Avalon Drive Bypass, Hamilton

Client: Ontrack

Designer: Ontrack

Main Contractor: Brian Perry Civil

The New Zealand Transport Agency constructed the new State Highway 1 Avalon Drive Bypass in Hamilton to reduce congestion, improve safety, and separate inter-regional state highway traffic away from internal city traffic.

The bypass includes a new railway overbridge, constructed over a lowered road and replacing a former railway level crossing. The bridge carried freight and passenger services on the North Island Main Trunk Line, with this particular section carrying more freight than any other in New Zealand.

In a two-month project, BBR Contech worked with main contractor Brian Perry Civil and designer Ontrack to post-tension the bridge’s cast in-situ concrete deck.

The post-tensioning process was considerably more complex than for most similar bridges – mainly owing to the extensive use of reinforced steel in the bridge’s deck, which was 1.5 metres thick, 19 metres wide and about 26 metres long.

The work required post-tensioning tendons to be carefully interwoven with the heavy layers of conventional reinforcing. In total, 61 BBR Cona Compact 1905 tendons, were installed in the bridge decking – comprising a total of 31 tonnes of prestressing strand.