ABSTRACT
Designing a major bridge in the heart of a city presented challenges of adequate clearance over a tidal river, limited gradient and length of approaches. Suspending the deck from the main truss and approaches beneath the anchor truss addressed these problems.
The 65.3 m high towers separated the anchor and cantilever trusses. The 172 m suspended span is freely supported on the cantilever arms by pins. The trusses were statically determinate to avoid secondary stresses.
Use of high tensile steel effected a substantial reduction in steelwork and foundation loads, resulting in reduction of costs.
Optimum economy was achieved by the choice of spans, the use of K-truss with subpanels for the cantilever part and N type for the suspended span. The 21.6 m deck hung from trusses by pins had a grid system of girders topped by 7.5 cm of concrete with a 5 cm wearing coat. Expansion joints prevented a secondary effect on trusses. The 65.3 m high towers of rectangular cross section are also K-braced and taper towards the top.
The end anchor frames transfer the load to the foundations through vertical links, anchored inside the concrete block by a grillage, permitting adjustments with hydraulic jacks and packs.
Pre-stressing was adopted, a first in a major bridge, to avoid secondary stresses. The sagacious designers provided for all foreseeable contingencies.
