Bridging the gap

Keeping it on track

After being awarded the contract to replace KiwiRail’s Bridge 23 in the Wellington region, the Pōkeno manufacturing team swung into action.

The upgrade of the rail bridge, located halfway between Paekākāriki and the SH1 exit to Queen Elizabeth Park, was part of the Wellington Metro Upgrade Programme work being undertaken during the annual network shutdown over the Christmas holiday period.

Precast BDM Bernie Sloane said manufacturing and delivery of the eight culvert units, two headwalls and eight wingwall sections required a unique approach.

“What set this job apart was the tight timeframe and the sheer magnitude of the culvert units, each weighing a staggering 23 tonnes, and the wingwall sections tipped the scales at over 18 tonnes each.”

All reinforcing was 3D modelled to provide insight into the final products before manufacturing and to allow for input from all parties.

The 5 by 2.6 metre box culvert units, with 400mm thick walls and 500mm thick roof and floor, and 2.4 metre box culvert reinforcing cages were constructed on precision jigs before being welded to ensure dimensional accuracy. The units were type tested to ensure quality.

“In order to meet the challenging delivery timing, we developed unique casting methods. The four unique wingwalls and four extension wingwalls were cast with floor slab,” explains Bernie.

Collaboration between the designers, Beca, installation contractor, Jon Holland, drafters, MGL, reinforcement by NAR and transporter, PTS saw the project unfold seamlessly, and was delivered on time and within budget, much to the delight of the client.