Design and Construction of the Narrows Bridges
Editor: James Trevelyan (October 2023)
Introduction
The Narrows Bridge serves as a scenic gateway to the city of Perth.
The Narrows appears as one bridge. However, it is in fact three separate bridges, built between 1955 and 2005. They are so similar in geometry, that they appear to be integrated as a single bridge, achieving the intended elegant architectural aesthetic, which was the primary design objective for all three bridges.
Approaching from the west, from the broad stretches of Melville Water by car or boat, one passes under the Narrows bridge.
Approaching from the south by road along the Kwinana Freeway, one passes over the Narrows Two bridge.
Even from the north, approaching on the Mitchell Freeway, one glimpses the bridges as one takes the exit towards Elizabeth Quay on the Perth Water side of the city.
Designing or involvement in the construction of a large bridge is one of the pinnacle achievements, an aspiration for many civil engineers, an achievement associated with great prestige among their peers. The aura associated with a large bridge is all the more intense with a bridge in a prominent location, as in the case of the Narrows Bridge, which is on display to the main commercial hub of the city and where the three individual bridges were observed on a daily basis during construction.
A large bridge is also a hallmark achievement for any engineering firm, both in design and construction. The two Narrows road bridges were technical “firsts” in their day, and involved major technical challenges and significant unknowns in attempting to do things that have never before been attempted in this country, or in the case of Narrows Two, in the world.
Unfortunately, time has moved on, as have the various organisations and individual who were associated with the design and construction of the Narrows bridges. There is a need to acknowledge these organisations and identify their “succession” firms.
The first road bridge (Narrows One) was built by a joint venture of JO Clough and Son and the Danish firm Christiani and Neilson. Sadly, Harold Clough, the founder of Clough Group, passed away in 2022. The Clough organisation has gone through ownership changes and is currently a subsidiary of the firm WeBuild Group. Christiani and Neilson originated in Denmark and is now based in Thailand. Maunsell and Partners, the British consulting engineering firm responsible for the design of Narrows One is now part of AECOM, with offices in Perth and around the world. The second road bridge (Narrows Two) was built by Leighton Contractors which is now part of the international CIMIC Group and trades in Australia as CPB Contractors. The principal designer for Narrows Two was Connell Wagner which today is known as Aurecon.
Narrows Three (the rail bridge) was also built by Leighton Contractors and designed by consulting engineers GHD.
It is important that we acknowledge these engineering achievements as part of the engineering heritage of Western Australia. The story of the three bridges in the following paper has resulted from a special presentation to the Engineering Heritage Group in Western Australia in June 2022 by Duncan Robinson, Gerry Hofmann and Geoff Robinson. The presentation was to celebrate the (Covid-delayed) 60th anniversary of the opening of the first Narrows Bridge. In this paper, we present the story of the Narrows Bridge in five chapters, each of which is a separate downloadable PDF file with comprehensive illustrations.
Chapter 1: Recognising the Need
This first chapter is based on Duncan Robinson’s presentation, describing Perth in the years before 1956 when construction started on the Narrows One road bridge. His chapter describes the rapid growth in population and car ownership in Perth following the end of the Second World War in 1945. He described the remarkable foresight of city planners in the 1950s to set aside land for transport corridors long before they were needed, an enormous benefit for the Perth community in the 21st century.
Download Chapter 1: Perth before the Narrows Bridge
Chapter 2: The First Narrows Bridge
Chapter 2, based on Garry Hofmann’s presentation, then conveys the story of the Narrows One road bridge construction. Narrows One was the first major public infrastructure project in Western Australia constructed by contract with a private contractor.
At the time, there were no companies in Perth, or indeed Australia, with the necessary expertise to build a bridge of the form and complexity of the first Narrows bridge. Fortunately, Harold Clough, a young WA born engineer, had the enterprise, determination and persistence to form a joint venture with an experienced Danish company, Christiani & Nielsen who had constructed similar bridges before. Through them, he managed to bring the necessary prestressed concrete bridge construction expertise to Australia for the first time, and in doing so transformed the Perth and Australian engineering scene.
The bridge itself was constructed on time and within the original budget adjusted for a major variation, the foundations of the north abutment, when it was discovered that lateral soil consolidation was occurring both vertically and laterally, necessitating a re-design of the piled foundations.
When completed in 1959, the first Narrows bridge was the longest pre-stressed concrete bridge in the world and with the longest major span. Thanks to the input from Don Young, who worked on the bridge as a young site engineer and the technical presentation by Gerry Hofmann, we are able to present a far more detailed exposition of its design and construction than has previously been available.
Download Chapter 2: Narrows Bridge Design and Construction (updated November 2023)
Chapter 3: The Intervening Years
Forty years after Narrows One was opened, Perth’s population had doubled with much of the expansion north and south of the city located within twenty kilometres of the coastline. In Chapter 3, Duncan Robinson’s presentation is transcribed to outline the expansion of the Mitchell Freeway to the north of the city, and the Kwinana Freeway to the south. Inevitably, with further increasing car ownership, traffic on the Narrows Bridge became congested and successive state governments grappled with the necessity to expand transport capacity. However, the demand for road space outpaced government decision-making resulting in a somewhat urgent decision to construct the Narrows Two bridge immediately to the west of the first bridge. The WA government embarked on a tight, two-year program to deliver the second bridge, in about half the time needed for the first bridge. Main Roads decided that a Design-and-Construct delivery model would be the optimum contractual method for achieving this tight schedule and proceeded accordingly.
Download Chapter 3: The Intervening Years
Chapter 4 Duplicating the Narrows Bridge
This chapter is based on the presentation by Geoff Robinson and gives a detailed description of the design and construction aspects of Narrows Two.
Narrows Two was initiated when four prequalified consortia, each consisting of one or more construction contractors teaming up with one or more design consultants, were invited to submit their tenders for what was termed ‘The Narrows Duplication Project’. The D&C project scope included the Narrows Two bridge and additional auxiliary works, in accordance with an extremely stringent set of scope of work and technical criteria that had been produced by Main Roads. A non-negotiable requirement was that the second bridge had to replicate the first bridge, both architecturally and structurally, with exactly the same spans and similar width and lane configurations.
The normal method for constructing major concrete bridges in WA at the time was incremental launching. The Windan Bridge crossing the Swan River at East Perth is an example. The second Mount Henry bridge is another. However, being of varying cross sections throughout its length, it was initially considered that incremental launching was not appropriate for Narrows Two. As a result, each of the four bidders proceeded to prepare their designs and cost estimating based on alternative techniques, which, at that time, were usually more expensive than incremental launching. However, one consortium, consisting of Leighton Contractors together with their designers, Connell Wagner, realised that while the soffit (underside profile) of the bridge consisted of a series of arches, the upper flange followed a line of a constant radius curvature. The idea of incrementally launching the bridge was born. Instead of supporting the structure during launching on the underside of the main bridge girders, the bridge would be supported from under its upper flanges – like being “hung under one’s armpits”. Leighton and Connell Wagner proceeded to develop this concept during the remainder of the tender period, in consultation with specialist subcontractors, with all parties sworn to secrecy. After tender evaluation by Main Roads, the Leighton consortiums’ tender bid was selected as the winning proposal. They were duly awarded the D&C Contract and went on to complete the project using incremental launching technology.
It is understood that this was the first time anywhere in the world that an arched bridge with varying cross section had been incrementally launched. In any event, neither the designer nor the contractor had launched an “arched” bridge before, so they had to develop the design and the launching system from scratch.
While the final result was a world class engineering achievement, during the project, and to this day, there remain lingering doubts on the wisdom of choosing to incrementally launch an arched bridge, and whether that was the most cost-effective construction method. Indeed, to the authors’ knowledge, this system has not been replicated again anywhere in the world. One can only speculate as to whether this is due to financial considerations or lack of technical knowledge, since details of how this was achieved on Narrows Two have, to date, never been published. In any event, conceptual design of a typical incremental launched bridge would use a constant cross-section and other features for a practical and efficient launching process. This was not possible for Narrows Two where the bridge geometry was dictated by the need to replicate Narrows One.
At the time of Narrows Two, clients, designers and construction firms in Perth had accumulated considerable experience in the decades following construction of the first Narrows bridge. Private and public clients, including Main Roads could then rely on construction contractors managing technical and commercial risks, and undertaking their projects accordingly. The choice to deliver Narrows Two by Design-and-Construct, therefore, proved to be a sound decision by Main Roads.
With the wisdom of hindsight, the decision to incrementally launch the Narrows Two bridge was a brilliant and innovative concept. However, as is so often the case, the devil was in the detail. It did require considerably more detailed design, temporary works and materials than was originally anticipated, adding significantly to the construction consortium’s costs.
The bridge was completed 31 months after the call for design and construct tenders, close to the very ambitious schedule desired by Main Roads. By comparison, Narrows One was completed 50 months after commencing the design. This comparison clearly justifies the Main Roads decision to adopt the D&C approach to deliver the project in the least possible time.
The Leighton consortium team provided the people of Western Australia with a magnificent bridge at the originally agreed price, a feat matched by very few infrastructure projects today.
It is not easy to compare the cost of Narrows One and its twin, Narrows Two, built four decades later. The cost of both bridges was influenced by constraints at the time and the different scopes of work. For example, Narrows Two scope included the design and additional auxiliary works.
The construction (or delivery) method also influenced costs.
Narrows One was delivered by a “construct only” contract, with the Client providing design and in turn carrying the risk for cost increases due to design changes. Narrows One construction contract was awarded for just over 1.3 million pounds. Due to the foundation issues and subsequent variations to the construction contract, the final construction cost was approximately 3 million pounds or $6 million (pounds were replaced by dollars at 2:1 ratio in 1966). This figure did not include cost of design, nor of land reclamation on the northern shore.
Average weekly earnings in Australia provides one way to compare costs over several decades, increasing from $55 equivalent in 1956 to $749 in 1999 according to ABS data.
Narrows Two was delivered by a “design and construct” contract where any cost increases due to design or unforeseen circumstances were absorbed by the contractor. The Leighton Contractor’s D&C tender price was reported as $49 million and this compared favourably with Main Roads budget of $70 million for the project. Although there is nothing published in the public domain, it is understood the project was completed with no major variations to the Contract.
Relative to the change in average earnings, the cost was about $30 million less than Narrows One, demonstrating significant cost reductions for bridge construction over the four preceding decades.
Recognition for the achievements by the Leighton and Connell Wagner consortium is long overdue. Little has been written about Narrows Two since it was opened in 2001 until now. For the first time, therefore, we can tell the story of its design and construction, thanks in the main part, to the technical presentation by Geoff Robinson as transcribed in Chapter 4.
Download Chapter 4: Narrows Two Design and Construction
Chapter 5: The Third Narrows Bridge
Following Geoff’s talk, Duncan Robinson brought the presentation to a close with his account of the third Narrows bridge, the single rail bridge between the two existing road bridges. Chapter 5 describes the construction of Narrows Three. This outlines how the bridge had to be built in the limited space between the two road bridges, without disrupting traffic. It now carries the south-bound rail track. Unlike its predecessors, this bridge was built with a conventional steel box girder design, constructed in 100 tonne sections off-site, and lifted into place from the existing road bridges.
Download Chapter 5: Narrows Three Design and Construction
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The five chapters linked to this introduction have expanded the original hour-long presentation into a comprehensive account detailing the design and construction of the three bridges. We can all be proud of the achievements of the project teams for all of the 3 individual bridges projects. Until now, the people of Western Australia have had only occasional glimpses of this remarkable story which we have presented here for the first time.
About the Authors
Gerry Hofmann is a Civil Engineer with over 45 years’ experience in the construction industry, having worked on many and varied complex projects in various senior management roles.
After working in the public sector in Sydney for a few years after graduating, Gerry then worked for a construction contractor before moving to Perth, initially working in the deep foundation industry. In 1978, he joined Clough and worked there up until joining Leighton Contractors in 2004 to take up the position of Assistant Area Manager for the William Street Station for the Leighton-Kumagai Joint venture on the New MetroRail Project. In 2006, he was appointed Assistant Project Director for Southern Gateway Alliance on the New Perth Bunbury Highway project, which was successfully completed in September 2009. Gerry was then appointed to establish and lead the Wellington Dam Alliance team that successfully carried out the innovative and sensitive strengthening of the dam in an alliance with Water Corporation and other partners.
During his 25 years with Clough, Gerry was exposed to a wide range of experiences in all forms of construction projects and contracting formats. He worked in various roles on many large infrastructure projects including the Mount Henry Bridge, Wesfarmers LPG Plant, the Harriet Offshore Oil project, the Woodside Goodwyn Modules, the Graham Farmer Freeway tunnel, the Woodman Point Wastewater Treatment Plant and Dalrymple Bay Coal Terminal in Queensland. He also worked on numerous other projects in various roles, including pipelines, marine projects, bridges, tunnels, oil and gas and mining projects. During the same period, Gerry undertook various project roles and corporate roles, including project engineer, project manager, plant manager, business development manager, area manager and WA state construction manager.
Gerry is an exponent of relationship contracting and risk management, subjects in which he has presented papers at various conferences. He has experience in “hard money“ construct-only projects, design-and-construct, ECI and various forms of relationship contracts. Gerry was a foundation member of the Woodman Alliance, the first public sector alliance in WA and has since participated in a number of other alliances, notably Roe 7 (the first alliance for Main Roads WA), Southern Gateway Alliance and Wellington Dam Alliance. Gerry has often been in demand to provide advice on alliancing matters and to present papers at major conferences. Gerry ceased working as a full-time salaried employee in September 2012 and has since undertaken a number of consultancy roles through his consultancy business, GH Consulting Services. He has also undertaken a role of lecturing final year Civil Engineering students at Curtin University on a part time basis in the first semester each year for the past ten years. There, Gerry runs a course in contract management, which includes the legal side of contract law, tendering and contract award processes, dispute management, variations and claims, scheduling, various forms of contract conditions, risk allocation and management and general contract terms and conditions. His tasks includes delivering formal lectures, arranging guest lecturers from government and industry and setting and marking the mid-term project and final exam.
As a current member of the Engineering Heritage WA (EHWA) Committee within Engineers Australia, Gerry has undertaken a number of write-ups for projects in WA in order to have them recognised and included on the EHWA website. This also included the submission of a project for heritage recognition.
Duncan Robinson has worked in Engineering for over forty years, working for ARC, Arup and ultimately, thirteen years at Clough. Duncan commenced as a site engineer on bridge construction, before going into structural design and then systems/data management on oil and gas projects. Duncan finished full time engineering work in 2015. Throughout his career, Duncan has been involved in teaching, and is currently teaching on a casual basis in higher education.
Geoff Robinson is a retired structural engineer. He began his engineering career in 1975 after graduating with honours in Civil Engineering from the University of Western Australia. This led to a career of professional practice spanning 47 years. In that time, Geoff has held senior and executive roles in various organizations. In 2001, Geoff commenced private practice by establishing Robinson Engineers Pty Ltd, a consulting engineering firm specializing in building structures.
Over his working career Geoff was involved in the design of an extensive range of building structures, infrastructure projects and structures for the mining and resources sector. A sample of major projects include:
Building structures - the QV1 Office development, Terminal T4 at Perth domestic airport, the Vines Resort, redevelopment of Council House Perth, the Perth Duxton Hotel development and various buildings for the school campuses of Christ Church Grammer School, St Marys’ Anglican School, St Marks Anglican School and Mercedes College.
Civil and transport infrastructure – Kenwick Link and Roe Highway Stage 3 , Eddystone Avenue Bridge over the Mitchell Freeway, cofferdam structures for the construction of the Domain tunnel under the Yarra River for Melbourne Citylink project.
Marine and port works - structural design of LNG and LPG loadout jetties for Woodside Petroleum, ore handling infrastructure for the expansion of Port Hedland Inner Harbour at Nelson Point and Finucane Island for BHP.
Mining and resource projects – iron ore processing plant for Cloudbreak mine for FMG, Yandi Junction South East and Western Turner 2 mines for Rio Tinto, Motheo Copper mine and processing plant in Botswana for Sandfire Resources and non-process infrastructure for Talison Lithium at Greenbushes.
Geoff was an Associate with the consulting engineering firm of Connell Wagner, the principal designers for the Narrows Bridge Duplication Project. Geoff's project role was design manager for structures, and he played a significant part in the conceptual and detailed design of the second Narrows Bridge.
In retirement, Geoff has a maintained a continuing interest in engineering and remains a Fellow of the Institution of Engineers Australia. He served on the committee of the WA Division Structures Panel for many years, including a term as chair. He was also a committee member of the National Committee for Structural Engineering, forerunner of the Structural College board.
James Trevelyan is an engineer, educator, researcher and recently a start-up entrepreneur, amd Emeritus Professor at the University of Western Australia.
As CEO of Close Comfort, he is introducing new energy saving, low emissions air conditioning technology for a global market.
His research on engineering practice helped define the Engineers Australia professional competencies for chartered engineers. His books “The Making of an Expert Engineer” and “Learning Engineering Practice” are influencing the future of engineering education in universities and workplaces.
He is best known internationally for pioneering research on sheep shearing robots from 1975 till 1993 and for the first industrial robot that could be remotely operated via the internet in 1994, one of the earliest demonstrations of the ‘internet of things’.
He served on the National Committee for Applied Mechanics from around 1990 till 2000, including a term as chair. He was the founding chair for the National Committee for Mechatronics which he and others set up in 2006, and he served with the committee until 2020. He has also served on the WA Division Engineering Education Committee. James is currently secretary of the Western Australian Engineering Heritage committee.
Other pages on this wiki include the following
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Place:Narrows Bridge Brief History
Narrows_Bridge_-_Heritage_Recognition
Place:Mitchell_Freeway,_Stage_1
Place:Narrows Bridge Duplication
Place:Narrows Railway Bridge
Here is a map showing you how to reach the location of these great bridges.
