Hutt River pipeline bridge spanning across the Wellington fault

This project originates from the need to provide seismic resilient solution for water supply to Wellington and Porirua. With other factors influencing the design, the pipeline crossing must withstand seismic loads including the rupture event of the Wellington Fault with movement of +/-6.5 m parallel to the river stream

The option study for the pipeline crossing concluded on using a bridge structure spanning the river and the geological Fault. This network arch bridge structure selected is provided with enough movement capacity to withstand the effects of the fault rupture movement without failure.

The length of the bridge structure is defined so to match the differential rotations between the supports to the allowable limits for the pipeline flex joints. To resist these seismic effects, the structure is provided with seismic restrainers that, at the same time as supporting the seismic load, provide enough rotation capability to accommodate movements on the foundations due to the Fault’s ruptureevent.