Queries over Opal Tower sup­port beams


En­gi­neers in­ves­ti­gat­ing de­fects at Syd­ney’s Opal Tower have raised doubts about er­rors in the de­sign of key hor­i­zon­tal sup­port beams.

As an in­terim re­port into the crack­ing of con­crete pan­els that trig­gered two evac­u­a­tions of the build­ing is ex­pected to be re­leased, in­ves­ti­ga­tors dis­agree as to whether the grade of re­in­forced con­crete used in the sup­port beams was strong enough to with­stand the pres­sure of pre­cast con­crete pan­els in­stalled on top of them.

Sev­eral sources close to the in­ves­ti­ga­tion have told The Aus­tralian that one the­ory is that the beams lacked suf­fi­cient strength, caus­ing pres­sure on the con­crete pan­els, which cracked and sparked the evac­u­a­tions.

But an­other the­ory is that grout­ing be­tween the pre­cast pan­els and the beams con­trib­uted to the crack­ing in the pan­els.

In­ves­ti­ga­tors’ re­ports handed to Plan­ning Min­is­ter An­thony Roberts last week ap­pear to have found the builder, Icon Co, ap­peared to have built Opal Tower ac­cord­ing to the spec­i­fi­ca­tions it was pro­vided with. The De­part­ment of Pan­ning had been ex­pected to re­lease an in­terim re­port last Fri­day.

Four sep­a­rate in­ves­ti­ga­tions are un­der way the de­fects at Opal Tower, but The Aus­tralian un­der­stands there has been sig­nif­i­cant dis­agree­ment be­tween the ex­perts on the causes of the prob­lems.

The in­ves­ti­ga­tion team com­prises WSP, Rin­cov­itch Part­ners, a third party hired by Icon, and Cardno, an en­gi­neer­ing firm hired by the body cor­po­rate. The NSW gov­ern­ment also ap­pointed two en­gi­neers to take part in the in­ves­ti­ga­tion: Univer­sity of NSW dean of en­gi­neer­ing Mark Hoff­man and emer­i­tus pro­fes­sor at the Univer­sity of New­cas­tle’s School of En­gi­neer­ing John Carter.

So far, the multi-party in­ves­ti­ga­tion team has agreed only on a re­me­di­a­tion and re­oc­cu­pa­tion plan for the build­ing, with the find­ings sub­mit­ted by some par­ties to the Plan­ning De­part­ment re­port­edly sent back to them for re­con­sid­er­a­tion.

Other sources suggested the pre­cast con­crete panel that failed on level 10 had cracked and been patched be­fore its in­stal­la­tion in Opal Tower, though its fail­ure was only a symp­tom, not cause, of the build­ing’s de­sign flaws.

It is un­der­stood that patch­ing of pre­cast pan­els — which do not af­fect the build­ings struc­tural in­tegrity — is a com­mon prac­tice.

Res­i­dents be­gan re­turn­ing to their homes at the week­end after its first evac­u­a­tion 22 days ago.

The build­ing’s strata com­mit­tee has told res­i­dents not to re­turn to the build­ing un­til all of the en­gi­neers re­ports from the in­ves­ti­ga­tion agree as to the cause of the de­fects.

WSP, the orig­i­nal de­sign en­gi­neer­ing firm hired by Icon to sup­ply the tech­ni­cal plan for the build­ing’s con­struc­tion, did not re­spond to re­quest for com­ment.

The 38-floor build­ing at Syd­ney Olympic Park gained na­tional at­ten­tion when 300 res­i­dents were evac­u­ated on Christ­mas Eve and again less than a week later after creak­ing noises were heard and cracks ap­peared across dif­fer­ent lev­els.

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