Hobart Floating Bridge
Background
The wide Derwent Estuary formed a natural barrier between Hobart on the western shore and the growing settlements and farms to the east. Crossings depended on a vehicular and passenger ferries but there was a growing need for easier access.
Many different designs for bridging the estuary had been suggested and abandoned over the years. At last in 1936 Alan Knight, Chief Engineer of the Public Works Department, proposed a curved floating concrete bridge with a lift span for shipping as a feasible and economic solution. The Hobart Bridge Company obtained Government approval in 1936 and financed the project, hoping to profit from land appreciation on the eastern shore. Construction began in April 1938 and the bridge opened for traffic in December 1943.
After 21 years of service, the two-lane floating bridge was removed and little evidence of this innovative structure remains. Its high level four-lane replacement immediately downstream opened in 1964. A floating concrete bridge was the first affordable concept. Such bridges elsewhere were straight structures. Sideways pressures from winds, tides and currents were prevented from bending straight bridges by a series of midstream anchors both upstream and downstream. However trial anchors in the Derwent proved unreliable due to the great depth of water (down to 30m) and soft deep mud below that level.
Alan Knight realised that a curved alignment would not require midstream anchors. It would be strong as an arch when the tide flowed out and strong in tension (like a suspension bridge) when the flow reversed.
Engineering Heritage Recognition Program
| Marker Type | Engineering Heritage National Marker (EHNM) |
| Award Date | May 2015 |
| Nomination Document | Nomination document |
| Ceremony Report | Ceremony report |
| Interpretation Panel | Interpretation panel |
