The new office complex that will soon be the corporate home of Office Depot posed quite a few challenges as a tilt-up project for concrete contractor Woodland Construction Co., Jupiter, Fla. Not only were the three towers five stories tall, the architect also wanted a stepped look on the exterior with a flush interior. Additionally, the elevated concrete decks had to meet strict flatness factors due to interior track wall systems.

“We got involved very early working with the construction manager,” says Woodland president Gary Fischer. “We worked with the design team to make sure it was constructible.”

That spirit of cooperation is very evident in the solution to one architectural challenge. Woodland formed the four-story panels of varying thicknesses with overlaps to achieve the stepped-back look the architect wanted. But to get the proper offset for the fifth floor required casting that wall as separate panels, then placing them onto the lower panels. Additionally, a 2-foot eyebrow parapet on the top floor of the main towers was placed as an integral part of the top panels.Going to a two-part exterior wall introduced an additional bracing challenge on the 90-foot-tall buildings. The solution was in the construction sequencing. After erecting the four-story panels, crews worked around the bracing to install the interior steel framing.

The elevated floors in the buildings posed an interesting challenge. The owner wanted them to be very flat, which ordinarily could be handled by designing them for composite action and using loose shores to control deflection during placement. However, in this case the floor slabs were being built from the top down. With no lower floors from which to shore, that approach was unfeasible.

Instead, Eldon Tipping of Richardson, Texas-based Structural Services Inc. was brought in to work with the engineering team to develop a design and placement plan for the composite metal deck floors. Again, early planning helped.

“We worked together to develop a cambering strategy,” Tipping says. “It turned out to be very close to the behavior we got in the field.” Observing how the steel framework and metal deck deflected as the concrete was placed allowed Tipping to guide the contractor's crew on where to make minor adjustments in the slab thickness.

“We also implemented a number of different quality measures,” Tipping says. One consisted of the contractor placing a horizontal chalk mark on panels and columns 12 inches above the finished floor grade so the finishers could use a template to confirm that the adjacent floor was at the proper grade. Crews also did preplacement surveys and post-placement surveys. “We worked with Woodland to produce floors that were level after they deflected,” notes Tipping. And the plan worked.

Things were a bit tense on the first placement, but that anxiety soon dissipated. “Following the engineer's design, the floor settled in just like it was supposed to,” says Gary Fischer.

To minimize shrinkage cracking, Tipping suggested using a combination of steel and synthetic fibers instead of wire mesh. Propex's Novomesh 850—formerly known as Stealth e3—was selected and used at the standard application rate. The reported performance to date has been good.