Bridges

Princes Highway connects Melbourne to agriculturally significant region of Victoria. The road was a single carriageway with one lane in each direction and a shoulder on each side. The rail corridor was a single, bi-directional, broad-gauge track that crossed beneath the highway at a 70º skew.

A short single span bridge, carried Princes Highway over the rail corridor, spanning perpendicular to the track centreline and with significant length along the tracks due to the high skew angle. Major Road Projects Victoria as part of the Princes Highway East Upgrade Project, proposed to add 43 km of dual lanes between Traralgon and Sale to improve the freight efficiency in the region. This necessitated the replacement of existing bridge that spans across the rail corridor.

The replacement bridge was required to meet the following key drivers:

• Improved safety for road users with open sight lines along the highway;
• Minimise road traffic and rail service impacts during construction; and
• A more sustainable design with efficient use of material and space.

In addressing the key drivers, a 95 m single-span network arch bridge was proposed. A network arch is a tied arch bridge with inclined hangers that intersect at multiple locations. The hanger pattern and the tension forces carried by these hangers mainly determines the efficient performance of the structure to produce a sustainable outcome.

This paper discusses the methodology adopted in developing a strategy for tensioning and then tuning of these important hangers during construction such that the design intent is met during the operation of the bridge. The guidance provided in this paper could assist other designers when they undertake design of such structures.