Lessons learned

More than a decade on from the Canterbury earthquakes, much has been learned about how to strengthen our heritage buildings. Structural engineer Dr Dmytro Dizhur has been embedded in that learning journey

WORDS: LYDIA MONIN • IMAGERY: DAVIDE ZERILLI

“We were inspecting a twostorey masonry house where one of the walls had collapsed into the kitchen and it looked like someone had been cooking their lunch when the earthquake struck. We had to call the fire brigade because we all felt that a person would be under the rubble.”

Dr Dmytro Dizhur had taken the first flight he could get into Christchurch after the 2011 earthquake, to join the emergency teams assessing the damage to the city’s buildings. He and another engineer walked ahead, while two search-and-rescue workers followed behind. As a University of Auckland PhD student researching earthquakestrengthening techniques for brick buildings, he’d witnessed the aftermath of earthquakes before. But Christchurch was “on a different level”.

No-one had been trapped in the kitchen with the abandoned pots and pans, it was ascertained, but it would later be discovered that about a quarter of the 185 people who died in the earthquake had been killed by collapsing masonry buildings.

Dmytro stayed on in Christchurch to discover exactly what had happened to the city’s iconic old buildings. He was joined by researchers from Portugal, Canada, California, Australia and Italy, and they inspected every masonry heritage building in the city to create a database of some 650 case studies.

Born in Ukraine, Dmytro moved to New Zealand with his family in 2001. Working as an apprentice on construction sites led him to study engineering.

“I believe the marriage between hands-on construction experience and a solid understanding of structural engineering concepts is crucial for any practising professional engineer,” he says.

These days Dmytro can be found on the 10th floor of a new waterfront building in downtown Auckland, with a lobby café and smart lifts that carry visitors directly to their chosen floors at the swipe of a touchscreen.

On his table is Structural Performance, a book he’s written to mark the 10th anniversary of the 2011 Christchurch earthquake. Recently highly commended in the Outstanding Contribution to Heritage Award category, sponsored by Heritage New Zealand Pouhere Taonga, of the Canterbury Heritage Awards, the book features some of the buildings he studied after the earthquake. All had been strengthened before the 2010–11 sequence of earthquakes, but some fared better than others.

The Chief Post Office building in Cathedral Square did well, thanks to strengthening methods that had included fixing steel elements to the original walls. But Dmytro flicks to the 1930s ‘Joe’s Garage’ building on Hereford Street and lets the photos of bricks carpeting the street “talk for themselves”. Two blocks from Joe’s, a much older building had been strengthened successfully and was quickly open for business again.

At the Carlton Hotel, little or no adhesive had been used to bond key structural elements that had been designed to withstand an earthquake. A 19th-century building on Bedford Row would have survived the shaking if it hadn’t been pounded repeatedly by its neighbour – a tall and flexible concrete carpark.

The Hawke’s Bay and Wairarapa earthquakes in 1931 and 1942 respectively showed that masonry buildings were an issue and parapets were made safer, says Win Clark, a structural consulting engineer with years of experience in heritage buildings.

From the 1980s onwards, guidelines for assessing brick buildings in particular were developed and expanded. But Win explains that it wasn’t until the turn of the century that there was a big push to assess existing structures and carry out more research into masonry buildings.

This led to a six-year University of Auckland research programme headed by then Associate Professor Jason Ingham, in which Dmytro began as a doctoral student and later continued as a key researcher co-supervising local and international students.

The Christchurch research led to further guidelines for strengthening existing buildings. It also generated international scientific interest, partly because of the data produced by instruments that had measured the ground tremors.

“You could do an electronic model of the building and you could input into it a time history that was appropriate for that site and be able to match the damage observed with the damage that you’re seeing in your model,” says Win.

New Zealand companies are now using lessons learned from Christchurch to help the Dutch. The Netherlands’ masonry buildings are of a similar style to New Zealand’s, but its earthquakes are man-made as a result of gas extraction.

Ninety percent of the masonry heritage buildings in Christchurch studied by Dmytro and his colleagues were eventually demolished. Piece after piece of the city’s history was lost. The Press and the Lyttelton Times buildings were grand symbols of a thriving local newspaper industry praised by author Mark Twain. A young Agatha Christie stayed in Warner’s Hotel and the touring Beatles greeted fans while standing on a Clarendon Hotel fire escape. Only the facades of the Clarendon were left in 2011 and now they’re gone too.

Dmytro was in Italy after that country’s 2016 earthquake and says very few centuries-old buildings were demolished.

“We see a crack and that’s a no-no – the whole building has to be pulled down. An Italian looks at a crack and says, ‘We can repair that crack and we know the methodologies and the techniques needed to repair that crack’. So a repair becomes a relatively routine procedure, rather than saying, ‘This building isn’t safe. It needs to be demolished’.”

Win hates the term ‘earthquakeproof’. Not even a modern

building can be earthquakeproofed, he says, because every building has some risk. It’s a matter of working out what that risk is and then upgrading the building if it doesn’t meet the legal minimum of 34 percent of the New Building Standards.

However, being too risk averse can drive up the cost of an upgrade. In Win’s experience, engineers who don’t usually work with heritage buildings tend to over-compensate with strengthening because they don’t fully understand how a particular building is likely to perform in an earthquake.

Dmytro has worked on several Category 1 Heritage New Zealand Pouhere Taonga properties, including Kemp House, the Stone Store and Antrim House, and he owns his own heritage building in Whanganui. His Italian partner, Dr Marta Giaretton, is also an earthquake engineer who works with historic structures, and they recently welcomed a baby boy.

As a young child, Dmytro always wanted to figure out how things worked. He’d pull his toy cars apart and rebuild them with improvements – turning one into a remote-controlled boat – before moving on to VCRs, TVs and computers.

He can’t pinpoint exactly when his love of heritage buildings began, but it intensified after Christchurch. It was the experience of seeing and touching materials, he says, that someone had worked with 120 years earlier – before they were scooped up by a digger to be dumped in landfill.

“I was just imagining a girl born 10 years ago, now walking around Christchurch. She’ll never see or understand how it felt or what it looked like where her granddad used to work or where her mum used to work. That whole connection with a past generation just disappeared.”

IMAGE: MARCEL TROMP

I first visited Rotorua Museum around 20 years ago. The presence and the features of the building really captured my imagination.

When you go into the beautiful Government Gardens, you see this magnificent building up on the hill with very defined, dark lines and a grand entrance as a focal point. It has a bright-red tiled roof and the dark timber that frames the lighter-coloured infill makes the whole thing stand out, with beautiful windows and joinery that you can see from afar.

As the home of one of the first official bathhouses in New Zealand, Rotorua Museum attracted local and international tourists to Rotorua, so it is a unique piece of history.

The museum stands near the edge of Lake Rotorua in a young volcanic area. As it was built on relatively soft pumice soil, it was a challenge from the very beginning.

Local tōtara was sourced for the timber framing and the museum has some of the earliest pre-cast panels used in New Zealand. Lightweight pumice concrete was poured into moulds lined with newspapers and very thin wire was embedded into the panels as reinforcement.

When the panels were cured, they were removed from the moulds and inserted into the timber frames. The museum is currently undergoing earthquake strengthening and renovations and the backs of these panels have been exposed. So you can stand in front of a wall and read the newspapers from 1906 – isn’t that fascinating?

Over the years, the museum has undergone many changes, so only a few parts of the building are original. I hope those parts are preserved with minimal intervention so that someone else in 100 years can read those newspapers, feel the history and be as astonished by it as I am every time I walk into the building. n