HOW WE PREPARE
Renovations can help reinforce older buildings to resist collapse
Q How would you and I respond to a major earthquake in the capital?
AA natural disaster would test us in ways we rarely contemplate. Today, we can go to the hospital if we are sick, and a doctor will see us. Ambulances will respond, buses will run, we can drive down any street with only ordinary delays due to traffic or snow. We can go where we need to, and so can everyone else. Stores have food. Water comes out of the taps. Street lights work, so that emergency crews can see what they are doing at night.
What if, suddenly, all that stops?
Even with the modest earthquake of 2010, “We lost phone service because of saturation,” Kate Ploeger says. “There are so many people who picked up their phones and used them, it saturated the network. So even if infrastructure is undamaged, you’re probably going to have nonfunctioning communications systems because of saturation alone. It’s really important when you have decision-makers trying to communicate, or when you need to call 911.”
That’s another issue: What happens when thousands of people all dial 911 at the same time? “There are probably going to be issues with 911,” all because people who aren’t in urgent danger phone the service anyway to report that there has been an earthquake.
Even if calls do go through, Ploeger says, history shows emergency services will likely have too much on their plates to deal with every problem.
“People will have to be self-sustaining,” which is unlike our modern North American experience. We’ve become accustomed to the idea that help will always come quickly when we dial a phone number. Not so, during some natural disasters.
The time of day will matter, too.
The earthquake of 2010 struck at 1:41 p.m., and in sunny June. But the Earth’s plates can shift at any time. The next quake could as easily come in the middle of the night, and in cold weather, when shutting off ruptured gas lines and failures of the electrical system could leave both residents and rescuers cold and in the dark.
Of course, all of this is based on a what-if.
TOM SPEARS
There are engineering solutions to keep buildings standing: Some years back, the federal government decided the Canadian Museum of Nature, for one, was in need of earthquake protection. It had unreinforced stone walls. It also sits on 30 metres of soft “Leda” clay, which is extra-sensitive to shaking.
“It was forecast that we could get a 6.0 to 6.5 (magnitude earthquake) in this region,” says architect Barry Padolsky, who worked on the renovation, which lasted from 2004 to 2010.
“We built a whole steel birdcage that was inserted just inboard of the perimeter walls,” and fastened to the stone every 1.5 metres.
The major renovations of the West Block and Centre Block also call for similar reinforcement, he said.
To help our buildings resist earthquakes, Saatcioglu builds walls at the University of Ottawa, adds strengthening measures, then torture-tests them.
His giant, piston-driven wallshaker increases its force steadily. Zigzag cracks appear between blocks of the test wall first, then corners of blocks shear off before, finally, the wall crumbles at its base.
“Most of our schools are masonry schools and, typically, for low-rise construction, we use masonry,” he said.
If there’s a worst-case scenario for earthquake planners to imagine, it involves many small children in an elementary school.
“School gyms are notorious for being covered with concrete block without reinforcement,” he said.
Newer schools may have steel supports in the wall. Older ones don’t — and that includes the cavernous “structures lab” where Saatcioglu himself works at UOttawa — a couple of storeys tall, built in the 1960s, concrete block walls from floor to ceiling.
There is a steel frame of sorts — but it is there to support the crane that does the heavy lifting. It would stop the roof from caving in, but would not hold up the walls.
“So schools do pose a threat and this is why, in B.C., they implemented a school-retrofit program funded by the province.
“If we were to start retrofitting buildings, it is very costly. This is why it is not a mandatory part of the (building) code. But if we were to retrofit public buildings, I would start with schools. The whole school, of course.”
It doesn’t take a full collapse to hurt people, he notes. All it takes is some falling blocks indoors, or a partially collapsed wall.
There are commercial methods available that can help. Carbon fibre fabric mixed with epoxy can be applied to the inside or outdoor surface of a wall “like wallpaper.”
The stuff looks like a fibreglass patch, but the carbon fibre is some 10 times stronger than the corresponding amount of steel. The official term is fibre-reinforced polymer, or FRP.
“You can glue it on the surface of masonry walls and they perform beautifully during earthquakes. I have done a lot of tests. And they can be installed fairly quickly from outside,” so there’s no need to shut down the school for a long period.
It is, however, expensive: about $400 per square metre, installed.
Another method is to brace a building against lateral movement. The finished building looks as though someone has built a new metal skeleton on its outside. This is now part of Levi Stadium in San Francisco, home to the NFL’s 49ers.
For concrete columns, a system of steel ropes around the column squeezes it like a corset, so that the concrete cannot expand and pop outward when shaken.
We built a whole steel birdcage that was inserted just inboard of the perimeter walls ... BARRY PADOLSKY, on the renovations at the Canadian Museum of Nature