Hobart Bridge - Construction

Construction

The Hobart Bridge was of unique design and construction, and the first of its type anywhere in the world. It was a floating bridge with a lift span, constructed of hollow concrete pontoons, 24 in all, connected together forming a crescent shape curved upstream, and anchored in the middle.

The bridge was constructed in 12-pontoon sections which were then towed out into the river and connected to the banks and to each other in the middle. The total volume of concrete used in making these pontoons was 11,000 cubic yards (8,400 m³). The two halves of the bridge were made of ten 131 ft 6 in (40.08 m) pontoons, one 124 ft 6 in (37.95 m) section, and one 138 ft 6 in (42.21 m) section, joined in the middle by a 12+3⁄₄ in (324 mm) vertical locking pin, which was saved when the bridge was demolished and is now on display outside the Royal Engineers Building in Hobart.

The total length of the roadway was 3,154 feet (961 m). The total width of the bridge was 40 ft 6 in (12.34 m). It had a two-lane roadway and a footpath on one side. At the western end a large lifting section was provided to allow ships to pass. It provided a vertical clearance of 145 ft 6 in (44.35 m) at low tide, and the opening section was 180 ft (55 m) wide. Four 600 horsepower (450 kW) electric motors were used to open the bridge, which took two minutes. The total weight of steel used in the construction of the bridge was 3,100 long tons (3,100 t).