RC107 JulyAugust2023 - Magazine - Page 15
According to Silverstein, the building’s signature
design characteristics are a direct result of GBC’s stated
need in the international competition for a smart, low-carbon, future-proof building with open spaces and net-zero carbon emissions (meaning an absence of gas-fired
equipment).
“The only way to do that was through the use of mass
timber,” he said. “Our mandate was to develop a mass
timber approach that is simple to install and can be used
across different platforms and design concepts, including
industrial, commercial and residential.”
Silverstein notably pointed to the unique slab band
concept that was developed specifically for the Limberlost Place project. The new beamless structural system,
which provides a column grid of 9.2 metres, allows for
column-free classrooms and future adaptability. It also enabled designers to get around zoning height restrictions
and add a tenth floor.
“Having no beams means you can lower the floor and
the ceiling height,” said Silverstein. “We needed a structural system that could span that, and we also needed to
make a 10-storey building to get federal funding to test
our structural system, to confirm proof of concept.”
Backed by nearly $7 million from Natural Resources
Canada’s Green Construction through Wood (GCWood)
Program, the new 9.2-metre-long slab bands—also called
Timber Concrete Composite (TCC) panels—were successfully tested to breaking force at the University of Northern British Columbia.
“They help make the floors less bouncy,” Silverstein
said about the panels, which are 400-millimetres thick and
have a 100--millimetre concrete topping. The building’s
high ceilings and open spaces, he added, never fail to impress visitors who take the public tours that are organized
every second Friday. “They are visually stunning,” said
Silverstein. “Everyone who visits is amazed.”
Robert Jackson agrees. A structural engineer and mass
timber design specialist in Fast + Epp’s Vancouver office
who has worked on the Limberlost Place project for five
years, he said ground-breaking work has been done for
the architecturally expressive building, where the design
and structure does triple duty, acting as the finish, dealing
with acoustic challenges, and concealing mechanical
components.
“Our vision was based on and revolves around the slab
band idea,” said Jackson. “This is the first big project that
applies and uses that concept.”
He notably credited the R&D work at UNBC, where
three concepts—screws, perforated plates and kerf plates,
which was ultimately chosen—with helping to get connector costs down for the use of cross-laminated timber
(CLT) panels, which is growing exponentially across
Canada and the United States, where some 500 projects
using mass timber in combination with steel brace frame
core plus concrete plus CLT are active or completed.
“It’s a good way to connect concrete and timber,”
adds Jackson about the kerf plates, where steel plates
are inserted into a saw kerf in CLT panels. “It’s all about
proportions of concrete and wood. We’re trying to use
the best materials in the right place. Concrete is good in
compression, while timber is good in tension.”
RENEWCANADA.NET
”Because Limberlost is for students and it’s
on the lakefront, where it’s breezy and open, we
wanted to give the impression or feeling that it is a living,
breathing thing, like a tree rooted in the ground.”
Limberlost, he added, is using 60-foot-long black
spruce panels made by Nordic Structures in Chibougamau, Que. Bare CLT panels are delivered to a satellite
facility, a seven-minute drive away from Limberlost Place,
where trucks are staged with mass timber components
to ensure just-in-time delivery to the job site and composite slab bands are prepared by putting screws, rebar,
kerf plates and then cast a layer of concrete on the bare
CLT panels, which are then left to cure a month and used
when needed. Construction is done using two stories of
steel, then two stories of wood.
“It’s like watching this cool dance going up like a
construction ballet,” said Jackson, who visits the site
regularly to ensure construction follows design. “It’s a
real puzzle that requires a lot of organization. You need
multiple trucks carrying prefab steel and timber and
panels in the order they’re installed. You have to organize
that whole sequence—but in reverse order.”
It’s that needlepoint need for planning, coordination
and engineering that makes the Limberlost Place project
so unique for Mike Love. “We have to sequence, and
phase engineer every CLT panel, glulam column and steel
component,” he said. “It’s a big coordination effort.”
He added that every piece of the building, “right down
to the screws,” was first modelled in 3D, an effort that
began in 2020 and took a year to complete. “We built the
entire building in 3D beforehand,” said Love. “We used
actual 3D models from the trades, including wood, steel,
mechanical and electrical suppliers. Then our 3D modelling team merged them all together. We were then able to
use this model to help inform the installation sequence
and ultimately create a 4D schedule and virtual construction video that we’re still using to this day.”
He also lauded the custom engineering work that’s
been done on the fly by his team regarding hoisting, lifting and rigging devices.
One example is a device dubbed “The Rocket”— pointed yellow pieces of steel that sit atop HSS tubing—that
help to align and join the 20-plus connection points when
the massive CLT panels are landed into place.
“Because it’s mass timber there are only about 50 workers on the Limberlost site, which is about half the number
you would have on a regular construction project using
steel and concrete,” said Love. “With a concrete building
more people are needed because you’re building forms,
installing, and reinforcing steel, pouring concrete, and
then stripping and cleaning up the formwork. With mass
timber the pieces come prefabricated, so they can simply
be lifted into place. It’s a completely different process and
it’s amazing.”
JULY/AUGUST 2023 – RENEW CANADA 15
