2014 Case Study

Tahune AirWalk & Visitor Centre,

PROJECT TEAM

Asset Owner: Forestry Tasmania

Architects: JAWS Architects

Principal Builder: Crisp Brothers The spectacular views from the Tahune Airwalk have been made possible by the installation of a long-lasting, elevated galvanized steel walkway and viewing platform that is 48m above the river below. Photo: Industrial Galvanizers Galvanizing: Industrial Galvanizers Introduction forest floor. The AirWalk culminates in a spectacular cantilevered walkway and viewing (Tasmania) The Tahune AirWalk in Tasmania’s was opened in July 2001. It provides a platform, which looks out over the Harz

spectacular walk through the forest canopy, Mountains and the junction of the Huon and which is enjoyed by over 120,000 visitors Picton Rivers. each year. In addition to the wonderful views, the This steel structure was galvanized by presence of existing logging roads, some ® existing infrastructure and disturbed areas Industrial Galvanizers (Tasmania) in early 2001. Now 13 years old, Industrial meant that construction of the AirWalk would Galvanizers has revisited the structure to have minimal impact on the surrounding assess the condition of the original forest. galvanizing. The structure comprises 120 tonnes of

Overall, it has lasted longer than its original galvanized steel sections, connected using average life expectancy; and the coating is 9,000 fasteners. It was designed to meet size This spectacular structure expected to last for a further 8 - 13 years, and weight restrictions, meaning the largest has won many awards for based on recent thickness testing. steel section was only 6 meters long. The its architects, engineers Background AirWalk was fabricated over a two month period by Crisp Bros, using tube sections, and owners. The $3.6m Tahune AirWalk and Visitor centre steel plate, angles and mesh. This was development is located in the magnificent followed by three months of on-site Galvanizing helps award- rainforest of the Huon Valley, 94 kilometres construction. south west of , Tasmania. This winning designs look great The viewing platform is engineered to support impressive 619 meter-long steel structure a mass of 10 tonnes (120 people) and to year after year. allows visitors to walk above the tree canopy withstand winds of 180 kilometres per hour. at heights of up to 37.5 metres above the

Industrial Galvanizers and its representatives have made reasonable efforts to ensure the accuracy of the information provided in this publication, but it does not constitute product advice. The information is of a general nature only and does not take into account your individual situation or needs. It should not be used, relied upon, or treated as a substitute for specific professional advice. Industrial Galvanizers recommend that you obtain your own independent professional advice before making any decision in relation to your particular requirements or circumstances. © Industrial Galvanizers Corporation Pty Ltd 2013 INDUSTRIAL GALVANIZERS (AUSTRALIA) Townsville | Brisbane | Newcastle | Sydney | Port Kembla | Melbourne | Launceston www.ingal.com.au 1300 INGALV

Tahune AirWalk & Visitor Centre, Tasmania

Industrial Galvanizers has The local climate & life expectation an average coating loss of 80.6µm - which collaborated with Crisp The AirWalk is located in the Southern would be nearly the entire standard HDG600 o o coating thickness. Bros. on many successful Forests of Tasmania (147 E, 43 S) where the closest town is . The local climate However, the predicted coating life may be galvanized projects. is summarized below:- extended by the inherent Model variability (life expectancy 5 - 22 years, average of 11) and Longterm averages (Annual) an HDG coating that is generally thicker than the standard. Temperature Max 17oC Recent Test Results Hot Dip Galvanized steel In late October 2013, coating thickness tests Min 6.3oC has performed well in this were taken on site using a calibrated Rainfall 866mm PosiTector® thickness gauge. The main areas outdoor application. It has Rain Days 158/365 Source: Bureau of M eteorology (Site 094137) of interest were handrails (in both high and exceeded its predicted general traffic areas); handrail stanchions; average coating life. Using this location in Industrial Galvanizers’ pipe trusses and vertical pipe supports. The results for average coating thicknesses are Recent tests and Corrosion Mapping Model (developed with the tabulated below:- inspections indicate that CSIRO), gives the following average coating life predictions:- Average Coating Thicknesses (µm) - the average coating life October 2013 results, selected areas. Long: 147o 00' E Coating Mass (g/m²) will extend for another 8 - Lat: 43o 00' S 150 300 450 600 Handrail (high traffic) 51.1 14 years. Nominal Coating Thickness (µm) Handrail (general traffic) 71.4 Distance from coast: >1km 21 42 63 84 Handrail stanchions 49.3 Calculated Average Coating Life (yrs) Open: 2 5 8 11 Pipe trusses 82.9 Sheltered: 1 2 4 5 Main pipe support 89.3 Open Facade (Face): 3 6 9 12 Source: Industrial Galvanizers. Average of 30 points over 3 random locations Sheltered Facade (Face): 2 3 5 6 Open Facade (Edge): 2 5 8 10

A tight construction Sheltered Facade (Edge): 1 2 3 4 Assuming that standard pipe and handrail Environment schedule and limited Roof Cavity: 99+ 99+ 99+ 99+ sections have been used in construction, the Wall Cavity: 99+ 99+ 99+ 99+ wall or section thickness would lie in the range Sub-floor: 96 99+ 99+ 99+ storage on-site required a of 3-6mm. The Australian Standard for Hot coating that could be Salt Deposition (mg/m²/day): 23.8 Dip Galvanizing (AS 4680) dictates a minimum applied off site and was Based on a hot dip galvanized (HDG) coating average coating thickness of 70µm for newly of 600g/m2 (‘HDG 600’) the coating has an galvanized steel in this thickness range. not going to be delayed by average life expectancy of 11 years in an Applying the Standard to the average readings poor weather. Open location (i.e. one where the galvanized above, three out of five measured components have a coating thickness that would comply coating is exposed to rainwater and a wet/dry cycle). However, the Corrosion Model also with the ‘as new’ requirement - after 13 years

indicates a range of life expectancy: in this in service!! case the range is between 5 and 22 years. Based on coating thickness readings and The team at Industrial It should also be noted that most HDG output of Industrial Galvanizers’ Corrosion coatings are thicker than the required Mapping Model, the average coating life Galvanizers (Tasmania) was standard, with HDG 600 regularly returning expectancy for the existing galvanizing is able to supply a quality average recorded thickness results in excess between a further 8 and 13 years - making the product to meet a short of 100µm. So it is expected that the average whole life coating between 21 and 26 years. coating life will be proportionately longer than It is expected that some areas will require construction schedule. that shown by the Corrosion Mapping Model. localized repair with proper surface Corrosion Mapping predicts a coating mass preparation and the application of a zinc-rich loss of 497g/m2 in a 10-year period - an coating. Given the construction method used, average of 49.7g/m2 or 6.2µm per year. In the end-of-life repair by replacement of galvanized 13 years since construction, this equates to sections is a possibility. INDUSTRIAL GALVANIZERS (AUSTRALIA) Townsville | Brisbane | Newcastle | Sydney | Port Kembla | Melbourne | Launceston www.ingal.com.au 1300 INGALV

Tahune AirWalk & Visitor Centre, Tasmania

Forestry Tasmania have Why galvanizing? Summary developed an outstanding Steel galvanized by Industrial Galvanizers The Tahune AirWalk & Visitor Centre has tourist attraction in the (Tasmania) was ideal for this project, based made extensive use of galvanized steel in the on:- construction of all its assets. Initial indication of Tahune AirWalk & Visitor  Forestry Tasmania’s desire to minimise average coating life was 11 years but with a Centre. It contributes to impact on the natural environment; model variability of 5 - 22 years. Visual inspections and thickness readings taken in their concept of Multiple  The need for a tough finish that could be October 2013 indicate that the majority of the Forest Usage (forestry, easily applied offsite and withstand damage during installation; galvanized steel is in good condition and has tourism, habitat, education) the prospect of a life that will approach or  Aesthetic appeal and ability to blend in with exceed the longest predicted outcome of 20+ the natural tree-scape; years.  Long-lasting corrosion protection; Regular rinsing by plentiful rainfall, a wet/dry  Corrosion products (oxides of zinc) that are cycle that has allowed the development of the naturally occurring and beneficial to plant Galvanized steel has an protective zinc patina and a sound galvanizing life. application by Industrial Galvanizers have all aesthetic appeal and blends  A fully recyclable steel-based product; contributed to this sustainable outcome. The with the natural canopy  A goal to maximise Tasmanian content AirWalk will probably not outlast the Huon better as it ages. (ultimately 93% of the project was locally pines of this spectacular forest region - but it sourced. will entertain and enthrall well over another

million visitors in its lifetime.

The AirWalk will probably not outlast the Huon pines of this spectacular forest region - but it will entertain and enthrall well over another million visitors in its lifetime.

Galvanizing on the 13 year old main (upright) pipe support and pipe truss supports have coating thicknesses of 89.3µm and 82.9µm respectively- both in excess of the Australian Standard requirement for newly galvanized steel of this thickness. Photo: Industrial Galvanizers INDUSTRIAL GALVANIZERS (AUSTRALIA) Townsville | Brisbane | Newcastle | Sydney | Port Kembla | Melbourne | Launceston www.ingal.com.au 1300 INGALV

Awards for this attractive Tahune AirWalk & Visitor Centre, Tasmania project include:-

Project Gallery

Best Tourism Project in Tasmania Award (2001)

Best New Tourist Development (2002)

Australian Institute of Building Awards for Innovation (2002)

Australian Institute of High traffic galvanized handrail (on cantilevered section) Building Awards for exhibits increased wear. Photo: Industrial Galvanizers Professional Excellence in Building (2002)

Royal Australian Institute of Architects Awards 2002 - Commercial Building under $10m The galvanized structure has been carefully threaded through the new-growth forest, which continues to grow Royal Australian Institute under and around the structure. Photo: Industrial Galvanizers of Architects Awards 2002 - Colourbond® Steel Award

Australian Steel Institute - Steel Construction Awards 2002

EcoTourism Australia Award for Excellence 2003

Association of Consulting Engineers Australia Awards 2002 Rinsing of the steel by regular rainfall and a wet/dry cycle Major structural supports and pipe trusses all retain an ‘as have contributed to the longevity of the galvanized new’ coating of galvanizing. Photo: Industrial Galvanizers coating. Photo: Industrial Galvanizers

References

‘Forestry Tasmania - The Tahune Forest AirWalk Australia’: Green Globe Case Studies, Jan 2004 ‘Tasmanian Company Walks on Air’: BlueScope Steel website, accessed December 2013 ‘Tahune AirWalk and Visitor Centre’: JAWS Architects website, accessed December 2013 ‘Climate Data Online’: Australian Bureau of Meteorology, accessed December 2013

A.C.N. 000 545 415 ‘Socioeconomic Benefits of the Tahune Airwalk’: Bruce Felmingham, University of Tasmania, Nov

Registered Office: 2005 11 Talavera Road, Macquarie Park, NSW 2113 Industrial Galvanizers Coating Data, 2013