BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

Repair Scope: Although the timber masts are currently sound with no significant decay, the size
and depth of the current splits and checks, the limited remaining preservatives in the wood, and
the current exposure introduces conditions conducive to fungal decay. As such, the remaining
service life of the existing timber stringers may be limited without corrective action.
Similar to the stringers, there are options
for in-place preservative treatment of the
masts including both internal and surface
treatments (see 4.3.1 above). However,
many of the same risks and concerns for
in-place preservative treatments exist for
the masts with exception that the drilled
holes for internal treatment are not likely
to significantly reduce the capacity and
there are no access concerns. Due to the
location of the timber masts along the
sidewalks, there are significant concerns
with human contact with the toxic
chemicals and concerns with
environmental contamination from spills
or run-off of chemicals that leech from the
masts. As such, in-place preservative
treatments are not recommended for the
masts.
Rehabilitation Scope: It may be necessary
to increase the size of masts in order to
resist larger operating forces meeting
current design standards and to
accommodate the details of conjunction of
the new operating equipment including
new larger deflector sheaves (see 4.3.6
below).
Photo 6 - Sheave Pole (Mast)
Alternatively, the masts can be strengthened with the addition of fiber reinforced polymer (FRP)
sheets to the exterior faces of the members. However, as FRP is expensive relative the cost of
the timber and a relatively new technology without a long track record of use in extremely
aggressive saltwater environments, it may be more economical and prudent to replace the
substandard timber members than to strengthen them with FRP.
In order to provide the required minimum clear sidewalk width of 3’-0” with the new crash
tested timber traffic railings, the operating winches and sheave poles will need to be moved
outward approximately 2’-0”. In conjunction with this modification, the lifting beams will need
to be lengthened by approximately 2’-0” on each end.
Repair/Rehab. Feasibility Study March 10, 2011
Bridge No. C-07-001 (437) 28 Final Report