Hughes Aircraft Sunny Hills Expansion in Fullerton, California consisted of two connecting office buildings, each designed as an interior steel frame with exterior concrete tilt-up panels. The tilt-up panels were both structural and architectural. The tilt-up panels for these three-story buildings were designed about 30 feet wide and 60 feet high. Casting and erecting such large panels would not only be costly, but the required bracing would interfere with steel erection. By converting 3-story-high tilt-up panels into smaller wall and column panels, the contractor reduced the amount of bracing required. Column panels had to be braced for only 7 days while the footings reached sufficient strength, then the first-floor wall panels and the steel frame could be erected. After the frame was up and the second-floor diaphragm in, the spandrel and parapet panels could be set.
Wall panels were held in place by waler-type clamps, which eliminated bracing and eliminated a crane waiting while the panels were welded to the column panels. Later, after these welds were made, the pockets in the wall panel that surrounded the welds were filled with concrete. Steel plates embedded in the middle of the column panel were used to bolt precast concrete to the steel frame.
The form used to cast the sloped surface near the top of a wall panel was set on pipe rollers so it could be stripped without having to lift the panel. Small wood wedges shimmed under the backside of the form kept it from rolling when concrete was placed. After the concrete had cured, the wedges were removed and the form was easily rolled out.
The architect specified architectural concrete with a special blend of aggregates and a heavy sandblast finish. The reveals, protected from sandblasting by the wood rustication strips used to form them, were to be painted red.
In the lobby area, trough-shaped precast pieces were used to create planters and hide structural steel beams and columns. The precast troughs were cast in two steps: the sides were cast, then the sides were tilted up by crane and braced, after which the bottom of the trough was cast.