TransCanada Highway served by concrete box culverts
By Ryan Finley, P. Eng. and
Khaled Nasery, E.I.T.
Preparing seal for placement of box unit.
The TransCanada Highway is the world’s longest national highway,
stretching 7,821 km. It is vital to Canada’s economy that
the highway be maintained without disruption and premature
structural failures.
Use of precast concrete box units under the TransCanada Highway
was based on past performance and the expected service life of precast
reinforced concrete box culverts. At two crossings of the highway, one
kilometre apart, cast-in-place double cell concrete box culverts were
installed in 1955 to carry the flow of Hartell Creek. The culverts, located
east of Calgary, Alberta, near the Town of Strathmore, were extended
across new eastbound lanes with arched structural plate corrugated
steel pipe (SPCSP) when this section of the highway was twinned in
1974.
Replacement culverts had to meet a 75-year design life as specified
in the Canadian Highway Bridge Design Code (CHBDC). An advantage
of precast box culverts was a better fit with the existing cast-in-place
culvert.
Khaled Nasery, E.I.T. of Mish Engineering designed the culvert
replacements under the supervision of Ash Morjaria, P.Eng. Mish
Engineering presented Alberta Transportation with three different size
pre-cast concrete box alternatives:
Twin 2.4 m rise x 1.8 m span
Single 2.4 m rise x 3.0 m span
Twin 2.4 m square
The single 3 m span x 2.4 m rise boxes were chosen, based on cost
and optimum sizing to handle the design flow, and awarded to Mesken
Contracting Ltd. after being tendered in December, 2002. Lafarge
Canada, Inc. supplied the box units from their Calgary pipe operation
after designing the units in accordance with CHBDC for CL-800 truck
loading and cover ranging from 0.2 m to 2.65 m above the top of the
culvert. The 44 box units, each 2 m long, were produced in February,
with AMEC Earth and Environmental inspecting the production. The
west culvert required 19 units and the east culvert 25.
Construction took place in two stages. First, eastbound traffic was
reduced to one lane and moved onto the south shoulder. The failed
SPCSP was removed and 10 sections were installed at the west culvert
and 11 at the east culvert. The first box units were cast with exposed
reinforcing to facilitate an easy field connection to the existing culverts.
After the first stage installation was backfilled, the contractor moved
the traffic to the north shoulder over the newly installed boxes and
installed the remaining box units at each site. The roadway was surfaced
and the eastbound lanes opened to two-lane traffic.
The westbound lanes were unaffected by the construction; however,
eastbound traffic was reduced to one lane for 16 days at the west end,
and 18 days at the east end. The contractor worked at both sites simultaneously
on a 24-hour basis in extreme cold conditions. Construction
was complete in 22 days at both sites. A steel strut was placed at the
upstream end of the new culvert sections to block large debris, not for
structural support.
Installation of the precast concrete box culverts provided minimal
disruption to traffic and an economical, long-lasting product that will
stand up to the existing environmental and load conditions.
Ryan Finley is with Lafarge Canada, Inc., and Khaled Nasery is with
Mish Engineering, Ltd. Contact ryan.finley@lafarge-na.com for more
information.
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