image

SOCIETY


Foundations of resilience

We’re seeing an increasing focus on designing a more resilient built environment for extreme weather events, but about shocks beneath the surface? Seismic resilience is a foundational piece of the puzzle when it comes to creating spaces that can withstand environmental stress. How can we build better structures that minimize the fallout from seismic events?


In February of 2011, a 6.3 magnitude earthquake rocked the small city of Christchurch, New Zealand. This was an aftershock from an even larger 7.1 event that occurred a mere 5 months earlier. In single day, the community lost 185 lives, while 80 per cent of the city centre was razed to the ground.

The disaster created shock waves that toppled more than just buildings. Tens of thousands of people were displaced with nowhere to go, businesses and jobs were literally crushed overnight, and the city was left with an overwhelming list of services and structures to rebuild.

The cost of recovery has been estimated at $40 billion, though experts suggest it was likely more than that. Ten years afterward, we’ve learned a lot of lessons about seismic resilience — lessons that leading experts at WSP in Canada are applying to new buildings, particularly in our earthquake risk zones of British Columbia and Ottawa.

Unanticipated fallout

There’s a general perception that after an earthquake hits, engineers will rush in and rebuild. But people tend to underestimate the amount of time recovery takes, and the sheer amount of fallout from the disaster.

With modern building codes and seismic loading, there is a good chance that many of the buildings will remain standing. Even older buildings may stay upright, but they may not be operational — and they certainly won’t be safe.

Businesses, offices, and stores may not be open; people may want to work from home but might be displaced from their condos or houses indefinitely because of earthquake damage; transit and roads may be significantly impacted. Even if your building isn’t damaged, the neighbouring one might be — making it unsafe to enter some buildings that are intact. There is massive potential impact that could halt functionality for an entire city.

There’s a general perception that after an earthquake hits, engineers will rush in and rebuild. But people tend to underestimate the amount of time recovery takes, and the sheer amount of fallout from the disaster.

The time it takes to rebuild is significant. Alongside processes like insurance and assessments, there’s also the process of prioritization. In the time that it takes to get the city up and running again, people who are not involved with the rebuild may find that their jobs have ceased to exist. In a post-disaster city, it’s not unusual to see mass migration to other urban centres as people search for new jobs and new places to live while their hometown is essentially frozen in limbo.

If a significant earthquake were to hit Vancouver, for example, we could expect to see swaths of the population relocating to Calgary, Kelowna, Abbotsford and other nearby cities to find a home, a job, and a school after being displaced. An important lesson from Christchurch was to provide incentives for people to stay or return to the city post-disaster, to bolster its economic recovery.

Designing to higher standards

All of these far-reaching and long-lasting impacts teach us one key thing about designing for seismic resilience: keeping our buildings standing through an earthquake may not be enough.

With seismic codes, we generally design buildings for life safety; the main goal is that they don’t fall down and the impacts are survivable and as safe as possible for the people nearby. But these design standards are not focused on operational use afterwards. At the very least, you’ll be left with an upright building with smashed windows, shifted internal panels, broken walls between apartments, and busted utility pipes. And almost certainly not with a building capable of withstanding a significant after shock.

Our cities may design utilities like water supply lines to be post-disaster functional, but on the micro level of individual condo buildings, you might not have functional water, gas or sewage.

We have a proactive opportunity to design buildings that can better withstand seismic activity. They don’t have to be significantly higher-cost or designated to a post-disaster code, but with a few changes, we can design high-performance buildings that are much more resilient in the event of an earthquake.

We have the tools and skills to design buildings that remain elastic, limit inter-storey drift and manage residual drift. To put it simply, if the floors move laterally or the entire building moves, it’s designed with the elasticity to bend and not break. That way, we have a building that isn’t that damaged during the earthquake and has a much higher chance of being functional afterward. Even more importantly the buildings are likely to be able to cope with a subsequent follow up seismic event, so tragically not the case in Christchurch.

Investing in resilience

Although designers and engineers do have these capabilities, there are a couple of aspects to consider. First of all, do we do this for all our buildings? It would extremely costly and disruptive to retrofit all of the older and existing buildings in a major city centre. But we can certainly do it for new builds going forward.

Designing official, to-code post-disaster buildings comes with a much bigger price tag — a post-disaster rated facility can carry a cost premium of up to 30 per cent. But leading designers can build structures at a one to two per cent premium, which can provide an estimated 90 per cent higher chance the building will be functional afterwards.

By comparison, that cost is pretty negligible — and it creates a strong business case. As these buildings lower the risk for tenants, the owner or operator is offering more value and can charge more for tenancy. It’s also a strategic move to ensure your structures remain functional post-disaster, when many others may not be.

It’s important to think beyond residential and commercial structures and consider institutional and community centres. Post a disaster, people will flock to these shared spaces that form the focal point of a community and the logistical hub of emergency response — so it’s imperative that we invest preemptively to keep these structures operational after an earthquake.

By rethinking the way we design buildings against environmental risk, we can greatly minimize the economic fallout and social shock waves of a seismic event.

To learn more about how WSP is reimagining Canada from coast to coast, please visit our campaign page.

Share:

More stories: