Response to Bridge Technical Reports
This document outlines the recommendations of six (6) technical reports on bridges across the NSW rail network, carried out by an independent auditor of bridges, URS Pty Ltd. The subjects of each report are:
- Timber underbridges
- Overbridges
- Wrought Iron bridges
- Pre-stressed concrete rail bridges
- Structures health
- Bridge painting
Brief background is provided on each issue, and the key recommendations and findings of the Technical Reports are listed, noting actions taken to date by Rail Infrastructure Corporation (RIC), and additional planned actions, where applicable.
Technical Report TR.036 - "Strategic Study Timber Underbridge - Stage 1 Condition Survey (Feb 1998)"
Background
Timber underbridges were designed and built to meet the requirements at the time of construction. In the past, this produced extensive rail lines constructed from cheap and abundant local resources, with comparatively low labour costs.
Over time, increased labour costs, a scarcity of appropriately skilled workers and a lack of timber in suitably large dimensions, led to a move away from these types of structures. Traffic volumes and average axle loadings have also substantially increased since these bridges were built. As a result, materials able to carry a greater load have been sought.
Today there are no timber bridges on the Metropolitan operational network or on the main interstate lines. Existing bridges are on the lower traffic secondary and branch lines.
Due to budgetary constraints applied over the past 20 years, there is now a significant backlog of renewal of timber bridges that have reached the end of their economic life. These bridges are maintained in a safe condition through increased routine maintenance and short-term repairs.
Technical Report TR 036 "Strategic Study - Timber Underbridges: Stage 1: Condition Study: February 1998" was commissioned in the early days of Rail Access Corporation, ("RAC"), predecessor to the Rail Infrastructure Corporation, to assess the magnitude of the backlog. The Report investigates 718 timber underbridges and 110 timber box culverts with openings ranging from less than a metre up to 330 metres in length.
All underbridges are inspected in detail every two years. They are subject to visual inspections by track patrol twice a week on passenger lines, and at least once a fortnight on freight lines.
While this report rates 278 of the bridges in poor condition, this does not mean the bridges are unsafe. It means they need maintenance.
Where necessary for operational safety, temporary repairs such as propping or packing (providing additional support to the structure taking stress away from the strained area) have been undertaken.
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Key Report findings and Recommendations |
Actions to date |
Actions planned |
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Findings 40% of timber underbridges had defects at or exceeding permissible limits. These underbridges will require an estimated expenditure of $10 million to rectify. The total maintenance requirement within the next 5 years will involve around 450 underbridges, at an estimated cost of $40 million, including $15 million for removal of temporary supports. RecommendationDevelopment of Strategies to address the backlog. |
With the increase in available maintenance funding since the formation of RIC, a limited prioritised renewal/replacement program has resumed. Significant progress has been made on the Narrabri to Moree, The Gap to Binnaway, Parkes to Stockinbingal, Joppa Junction to Canberra sections, and on the Murwillumbah Branch. Substantial additional work still needs to be carried out, particularly on the wheat Branch Lines and the Murwillumbah line. Where practical, individual components of some bridges have been replaced in modern equivalents - eg timber pier replaced with a steel or concrete pier. This will allow a staged replacement in more durable/modern materials. |
On smaller structures, to continue the program of component renewal in durable/modern materials or replacement with alternate structures. Larger structures will be replaced with alternate structures as part of the current on-going MPM (Major Programmed Maintenance) Program. RIC is planning for the replacement of all timber underbridge structures on all operational lines within a 20-year horizon, subject to funding availability. |
Technical Report TR.048 - "Overbridge Design Rating, December 1998"
Background
Road overbridges (road bridges over railway tracks) were designed and built to meet the requirements of the time. Traffic volumes and loads have increased dramatically since most of the bridges were built.
RIC is obliged to maintain bridges to their `as built' rating, making them safe for the traffic for which they were designed.
Routine maintenance is programmed as required.
All road overbridges are inspected in detail every two years, and undergo visual inspections by track patrol twice a week on passenger lines and at least once a fortnight on freight lines.
RIC standards on inspections cover frequency of inspections, inspection methodology, defect identification and repair response.
This Report investigates 625 steel, timber, concrete/brick arch overbridges (of approximately 870 in NSW).
It found 298 bridges have a capacity that is less than the maximum allowable road vehicle.
The majority of overbridges with capacity restrictions now have their load capacities sign-posted.
In addition to this, an extensive program of overbridge parapet strengthening has occurred in recent years, and will continue in the future.
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Key Report Findings And Recommendations |
Actions to date |
Actions planned |
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Recommendations That load capacity requirements be confirmed for all road overbridges, particularly where load capacity rated as less than T30 design loading. Overbridge signage to be improved. Follow up studies for guardrails, barriers and parapets. |
Bridges load capacity, signage, guardrails, barriers and parapets are assessed during routine maintenance and are upgraded if necessary, on a priority basis. Between the 1998-99 and 2001-02 financial years, over $25.6 million was spent on improving overbridges. $19.5 million of this figure was spent on maintenance work, which included overbridge renewals at Wirragulla, Burwood and Karangi. Other works included blast and paint repairs to steel structures, parapet renewals, safety screen replacement, white ant treatment to timber structures, deck repairs and upgrading. Over $3.5 million was spent through capital expenditure, including the Flemington Junction and Lidcombe Shuttle overbridges. Around $2.6 million was spent on the following projects; the abutment stabilisation at Ocean View bridge in Robertson, an upgrade to Medlow Bath Great Western Highway overbridge and work to Horsley Drive Overbridge in Metro South. The overbridge on Wilsons Parade Heathcote, was renewed during the 2002/03 financial year. Work on the bridge amounted to over $2 million, improving infrastructure on the Illawarra line in the metro area. A risk assessment of over-line structures was also undertaken. Ongoing signage improvements to load rating signage are being completed in cooperation with Councils and RTA, on a priority basis. In 2002/03, approximately $2 million was spent on overbridge inspection, repair, and renewal in country areas. This amount is typical of past and planned future expenditures. In the last five years there have been five overbridges replaced in country NSW: three on the North Coast at Upper Orara Rd, Karangi, ( $1 million); Cowper St, Taree, ($400,000); Clarence town Rd Wirragulla, ($500,000); and two in the North West at Booralong, near Dumaresq ($450,000) and Bolivia, north of Glen Innes ($150,000). |
Overbridge renewal/modifications for Metro in the next two years are $900,000 for Lawson St overbridge in Redfern, and $2.5 million for Erskineville Rd Newtown. Continuation of the review of overbridge signage - consistent with capacity of bridge and traffic requirements. RIC Engineering are managing a project to identify candidate bridges for renewal or upgrade based on road user needs, in cooperation with the RTA and local government. |
Technical Report TR.056 - "Strategic Study - Wrought Iron Bridges, July 1999
Background
All of the major bridges discussed in this report, with the exception of Menangle, were the subject of the Coordinator General of Rail's inquiry into wrought iron bridges.
This Technical Report, TR.056, covers wrought iron metallurgy, wrought iron bridge components and wrought iron bridge maintenance requirements. It provides specific information and pictures of some bridges in the network. However, it does not seek to duplicate the work of the Coordinator General, and therefore does not deal with the condition of wrought iron bridges.
All wrought iron bridges discussed in this report have been deemed safe, with current weight and speed restrictions.
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Key Report Findings and Recommendations |
Actions: To Date and Planned |
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Finding This report illustrates the difficulties involved in assessing the rating and fatigue, and repair and strengthening of wrought iron bridges. |
Since March 2003: RIC received recommendations by RIC's independent auditor of the major wrought iron bridges, URS Pty Ltd, on short-term and ongoing actions required for major wrought iron bridges. The urgent short-term actions, such as weld testing at Wagga, are complete, while the longer-term actions will be incorporated into the 2003/04 Asset Management Plan. The RIC Board is monitoring the replacement of the wrought iron bridges at Menangle, Wagga, Bathurst and Wellington. Monthly updates to the Board on this process commenced in June 2003. A review of asset management plans and processes for all bridge structures is underway. This review includes asset management plans for all major bridge structures, commencing with the nine wrought iron bridges. URS have been engaged to produce the Asset Management Plan for wrought iron bridges and has provided draft documents to RIC for review and field staff input. Detailed maintenance plans will be incorporated into the asset management plans developed for major bridge structures. Commencing in 2003/04, as the asset management plans are developed, qualified management will provide annual certification to the RIC Board, that the maintenance plans have been implemented and assured. RIC will continue to regularly brief the Rail Safety Regulator on the progress of these issues. |
Technical Report TR.035 - "Prestressed Concrete Rail Bridge - Investigation of techniques available for the detection of tendon loss due to corrosion/electrolysis, February 1998
Background
A significant failure mode of prestressed concrete structures is loss of prestress due to corrosion.
This Technical Report, TR.035, documents an investigation into techniques available for the detection of tendon loss due to corrosion and electrolysis (leakage of electrical current).
The investigation covered the latest technology available for detection of tendon loss in prestressed concrete bridge elements.
The study identified ten techniques that had the potential for use. However, an evaluation by an engineering consultancy reduced this range to two.
It was later established that these two techniques were still undergoing field verification in the USA, and were not yet commercially available.
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Key Report findings and Recommendation |
Actions to Date |
Actions Planned |
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Finding It has been established that, world wide, there is currently no specific technique available, which can be used in a random examination mode, for the detection of tendon loss in prestressed concrete structures. However, the need for such a safety assurance aid remains. Recommendation That the results of this research project be updated in 2 years time. |
Research has not yet been updated due to allocation of resources to higher priority projects. |
The research will be updated during 2003/2004. RIC's independent consultant for the Georges River bridge at Como, Ove Arup & Partners, is investigating techniques that may be appropriate for this location. |
Technical Report TR.045 - Structures Health Report, November 1998. (Updated in 2001 and 2003)
Background
Technical Report TR.045 Structures Health Report 1998 was commissioned in the early days of the Rail Access Corporation to provide Asset Managers with a better understanding of the condition of structural assets and to optimise their management.
The report is a snapshot of the infrastructure condition at that time, and provides an understanding of overall maintenance needs and the special risks associated with various structures.
The information allows individual sites to be targeted and assessed for prioritised action.
Functional issues, including the risk of road motor vehicle collisions with underbridges, the need for protection of columns supporting underbridges, and provision of walkways and guard rails on underbridges, are also addressed within the report.
Progress has been made on the implementation of the numerous findings and recommendations.
RIC will take action to ensure the findings and recommendations are fully investigated and implemented as appropriate.
Details on specific bridges, mentioned in the Structures Health Report, are being reviewed by RIC, with the Rail Safety Regulator kept informed of progress.
Performance Indicators for bridges have been developed and will be reported on from October 2003.
The table below lists the key recommendations from the Structures Health Report, the actions taken to date by RIC, and further actions planned, where necessary. If the recommendations overlap with issues dealt with in more detail in another Technical Report, a reference to that document is provided, in place of lengthy repetition.
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Report Section |
Key Report findings and Recommendations |
Actions to Date |
Additional Actions Planned |
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Overall |
No structural or geotechnical adjustments should be made at any bridge site without investigation and certification from appropriate discipline experts. |
This requirement has been included in the new RIC Design Standard and is supported by Engineering Authority, which is granted to qualified staff. |
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Underbridges General |
Develop and implement strategies to achieve consistent, relevant examination reporting, including reviewing examination rules and procedures. |
The "Teams II" defect management system has been implemented for defect recording. A Bridge Management System is under development, with a draft Bridge Inspection Manual nearing completion. The first draft of standards for bridge-rating has been developed. |
RIC is reviewing its bridge examination and maintenance standards. Finalisation and publication of the standards will occur as part of the 2003/04 Civil Standards development programme. |
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Investigate and rate all bridges of concern and verify that other bridges are of adequate capacity. Repair and renewal should be done as appropriate. |
A "desktop rating", using design drawings of North Coast bridges, was completed in 1999/2000. (More detailed ratings are required based on field studies of current condition). Investigation and rating of Murwillumbah line bridges is in progress. Ulan line bridges have been strengthened for 120 tonne coal wagons. RIC commissioned independent investigations for 42 separate bridges during 2003. |
RIC is developing programmes for rating all bridges. Priority repairs have been, and are continuing to be undertaken. | |
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Steel & Wrought Iron Underbridges |
The Structures Health Report made a range of recommendations in relation to Steel & Wrought Iron Underbridges. These are addressed in greater detail in the Strategic Study - Wrought Iron Bridges, July 1999 (TR.056) and the Technical Report TR.067 on Bridge Painting. | ||
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Timber Underbridges |
Recommendations made in the Structures Health Report regarding Timber Underbridges are covered in Strategic Study - Timber Underbridges: Stage 1 Condition Study February 1998, Technical Report TR 0.36. | ||
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Masonry and Concrete Substructures |
The recommendations made in the Structures Health report regarding Masonry and Concrete Substructures are addressed in the notes provided on Technical Report TR.035 Prestressed Concrete Rail Bridges. | ||
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Overbridges |
The recommendations regarding overbridges are addressed in greater detail in Technical Report TR.048; Overbridge Design Rating, December 1998. In addition to our response to that document, it can be noted that RIC's "Structures over Line" project produced a risk assessment model, that includes overbridges, which is currently being implemented. | ||
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Overhead Wiring Structures |
The overhead wiring system is a key component in the reliability of the suburban passenger system and it is important that the modernisation be completed within a reasonable period. |
The programme of modernisation is continuing. Within the last 12 months, major works have been completed in the CBD (Goulburn Street carpark to Redfern), on the North Shore line, the Bankstown line, the Richmond line and on the western line at St Marys. |
Replacement of overhead wiring and power substations will continue throughout the metropolitan area during 2003/04. |
Technical Report TR.067 Bridge Painting, June 2000
Background
Rail bridges were painted with red lead paint from the commencement of railways in NSW in 1855, until the early 1980s.
Red lead primer was used because if its superior corrosion protection in less than perfect preparation conditions.
Red lead is now unacceptable because of environmental and occupational health aspects.
Compliance with environmental and occupational health standards makes repainting of steel rail bridges very expensive.
The cost to remove and recover red lead and repaint, or encapsulate red lead, in all bridges is of the order of $200 million. This does not include the cost of doing necessary repairs prior to repainting.
The report provides some general recommendations for treatment of bridges on various rail lines and identifies the priority bridges for painting. The overall approach to bridge painting is discussed below.
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Key Recommendation |
Actions to Date |
Additional Actions Planned |
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A major programme of bridge repair and repainting is required. Eight bridges with the highest priority are recommended for work first. Work must commence within two years and be completed within four years. |
Priority repairs are being carried out. Work was completed in July 2003 on Coopers Creek underbridge at Woodlawn. During 2003/04, $800,000 will be spent at Repton, and $300,000 at Eltham. Some repairs have been done at Urunga, and repairs are in progress at Booyong. All repairs are painted after work has been undertaken. |
A programme of priority steel repairs and painting will continue to be implemented. Repairs are prioritised and funded on the basis of structural integrity. A strategy for managing red lead issues will be developed and implemented. |