On­go­ing bridge re­pairs for fu­ture traf­fic growth

Central Leader - - News - By Rhi­an­non Hor­rell

The Auck­land Har­bour Bridge turns 50 this week­end dur­ing a multi-mil­lion dol­lar strength­en­ing project and low-key an­niver­sary cel­e­bra­tions.

The bridge opened at the end of May in 1959 af­ter four years of construction.

Thou­sands crossed the bridge dur­ing its open­ing but the New Zealand Trans­port Agency has de­cided against an an­niver­sary bridge walk.

Re­gional di­rec­tor for North­land and Auck­land Wayne McDon­ald says he re­alises peo­ple will be dis­ap­pointed they won’t be able to walk over the bridge for the cel­e­bra­tions.

“The NZTA’s de­ci­sion was taken re­luc­tantly and one of the main rea­sons be­hind it was the sheer num­ber who would want to take part – a sur­vey in­di­cated up to 300,000 peo­ple – and our abil­ity to safely man­age them and the wide­spread dis­rup­tion that would oc­cur on roads through Auck­land.”

NZTA chief ex­ec­u­tive Ge­off Danger­field says that the clip-ons are not a vi­able al­ter­na­tive for a bridge walk.

“They are more flex­i­ble than the truss [the cen­tral four lanes] and large num­bers of peo­ple walk­ing on them at the same time would cause sig­nif­i­cant move­ment and chal­lenge our abil­ity to en­sure their safety.”

Heart of the City chief ex­ec­u­tive Alex Swney says he has mixed feel­ings about the bridge.

“It is won­der­ful that it has been here 50 years.”

But he says it is in a con- stant state of re­pair.

“We should cel­e­brate what it has done. It’s a pity that in th­ese dif­fi­cult times we can’t have a cel­e­bra­tion.

“Syd­ney-siders do it ev­ery New Year’s Eve, why can’t we do it once ev­ery 50 years?”

The $45 mil­lion strength- en­ing project will see more than 760 tonnes of steel added to the bridge’s box gird­ers – the clip-on lanes – and when fin­ished will cater for 10 to 20 years of fu­ture traf­fic growth.

Mr McDon­ald says the box gird­ers have been closed up to six nights a week for cer- tain as­pects of strength­en­ing like weld­ing, fi­nal torquing of bolts and sur­vey­ing of ex­ist­ing com­po­nents.

“Paint­ing of the new steel sec­tions will con­tinue through into 2011, al­though re­paint­ing of the bridge is a con­tin­u­ous process.”

Up to 204,000 ve­hi­cles use the bridge daily.

Mr McDon­ald says work started on the north­bound box girder in Septem­ber last year and strength­en­ing of the south­bound box girder should com­mence by Au­gust.

“Over 300 tonnes of steel have now been fixed into place in the north­bound box girder.”

In Oc­to­ber 2007, it was re­ported that the clipons were at risk of “cat­a­strophic fail­ure” if heavy trucks were bumper to bumper in both lanes of each.

But the NZTA says the bridge has al­ways been safe to use.

“If the NZTA thought mo­torists’ safety was at risk it would be closed im­me­di­ately,” says Mr McDon­ald.

He says the up­grade is an es­sen­tial part of on­go­ing main­te­nance for the bridge and about 100 work­ers are on site, some of who work by ab­seil.

Since mid-2007 the outer lanes on each side of the bridge have been closed to ve­hi­cles over 13 tonnes, but once the strength­en­ing up­grade is com­plete, the lanes will be able to han­dle the weight.

“With reg­u­lar mon­i­tor­ing and main­te­nance, and fu­ture im­ple­men­ta­tion of load re­stric­tions when nec­es­sary, the box gird­ers may be in ser­vice for an­other 50 years or more.”

Photo: JA­SON OX­EN­HAM

Un­der the bridge: Wayne McDon­ald of NZTA says all steel in­stal­la­tion on the 50-year-old bridge should be com­plete by the sec­ond half of next year.

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