Auckland Harbour Bridge: Permanent fix expected in four to five weeks, NZTA says
Wednesday, 23 September 2020
Permanent repairs to Auckland’s battered Harbour Bridge should be complete in four to five weeks, the NZ Transport Agency said on Wednesday.
Two lanes on the bridge reopened on Wednesday morning after the installing of a temporary fix overnight was a success.
NZTA general manager of transport services Brett Gliddon told reporters people should continue using public transport and heavy vehicles should try to avoid going over the bridge for the next four or five weeks until the permanent repairs were done.
“We went in last night and closed the Harbour Bridge and put in a temporary strut. The work went incredibly well, we are really pleased we were able to complete that work in one night.”
While the work carried out would improve congestion, Gliddon said they were not out of the woods yet.
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“We do still have to manage the bridge until we get a permanent solution. It is not at its full capacity for carrying loads.
'The bridge is still in a vulnerable state. That temporary strut is not taking any load, so that load on the bridge is still being distributed across the whole bridge.”
The focus was now on designing a permanent solution, creating a design and sourcing steel for a new strut.
Heavy trucks were a concern on the bridge, Gliddon said, and NZTA was encouraging heavy vehicles to travel via the western ring route.
Auckland commuters have faced extensive delays this week after damage caused by a freak accident on Friday when two trucks were hit by high winds, resulting in half of the lanes on the bridge being closed.
NZTA said the lower half of the damaged 22.7 metre strut was replaced overnight with a section of “freshly fabricated” steel.
The temporary fix was completed after specialist bridge engineers and fabricators assessed the damage, designed a new strut, and planned the repair before manufacturing the strut.
Gliddon said there were perfect weather conditions on the bridge overnight and progress was quicker than expected.
“There was very little wind, good temperatures and visibility which meant the team were able to get the new section installed and carry out the testing all in one night.
“This temporary repair allows two extra lanes (one northbound lane and one southbound lane) on the centre span of the bridge to open to traffic. The two outer clip-on lanes are also open, which means three lanes in each direction.”
The centre span lanes remain closed.
Gliddon said although the reopening of lanes was good news, the temporary strut on the bridge is still in a compromised state and loads on the bridge will need to be managed carefully.
“This will remain until the permanent solution is in place and the bridge can support its full weight capacity again.”
The agency is now working on a permanent repair to the damage which will see all lanes reopen.
Just after 7am, the third citybound lane reopened. Ninety minutes later, a third lane heading towards the North Shore reopened.
Traffic has greatly eased across the network, however NZTA said overall lane capacity remains reduced.
“Please continue to consider working from home, using public transport or re-routing via Western Ring Route if possible.”
More ferry services in place
Fullers360 is bringing back 30-minute off-peak sailings on its Devonport route – almost doubling the frequency of this service throughout the day – in a bid to reduce congestion on the bridge.
This means services will run at a 30-minute frequency from 5.45am to 12.00am on weekdays. This is in addition to the current 15-minute frequency available from 7.30am to 8.30am during the peak commute hour on weekdays.
The timetable change will provide 14 more services to and from the Auckland CBD each day.
Fullers said the added frequency will be a temporary measure for at least the next two weeks and reassessed as the situation evolves.
Fullers360 chief executive Mike Horne said the timetable changes were a measure to urgently support Devonport and neighbouring communities.
“We recognise our role is crucial to the wider public transport network, particularly now, where there are added challenges for all North Shore communities trying to get in and out of the city.”
How exactly did this happen?
About 11am on Friday, strong and sudden gusts toppled two trucks as they crossed the bridge, Gliddon said.
One was at the peak of the bridge when it was knocked over by a gust and slammed into a steel beam, twisting the metal and shearing it clean off where it connected to the bridge below the road surface.
Gliddon said the wind was 60kmh before it shot up to a gust of 127kmh before dying down again.
“We were hit by an absolute freak gust of wind which caught a truck as it was right on the top of the bridge.
“That’s really hard to design for.”
The beam did what it was supposed to, shearing off at the bolts, rather than pulling on and damaging other support members, with its load transferred to other supports on the steel truss.
The bridge continues to be able to support itself, but engineers are unwilling to allow traffic over the original inner lanes, which opened in 1959.
The outer two lanes on each side, clipped on 10 years after it opened, have their own support structure and do not rely on the damaged truss.