The expansion of a malting plant in Idaho Falls, Idaho called for two elevated, post tensioned slabs in each of its two germination silos. The design and construction of these slabs was a truly challenging and unique application of multistrand post-tensioning.

The silos were slipformed leaving only a 6 inch keyway in an 18 inch thick wall, where the 100 ft. diameter slabs would rest. Designed as a simply supported structure, each slab was completely isolated from the silo, and placed on an elastomeric bearing pad. Formwork was constructed from the bottom of the silo to support the slabs during construction. VSL chose to use 5-31 tendons, Type L (loop) anchorages to support the slabs. The tendons were draped in a basket weave pattern, and stressed through large blockouts in the top of the slab. The tendons were fabricated into coils offsite and tugged into place. The loops were then stressed simultaneously from each end.

The upper (steep) slabs are elevated 70 feet from the ground and are 54 inches deep at the perimeter, and slope to 46 inches at the center. Rigid design requirements allow each 4.7 million pound slab to defl ect only 1.1 inches under dead and live loads. Each slab contains more than 100,000 pounds of post-tensioning. The force applied to the steep slabs actually raised them about 3/8 inch when subjected to dead load only. The lower (germ) slabs are located 30 feet below the (steep) slabs, and are 45 inches deep at the perimeter.