Client: Genesis Energy

Structural Designer: Roadlab

Waikato Falls Bridge is located on Kaimanawa Road, the prime access route to Rangipo Power Station.

The bridge is a two-span steel structure with precast concrete deck. Each span is approximately 32 metres and is 30m above the base of ravine. Construction of the bridge was completed in 1969.

In 2020 Contech was awarded a contract to carry out bridge strengthening so the weight and speed restrictions posted on the bridge in 2013 could be removed, and to allow transport of a 65- tonne transformer across the bridge. In addition, the two bridge pier columns and headstocks required strengthening to accommodate 500-year earthquake demands.

Strengthening work included replacement of the existing bridge bearings, FRP to bridge columns and headstock, installation of tension ties, new steel members and site welding. Traffic management, including bridge closure and temporary traffic diversion, was required during the jacking of the bridge and bearing replacement. While the overall strengthening scope was designed by Roadlab, the CFRP design was performance-based specification and was arranged by Contech.

One of the critical items was bridge jacking to allow bearing replacement. The specification required that all three bridge trusses are lifted simultaneously without imposing any tensile stresses to individual steel members. To accommodate this requirement a pair of hydraulic jacks was installed under each truss and connected to a hydraulic pump via manifold. Once the load of the bridge was transferred onto the jacks, locking rings were used to secure the load during the removal of the existing and installation of the bearings.

Strengthening work was successfully completed and weight and speed restriction removed in May 2022.