Walking in
Banff central park, my eyes were caught by the pedestrian bridge, which is like
a rainbow over Bow River. This is a slender 113m long timber
bridge
with maximum 5% slope, both serving pedestrian traffic and providing a
sensitive sanitary crossing replacement.
The two
sanitary pipes and one water pipe are sitting just underneath the bridge deck.
They look around 12 to 16 inches in diameter, along the bridge slope without a single
bend. As a piper, it is a rarely seen in normal facilities. Obviously great
care was put in this design and execution to make it happen.
Why can it
be accomplished? Two reasons I from my point of view.
First, the
use of timber, which is less stiff than steel, also contributed to creating a
more flexible and less thermal movement structure.
Second, the
steel diaphragm trussing serves a dual purpose, both connecting the pairs of
glulam beams and creating support for the three service pipes. Rollers are
attached to the steel webs, allowing the pipes to be easily deployed across the
bridge, and accommodating thermal movement of the pipes during the year.
The roller
supports are really creative. Friction force is dramatically reduced while sufficient
support can be provided.
The bridge
received the Engineer Award at the 2014 Wood Design Awards, as “one of the
longest timber bridges of its kind. This beautiful structure was carefully
designed, given the highly visible and historically significant location, and
through design and construction detailing, thoroughly addressed durability and
longevity.”
