Structural Conservation

Scope of work: The scope of work included supplying labor, equipment and construction materials to remove and replace all the deteriorated mortar joints (inside and out) and strengthening of the chimney to accommodate the new loads created by the cell antennas. 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. Extensive re-pointing of interior and exterior joints was carried out to stabilize and restore the integrity of the chimney; with the bricks at the top 4 feet so much degraded that 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.

Our Approach: 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 laminated plates were installed in single, 30.5-m (100-ft) long pieces extending to the chimney’s full height. Since carbon FRP is only a quarter 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.