The Folsom Cordova Unified School District Education Services Center is a four-story building with precast exterior concrete special moment frames and interior steel moment frames. Special concrete moment frames were required as Ordinary and Intermediate types are not permitted in areas with a Seismic Design Category 'D'/
The frames are 52'-0" tall and 30'-0" wide from panel joint to panel joint. They are 16" thick with 3'-0" wide columns. The spandrel beams are 5'-0" deep in overall depth, however the actual structural section used in design was 3'-0". This was accomplished by placing 3/4" wide vertical and horizontal slots at the ends of the beams which released the top and bottom 12" as they interfaced with the column joint. At these proportions, the typical concrete frame weighs 125,000 pounds.
Along the east and south wall lines, the frames have a single 3'-0" wide concrete Architectural feature within the typical opening. These "window mullions" have similar 3/4" wide slots at the top and bottom where they interface with the spandrel beam and as such were designed as non-structural elements. These gaps at the top and bottom will allow for the concrete moment frames to move without being restricted by the "mullions." The weight of one of these frames with the "mullions" grows to almost 146,000 pounds.
On the north wall, the typical concrete moment frames needed to be modified as the openings at the first floor needed to be infilled. To allow the contractor to maintain the same geometry for the formwork, and to reduce the weight of these 3 panels, 6" thick concrete pre-cast panels were used to close-off the openings. A metal stud infill wall was not used as the finishing method for the building necessitated the use of concrete - the exterior face of the building will be sand-blasted to provide an aggregate exposed finish. The concrete infill panels have a 2" gap on the sides and at the top to prevent them from restricting any movement by the moment frames. The contractor chose to tilt these frames with the infill panels in-place. As a result the weight of one of these panels is approximately 206,000 pounds.
Precast panels were erected in 2 days utilizing a track mounted crane. The precast system and erection operation went together flawlessly saving the owner both time and money.
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