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Duplex to Shine in DNA Design

An Australian-led design consortium will put a new twist on bridge construction with a 280 metre long stainless steel pedestrian bridge spanning across Marina Bay, the foreshore to Singapore's CBD. The bridge will link the highly anticipated Marina Bay Sands resort to a bayfront promenade linking major cultural, tourist and recreational sites.

Selected from a field of 36 international teams, the design team, incorporating Australian architects the Cox Group, engineers Arup and Singapore-based Architects 61, has designed an entirely new concept in bridge construction, based on the double helix structure of DNA.

The double helix will carry a metre wide pedestrian walkway running parallel to a six lane vehicular bridge, which is part of the same $68 million project.

Arup senior associate Greg Killen said the pedestrian bridge was a true world first, in that it did not use any of the known support mechanisms which categorise all bridges built to date. The shape of the bridge can be described as two slinkies, one stretched out slightly further than the other, flipped, and then placed inside the first. This shape is then doubly bent to form a smooth curve.

As far as we know, this design direction has not been explored before, Mr Killen said.

An Arup-designed structural optimisation program confirmed the unique design concept offered substantial structural performance.

Mr Killen said the helix tubes touch only under the deck and the unravelling forces were captured elsewhere by light stiffening rings that hold the opposing tubes apart (rather than together) in a kind of structural magnetism.

The concept enabled the use of five times less steel than a conventional box girder bridge of the same length, which meant the budget would run to the use of stainless steel.


We chose to design in duplex stainless because we've used it on a number of projects before and while the strength is comparable to structural mild steel, the maintenance costs are reduced and the total life of the bridge is extended beyond 100 years, Mr Killen said.

There is a perception in the marketplace that the cost of grade 2205 duplex is much more than austenitic varieties such as 316. This is not the case and while there is great fluctuation in both prices, the fabrication costs are similar (although some of the processes are slightly different).

The higher strength of 2205 makes a big difference, especially on longspan structures where the self weight is often the major design driver. 2205 also has superior durability including resistance to the tea staining that plagues many austenitic structures.

Singapore, a busy air hub with a very small land area, has become well respected for the quality of their buildings and infrastructure.

Singapore is not only clean and leafy, there is a noticeable emphasis on quality urban design. The urban landscape includes extensive use of materials such as stone, glass and metals where Australian cities may favour cheaper, less durable solutions. This makes Singapore the perfect platform for the world's first double helix bridge, Mr Killen said.

The project will use 370 tonnes of duplex stainless steel for the superstructure, including pipe, and welded plate and tapered sections. Stainless finishes selected by the Cox Group include a combination of bead blasting and polishing, with one of the slinkies to be highly polished and the other bead blasted, using olivine, a magnesium silicate medium.

The project, which is currently out to tender, is expected to begin construction at the end of this year and be completed in 2009.

Images courtesy of Arup + Cox + Architects 61
This article featured in Australian Stainless magazine - Issue 37, Spring 2006.

Curved Spine Leaves Strong Impression

If you’re investing in a home overlooking the water at Noosa, Queensland, you will almost certainly want the fittings to be impressive.

Sunshine Coast ASSDA Accredited Fabricator, Bell Stainless, rose to the challenge at this Noosa property by designing and building a single stringer staircase and balustrade that leaves a lasting impression.

The curved staircase features 15 timber treads which are bolted onto 6mm grade 316 stainless steel plates, which are then welded onto the stringer.

The handrail is made from grade 316 with a No 4 finish and the balustrade in-fills are made from 10mm solid rod.

Bell Stainless General Manager David Vine said the more than 90 degree curve of the staircase created some design challenges.  
“Because you can’t roll the pipe in a corkscrew for the stringer we started with a curve on a flat plane then used a series of cuts to corkscrew it,” Mr Vine said.

“Of course, we also had to be careful not to distort the angle when the tread plates were welded on.  It was an interesting challenge.”  
Mr Vine said even though the staircase was indoors, the salty coastal environment meant grade 316 stainless was the logical choice for this upmarket home.

“We steered away from stainless steel wire for the balustrades because of the inherent difficulties with teastaining in the crevices, and because we needed to maintain an even curve to match the top rail,” Mr Vine said.

The stringer was fabricated in two halves and assembled on-site.

Mr Vine said because of the high tensile strength of stainless, there was very little flexing as people move up and down the staircase.

“The owners were really happy with the final outcome and we’ve had a number of enquiries from people who’ve seen it.”

The stainless steel was supplied by Fagersta, Brisbane.

This article featured in Australian Stainless magazine - Issue 42.

Celebrating Melbourne City's Cultural Links in Stainless

Piazza Italia at the northern end of Argyle Square on Lygon Street, Carlton is Melbourne's newest public open space and meeting place was officially opened on 29 January 2006

 

Lord Mayor John So said the Piazza will be a wonderful addition to Melbourne's famous Italian cultural precinct.

 

“For generations, Argyle Square has been a place where city residents, workers and visitors have stopped to soak up the atmosphere of Lygon Street, eat gelati and catch up with friends and family,” the Lord Mayor John So said.

The northern end of Argyle Square features new gardens, traditional porphyry stone paving, a giant 45m2 solar clock and stainless steel street furniture.

ASSDA Accredited Fabricator T.R.J. Engineering fabricated the 16 stainless steel double bench seats for the redevelopment.

In December 2005, Melbourne City Council released a statement announcing that all powder-coated seats, litter bins, benches and drinking fountains in the city centre will be replaced with stainless steel finishes over the next ten years to give the streetscape a sleek, modern feel.

Lord Mayor John So said the stainless steel replacements would be designed to improve its functionality for the elderly, the young and people with disabilities, while withstanding high levels of wear and tear.

“The maintenance cost of stainless steel is half that of powder-coated items, while its lifespan is twice as long,” the Lord Mayor said.

Also, to celebrate Melbourne's successful hosting of the 2006 Commonwealth Games and to recognise the many athletes who participated, Melbourne City Council commissioned T.R.J. Engineering to fabricate stainless steel cladding for existing street poles in Bourke Street.

These cladded fabrications proudly feature the names of all the teams that competed in the Melbourne 2006 Commonwealth Games acid etched into the stainless steel.

This article featured in Australian Stainless magazine - Issue 35, Autumn 2006.

Brisbane RiverWalk: Floating in Stainless

Brisbane residents can now walk on water with the completion of the Brisbane City Council's RiverWalk floating walkway.

Stainless steel is at the heart of the 850 metre-long, 5.4 metre-wide pontoon system that effectively connects the city and the inner suburb of New Farm.

The pontoon structure, positioned 35 metres from the riverbank, has been designed to allow people to experience the feeling of being on the river - of literally walking on water.

Brisbane Lord Mayor Tim Quinn said "Brisbane is now truly Australia's River City as we're making greater use of our river system than any other state in the country.

"Completion of this vital section of RiverWalk will also have the added benefit of enhancing the city's public transport network by offering immediate access to interchanges including City Cat, ferry services, bus and rail."

Made up of a state-of-the-art pontoon system that wraps around the shoreline, it boasts world first technology that was designed and engineered in Queensland.

ASSDA supported the project by responding to more than 40 enquiries for technical assistance for the Brisbane City Council project.

Fabricating the Top-Side Structure

ASSDA member, Pryde Fabrication, supplied 35 tonnes of handrails and posts to the $13.5 million project and was instrumental in fabricating many of the environmental design elements featured on the walkway.

Pryde produced 60 individually curved handrails to create a visual effect of the ebb and flow of the Brisbane River, whilst support posts and the straining posts that holds all the load incorporates a distinct 'mangrove' design.

Grade 316 stainless steel was used throughout the fabrication of handrails, balustrades and staunches with a smooth surface finish enhanced by electropolishing.

RiverWalk Stainless Steel - ASSDA Members Suppliers

Pryde Fabrication Top-side structure - handrails, balustrades and staunches
Arminox Australia Reinforcing bars in pontoons
Ronstan International Cables and rigging materials
Sandvik Stainless steel supply to Pryde Fabrication
Atlas Speciality Metals Stainless steel supply to Pryde Fabrication
Condamine Wellscreens Electropolishing services to Pryde Fabrication
Johnson Screens Stainless steel supply to Pryde Fabrication
Tom Stoddart Pty Ltd Supply of stainless steel pole guides

Reinforcing the Pontoons

The key to RiverWalk's extended lifecycle was the use of stainless steel reinforcement by ASSDA member, Arminox Australia in the design of the 287 floating pontoons.

Most concrete reinforcing uses carbon steel, however, in marine structures where the material is exposed to chlorides in the salt water, it can corrode and cause the concrete to crack and deteriorate over time.

Arminox supplied 140 tonnes of reinforcing bar material, cut and bent to the customer's schedule in 10, 12 and 16 mm diameters.

Using specialised machinery, Arminox was able to save Brisbane City Council thousands of dollars by cutting out and tying a number of lap joints with a 40mm diameter overlap.

By reducing the thickness of concrete cover the Council saved two cubic metres of concrete per pontoon.

This initiative resulted in a lighter pontoon that contributed to increased buoyancy and lower costs for the Council.

With a total of 450 kg per pontoon, tighter tolerance control meant enhanced low material wastage.

Stainless reinforcing builds corrosion resistance into the concrete and durability has been proven over many decades.

World Class Achievement

ASSDA congratulates all members who supplied stainless steel to the Brisbane City Council's RiverWalk floating walkway, naming the project "a Queensland world class achievement designed to last 100 years with minimal maintenance".

ASSDA Executive Director, Richard Matheson inspected the 850 metre floating pontoon system after its official launch in December 2003 and congratulated the Brisbane City Council on a durable feature that would only have been made possible with stainless steel.

"The RiverWalk is a world class achievement designed to last 100 years and to achieve this aim 181 tonnes of stainless steel was specified for its durability in not only handrails, posts and cabling but also for reinforcing in the pontoons," Richard Matheson said.

"Stainless steel is at the heart of the RiverWalk project because of the material's non-corrosive properties and excellent presentation despite harsh environments," said Mr Matheson.

The RiverWalk will now provide direct riverfront access for around 20,000 walkers, cyclists, joggers and rollerbladers everyday.

RiverWalk Stainless Steel Specification Checklist

  • 850 metre floating walkway
  • 287 floating pontoons
  • 181 tonnes of stainless steel
  • 20 km of stainless steel wire
  • 2,534 kg of stainless steel wire cable
  • 135 kg of stainless steel rigging fittings
  • 1,800 linear metres of handrail
  • 1,750 support posts/staunches
  • 60 individually curved panels
  • 140 tonnes of reinforcement bars
  • 35 tonnes of handrail and posts

This article featured in Australian Stainless magazine - Issue 27, February 2004.

Stainless Vision

Inspiration from Medieval Tale

The lance used by St George to slay the dragon in Medieval mythology - Ascalon - has inspired a stunning addition to Perth’s St George’s Cathedral forecourt.

Ascalon portraitAscalon, designed by Perth artist Marcus Canning and New York based Christian de Vietri, was chosen as the winning piece from an international competition attracting 99 entries.

The sculpture features an 18m grade 316 stainless steel telescopic pole with a mirror finish, surrounded by a billowing white fibre reinforced plastic (FRP) ‘cape’, which represents St George on his steed.

ASSDA Accredited Fabricator Diverse Welding Services was commissioned by engineers and project managers Capital House Australasia to create the pole, which weighs about 2 tonnes.

Capital House managing director John Knuckey said the artists had a vision for the sculpture and his team’s role was to make it happen. He said the strength of the central pole was a concern for the artists, while the structural engineers were strongly focussed on minimising vibrations and maximising stiffness.

Capital House’s research indicated that 316 would be the most appropriate grade and their interest in selecting from standard sections determined the dimensions.

“The pole also had to be dead straight because people would pick it by eye if it wasn’t,” Mr Knuckey said. “We had no desire to compromise on quality but we were concerned that polishing would be too expensive, so originally only the bottom third was going to be mirror polished. In the end Diverse Welding Services said they could achieve a mirror finish on the entire pole and they did an excellent job.

“At first we weren’t sure who to trust with the job, but once we had visited Diverse Welding’s factory, we knew they were the right people.”

Diverse Welding Services director Karl Schmidt said their main challenge was determining the weld design to ensure the work conformed to AS1554 Part 6.

They welded together stainless steel pipe in differing dimensions to create the telescopic shape of the pole and produced joining spigots from plate (supplied by ASSDA Member Stirlings Australia), enabling the pole to be bolted to the FRP ‘cape’.

Ascalon joining spigotsThe sections were rotated on horizontal positioners and welded using stainless steel flux cored wire and TIG welding processes. The pole was given a full mirror finish and passivated using a citric based product.

Artist Marcus Canning said Diverse Welding and Capital House were fantastic to work with on the project.

“It was a late decision to shift to a telescopic design, which increased the complexity of the job under a pressured timeline, but they rolled with it and did what they had to do to get the job done, and done right,” Mr Canning said.

“The pole is such an important element to the work now it’s in situ and responding to the elements - the mirror finish makes its quality shift dramatically throughout the day and night as lighting conditions change.”

The sculpture was created following a $500,000 donation from Australian prospecting geologist Marc Creasy to the Cathedral Arts Foundation, and the only guideline was the theme of St George and the dragon.

Images courtesy of Marcus Canning.

This article featured in Australian Stainless magazine - Issue 48, Autumn 2011.

Whole of life costing

19 years plus points to stainless

A fresh focus on whole-of-life costing at Gold Coast City Council has led to the specification of stainless steel for long-term structures in the foreshore zone.

The philosophy, which was adopted following the publication of a study by Griffith University and GCCC, is likely to have flow on effects to other councils and government bodies.

GCCC’s co-ordinator of technical governance Paul Conolly said the seed was planted in 1998 when Council’s Technical Services Branch specified stainless steel for a modular toilet structure in a foreshore zone park. The material was deemed at the time to be cost prohibitive on a capital expenditure basis but the process sparked an interest in lifecycle costing.

Mr Conolly said Council’s growing interest in lifecycle costing, combined with an expectation among locals and tourists that public facilities showcase a ‘resort style’ finish, had brought the focus back to stainless steel in recent years. “There has been a clear trend towards lighter, more open structures for public facilities and these lend themselves to steel work,” he said. “A lot of our public facilities are in the foreshore zone and some materials weren’t performing as well as we wanted, so we started to look at corrosion issues and how to best manage this. We started using stainless steel for critical elements, such as joint interfaces for concrete works; bolts, brackets and cleats for boardwalks; and for high use facilities such as rubbish bins.

“Our observations led us to believe that stainless was the way to go in the foreshore zone, but we had no tangible justification which the designers could use to validate the decision for our asset custodians. We needed clear evidence to prove the initial cost of stainless steel was justified over the life of the structures.”

Griffith University scholarship student Jordan Cocks was called on to research the topic in conjunction with industry affiliate GCCC as partial fulfilment of his Bachelor of Civil Engineering.
Mr Cocks investigated multiple structural scenarios from the perspective of what would represent the most cost-effective solution: hot dipped galvanized (HDG) steel, paint systems, duplex systems using both HDG and paint, or stainless steel.

The result was a report containing a design guide, a life cycle cost analysis and a life cycle costing spreadsheet for structures in the foreshore zone. The report indicates stainless steel is a viable option based on cost alone for structures with a design life greater than 19 years. Conversely, the study indicates a HDG coating would theoretically have a life span of 14 years, leaving the exposed steel subject to rapid corrosion unless protected by an increasingly costly maintenance regime.

Mr Conolly said the report had delivered a workable tool enabling designers to input various parameters, such as current prices and design life, producing a guide for selection of the appropriate material or finishes based around optimising whole-of-life costs.

Similar principles were used to shift the specification of a park arbour in Broadbeach towards stainless steel. The material was essential due to the warm, humid environment of the foreshore, regular spraying with water and fertiliser, and the fact that the arbour would have plants growing over it that would take many years to fully establish. The report has now been used to guide material selection for a number of projects, including toilet blocks in Jacobs Well, Miami (pictured) and Burleigh Heads.

“With these projects, we have gone to the asset custodians and our first question was – what is the design life?” Mr Conolly said. “The report has helped reinforce the need for a ‘cradle to grave’ approach to responsible and sustainable asset management encompassing all stakeholders. This includes not just the designer and asset custodian but all the operational and maintenance personnel involved with a structure.

“For stainless steel structures, the asset custodians now recognise that to retain an asset over the long-term and to satisfy the whole of life cost advantage there must be regular wash downs as part of the maintenance program. The higher initial construction costs are offset by the lower cost regular wash downs which form the major component in the new maintenance regimes. The buildings are also being designed to be hosed from ceiling to floor. The overall process has really helped improve the relationship between the asset custodians, designers and maintenance staff.”

Mr Conolly said the report had also been used to promote the use of stainless steel in playground equipment and shade sail structures. “It is just a matter of making that little leap towards recognising the whole-of-life cost and ensuring delivery of a durable product – it’s not rocket science, just common sense when you think about it.”

GCCC is also now favouring ASSDA Accredited Fabricators and looking to ASSDA to provide third party technical expertise or adjudication should conflicts arise relating to material performance. The ASSDA Accreditation Scheme requires fabricators to conform to stringent standards of competence, training and education and encourages a consistently high standard through industry self-regulation.

ASSDA Executive Director Richard Matheson said GCCC’s decision to favour ASSDA Accredited Fabricators and specify stainless steel in the foreshore zone was a welcome one. “I believe we will see this initiative mirrored by other councils and government bodies in the near future,” Mr Matheson said.

“There is no doubt that informed specification and quality fabrication by people who know and understand the material will offer long-term cost savings and extend the life of the product. This is why ASSDA places so much emphasis on education and technical expertise – Councils and other government bodies need to get it right the first time and ensure value for money for their constituents.”

Mr Conolly said for long term structures, stainless steel was becoming the default specification in the foreshore zone and the trend was even moving inland.

“We’re asking the question: what will look and perform best from cradle to grave? It’s making people think differently,” he said.

Download the the final report here (4.6MB) - Whole of Life Cost Comparison and Cost Benefit Analysis for Steel Structures Constructed in the Foreshore Zone.

GCCC close up GCCC close up 2
This article featured in Australian Stainless magazine - Issue 48, Autumn 2011.