This contract was a subcontract for the construction of double span reinforced concrete bridge over a gully as part of a land development in Northcote. The work involved the installation of piles, construction of two abutments and a pier cap, installation of precast, pre-stressed hollow core bridge beams, pouring of a deck slab and footpath and the installation of guardrail. This bridge had to be constructed to NZTA HN-HO-72 standard and was 30m long and 8.6m wide.
The main challenges involved with this project were working in a low-lying gully through the middle of the winter months and the subsequent deterioration of the access road. This gully formed the sole access to the back half of the development so at all times we had to allow access past our work and keep our footprint confined to the width of the final bridge structure. A close relationship with the other contractors on site meant the difficulties were managed effectively. The access track to the work area was regularly maintained by the main contractor, which assisted with its rapid deterioration. Issues with groundwater seeping into the piles was mitigated by permanently casing the piles. Another benefit of the permanent casing of the piles was that we were able to weld engineered staging to the pier piles to support our pier cap formwork.
The major innovation for this project was to offer an alternative tender, whereby we offered a design and construction substitution for the 14 no. specified bridge beams for a double hollow core solution which saved the client approximately 10% on the tender price whilst still satisfying the NZTA HN-HO-72 loading criteria. This solution was a real value alternative which improved the competitiveness of our tender proposal, and provided the client’s value for money.
