Cities look to Christchurch for earthquake lessons

Andrew Turpin (rear), who owns character buildings in Kingsland, and Kingsland Business Society manager Christine Foley. Photo / Steven McNicholl

The story so far: The February earthquake in Christchurch lays bare the complacency which surrounds our risk-management of older buildings. While hundreds of unreinforced masonry (brick and stone) buildings collapse, the big killers are two reinforced concrete structures built before 1976. Under pressure from the Herald, Auckland Mayor Len Brown orders release of an incomplete list of Auckland's pre-1940s earthquake-prone buildings. What happens next?

Building time-bombs
They are buildings that lend identity and character to our suburbs and city centres - main street shopping strips with two-storey brick and stone buildings which, as Christchurch has shown, can crumble and kill in a decent shake.

They are the cafes we go to for brunch on Mother's Day, fashion houses stripped back to expose bricks and hardwood beams, edgy upstairs spaces for design and media firms, the local dairy and op shop. New Zealand cities are studded with these unreinforced masonry (URM) buildings built between the 1880s and 1930s.

It didn't take Christchurch to confirm they are potential deathtraps.

"We've known since Napier in 1931 that URM buildings don't perform that well in large earthquakes," says Associate Professor Jason Ingham of Auckland University, a specialist in earthquake engineering. "They rely mostly on gravity to keep together. They generally have no physical connection between floors, walls and roof - and the mortar is not very strong."

The two Canterbury earthquakes raise difficult issues for communities up and down the country, even those as distant from plate boundaries and known faultlines as Auckland.

While the 2004 Building Act requires councils to identify earthquake-prone buildings, it is owners who must pay to upgrade them. A building assessed as below 33 per cent of the design level which a new building must achieve to withstand a moderate earthquake is officially earthquake-prone. Councils can order owners to fix them up or have them demolished.

Most councils, especially those in low-risk areas, have taken a softly-softly approach to date, giving themselves long deadlines to identify and assess buildings and owners even longer - up to 30 years - to fix them.

"The last thing we want is to end up with areas of the city where we have totally vacant lots because property owners haven't got the money to upgrade these buildings at the present time," says Bob de Leur, the Auckland Council's building control manager.

Ingham agrees. A crackdown in the name of public safety risks demolition contractors "going gangbusters", he says.

"In Auckland in many cases you could wipe out three-quarters of URM buildings."

Community action needed
The alternative is a carrot and stick approach - but that will require ratepayers and taxpayers to put their money where their mouths are. Ingham says ultimately, it's over to communities to contribute if they want to save earthquake-prone buildings.

He stresses it is, in most cases, not as expensive as people fear. He and colleagues have spent six years promoting retrofitting options to building engineers, techniques as basic as fixing parapets to roofs. [Go to: earthquake strengthening graphic and story]. But each building is different.

Like other engineers, Ingham is sympathetic to calls from owners and heritage lobbyists for incentives to help owners, ranging from fee waivers and rates relief to low interest loans and seeding money from the Government. "It comes down to the community spirit to participate in saving these buildings."

But the natural, public safety reaction to Christchurch is to demand that councils get cracking on assessments and bring forward the deadlines - so owners have to fix or flatten.

Most councils have dragged the chain on 2004 Building Act requirements to identify earthquake-prone buildings and set deadlines for owners to fix them. The Department of Building and Housing says most have taken the "passive" approach which the act allows for, based on assessed likelihood of a major earthquake.

In high-risk Wellington, the council gives owners 10-20 years (depending on the building's importance) to fix up earthquake-prone buildings and is considering making the deadlines shorter. But when the council released a list of 800 suspect buildings in April, some owners threatened to pull them down.

The Tauranga City Council in March released a list of 62 earthquake-prone buildings, most on a 10-year deadline for upgrading. Soon after, the owners of a block of heritage harbourside buildings on The Strand unveiled plans to demolish them for a new office and hospitality complex, saying earthquake issues made it more economic to start afresh.

In Auckland, the public will soon have a chance to influence policy. The Auckland Council began work in November to draft a new earthquake-prone buildings policy, merging those of the seven pre-amalgamation local bodies, which will go to committee next month and then out for public submissions.

"The council won't be [dictating] - there will be community debate," says emergency management boss Clive Manley. "Building owners will have a view; Historic Places will have a view.

"If we use incentives, that's ratepayers' money that could be used for other [things]."

How strong is enough?
Engineers will also want input. Christchurch has reignited debate about the minimum earthquake load resistance which an old building should achieve.

The intensity of shaking on February 22 far exceeded seismic modelling for modern Christchurch buildings, designed to cope with maximum ground acceleration (G-force) of 2.2g. Engineers have long argued the minimum should be 67 per cent, double the current 33 per cent threshold.

The Royal Commission of Inquiry into the Christchurch building failures will look at building design, construction and maintenance regulations, including the minimum levels and timeframes for upgrading older buildings.

"People should know that anything below 33 per cent of the new building standard is awful," says Associate Professor Stefano Pampanin of Canterbury University's civil engineering department.

"Going to 34 per cent is not appropriate. Even going to 50 per cent is not good enough," says Pampanin, a member of the Department of Building and Housing inquiry into the performance of four comparatively modern buildings in Christchurch.

Wellington engineer David Hopkins, a consultant to the Department of Building and Housing who helped draft the 2004 regulations, admits that 33 per cent is "pretty low" and means the building is 10 to 20 times more likely to fail than a new building.

"We need to thnk about the 'what if' scenario - what have we got up our sleeve [in the building's capacity to absorb earthquake forces]," says Hopkins. "There could well be something around Auckland that has that incredibly low probability."

Consulting engineer Barry Davidson goes even further - he says many buildings should be demolished for public safety reasons.

"It is now very obvious to the public of New Zealand that old brick buildings are death traps and some pre-1976 under-reinforced concrete buildings are not much better," says Davidson, a former president of the Structural Engineering Society.

He believes the best solution is to pull down old brick buildings - except for those deemed heritage buildings. "These are chosen by society so society should pay for them to be properly retrofitted and not burden the owner."

"You will hear loud calls of these suggestions being too costly. I suggest compared to $16 to $20 billion [the estimated cost of recovery in Christchurch], and the enormous pain of some people, they are not."

Such talk worries heritage advocates who point out that few of the old masonry buildings which define our mainstreet shopping strips are protected by heritage listing.

Kingsland Business Society manager Christine Foley says old buildings are a drawcard for tenants and employees and are the key to keeping communities such as Kingsland vibrant. But while some owners are happy to do them up, others are long-term passive investors who, if pushed, would probably bowl them.

Foley says while older shopping strips have a collective character, few buildings satisfy criteria for individual heritage listing and are vulnerable to demolition. Kingsland is calling for a new category called "character linking" buildings.

Above all, she says, the council needs to abandon its "nitpicking" approach to building improvements and work cooperatively with building owners. "And the community needs to come in behind with ratepayers supporting initiatives such as rates rebates and low interest loans so more landlords want to bring these buildings up to standard."

Hundreds of buildings
The council yesterday released an incomplete list of some 400 pre-1940s buildings in the old Auckland City area which desktop analysis suggests may be below the 33 per cent threshold. After detailed engineering assessment, the council can order owners to fix them or eventually force demolition. But the existing (inherited) policy gives most owners in Auckland City until 2045 to fix them.

Andrew Turpin, who owns several character buildings in Kingsland, is dismissive of the notification that one of his is on the suspect list. "I threw it in the bin. I tend to keep away from councils - everything is so slow and costs too much." He's taking a "sit and wait" approach.

Turpin doesn't believe old buildings can be brought up to modern earthquake standards but accepts they can be made more resilient. "My question is at what cost?"

He laughs at the thought that councils might bring in incentives to help owners but then concedes it's possible if ratepayers want older buildings to escape demolition.

He points out that many people in Christchurch were injured or killed by falling parapets and awnings. He's keen to install posts on the footpath to support the cantilevered awning outside his heritage-listed Page's building - but is now dealing with his third council department.

High cost fears
Published research by PhD student Temitope Egbelakin of Auckland University's civil engineering department highlights the reluctance of most owners to undertake earthquake "retrofitting" and the perceptions which threaten progress. The 2-1/2 year study supervised by Associate Professor Suzanne Wilkinson found most owners had little understanding of earthquake risks, retrofitting options and costs while there was confusion about the threshold levels.

The study found a fatalistic attitude towards earthquakes and scepticism that buildings could be satisfactorily upgraded for a reasonable price. 90 per cent of owners in low risk cities were unwilling to take mitigation steps within five years. The paper, published in Building Research and Information, calls for agencies to undertake awareness programmes and look at incentives to encourage retrofitting.

Consulting engineer David Hopkins says owners are unlikely to show enthusiasm for earthquake strengthening until it earns market value - such as a rental premium for a safer building. That may happen in Christchurch and Wellington, but is less likely in the north.
Hopkins worked in Turkey after the 1999 earthquake on a project to upgrade apartments, and found the Government reluctant to contribute. "We argued there was a benefit for the overall community in the lack of destruction and ongoing effects on a horrendous scale of the kind we are now seeing in Christchurch."

In 2002, he carried out benefit-cost research on strengthening older buildings, based on retrofitting costs varying from $120 to $500 a square metre and assigning values for fatalities and business and social disruption. wide variation in the benefit cost ratios based on the area's earthquake risk with the net benefit in Wellington much higher than for Auckland. He estimated retrofitting pre-1935 buildings in Auckland would cost $65.8 million and produce a b/c ratio of between 0.3 and 2.4, if a quake occurred reasonably soon after retrofitting.

Auckland City's earthquake prone buildings policy was approved, following consultation, in 2006 in response to the Building Act. The council set a performance target of 34 per cent for upgrading a pre-1976 building - one percentage point above the legal definition of an earthquake-prone building. Council staff were to compile a desktop list of potentially earthquake-prone buildings by June 2007, and complete an initial performance evaluation by December
2012.

As the act required, buildings would be prioritised by their importance: those needed for post-disaster functions (such as hospitals) would be assessed by December 2008 and strengthened or removed by 2018; those that house large numbers of people (such as office buildings) or contents of high community value (eg: museums) were to be assessed by December 2009 and fixed or removed by 2019.

For most buildings, engineering assessments would be completed by 2015 and owners given 30 years to strengthen them. But as the Auckland Council's reluctance to release an incomplete and preliminary list of suspect pre-1940s buildings confined to Auckland City shows, the work went straight to the backburner.

De Leur says all Auckland's councils were behind on their assessments, partly due to the city's low risk and partly due to amalgamation. That's why lists for suspect URM buildings in Rodney, North Shore, Waitakere, Manukau, Papakura and Pukekohe are not yet available, he says. Since Christchurch, the council has got cracking on the highest priority buildings including hospitals.

Lessons learned from Christchurch
Indications are that Christchurch has not prompted a knee-jerk public safety response by officials in the new draft policy. Any changes must bear in mind the region's low risk of a damaging earthquake, says de Leur.

Emergency manager Clive Manley points out that Auckland is more at risk from a volcanic eruption or tsunami than from a quake.

"As a city we can't safeguard against every risk - we rely on the science to tell us what the risk is and that's why the previous council treated it as a low priority."

But isn't there another lesson from the two Canterbury quakes - that seismologists can't give certainty? Both were on unknown faultlines and the intensity of the February shaking confounded predictions. The Wairoa North fault south-east of Auckland may have a one in 20,000 year return period, but it could come tomorrow. There could be active faults without surface expression - and earthquakes are not confined to faultlines.

Small quakes happen regularly in the Auckland region - an indication that the region is seismically active. [Go to: Seismic Doubts for more on Auckland's seismicity]. Until more is known - requiring costly geophysical surveys - shouldn't we err on the side of caution?

De Leur counters that the lessons of Christchurch and the risk associated with Auckland are "different animals."

Canterbury's Pampanin says Auckland should not take comfort from its low risk status. Design modelling already acknowledges the city's risk profile so buildings are designed to withstand lower ground acceleration than in Christchurch or Wellington.

"As soon as something comes along that is a little bit bigger than the design level in Auckland there is no redundancy in terms of lateral design. Those [unstrengthened URM] buildings basically are in huge
trouble if acceleration goes to a higher level."

Concrete buildings danger
And what of the other class of buildings - reinforced concrete (RC) buildings built from the 1940s to mid-70s - which have known earthquake design limitations? Evaluation of these is still some time away.

Two RC buildings, Pyne Gould and the CTV building, were the big killers in Christchurch when they collapsed, pancake fashion, on February 22. The deficiencies in this era of building were exposed in the 1971 California earthquake and led to the introduction
in New Zealand of a new earthquake design code in 1976, incorporating ductile (flexible) design techniques developed by Professor Bob Park and Tom Panley at Canterbury University.

The principle of "strong columns, weak beams" has since spread around the world. But in pre-76 concrete buildings, the beams are often of equal or greater strength than the columns, increasing the possibility of column failure. In engineering terms they are known as brittle buildings, lacking the flexibility to absorb sideways forces.
Modern buildings follow the principal of "capacity design" and are built to remain standing even if weak points fail.

"Ductile design was a breakthrough because it teaches you not to try to be stronger than the earthquake - there could always be stronger shaking than you design for," says Pampanin.

Much can be done to improve the pre-76 buildings' resilience, he says. But whether many of Auckland's RC buildings have been upgraded remains to be seen.

Pampanin has worked in earthquake rebuilding in California and his native Italy where, he says, the state provides a 40 per cent subsidy for earthquake strengthening. He agrees responsibility needs to be shared if communities want to keep their heritage.

"The trouble is the problem is so big to fix in one hit you don't get started. But if in each budget there is a sum for safety then in 30 years you are going to start to fix the problem.

"We need to raise the bar and think not about the 2010 [design] level but 2050 should be the target. The Government has to step up and say we are going to invest not only in infrastructure but in safety."