The giant damaged strut on the Auckland Harbour Bridge will have to be completely removed, says the New Zealand Transport Agency Waka Kotahi.
There will be a temporary solution for Auckland Harbour Bridge beginning tomorrow for a temporary piece - it will be tested and if all goes well, there should be two new lanes opened by the end of the week.
Prime Minister Jacinda Ardern said there were teams working on both the temporary and permanent solutions to repairing the strut.
Ardern said it should be remembered this had been described as a "one in 50 year event".
In a matter of seconds we had the windspeed almost double and at the same time a truck happened to be on the bridge at the same time, said Ardern.
Ardern said the temporary and permanent fixes were "incredibly complex".
The temporary solution to repair the damaged strut which would allow one extra lane in each direction to be opened on the centre span of the bridge. Work to install the solution is set to begin overnight on Tuesday.
"This is a complex undertaking and has never been done before so the bridge team must do extensive testing on the bridge before opening it up to live traffic."
The fix is being peer-reviewed by "mathematical experts" and in parallel it will be tested with heavy vehicles before opening.
Only after it has been tested will a decision be made whether the temporary fix is suitable for general traffic, said Ardern.
But in order for the temporary fix to be installed, the southbound lanes into the city will be closed overnight from tomorrow night.
"Repair work may not be visible on the bridge right now, however there are teams working to design, peer-review the replacement parts for both the temporary and permanent solution, source materials, manufacture the part and plan for installation.
"The bulk of this time is in the design, calculation peer-review of the strut and how it will impact on the performance of the whole bridge," said Ardern.
Ardern said the new modelling was necessary because the materials of the new strut didn't exactly match those which were installed 60 years ago.
Transport services manager Brett Gliddon today said the wrecked 22m strut would have to be cut at the top and the bottom, taken out and a new piece manufactured and installed back in place.
He said to do this they would need to put load back into that strut.
He said this would be accomplished by using big jacks at the top and bottom and tension would be put back into the strut so it would operate as it was supposed to and the load across the bridge was redistributed.
Gliddon revealed details of the temporary fix which included cutting the damaged strut halfway up, putting in a new section of steel and bolting it to the bridge at the bottom.
"It will allow us to open the main part of the bridge to have light vehicles running on it and if load needs to run through the strut the new piece of steel will allow that to be transferred," he said.
This meant only a limited level of vehicles would be able to use the bridge near the repair.
Yesterday Gliddon said the temporary fix would take at least a week to have in place.
Today transport agency today said it was focused on doing everything possible to re-open the centre lanes of the bridge as quickly as possible with a temporary fix to re-open some lanes even sooner, in a matter of days.
How long it will take to get the replacement strut manufactured and inserted into the bridge is still unclear but earlier estimates put it as far out as many weeks.
New northern bus lane
Meanwhile, a new priority bus lane is to be installed on the motorway ready for rush hour tonight heading over the bridge.
And Curran St on-ramp to get onto the harbour bridge is now closed for the forseeable future.
NZTA said the bus priority system meant buses would get on SH1 at the Fanshawe St on-ramp via a new priority lane, bypassing queuing traffic.
The dedicated bus lane onto the motorway would then merge with the general highway traffic.
"Drivers need to take extra care and look out for merging buses on their right-hand side," said senior journey manager Neil Walker.
To improve safety for both bus and motorway traffic at the new bus merge point, the Curran St northbound on-ramp would be closed to all traffic.
Motorists who would normally usually use the Ponsonby on-ramp were advised to follow the sign-posted detour route to the Fanshawe St to get on the motorway.
The bus priority lane and Curran St on-ramp closure would be in place until the Auckland Harbour Bridge was fully operational again, potentially a number of weeks away.
Auckland Transport was confident there was enough seats for passengers for the coming week as buses were still only half full compared to normal pre-Covid levels.
The joint operations centre would be monitoring the network day and night managing traffic lights and other systems to optimise traffic flows.
A North Shore commuter has taken two hours and 35 minutes to travel from a northern suburb to the city this morning.
Newstalk ZB newsreader Malcolm Jordan said he was confronted by a staggering level of traffic congestion.
For most of the journey from Torbay to the CBD he was moving an inch every 10 minutes.
"I could have driven to Hamilton and back by the time it took to get me into work today," he said.