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Concrete In Australia : June 2013
26 Concrete in Australia Vol 39 No 2 Are Australian Super Tees the world s cleverest bridge design? Joe Wyche -- Director, Wyche Consulting Most construction professionals, and even the general public, are awed and impressed by spectacular large bridges. A couple of fine Australian examples have even won two of the Concrete Institute of Australia s last three Kevin Cavanagh medals. But for every Lawrence Hargrave Drive Bridge, there are hundreds of lesser bridges -- the sort of thing that we take as much for granted as switching on a light or turning on a tap. e sheer volume of investment into these unobtrusive structures, and the huge return they give our economy and lifestyle, makes them worthy of at least our passing attention, and I believe a strong case can be made that Australia has quietly developed the most efficient solution in the world for this fundamentally important type of structure. Over the last 20 years, bridges in Australia have been procured by design and construct. is is increasingly being carried out by alliance contracting, where the construction contractor has a high degree of input into the design. In a very competitive market, for most bridges in the commonly-used span range of 20m to 55m, two basic designs have evolved which cover all but the most specialised situations. Super Tees reign supreme where there is reasonable cranage access and for spans to about 38m (even in excess of 40m in Western Australia), while for longer spans or difficult access such as over water, incremental launching is almost universally the choice. However, it is the Super Tee which is by far the most common new bridge these days. Where did Super Tees come from? e idea originated in Victoria in what I understand was a cooperative effort between VicRoads and the local precasting industry. ey developed the first version of the Super Tee, which is the name I still like to use in recognition of that achievement, but an important improvement came shortly thereafter from RMS in NSW, which introduced the requirement that the central beam be cast with an open top, and re-named it the T-Roff. e original Victorian version had a styrene void former, and especially as they allowed webs as thin as 90mm, provided a challenge for even the very best of our precasters. When I first saw a drawing of one of these I thought it was a terrible idea -- I just didn t believe that the precasting industry could provide the consistent quality required with such a difficult section. I was particularly worried about the webs and also the densely packed prestressing strand under the central void former. I am pleased to say that I have been proven Figure 1. The Western Australian T-Roff type Super Tee.