When the design team responsible for the renovation of Ottawa’s Centre Block wanted to protect Canada’s historic seat of parliament from earthquakes, they went with a technique known as base isolation. Here’s why.
The Centre Block Renovation Project is the largest, most complex project to rehabilitate a heritage building in Canada’s history. And upgrading the building to meet modern seismic standards was one of the first orders of business.
Ottawa has experienced a handful of serious earthquakes over the years—there have been two magnitude 5+ earthquakes in the last 25 years alone. The National Building Code of Canada (2020) requires buildings in Ottawa to be able to withstand even larger earthquakes. Centre Block, built in the late 1910s, simply wasn’t up to modern seismic codes.
The consensus choice
Public Services and Procurement Canada—the project lead—had two options. They could either go with a traditional approach that involved strengthening walls, floors and foundations with steel bracing and concrete, or they could choose a solution that would instead focus on minimizing the transfer of seismic energy to the building itself; a process known as base isolation.
“It was a slam dunk really; the cost savings, the time savings and its performance record made base isolation the consensus choice,” said Senator Don Plett, chair of the Senate Subcommittee on the Long Term Vision and Plan, which is helping to oversee Centre Block’s rehabilitation.
In very simple terms, base isolation works by decoupling the base of the building from the ground it rests on. Base isolators (essentially laterally flexible columns that absorb the energy generated by earthquakes) are placed between the ground and the building. When an earthquake strikes, the building simply sways back and forth within a purpose-made moat, thereby significantly reducing damage and speeding up recovery.
Now coming to Canada
Base isolation techniques are immensely popular in active earthquake zones, and for good reason; data collected following the tragic earthquakes in Turkey in early 2023 showed that hospitals with base isolation were able to return to operations faster (many immediately), with less non-structural damage versus fixed-based hospitals. In earthquake-prone Japan, more than 9,000 buildings use base isolation technology.
Yet base isolation has seen slow adoption across Canada. In part, this speaks to some lack of public awareness about seismic risk. “Canadians don’t have a lot of first-hand experience with earthquakes so they don’t really have an appreciation for the devastating impact they can have on buildings and communities,” said John Sherstobitoff, Principal Seismic Engineer at Ausenco. “What that means is that building owners and developers are more focused on meeting code requirements and minimizing initial construction costs than they are on improving earthquake resilience and accelerating post-earthquake recovery.”
When replacement isn’t an option
Heritage buildings—like Ottawa’s Centre Block—have an intrinsic national and community value that simply can’t be replaced. As a result, for owners of heritage buildings, this changes the focus somewhat. Versus other approaches, base isolation tends to spare the building from all but superficial damage, meaning far less impact on the building’s heritage fabric.
Base isolation is also a more valuable solution for critical infrastructure that can’t fail. Those hospitals in Turkey are a good example. And, since Canada’s Government sits in Centre Block, it is also considered a critical piece of infrastructure that can’t fail.
“If you think there is value in rapidly restoring operations in your buildings after an earthquake, you should probably investigate base isolation technologies,” notes John. “With early planning and experienced professionals, base isolation can result in a more resilient, recoverable and reliable building at very comparable costs to other more traditional technologies.”
According to the Government of Canada, implementing base isolation in Centre Block will save the taxpayer more money than other technologies.
Placing trust in Ausenco
Perhaps not surprisingly, the CENTRUS, a joint venture of WSP Canada and HOK, who are the design team responsible for the Centre Block project came to Ausenco to lead the base isolation work. “We have more than 30 years of experience leading seismic upgrades at sites across Canada,” said John. “And we are the only Canadian engineering firm with experience designing and installing base isolation solutions. We were a natural fit for this project.”
It was John and his team that led the country’s very first base isolation seismic upgrade at the Lord Strathcona Elementary School in Vancouver, for which they were awarded the Lieutenant Governor’s Award for Engineering Excellence. The team also has experience conducting seismic studies on heritage buildings (such as Vancouver’s City Hall, schools, and several cathedrals), and for major infrastructure projects, including transit assets, hospitals, and water reservoirs; many of these studies have continued through design and construction.
“There are a lot of specialist skills that go into designing and implementing a base isolation project,” John noted. “Few engineering firms in Canada have the capabilities required to conduct reliable non-linear time history analysis on large buildings; fewer still have the experience needed to design these systems in a way that maximizes resilience and minimizes cost while preserving the heritage fabric.”
Protecting a legacy
John and his team are proud to have the opportunity to play such a critical role in protecting the Centre Block and its occupants.
“As seismic engineers, we take great pleasure in knowing that we are helping protect people and places from earthquake-induced risks. What’s special about this project is that we’re not just protecting people and places, we’re also protecting our government and national leaders and an iconic piece of Canadian heritage,” added John. “And if it gets more people talking about base isolation, all the better.”
For more information on our seismic engineering capabilities, contact John Sherstobitoff.
Rapid report of seismic damage to hospitals in the 2023 Turkey earthquake sequences; Zhe Qu, Feijian Wang, Xiangzhao Chen, Xiaoting Wang, Zhiguang Zhou; Earthquake Research Advances; 9 May 2023