Dmytro Dizhur outside his Whanganui building in Taupō Quay. Photo / Lewis Gardner
Dmytro Dizhur outside his Whanganui building in Taupō Quay. Photo / Lewis Gardner
[A_190214WCBRCQuake01.JPG] Dizhur and team test the way the timber floor at 35B Victoria Ave responds to strong shaking. Photo / Bevan Conley
Laurel Stowell
A structural engineer who got valuable experience with Whanganui's old buildings will return to the city this year to strengthen his heritage Johnstone & Co building.
During the past 10 years he has also documented the effect of earthquakes on Christchurch buildings, written a book on the subject and completed his PhD degree.
Ukrainian-born Dmytro Dizhur became interested in the way buildings work while he was labouring on construction sites to pay for his university study.
"It has one of the highest concentrations of heritage in any particular town. There are over 400 buildings. It's just a fascinating place with a lot of character and history behind it."
He was involved in work to strengthen Taupō Quay buildings to house the Department of Conservation and Sarjeant on the Quay, and he was offered a building to test towards destruction.
It was 35B Victoria Ave, the two-storey unoccupied brick building behind George's Fisheries.
His team set up experiments to see how its upstairs wooden floor - in far from ideal condition - would perform under strong shaking. At the same time they protected the building's other elements and kept themselves safe.
Dizhur and team test the way the timber floor at 35B Victoria Ave responds to strong shaking. Photo / Bevan Conley
"That was one of the more exciting testing that we were doing," Dizhur said.
It achieved international recognition and got New Zealand building guidelines updated.
Then the Christchurch earthquakes happened, and Dizhur and team were there for nearly a year to record the result of the shaking on the city's many masonry buildings.
A good portion of them had been strengthened already, which made the results especially interesting.
The team "documented every single masonry building in existence, the biggest database in the world".
The shaking produced a mishmash of results. Some of the strengthening worked and some didn't. Christchurch lost more than 90 per cent of its old brick buildings.
Thirty-nine people were killed by masonry buildings in the quakes - about 20 per cent of the deaths. Most of the fatalities were caused by items like parapets falling on people.
With other buildings, whole facades collapsed and crushed cars and buses in the street below.
For several years Dizhur studied the Christchurch results and found a lot of tools and methods for strengthening buildings.
He compares a large rectangular building to a cardboard shoebox.
"If you remove the lid, the box is quite flimsy. Put the lid on top and it's much sturdier."
So, in a building, tying the walls, floors and roof together makes for more strength. Other means of strengthening include coatings to exterior surfaces, or carbon fibre strips cut and glued into brickwork, or the addition of extra columns and pillars.
There is no one solution for strengthening, he said, but a "toolbox" available.
Which methods are used will depend on the building itself and the values it must retain.
"Each one is unique and has to be addressed in a unique way."
The result of the study is Dizhur's book Structural Performance, an illustrated case study of 52 of the 650 Christchurch buildings.
Dmytro Dizhur's book, Structural Performance, was launched in February. Photo / supplied
Dizhur said he hoped it would make buildings better and save lives and businesses, and that research would continue to find new and better "tools". To that end all the money from sales would be put into scholarships for passionate young engineers.
He's hoping new tools will make it cheaper and more attractive for owners to strengthen buildings than to demolish them.
He has his own project, the Johnstone & Co building that stands beside the Whanganui City Bridge in Taupō Quay. It's quite a challenge - 30m wide with 10m facing onto the street, and three storeys tall, with an earthquake rating less than 33 per cent of new building standard.
He could have started with an easier building, but this one would be interesting and show others what's possible, he said.
"The reason why I like [old masonry buildings] is because they are so challenging, working with what you have got. You need to understand how it was built, how it was changed during its 120-year life, what alterations have been done, how your new structure will impact the current tenants and how it will change the architectural feel for the space."
He bought the building in 2013, had it painted last year and now has a plan for strengthening it, a resource consent and some Heritage Equip funding. The Johnstone building is not listed with Heritage New Zealand, but it is important for the Whanganui streetscape, he said, and it has a rich history.
One of the main changes will be to extend a partition wall in the lower storey up through the other two. He'll also remove some parapets, and stiffen the ceilings by adding a plywood layer.
The facade will be tied to the floors and roof, using a system of screws that link timber to brick.
He intends to begin "hands on" strengthening work within the next six months.
