Bridge over the Parramatta River, Australia

Abstract

A bridge is now being built at Gladesville, Australia, of reinforced and prestressed concrete, which having a span of 277 m, will be the largest of its type in the world. The main arch consists of four parallel ribs, each 277 m in span. These ribs are hollow, and constitute the main structure of the arch. There are four secondary access spans on each side. The initial project was somewhat altered by the Sydney Dept. of Public Works. Each of the four main ribs of the central arch leaves 36 m clear height for fluvial navigation. The arched ribs are made up of 108 hollow units, each weighing 50 tons. At suitable intervals a number of transversal, prestressed diaphragms have been fitted, which serve to mutually stabilise the ribs. On the ribs a palisade of vertical supports carry the bridge deck. This is 22 m wide and has two sidewalks, each 1.80 m wide. The prestressed deck girders were made at two nearby workshops, one on each side of the bridge. The construction of the ribs was completed with the aid of a metallic scaffolding, which was moved from one rib to the next and served for the erection of all of them. Prestressing was done with Freyssinet type plane jacks. These were placed between the rib units, which were compressed, at the same as forcing the arch to lift off the scaffolding. After the oil had compressed the concrete, it was substituted by cement mortar. The operation was repeated at various points for each rib.