Brisbane City Council has announced the opening of the New Farm Riverwalk
connecting New Farm to the Brisbane City via the Howard Smith Wharf Precinct.
One of the city’s beloved icons, the Riverwalk was originally constructed
in 2003 and used daily by over 3000 cyclists, pedestrians and runners before it
was washed away during the 2011 floods. Engineered by Arup, the new Riverwalk has
a design life of 100 years and sits 3.4m above mean sea level on robust piles.
Contributing to design as well as life expectancy, stainless steel has
been extensively used for structural and aesthetic purposes. Brisbane City Council’s
two key objectives for the project were to achieve a low maintenance, durable structure
as well as high aesthetic qualities. Stainless steel was deemed suitable to accomplish
both objectives while also providing the necessary strength required.
Key design elements featuring stainless steel include balustrades, skate
stops, help point enclosures, light posts, signage, electrical enclosures, deck
furniture and bins at the node structures. For additional durability, stainless
steel reinforcement conforming to BS 10088 and BS 6744:2001 was used in the soffit
of the precast concrete girders where the structure could be subject to wetting
and chloride contamination in the future.
Constructed by John Holland, the project involved a high level of collaboration
between multiple suppliers and fabricators to meet the exacting demands of the specification.
John Holland Project Engineer Cameron Pahor said one challenge was programming works
in accordance with project specifications to reduce contamination between carbon
steel and stainless steel, both of which were used within the precast concrete girders
incorporated into the Riverwalk.
Modelling of the reinforcing in 3D by Vectors Computer Aided Drafting also
ensured exact dimensions, reducing waste of stainless steel reinforcing. ASSDA Sponsor
Valbruna Australia Pty Ltd’s Queensland construction division was contracted to
supply 385 tonnes of stainless steel reinforcing bar, with the Australian Reinforcing
Company (ARC) sub-contracted to schedule, cut and bend the rebar in a specifically
prepared quarantine location to prevent processing and storage contamination issues.
Valbruna Special Products Manager Scott Ford said the majority of the rebar
(in diameters ranging from 12mm to 40mm) were produced to precise precast tolerances
predominantly using Reval special grade AISI 2304 (1.4362). Grades 2205, 316L and
304L were also used to meet the unexpected increase in tonnage requirement - nearly
40% more than original project calculations - making the Riverwalk the largest application
of stainless steel rebar in Australia to date. The use of stainless steel rebar
ensured the Riverwalk met the required 100-year lifecycle objective, while minimising
ongoing maintenance costs.
To minimise maintenance for the visual elements of the Riverwalk, ASSDA Sponsor
Midway Metals supplied 275 tonnes of grade 316 stainless steel and two tonnes of
welding consumables for the construction of around 1900m of balustrading. Midway
also supplied 100 litres of Avesta pickling gel to passivate all welds on the balustrades.
Midway Metals Brisbane Branch Manager Sean Lewsam said some of the specified
handrail sizes were not available in Australia and had to be air freighted into
the country to meet strict deadlines. Midway supplied the project with 3,522 metres
of RHS, 14,500 metres of round bar, 1,924 metres of HRAP flat bar, 1,500 metres
of flat bar from their slitting and flat bar machines, and 2,000 metres of mirror
tube, storing the material in a dedicated holding area for the duration of the project.
Specific-sized Grade 316 plates were acquired (132 tonnes in total ranging
from 10mm to 16mm) to minimise off cuts and wastage during the plasma cutting of
stiffener plates, 1500 base plates and 1000 stanchions for the balustrades. Around
26 tonnes of laser cut profile plates ranging from 5mm to 20mm were also supplied.
ASSDA Member Southern Stainless was contracted to fabricate and install three
different types of balustrading (solid uprights, mesh wire and glass infill), as
well as other visible stainless steel elements of the project using the stainless
steel and welding consumables supplied by Midway Metals.
Southern Stainless General Manager Matthew Brown said all stainless steel
components were manually polished to a 600 grit finish prior to assembly and welded
in compliance with AS1554.6. After fabrication, the 960 balustrades panels (each
weighing between 180 and 220kg) were electropolished in-house to Ra<0.5 and then
hand polished with silicone-based polish prior to being wrapped and delivered to
site for installation. The end product is both visually appealing and certain to
stand the test of time.
Strength testing was undertaken for the balustrade/girder connections to
ensure the stainless steel couplers, bolts and ferules (supplied by ASSDA Member
Ancon Building Products) would not damage the cast-in items during a flood occurrence.
In addition to the robust design that makes the Riverwalk resilient to future
flood events, the opening span has been relocated to reduce the likelihood of debris
getting caught on the structure, and some elements have been designed to collapse
in extreme events, reducing the force on the piles.
With the re-imagined Riverwalk now a fixture on the Brisbane riverscape once
again, residents and visitors can look forward to enjoying the unique experience
well into the future.
Australian Stainless, published by Australian Stainless Steel Development Association (ASSDA) is a leading industry magazine devoted to showcasing the unique
diversity and durability of stainless steel.