Vincents Rivulet Bridge, Proctors Road
Background
This is the first composite beam bridge in Australia. The Bridge was designed by A W Knight and Built by the Public Works Department in 1932.
When the bridge is loaded, the effect of joining the concrete deck to the underlying steel girders is to develop a compressive stress in the concrete and a corresponding tensile stress to the girders. This makes better use of the strengths of those materials.
When the bridge was tested with a loaded truck, the measured deflections, as predicted, were much smaller than for a non-composite beam bridge in which the concrete and steel carry the load independently.
The method was the adopted for much larger bridges in both Tasmania and in other states, with significant cost savings.
Sir Allan Knight (1910-1998)
Vincents Rivulet Bridge is a single lane structure spanning about 10 metres and 3.66 metres overall width.
The Public Works Department approached Professor Alan Burn in 1932 to see whether he could assist them in determining the distribution of wheel loads on a concrete deck to the supporting steel beams. At that time Allan Knight was working as a Demonstrator at the University of Tasmania under Professor Burn.
Burn asked Allan Knight to investigate the problem and he constructed a structural model with timber beams and a Bakelite deck. He then applied loads to the model and measured deflections using an extensometer. In subsequent tests Knight glued the deck to the beams and noted a significant decrease in beam deflections. He concluded that if a concrete deck could be made to act with the supporting beams without slippage or separation along the interface, economies could be afforded in bridge decks.
Allan Knight joined the Public Works Department and designed and tested Vincents Rivulet Bridge. He went on to design the Leven River Bridge at Ulverstone with seven spans of 18.6 metres using this method. Allan Knight was Chief Engineer of the Public Works Department for 10 years and Commissioner of the Hydro-Electric Commission for 30 years, overseeing the rapid expansion of the electricity system in Tasmania.
Engineering Heritage Recognition Program
| Marker Type | Historic Engineering Marker (HEM) |
| Award Date | November 1999 |
| Nomination Document & Ceremony | Nomination document & ceremony |
