Wellington Library attains 63% of earthquake rating but building code is wrong!

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Batman

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#249369 8-May-2019 08:39

So I read on the news that despite achieving an earthquake rating of 63% of the current codes, they don't trust the current code and it's probably only "15-20" safe.

So the current code is rubbish it seems.

You see, every non residential building (correct me if I'm wrong, I'm sure the word every is a bit too strong here) is required to be upgraded to about 65% earthquake rating in this country IIRC.

And now you're saying that all the millions spent is probably going to get you to about 25% in reality.

https://www.stuff.co.nz/dominion-post/news/112520867/wellington-central-library-knock-it-down-and-start-afresh-option-with-earthquake-rating-pending

"Technically its earthquake rating under current code is 63 per cent but when you apply the lessons that we've learned from the Statistics Building it is almost 15 to 20 per cent which means it needs significant work."

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#2232650 8-May-2019 08:47

I guess there is a defined process and standard for assessing buildings, which probably isn't updated all that often. It's good that they are learning from past problems. I expect the standards and process will be evolved over time.

WCC definitely has no problem spending our money. Much of it seems frivolous. A library will be used a lot less going forward with everything going digital, or at least differently, but it's important to have a library even if just a place for people to gather, stay warm, etc.

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#2232651 8-May-2019 08:49

But what if you had a building(s) and spent millions upgrading to meet the code and then be told that it's no good?

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#2232674 8-May-2019 09:29

The converse of this is that the Building Code appears to be at odds with reality in the other direction when applied to single-story timber-framed buildings.

I saw an engineering report about such a public-use building that said, in adjacent paragraphs, that the building was "approximately 28% of NBS" but that it "posed no threat to occupants". You may have seen TV News footage of a pair of bulldozers being used to apply twisting stresses to a standard 1960s Education Department wooden classroom block, with much less success at causing damage that was expected.

The whole earthquake engineering business, and the related Building Codes, are in need of serious revision in light of actual experience from the Christchurch, Eketahuna, Seddon and Kaikoura earthquakes.
Theory and experience do not appear well lined up at the moment

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#2232675 8-May-2019 09:33

They talk about lessons learned...

One I learned 8 years ago was that in an EQ you're maybe 100 times more likely to be killed in or around a commercial or public use building than in your own home.

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#2232696 8-May-2019 10:11

Fred99:

They talk about lessons learned...

One I learned 8 years ago was that in an EQ you're maybe 100 times more likely to be killed in or around a commercial or public use building than in your own home.

I know of many many lucky people in their homes.

- brick chimneys crushing the entire lounge but nobody was there

- a few other giant brick blocks caving into bedrooms etc but nobody was there

but these were always the old houses with top heavy brick features

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#2232710 8-May-2019 10:28

There were many people who had near misses / lucky escapes in commercial / public use buildings too.

One overlooked feature of the Chch quake injury / death toll was that many vulnerable mainly old buildings were damaged from the 4 September 2010 quakes, and were unoccupied / abandoned when the Feb 22 quake hit. As it was, some of these buildings were under repair at the time and workers were killed. If they'd been in "normal use" then the death toll would have been (much) higher.

A double-brick chimney toppled at our house. The entire top section, about 2m high x 2m wide x 1m deep dropped 3m on to a suspended concrete slab deck. If it had fallen the other direction, I'd have probably been killed. The chimney had been inspected by EQC a few days before, and declared "safe". I'd decided it wasn't, and was going to remove the top section at my own cost. The quake saved me from that DIY job.

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#2233555 9-May-2019 11:24

Fred99:

There were many people who had near misses / lucky escapes in commercial / public use buildings too.

One overlooked feature of the Chch quake injury / death toll was that many vulnerable mainly old buildings were damaged from the 4 September 2010 quakes, and were unoccupied / abandoned when the Feb 22 quake hit. As it was, some of these buildings were under repair at the time and workers were killed. If they'd been in "normal use" then the death toll would have been (much) higher.

A double-brick chimney toppled at our house. The entire top section, about 2m high x 2m wide x 1m deep dropped 3m on to a suspended concrete slab deck. If it had fallen the other direction, I'd have probably been killed. The chimney had been inspected by EQC a few days before, and declared "safe". I'd decided it wasn't, and was going to remove the top section at my own cost. The quake saved me from that DIY job.

Quite a few people had what could be considered to be a lucky escape with the Stats Building given the quake hit in the middle of the night when it was effectively unoccupied vs during a work day when it would have had many people either on or under the affected floors.

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#2233573 9-May-2019 11:40

timmmay:

I guess there is a defined process and standard for assessing buildings, which probably isn't updated all that often. It's good that they are learning from past problems. I expect the standards and process will be evolved over time.

WCC definitely has no problem spending our money. Much of it seems frivolous. A library will be used a lot less going forward with everything going digital, or at least differently, but it's important to have a library even if just a place for people to gather, stay warm, etc.

Money is no object when it comes to other peoples money.

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#2233584 9-May-2019 11:48

Batman:

So I read on the news that despite achieving an earthquake rating of 63% of the current codes, they don't trust the current code and it's probably only "15-20" safe.

So the current code is rubbish it seems.

Correct.

Where I work, it was decided subsequent to the last Wgtn earthquake to upgrade our buildings to some higher percentage of code.

In our building, this consisted of changing one of the wheelchair-accessible toilets to have a sliding door instead of swinging, putting a sign on the other wheelchair-accessible toilet, and changing 2 emergency exits from 3 steps directly to the door, to a small landing and 3 steps, plus a handrail.

I feel so much safer now.

evilengineer

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#2233593 9-May-2019 11:56

Batman:

So I read on the news that despite achieving an earthquake rating of 63% of the current codes, they don't trust the current code and it's probably only "15-20" safe.

So the current code is rubbish it seems.

You see, every non residential building (correct me if I'm wrong, I'm sure the word every is a bit too strong here) is required to be upgraded to about 65% earthquake rating in this country IIRC.

And now you're saying that all the millions spent is probably going to get you to about 25% in reality.

https://www.stuff.co.nz/dominion-post/news/112520867/wellington-central-library-knock-it-down-and-start-afresh-option-with-earthquake-rating-pending

"Technically its earthquake rating under current code is 63 per cent but when you apply the lessons that we've learned from the Statistics Building it is almost 15 to 20 per cent which means it needs significant work."

The legal definition of Earthquake Prone is less than 33%NBS (New Building Standard).

Under this level you are legally required to strengthen or bowl the building within a set time frame that varies from region to region and type of construction depending on the earthquake risk.

The legal minimum strengthening target is 34%NBS but the New Zealand Society of Earthquake Engineering (NZSEE) recommend targeting 67%NBS and ideally as close to 100% as can be reasonably achieved.

Most big corporate and public sector tenants like to see at least 67%NBS.

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#2233594 9-May-2019 11:58

The Kaikoura earthquake has fundamentally changed a *lot* of things that we thought we knew about earthquakes. The lateral forces and the way that the ground moved was very different to any quake we'd had previously - and the consequences were significant.

Many buildings constructed with precast slabs and beams saw movement (Stats house being the classic example) that was never foreseen or allowed for in many designs. This resulted in a lot of work with MBIE who released a lot of information around this late last year.

The initial report into the library several months ago showed that it still met 100% of NBS in many areas, however the same precast floors and beams that were 100% of NBS using some testing and lateral forces are now dangerous when this new information is used to calculate how they will perform.

The library closure is merely the tip of the iceberg. This particular issue is going to be huge, and we're only in the early days of it.

evilengineer

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#2233612 9-May-2019 12:16

The Building Code isn't "rubbish".

But lessons are learnt from every earthquake (not just those is NZ) which moves on understanding of particular issues within the Structural Engineering profession, as well identifying new ones, at a rate faster than the design codes and legal framework can keep pace with.

Fred99

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#2233647 9-May-2019 13:05

sbiddle:

Many buildings constructed with precast slabs and beams saw movement (Stats house being the classic example) that was never foreseen or allowed for in many designs. This resulted in a lot of work with MBIE who released a lot of information around this late last year.

Shouldn't have been unanticipated for Wgtn. PGA recorded in Wgtn was only 0.2-0.3g, and it was lateral movement. Damage exacerbated by duration (about 90 seconds IIRC).

From Seismic Hazard maps, Wgtn has >10% probability of a >0.6g event per 50 years. The Kaikoura event was less than half that, so it damned well should have been foreseen and allowed for. It was not "the" big one - not even close.

Fred99

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#2233666 9-May-2019 13:14

evilengineer:

The Building Code isn't "rubbish".

But lessons are learnt from every earthquake (not just those is NZ) which moves on understanding of particular issues within the Structural Engineering profession, as well identifying new ones, at a rate faster than the design codes and legal framework can keep pace with.

Yup.

Increased urbanisation (globally) means that there's more chance of a "direct hit" somewhere, and the number of instruments already in place to record an event when it happens has increased. IIRC Northridge (California), Kobe, and Chch all produced unexpected and record-breaking high shaking intensity. I think Kaikoura holds the present record at 3.0g, recorded near the epicentre.

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#2233669 9-May-2019 13:22

Fred99:

sbiddle:

Many buildings constructed with precast slabs and beams saw movement (Stats house being the classic example) that was never foreseen or allowed for in many designs. This resulted in a lot of work with MBIE who released a lot of information around this late last year.

Shouldn't have been unanticipated for Wgtn. PGA recorded in Wgtn was only 0.2-0.3g, and it was lateral movement. Damage exacerbated by duration (about 90 seconds IIRC).

From Seismic Hazard maps, Wgtn has >10% probability of a >0.6g event per 50 years. The Kaikoura event was less than half that, so it damned well should have been foreseen and allowed for. It was not "the" big one - not even close.

Pure size/strength alone doesn't tell the whole story. From what I've gathered it was a combination of the strength, the direction of movement, the frequency of the waves and the duration. Plus the distance from the two near simultaneous epicenters and the way the waves traveled up the coast meant it was a very different movement to anything previously known about. So, no, it wasn't "the big one" as such but the way it affected buildings of a certain height and construction was very big.

Quakes are not all the same. Even the two Chch ones were very different with lateral movement in one and up-thrust in the other.

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