Green-tagged Buildings In Christchurch Should Probably Have Received Foundation Improvements After First Quake

Today it was announced that a Royal Commission of Inquiry is to be held into the collapse of some of the buildings in the Christchurch earthquake. The inquiry “will examine issues around the built environment in the Christchurch CBD including the CTV and PGC buildings which collapsed in the disaster” Prime Minister Key said

“We are determined to get those answers, and I believe that this Royal Commission, along with the technical investigation (by the Department of Building and Housing), will do that.” source

A while back we came across an article in the Wall Street Journal that raised questions as to the structural integrity of some buildings in the city of Christchurch. Here’s what we found.  Will information such as this be examined in the inquiry? We’ll know soon enough.

By GEOFFREY ROGOW

New Zealand Building Code Gave All-Clear Before Quake

“CHRISTCHURCH—Disaster experts are questioning why so many of the buildings damaged in last year’s earthquake in New Zealand were given the all-clear, an alleged oversight that some say added to the calamity brought by last week’s quake in Christchurch.

“Everything had been weakened by that first quake, that’s for sure,”said Steve Calanog, a federal “on scene” coordinator for the U.S. Environmental Protection Agency’s emergency-response team in San Francisco.”

Sounds like this guy may know what he’s talking about, he was also an incident commander following Hurricane Katrina

“Following the first quake, buildings were assessed by local engineers and given green, yellow or red tags to show whether the structures were fully cleared, required structural changes or needed to be condemned. Codes that determine the tags—updated in New Zealand about five years ago—have provoked the most debate among experts.

Mr Calanog told the WSJ that Environmental Protection Agency staff said that even green-tagged buildings in Christchurch should probably have received structural improvements to their foundations after the initial quake.

New Zealand’s Department of Building and Housing, who oversees the classification of buildings, declined to go into detail about its tagging system, saying only that it took its lead from “industry experts on the ground” which included ” educators and workers in the public and private sectors.”

You’d hope that in a country colloquially known as The Shaky Isles the Dept would have a few of its own experts among its permanent staff.

The WSJ goes on to quote engineer and educator, Quincy Ma, outside of the fallen Canterbury Television (CTV) Building who said that New Zealand needs better regulations. Something we’ve heard said before about the NZ mining and adventure tourism industries. Is a common theme emerging here?

“We should have a more defined process of how buildings are reviewed after an earthquake,” said Quincy Ma, a structural-dynamics expert at the University of Auckland. “Hopefully, our current standards will improve over time as we continuously look at our buildings and see how they develop.”

Consider the next section alongside what was said in the the 1996 documentary about liquefaction, building resonance and old buildings being dangers during an earthquake in Christchurch. Bear in mind these hazards have been known about for 15 years. Even as far back as 1996 the strengthening work being carried out at that time was dismissed as a “waste of time” if a big quake hit because it only had to meet a fraction of the current standard.

The WSJ continued

According to Miyamoto International, a global earthquake and structural-engineering concern, brick buildings and concrete structures built in Christchurch in the mid-1970s—before improved standards were put in place in response to better understanding of seismic events—are in dire need of reinforcement.

Kit Miyamoto, the company’s chief executive, said New Zealand building standards are among the world’s most rigorous, but not thorough enough given the scale of the September seismic activity and the level of ground liquefaction. Liquefaction happens when soil loses its strength because of an applied stress—such as an earthquake.

Building codes are minimum guidelines and give a false sense of security,” he said. “A building is not earthquake-proof because it passes some guidelines; these buildings must be anchored.”

In 2004, authorities in New Zealand required that older buildings be strengthened to at least one-third of the preferred standard. Buildings in Christchurch and other areas were given 20 years or more to meet the standards due to the cost of improvements. Standards accounting for ground liquefaction weren’t included in the new rules.

After the September quake, some business owners decided to go beyond the law’s requirements. Stephen Mateer, owner of the Lyttelton Coffee Club, added reinforcements for his 110-year-old building that was full of lunchtime diners when the quake hit Tuesday.

“The seismic strengthening saved us,” said Mr. Mateer… Read the full article here

On March 2 we blogged about questions that were being asked about the stability of the CTV building, guiding our readers toward reports in the international media – The Mainichi Daily News and Asahi.com.

First, The Mainichi Daily News

CHRISTCHURCH, New Zealand — A building that collapsed in a powerful earthquake here on Feb. 22, leaving many Japanese students missing under rubble, was deemed fit for use after a 2010 quake, local authorities said.

In a survey conducted after Christchurch was shaken by a magnitude 7 earthquake in September last year, authorities decided that there was no problem with continued use of the Canterbury Television (CTV) building. But following the building’s collapse during last week’s magnitude 6.3 quake, people have been questioning that decision.

The media outlet went on to say

Christchurch Mayor Bob Parker said that tests were conducted according to international standards and that the responsibility to ensure safety lay in the hands of the building’s owner.

The building had been inspected by the council and ‘green stickered’ after the September 4 quake

But with buildings that had green stickers indicating they were fit for use, owners were supposed to conduct safety checks and carry out any necessary repairs themselves, and there was no obligation to report any reinforcement work.

Local media said that during the September 2010 quake, cracks appeared in the walls of the CTV building, and building users had worried about its safety.

Steel reinforcement fell short of international requirements

Controversially, the international site Asahi.com reported

The Canterbury Television building was damaged in a 2010 earthquake, but suggested reinforcements were not conducted before it was flattened last week by another temblor, trapping an estimated 100 people, local people said.

Architectural engineers had warned that some quake-proofing would be necessary for the six-story CTV building after the temblor in September 2010, but the owner of the building apparently decided that it was safe enough.

In addition, Christchurch municipal authorities said they found no problem with the continued use of the building following an inspection after the September quake.

The CTV building, erected in 1975, collapsed in the magnitude-6.3 earthquake on Feb. 22…

According to Rob Cope-Williams, 61, a CTV producer and newscaster, large cracks, some several meters long, formed on the interior walls of the building following the magnitude-7.0 quake in September.

A three-story building behind the CTV building was severely damaged, and demolition work began in December.

Cope-Williams said shockwaves from the wrecking ball caused many cracks to widen in the CTV building, raising concerns among CTV employees that the building would not survive another quake.

The demolition work was completed Feb. 21, the day before the latest temblor…

Hideki Miyamoto, head of a U.S.-based architectural design office specializing in quake-resistance structures, has dispatched a team of inspectors to survey the latest damage in Christchurch.

He said the inspectors reported that the amount of steel reinforcement in concrete samples collected at the CTV building site fell short of the requirements in the current quake-resistance standards.

The team also noted a lack of horizontal steel braces to bind the steel bars and keep them in place, Miyamoto said…” read the full report here

If the building had been brought up to present day standard would the CTV building still be standing now? should the building have been taken out of commission during repair work? Ironically Canterbury TV had already vacated its previous, older,  building after it was damaged in the September quake. Both buildings were destroyed in the second earthquake

Why weren’t structures in which hundreds of people work, study or live made as safe as possible, in a city where the dangers have been known about and understood for far too long?

Both questions that, hopefully, will be fully examined and answered in the inquiry.

Let’s hope that some good comes out of it and strong, effective legislation is introduced as soon as possible, well before before a similar horror befalls another New Zealand city.