In the shadow of the Cascadia megathrust, Vancouver is gearing up for a seismic showdown. The city's lead seismic policy planner, Micah Hilt, is on a mission to identify and grade Vancouver's most vulnerable buildings, a move that could save lives and shape the city's future. But what makes this story truly captivating is the interplay between tradition and innovation in the face of earthquake risk. As Vancouver inventories its building stock, the spotlight falls on engineered wood, a material that could be the key to resilient construction in the Pacific Ring of Fire. The question is: can timber help buildings bounce back from the next big quake?
The Vancouver Shake-Up
Vancouver's vulnerability to earthquakes is no secret. With a one-in-five chance of a major quake within 50 years, the city is taking proactive measures. Hilt's plan to inspect and grade buildings from the exterior is a bold step towards identifying and mitigating risks. The focus on single-room-occupancy hotels, many of which were built before seismic design was a priority, highlights the need for a comprehensive approach. But the challenge is not just about identifying risks; it's about managing public perception and the potential impact on leasing, insurance, and lending.
Timber's Resilience
What makes this story particularly fascinating is the role of engineered wood in earthquake-resistant construction. Christian Málaga-Chuquitaype, a structural engineering lecturer at Imperial College London, points out that timber buildings attract smaller seismic forces due to their lightness. This effect is amplified in taller structures, as demonstrated by shake-table testing at UC San Diego and the University of Auckland. The 10-storey cross-laminated timber tower at UC San Diego withstood over 100 simulated quakes without structural damage, showcasing the material's resilience. The same result was achieved in the University of Auckland test, where a cross-laminated timber building returned to its center after 100 strong shakes, its main timber elements undamaged.
The International Building Code
The performance of timber structures in earthquakes is not automatic, especially in the most violent zones. Japan's seismic codes, dating back to the 1923 Great Kanto earthquake, have pushed engineers towards framed systems and heavier connections. However, Vancouver's engineers are now embracing mass timber, judging it five times lighter than concrete and easier to design to higher seismic standards. The city's clearance of encapsulated timber to 18 storeys in 2024 is a testament to this shift. Shiling Pei, the principal investigator of the TallWood project, believes that the rocking-wall system proven at TallWood could feed into the International Building Code, the standard behind much of the timber world's seismic engineering.
The Future of Seismic Cities
As cities like Vancouver, Seattle, and San Francisco grade their building stock, the question of what to build next is increasingly centered on engineered wood. The material's lightness and resilience make it an attractive option for earthquake-prone regions. However, the challenge lies in managing public perception and the potential impact on leasing, insurance, and lending. The success of timber structures in earthquakes depends on a comprehensive approach that considers both the material's strengths and the broader context of seismic risk management.
In my opinion, the future of seismic cities lies in the marriage of tradition and innovation. While mass timber offers a lightweight and resilient solution, the success of earthquake-resistant construction depends on a holistic approach that considers the unique challenges of each city. Vancouver's journey is a testament to the power of proactive planning and the potential of engineered wood to shape the future of seismic cities.
