Scope: The scope of
work for repairing team included supplying all labor, equipment and materials
to remove and replace all the deteriorated mortar joints (inside and out) and
strengthening the chimney to accommodate the new loads created by the cell
antennas.
Structure Details: After
a century of natural deterioration, the chimney was in very poor condition,
with existing joints badly deteriorated - in some cases, completely through the
wall.
Repairing system: Extensive
re-pointing of interior and exterior joints was carried out to stabilize and
restore the integrity of the chimney, along with the bricks at the top 4 feet so
degraded they required replacement. The challenge in doing this was not only
rebuilding the unique architectural shape for historic purposes, but also
finding a source for the same type and color of brick. An extensive search of
the United States
found only one manufacturer who still had the materials available.
A structurally efficient, easy-to-install, and
cost-effective strengthening option was achieved by using an externally bonded
carbon-based FRP strengthening system that would increase the shear and
flexural capacity of structural elements. The thin carbon FRP plates were
bonded to the inside face of the chimney, serving as vertical tension
reinforcement. The continuous FRP laminate plates were installed in single,
30.5-m (100-ft) long pieces extending through the chimney’s full height. Since
carbon FRP is only a quarter of the weight of steel, the plates were easily
handled by workers inside a small diameter work area (only two workers could
fit in the structure) and added only minimal weight to the structure.
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