When we look at high rise buildings and apartment towers in Australia today, we take for granted that the façade will primarily be glazing supported by aluminium sections (called curtain wall). However, this system of façade construction has only been in the Australian marketplace since the late 1950’s. Prior to this period, buildings were not excessively high (usually less than 12 storeys) and thus heavy brick masonry was a very common façade in low to mid-rise construction.
Initially, it was a slow start but by the 1980’s it took off in a big way when an American company called Cupples bought into a company called HHRobertson. I was fortunate enough to have worked for HHR at the time when the transformation took place. I was appointed the structural curtain wall engineer as well as the NATA signatory for the façade test rig on site.
The HHR curtain wall test rig was the largest in the Southern Hemisphere at the time (being 11m high x 9 m wide x 2m deep) and was able to perform wind pressure tests on test facades to pressures of 10 kPa, water penetration tests as well as air permeability and deflection tests.
The highest profile project I worked on at the time in 1984 (with another engineer) was the State Bank in Martin Plaza. The site is now where the Channel 7 studio is located. Having visited this site recently, I was impressed to see how modern and classy the building still looks after nearly 40 years. One distinctive aspect of that project (as well as most projects during those years) was the fact that all the glass, aluminium and granite stone panelling was manufactured or came from Australia, nothing was imported in those days. We designed the aluminium sections to AS1664 and the glazing panels to AS1288, both of which still exist today albeit in Limit State format. In fact, AS1288 was revised just recently in 2021 to reflect new research done in this area. The Aluminium Standard AS1664 was and still is heavily based on American ‘Aluminum’ Standards.
The wind pressures we used for this building in Martin Plaza were derived by Dr Bill Melbourne, who is based in Melbourne. He was able to provide us with wind pressures more applicable to this site and building profile (which produced wind pressures less that those conservative values that would have been obtained using the Wind Standard at the time ie AS1170.2-1983). As most engineers involved in Wind design realise, the greatest wind pressures are found on the corners of buildings (local effects producing suctions often 2 to 3 times higher than pressures elsewhere on the façade). The design wind pressures for this building were in the order of 2.2 kPa and were proof tested accordingly in the 11m high test rig at Chipping Norton.
Another important aspect of any curtain wall design (besides structural and acoustic requirements) is thermal efficiency ie keeping the heat out (or in), depending upon the geographical location and the Building Codes/Standards that apply. When I received the curtainwall specification for the Sydney Airport Centre in the 1980’s, it nominated a transmission coefficient (or U value) of 6.4 W/m2/K and a visible light reflectance less than 20%. These days the technical requirements for glazing are much more detailed and more stringent than 30 years ago. Solar Heat Gain Coefficient is a more commonly quoted value that is required to be satisfied by a glazing system.
Engineers who do not have expertise in these aspects of curtain wall design can attend a two (2) day Glass and Aluminium Curtain Wall Design and Construction course that we conduct at the Engineering Training Institute Australia (ETIA).
For dates and details of ETIA courses, please visit: https://www.etia.net.au/events/course-list
This blog is the latest in a series produced for Construction Engineering Australia by globally respected engineering educator and reinforced concrete specialist, PAUL UNO BE MBdgSc MIE(Aust) CPEng NER RPEQ APEC Engineer IntPE(Aus), Director, ETIA (Engineering Training Institute Australia).