Shortly after New Zealand’s 7.8 magnitude Kaikoura earthquake in 2016, hundreds of structural engineers inspected thousands of buildings in Wellington to evaluate the damage. Unfortunately, not all were able to be saved.
Watching a relatively modern building being demolished just months before it was scheduled to be strengthened, is incredibly frustrating. It also highlights the importance of timeliness in retrofitting assets if the carbon impact of damage from earthquakes is to be properly understood.
Put simply, if a weaker building is not retrofitted it sits as a ‘carbon liability’, with considerably more carbon likely to be expended remediating damage after a shake. Retrofitting a building means a much smaller carbon investment, compared to what a new building would cost.
New Zealand’s building owners and engineers have learned a lot about seismic issues following a decade of significant earthquakes: the 2011 Canterbury earthquake, two Cook Strait shakes in 2013 and the Kaikoura earthquake in 2016. Guidelines used to assess the many 1980s and 90s buildings with precast concrete floors have been updated, new methods of strengthening buildings have been developed, and the co-ordination between engineers and contractors has come in leaps and bounds.
People’s understanding of seismic risk has changed as well. Most buildings are designed on the basis that they will not see significant damage in their lifetime, but post-Kaikoura very few people would bet against another significant shake damaging buildings in their lifetimes.
Yet five years on from the Kaikoura quake, there is still a disconnect between the thinking around seismic retrofits, and the implications for the building’s carbon footprint. In New Zealand (along with much of the rest of the world) the Building Code’s approach to embodied carbon anticipates buildings having a 50-year lifespan, and requires buildings to withstand a 1-in-500 year earthquake.
This completely changes if the assumption is that the earthquake occurs in the next 10 or 20 years, when issues around damage, demolition, and rebuild have to be resolved. It also makes for a very different carbon proposition, given that buildings could well be demolished after a code-level shake with the design focused on preserving ‘life safety’.
This means sustainable building design in seismic regions needs to provide extra resilience against earthquakes close to or just beyond their design limits: both for new buildings and for retrofits, where old structures are brought up to modern standards often with enhanced resilience.
Bringing seismic resilience and carbon best practice together in decision-making
Retrofitting older assets will play a big part in reducing the carbon profile of the buildings sector, particularly so given the vast number of existing assets (and embodied carbon) that are candidates for seismic upgrades – with the demolition of viable older buildings (often including heritage buildings) at odds with society’s desire for a lower carbon economy.
It’s a double win too. Breathing new life into a building’s structure is vastly more sustainable than the highest quality ‘green’ new builds, which are inherently more carbon intensive. And the upgraded building will also likely have modern building services and high-performance operations – gas boilers removed, improved glazing and smart building control systems installed. Indeed, some retrofits are indistinguishable from a brand new building.
Bringing seismic resilience and carbon best practice together in decision-making can open the door to commercially attractive outcomes, with retrofits that include structural and sustainability upgrades transforming the asset’s revenue generation. Across the global real estate market tenants are increasingly demanding the buildings they occupy be resilient and aligned with their own climate targets.
This is in part why the adaptive reuse of assets has boomed in recent years, and the sustainability benefits of these projects has become an increasingly important part of the construction industry.
It’s relatively simple for non-seismic areas, but is much harder once earthquake strengthening comes into the mix, and structural engineers who combine technical excellence and the ability to ‘play well’ with architects and the wider project team are a critical part of the mix.
A recent example of structural engineers unlocking an asset’s potential was the recently completed commercial office development at 8 Willis Street in central Wellington, where Beca’s innovative approach to seismic strengthening has seen a relatively weak 1980s office tower brought up to 130% of the Building Code – while adding five floors to the existing eight. The building owner now has a highly resilient asset on its books, and a considerable increase in rental yield.
Further, adaptation and reuse promote cultural heritage and social cohesion, which is critical to community resilience. Buildings connect communities on a personal and public level – particularly so after an earthquake, and those that survive are enduring representations of the city, but also stand as testament to good carbon stewardship by their owners.