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Repair Options
The first investigative consultant had suggested
installing an external post-tensioned system to restore the integrity
of the deck. However, it was felt that this approach would not be
suited to meet the needs of the station, either in performance or
future maintenance requirements. Several other modifications were
considered, including:
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Addition of steel framing to reduce the span of the concrete;
and
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The installation of a Carbon Fiber Reinforced Polymer (CFRP)
system to restore the lost tensile capacity of the deck.
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Complicating the repair selection was the access
restriction to the soffit of the deck, since all work had to take
place while the Station was operating. After considering the pros
and cons of all the repair options, including costs, the following
repairs were recommended and implemented:
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Provide CFRP reinforcing to the concrete deck in areas which
were considered to be unreinforced due to a significant or total
loss of pre-stress in the post-tensioning tendon(s).
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Provide a secondary CFRP reinforcement system to non-distressed
areas of the deck to ensure ductility of the concrete deck and
provide warning of failure of the deck in the event of overloading
or an undetected loss of pre-stress in the post-tensioning system.
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Repair structural cracking using both pressure and gravity injection
processes. Repair delaminated and spalled areas with polymer-modified
concrete.
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Replace
the existing deck coasting with an approved coating capable
of providing a minimum guarantee of five years protection to
the concrete deck, based on its expected use. |
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