Mangamahu Bridge

Wanganui District Council Bridge 47 Mangamahu Road spans over the Mangawhero River near Wanganui. The original bridge was spectacularly washed away by flooding in 2006.

Holmes Consulting Group was part of the successful team with an alternative design for the replacement bridge project for Wanganui District Council. The new structure is an 85-metre structural steel network arch bridge, and is the first of its type designed and built in New Zealand.

Overall the proposed network arch bridge design was the lowest cost tender received for this project and produced a 30% cost saving from the council's estimate.

Holmes Consulting Group performed extensive analysis starting from the preliminary design stage, developing several design tools specific for this project. We worked proactively with the contractor and fabricator to come up with an efficient use of steel sections and plates, minimising steel wastage and fabrication costs. The bridge was completed four months ahead of the client's envisaged programme.

In addition to the numerous advantages the network arch bridge brought to this project, the resulting bridge is also an elegant and innovative solution for the replacement structure, and definitely sets a milestone in bridge development in New Zealand. The bridge won an ACENZ award in 2009.