By James A.V. Bligh, Ian Robertson & F.P. Chan
Splinter Gardens for a Seismic City
A splint limits movement to promote healing to an injured body part, or to prevent hyperextension injuries. Injuries to the built environment is a certainty to cities like Vancouver, which is close to several major fault lines and has a shallow epicentre, and will no doubt experience high amplitude and high ground acceleration shaking. For Earth Sciences professor John Clague, Vancouver’s West End concrete residential towers built using pre-seismic construction code with thin exterior walls and columns are at particular risk. This design proposes to stabilise these old towers using an architectural scale wood splint.
Wood Support and Identity
Why wood? Wood is inherently an excellent structural material for energy dissipation, and allows the splint to maintain its own integrity while absorbing energy from the concrete tower during an earthquake. The splint is connected to the existing tower with a series of sacrificial, light gauge tuned steel dampers, which reduces the structure’s slenderness ratio besides being the mechanism that improves the existing building’s seismic susceptibility.
In the Pacific Northwest, wood construction is common from detached houses and mid-rises, to the new wood towers at the University of British Columbia. Wood defines not only the region’s architectural and socio-cultural identity, but also its economy with timber being a key industry. Also, as opposed to concrete which releases large amounts of carbon dioxide, wood construction can sequester carbon; thus it reinforces the region’s environmental reputation.
Bracing Social Goals
More than a seismic support, the splint also supports the West End Community Plan’s social goal to create more family-sized units for families to live and work in the downtown/inner-city. The splint can expand a typical 3,500 sf West End tower floorplate to ~5,500 sf, allowing the addition of an extra bedroom to most units. The expanded floorplate also creates opportunities for “wintergardens” - enclosable balconies that capture the indoor-outdoor spatial experience as a nod to West Coast Modernist architecture. To further achieve vertical density targets, the splint can build upwards over the existing tower to create additional floors. A bridge connecting adjacent similarly "splinted" towers is also possible, and this presents a new above-grade public space typology for the neighbourhood.
The West End’s other social goal is to activate the laneways by means of lane-oriented townhouses along the service lane. Our proposal activates the lane by an alternative method. The floor-area intended for these townhouses are ‘transferred’ back to the tower, freeing up the ground-plane along the lane for open spaces instead of built-up structures. Moreover, a splinted tower’s first (and second) floor non-load bearing walls could be removed, creating a permeable at-grade public realm that extends from the front yard to the lane.
The wood splint ties together the economic, socio-cultural, environmental and architectural dimensions by using a local resource to minimize a local environmental risk, while also addressing housing availability and public space issues. But, to achieve what is proposed above, rethinking and challenging conventional zoning, planning, engineering and architectural practices is necessary.