En­gi­neers sup­port pre­cau­tion­ary ap­proach to Welling­ton build­ings

DEMM Engineering & Manufacturing - - EARTHQUAKE -

En­gi­neers say some Welling­ton build­ings need tar­geted checks in the in­ter­ests of public safety.

New Zealand So­ci­ety for Earth­quake En­gi­neer­ing (NZSEE) Pres­i­dent Peter Smith says that after com­plet­ing hun­dreds of rapid as­sess­ments, en­gi­neers have de­vel­oped a pro­file of Welling­ton build­ings that suf­fered the most dam­age in the Kaik­oura earth­quake or are sus­cep­ti­ble to a sim­i­lar fu­ture event.

“The Coun­cil is be­ing proac­tive in re­quir­ing all build­ings fit­ting this pro­file to have tar­geted eval­u­a­tions. We fully sup­port the mea­sures that the Coun­cil is tak­ing.

“The build­ings that need tar­geted eval­u­a­tion share key char­ac­ter­is­tics. These in­clude be­ing medium height and hav­ing con­crete frames with pre­cast floors. Other char­ac­ter­is­tics in­clude be­ing sited on soft soils or ridge­lines, hav­ing sig­nif­i­cant dam­age to non- struc­tural el­e­ments, demon­strat­ing signs of stretch in car­pet tiles or ceil­ings, or dam­age to façades.

“This quake has gen­er­ated se­vere shak­ing in build­ings with these char­ac­ter­is­tics. Some of these build­ings have been tested be­yond their de­sign load­ings.”

Struc­tural En­gi­neer­ing So­ci­ety (SESOC) Pres­i­dent Paul Campbell says en­gi­neers now un­der­stand that dam­age from the Kaik­oura earth­quake in Welling­ton was highly se­lec­tive.

“As well as car­ry­ing out hun­dreds of as­sess­ments, en­gi­neers have been work­ing hard to an­a­lyse emerg­ing pat­terns of dam­age across Welling­ton build­ings.”

Campbell says the tar­geted dam­age eval­u­a­tions man­dated by the Coun­cil will in­volve re­view­ing struc­tural draw­ings and are likely to be in­va­sive. This means po­ten­tially tak­ing up some floor cov­er­ings, strip­ping off se­lected wall lin­ings and in­spect­ing ceil­ing spa­ces to look for spe­cific pat­terns of dam­age.

“How long it takes de­pends on the size of the build­ing and avail­abil­ity of draw­ings but you would nor­mally ex­pect the in­spec­tion com­po­nent to be com­pleted in a day.”

In­sti­tu­tion of Pro­fes­sional En­gi­neers New Zealand Chief Ex­ec­u­tive Su­san Free­man- Greene says en­gi­neers re­main con­cerned about public safety in and around build­ings cat­e­gorised as earth­quake prone, given the cur­rent height­ened risk of af­ter­shocks.

“The en­ergy of the Kaik­oura earth­quake wasn’t fo­cused on shorter, stiffer build­ings, some of which are cat­e­gorised as earth­quake prone.

“It’s im­por­tant to re­alise that earth­quake-prone build­ings are likely to per­form poorly in an earth­quake cen­tred closer to Welling­ton.”

Free­man- Greene says struc­tural en­gi­neers are be­ing brought in from out­side Welling­ton to help meet cur­rent de­mand.

“IPENZ ap­pre­ci­ates the close col­lab­o­ra­tion be­tween the Coun­cil and the en­gi­neer­ing pro­fes­sion.”

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