KEY POINTS:
Transit New Zealand is defending its maintenance and safety of the Auckland Harbour Bridge and rejects a report that the landmark is at risk of "catastrophic failure".
Papers released under the Official Information Act reveal Transit officials underestimated the traffic load on the bridge clip-ons, which failed to meet standards by a "large margin" when tested last year.
"If the level of load in this assessment representing a traffic jam situation with maximum heavy vehicle concentrations at the centre of span two (between piers one and two) in both lanes were to occur, there would be risk of catastrophic failure," said a report by Beca Infrastructure, commissioned by Transit.
Transit chief executive Rick van Barneveld said a Herald on Sunday article misrepresented the contents of the Beca reports.
It neglected "to mention correspondence from Beca confirming that Transit's approach to managing traffic and our plans for the next upgrade are sound", he said.
"I am confident that the bridge is safe. It has been tested against extreme loadings to understand what it would take to make it fail.
"This work by New Zealand experts and peer-reviewed by other international consultants reaffirms that the bridge is safe for all users."
The bridge opened in 1959. The two-lane box girder clip-on sections were added to each side in 1969, doubling the number of lanes to eight.
While they have an expected lifetime of 50 years, there were reports last year that cracks and signs of material fatigue had been found.
In May it was reported that Transit New Zealand would move to stop trucks using either of the outside lanes, a measure it said would make the bridge last longer.
Buses were not included in the ban, which will apply to any vehicle heavier than 4.5 tonnes.
Truck companies were asked to stay on the centre lanes. At the time, Mr van Barneveld said Transit was not keeping any problems with the bridge from the public.
He said trucks caused "fatigue stress" to the clip-ons, and reducing that would mean the additions would last at least a further 40 years.
He believed the main bridge structure was sound.
- NZPA
