Whangārei firm Culham Engineering making strut to repair Auckland Harbour Bridge

Culham Engineering fabricator/welder Albert Tuhiwai grinds off the sharp corners on the section of strut for the Auckland Harbour Bridge repair the Whangārei company is making. Photo / Tania Whyte

Aucklanders can thank the ingenuity and fabrication skills of Northlanders for helping get their traffic back to normality with Whangārei's Culham Engineering manufacturing the permanent struts for the Auckland Harbour Bridge repair job.

The bridge was seriously impacted when a truck hit struts on the inner lanes over a week ago, causing four lanes to be closed - though that is now down to two - and major traffic chaos as commuters struggled to find alternative routes through Auckland.

Work is under way on designing and fabricating a permanent load-bearing fix for the bridge - a 22.7m strut - but it will take weeks for the bridge to be fully restored.

The grade 350 L15 steel for the strut has been sourced and manufactured by NZ Steel and delivered to Culham Engineering in Whangārei, which is fabricating the struts, which will be delivered to Auckland for the repair job.

Culham Engineering managing director Rob Kirwan, who was in Auckland on the day the bridge was hit and witnessed the gridlock it caused, knows just how important the work is.

Fabricator/welder John Fryer discusses the details of the second section for the Auckland Harbour Bridge repair project with Culham Engineering Managing Director Rob Kirwan. Photo / Tania Whyte

"This job is not the hardest we have completed, but I would say it is right up there with the most important to be done within the company. The timeframes required and the ramifications of not getting it done on time are huge, so we do understand it is very important,'' Kirwan said.

"Every job is important, but this job being so high-profile and having the ability to work on the Auckland Harbour Bridge is something our guys are relishing."

Kirwan said he got a first hand idea of timeframe to get the job turned around as quick as the possibly could after witnessing the traffic chaos caused by the damage.

''I think everybody that has been involved in this project has pulled out all the stops to make it happen.''

Kirwan said it was pleasing to know that the company is helping to get the bridge back to normal as soon as possible so Aucklanders can get about their business easier.

"It's always nice to help out those Aucklanders aye?"

Waka Kotahi NZ Transport Agency said the design and fabrication of the permanent strut for the Auckland Harbour Bridge is now well advanced.

A strut on the Auckland Harbour Bridge was bent when a truck was blown into it last Friday, above. Whangārei's Culham Engineering is making the strut for the repair job.

The strut will replace the one damaged when 127km/h winds blew a truck into the bridge superstructure on Friday. The temporary repair has not restored the strut's load-bearing function, but when the new strut is installed it will return the bridge to its full load capacity. Two of the bridge's eight lanes will remain closed until it's installed.

"Teams are working at pace to design and peer review the replacement part for the permanent solution and to manufacture and plan for installing it," Waka Kotahi general manager transport services Brett Gliddon said.

"Fabricating the 22.7m strut and getting it into position is the quicker part of the process. It will take several weeks before it is tensioned up as a load-bearing part of the bridge superstructure.

"The bulk of this time is in the design, calculation and external peer review of the new strut in relation to how it will impact on the performance of the whole bridge. This includes careful calculations on how to re-balance its load-bearing function."

Installation of the new strut will require closure of the southbound lanes of the bridge and this installation will take longer than the temporary fix.

"On Tuesday night the team only had to remove the damaged part of the strut, install the temporary section and bolt it to the bridge deck. This time, they'll have to remove the temporary section and the old section connected to the top of the bridge and then install the new permanent strut. That will take much longer," Gliddon said.

A date for the installation is still not known.

As well as the safety and performance of the strut, Waka Kotahi is also paying careful attention to how the new piece will look on the bridge, which is an iconic piece of Auckland's infrastructure.

Culham Engineering fabricator/welder Elijah Niha checks measurements on the jacket plate he has been welding as part of the Auckland Harbour Bridge repair job the company is doing. Photo / Tania Whyte

The materials of the new strut will not exactly match those that were installed 61 years ago. For example, it will have welds where the old strut had rivets.
Waka Kotahi is working with a consultant conservation architect to ensure the new strut fits appropriately with the landmark status and heritage values of the bridge.

"The aim is that once it's installed and had a coat of paint, it will blend in with the rest of the bridge superstructure and the subtle differences will go unnoticed," says Gliddon.