The East Frankfort Concrete Elevated Water Tank is unique because it is the largest post-tensioned elevated concrete water tower in the continental United States and one of only four all-concrete tanks in the country. The tank’s principal components are a circular mat foundation, a hollow cylindrical pedestal, a conical transition, a conical outer wall of the water container topped with a short cylindrical wall, a central access tube, and a spherical dome roof. The conical wall has a varying thickness and is prestressed both circumferentially and meridionally. The cylindrical wall of the container is prestressed circumferentially and serves as the dome ring. The finished grade is ten feet above the mat foundation. A 7’ 3” x 8’ access door is located in the pedestal at ground level. The mat foundation is supported on weathered rock. The design process was complex, requiring shell design with complicated intersections and openings, seismic considerations using fluid structure interaction finite element response spectrum analysis, and post-tensioning of the tank vessel both meridionally and circumferentially. The structure required ten different concrete mixes, and several of the mixes included use of super plasticizer. Designing and constructing an all-concrete tank cost approximately $1 million more than a similarly-sized steel tank, but over the 75-year life cycle of a tank, the innovative design will save the Frankfort Electric and Water Plant Board millions of dollars, since steel tanks need to be repainted every ten years, costing $800,000 to $1 million for each painting.
