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Thirty
years ago, six reinforced concrete silos were built to store
Blue Circle Cement’s product in the Boston area. An
inspection revealed concrete spalls and structural cracks.
Over 30% of the vertical and hoop steel was missing due to
design and construction oversights. As a result, the owner was
limited to filling the silos only half way.
Due to the shared walls of the clustered silos, access around
the entire perimeter of the silos was limited. To address this
detail in an effective, constructible, and cost-efficient
manner, a new composite form, the FRP rod, was utilized to
strengthen the silo. The FRP rod was doweled into the shared
wall to ensure complete development of the rod. The rods were
inserted into grooves and embedded in an epoxy adhesive. The
150-foot (45 m) long rods could be handled in single pieces
due to their lightweight properties. A second layer of
adhesive was applied on top of the FRP rod. Overall, about 10
miles (19 km) of FRP rod was installed. The rod option
provided near surface-mounted reinforcement that could restore
the missing steel and offer the durability benefits of FRP
sheet. To monitor the performance of the existing
reinforcement and FRP, a new fiber optic strain gauge was
installed into the grooves of concrete. The silos were then
coated with a breathable, acrylic topcoat for durability and
aesthetics.
An open, common goal-oriented relationship between the owner,
engineer, contractor, and material supplier was formed. The
team allowed a true design-build environment to produce the
most viable and cost-efficient solution. The process of
building solutions and addressing challenges was limited only
to the team’s collective imagination, common sense, and
technical expertise.
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