Costing.

14. Bridge capacity assessment report requirements A written report based on the results of the bridge capacity assessment shall be prepared by the

bridge rating AEO.

The bridge capacity assessment may be part of a broader bridge investigation; however, the

bridge capacity assessment (load rating and fatigue) shall be contained in a separate report.

The bridge capacity assessment report shall contain information as described in Appendix E.




Appendix A Operating consist axle diagram Figure 1 illustrates the operating consist axle loads and spacing.

The overall vehicle length dimensions are measured to the coupler pulling faces and the dimensions are in millimetres (mm).


Figure 1 - Operating consist axle diagrams



Appendix B Historical design loads Figure 2 illustrates the E50 and E60 design load.

Loads are in pounds (lbs), length is in feet (‘) and inches (‘’).


Figure 2 - E50 and E60 design load



Figure 3 illustrates the M250 and M270 design load.

Loads are in kiloNewtons (kN), length in metres (m).


Figure 3 - M250 and M270 design load



Figure 4 illustrates the 300-A-12 axle group spacing.


Figure 4 - 300-A-12 axle group spacing



Appendix C Bridge load rating executive summary table - sample layout The bridge load rating executive summary shown in Table 6 provides an example of criteria required for load rating assessment. The notes provided indicates

information the assessor would capture.

Table 6 - Sample bridge load rating executive summary table

Bridge and type: Central Road Underbridge

Location: Central

Route and tracks: Main Suburban: Up Main & Down Main

km: 1.000 km

Design drawing load capacity: M270

Critical bridge components 300LA(2) MF(2)

As new As is As new As is

Bridge member or connection or critical section(1)

Design action(1)

As-is section loss (% thickness loss and element)

Rating factor (RF)

Rated load (LR)

Rating factor (RF)

Rated load (LR)

Rated load without DLA (α=0.0)

Reduced speed for RF=1 (If applicable)

Rating factor (RF)

Rated load (LR)

Rating factor (RF)

Rated load (LR)

Rated load without DLA (α=0.0)

Reduced speed for RF=1 (If applicable)

Main girder (mid-span)

Moment 10% bottom flange thick. 1.25 375LA 1.20 360LA 482LA N/A 1.75 1.75MF 1.7 1.7MF 2.3MF N/A

Main girder (end)

Shear 20% web thickness 1.00 300LA 0.91 273LA(4) 335LA 41 km/h 1.4 1.4MF 1.3 1.3MF(4) 1.6MF N/A

Notes: (Italic text is input by load rating engineer)

(1) The critical bridge structural member or connection or section with the critical design actions shall be included for each reference vehicle.

(2) Additional columns or tables can be added or deleted for the nominated rating vehicles and bridge specific items and actions.

(3) Additional rows can be added to note load rating subsequent to any bridge component proposed strengthening or repair.

(4) Critical load rating(s) shall be highlighted. In the example above load critical rating entries are in bold text © State of NSW through Transport for NSW 2018 of 31



Appendix D Bridge load rating assessment summary table – sample layout The bridge load rating engineering assessment shown in Table 7 provides an example of criteria required for load rating assessment. The notes provided indicates information the assessor would capture.

Table 7 - Sample bridge load rating engineering assessment table

Assessment Type: Ultimate Limit State (ULS) as new and as is [or Serviceability Limit State (SLS) as new & as is etc.]

Bridge & Type: Central Road Underbridge

Location: Central

Route and Tracks Carried Main Suburban: Up Main & Down Main

Km: 1.000 km

Design drawing load capacity: M270

Reference Rating Vehicle (LRV): 300LA + serviceability wind of 20m/s

Bridge component (1)

Design action (2)

Member length (L)

Member Character-istic length (L )

‘As is’ section loss (% thickness loss)

Capacity reduction factor (Φ)

‘As new’ design capacity (ΦRu)

‘As is’ design capacity (ΦRu)

Dead load factor (γg)

Super imposed dead load factor (γgs)

Factored permanent load effects PE [γgSg*+ γgsSgs*+ Sp*+Ss*+St*]

‘As new’ Available capacity for live load effects [ΦRu-PE]

‘As is’ Available capacity for live load effects [ΦRu-PE]

Live load factor (γQ)

Dynamic load allowance (α)

Multiple track factor (W)

Factored live load effects [γQ(1+α)W (SQ*)](3)

As new As is

Rating factor (RF)(3)

Rated Load (LR)(3)

Rating factor (RF)(3)

Rated Load (LR)(3)

Rated load (LR) (3) without DLA (α=0.0)

Reduced speed for RF=1 (If applicable)(3)

Reduced (γQ) for RF=1 (if applicable)(3)

Main girder

(mid-span) Moment 20m 20m

10% bottom flange

0.9 3960

kNm

3600

kNm 1.1 1.4 600kNm 3360kNm 3000kNm 1.6 0.34 1.00 2500kNm 1.25 375LA 1.20 360LA 482LA

Main girder

(end) Shear 20m 20m 20% web

thickness 0.9 1360kN 1260kN 1.1 1.4 260kN 1100kN 1000kN 1.6 0.23 1.00 1100kN 1.00 300LA 0.91 273LA(4) 335LA 41km/h(4) 1.26(4)

Intermediate Stringer

End stringer Intermediate X girder

End X girder X girder to Main girder connection

Deck slab Bearing Wind bracing Sway bracing

LOWEST RATING (4) 1.00 300LA 0.91 273LA(4) 335LA 41km/h(4) 1.26(4)

Notes: (Italic text in table is input by load rating engineer)

(1) All relevant structural members and connections and critical sections shall be included (examples shown only).

(2) Actions shall include AS 5100.2 railway traffic relevant possibilities such as moment, shear, torsion, axial, centrifugal, braking, traction, nosing, lateral, derailment, wind and combinations.

(3) Additional columns or tables can be added for other nominated rating vehicles and bridge specific items.

(4) The critical load rating(s) shall be highlighted.

(5) Substructure rating shall be in separate table(s)

(6) Modify table as required for combined actions




Appendix E Bridge capacity assessment report information

The bridge capacity assessment report shall contain the following information as a minimum:

1 Executive summary

The executive summary shall include a brief description of the bridge together with summaries

for the following:

• bridge ‘as-is’ condition

• results of the load rating and fatigue assessment

• critical members and load cases determining the governing rating factor (RF)

• discussion of results

• conclusions and recommendations

2 Introduction

• project introduction

• project scope

3 Bridge description

• description of the bridge structural form, both superstructure and substructure

• tracks and track form supported by the bridge; include description of track alignment, that

is, curved or tangent track

• list the design and as-built drawings

4 Condition assessment

• summary of the ‘as-is’ condition of the bridge

• paint condition assessment if applicable

5 Load rating

5.1 Methodology

• include a full description of analysis methods and assumptions made for the superstructure

• describe the software used and full details of the structural model or models used with

diagrams included to support the model or models

• for steel bridges with wind and sway bracing, the rating report shall specifically comment

on the condition of the bracing and how it has been modelled




5.2 Material and section properties

• list all relevant material strengths and capacity reduction factors adopted

• list all assumptions made in relation to ‘as-new’ and ‘as-is’ geometric properties (for

example. state whether ‘as-is’ section properties are based on actual section loss

measurements or assumed section loss based on qualitative condition descriptions)

5.3 Member capacity

• capacity reduction factors

• effective lengths of members

• tabulated design capacity of each critical component (member and section capacities)

• combined action effects shall be identified and reported. The sample layout table in

Appendix D shall be modified to account for the combined action equation (and equation

number) and relevant inputs.

5.4 Loads

• permanent and superimposed loads

• description of traffic loads including diagrams or tables displaying the assessed train

consists and rolling stock axle loads and spacing

• horizontal loads included in the analysis

• DLA for each main member and connection, including actual and characteristic lengths

• ULS and SLS load factors

• multiple track factor

• serviceability wind speed if included

5.5 Analysis results and rating factors

• Include summary tables for permanent load effects and live load effects for each main

structural component and connection for both as-new and as-is.

• Include summary RF tables for the design load(s) and the operating consist(s) for ‘as-new’

and ‘as-is’ conditions, with and without the serviceability wind load included.

• For bridges with load rating less than 1.0 for an operating train consist load, the additional

assessments required in Section 12 of this standard shall also be included.

• For bridge members without shear connectors and where composite action is possible,

such as jack arch decks, and has been assessed, include summary tables for member

actions and rating factors with and without composite action.

• The full results shall be presented in the form shown in Appendix C and Appendix D.




5.6 Rating factor discussion

• Discuss the results of the capacity assessment in relation to the bridge’s ability to support

the design load and operating consists.

• Identify deficiencies in the bridge capacity.

• Reduced α and associated speed restrictions if required

• The bridge capacity shall be compared to the original design load and comments made in

the report. If the design load is not stated on the relevant drawings, the historical design

loads in Table 4 may be adopted for comparison purposes.

• Where there are significant differences (>10%) in the calculated capacity and expected

capacity based on known design load or previous load rating reports, a reasoned

explanation for the differences shall be provided.

6. Fatigue assessment

• fatigue assessment methodology

• list assumptions made for load history. Identify sources of information used

• effective cycles

• load factors and DLA applied

• fatigue detail categories for main members and connections

• capacity reduction factors

• tabulated values for cumulative damage and remaining life for each main component and

connection

• discussion of fatigue assessment results and recommendations

7 Substructure capacity assessment

• describe the analysis methods used for the substructure assessment

• substructure rating and stability analysis results

• discussion of results

8 Conclusions and recommendations

• from the capacity assessment, identify issues and deficiencies with the bridge

• include any short term and long-term actions required to ensure safe operation of the

bridge




9 Appendices

The appendices should include the following:

• photographs of the underbridge (including an elevation view and a view along tracks, up

and down directions)

• relevant drawings for the bridge

• site investigations undertaken, such as survey measurements, thickness measurements,

geotechnical core and bore holes

• condition assessment reports – inspection report including detailed description and photos

of defects

• axle load diagrams

• load effects summary and rating factors

• fatigue damage and remaining life calculations


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