Client: Kaipara District Council

Designer: Roadlab

Main Contractor: United Civil Construction

The Kaipara District Council awarded the overall project to United Civil Construction who, in turn, awarded Contech the contract to install external post-tensioning on the bridge. The purpose of the scheme was to increase its load capacity to accommodate “100% Class 1 and 50 MAX heavy vehicles”.

In its proposal for the work, Contech suggested using BBR VT CONA CMW post-tensioning tendons, each made up of 16 x 15.2mm diameter strands. The proposal to use the CONA CMW system had a significant influence on the company winning the contract – as the large tendons would enable the team to work quickly and efficiently, while delivering a great result.

The week-long installation process involved stressing and grouting the post tensioned tendons, then lifting the bridge, installing bearings and grouting the bearing bases. This was the first time that the CONA CMW system had been used in New Zealand and Contech believes it could have great value in strengthening similar bridges of which many were built in New Zealand, around the middle of the 19th Century.