Smack Dab in the Middle
Everyone in the room must have had a hearty chuckle when Erik Kocher first presented his idea for adapting the old swimming and diving venue of 1996 Olympic Games in Atlanta.
Kocher's scheme: Suspend a new floor between the pool level and the 120-foot-high ceiling and turn the facility into a full-service recreation center for Georgia Institute of Technology, with basketball courts, a running track, and more.
To complicate matters, this new interstitial floor would have to span 175 feet between supporting columns to maintain column-free space in the pool area below. The existing roof would also have to remain intact during construction, as photovoltaic panels atop the facility were part of an ongoing solar research project. One other tiny detail: The aquatic center would have to remain open for business through much of the construction.
By comparison, the university's original plan looked pretty simple: enclose the aquatic center and construct the basketball courts on top of a new parking deck to be built next to the center.
So why did the university ultimately take on Kocher's ambitious, if somewhat crazy, plan?
Because it would yield more space for the recreation and athletic programs, and because several Georgia Tech engineering professors studied the plan and agreed that it could work, says Kocher, principal-in-charge with Hastings & Chivetta Architects, St. Louis.
Kocher says the plan would also significantly reduce overall program costs and help protect the existing structural steel roof support system by shielding the exposed frame members from the harmful effects of chlorine in the pool area.
"As often happens with innovation and invention, a light-hearted suggestion ultimately becomes a defining moment in changing the course of design," says Kocher.
Alas, it is one thing to propose such an outrageous design and another to actually construct it. In fact, several bidders turned down the job as unfeasible before the Atlanta office of Skanska USA Building Inc., Parsippany, N.J., took on the $43 million, 300,000-sf design-build project.
The Building Team found that many hurdles, some seemingly insurmountable, lay before them.
Tight site constraints, long spans, and the need to keep the weight of materials down made steel the obvious structural material for the interstitial floor. But engineering studies showed that a steel structure would allow too much vibration to support the basketball courts. As an alternative, the structural engineer team of ABS Consulting, Houston, and Continental Concrete Structures, Atlanta, designed a long-span, post-tension concrete floor system that adhered to the vibration criteria.
For the contractor Skanska, using concrete made the job even more complex. The added weight of the fully formed post-tensioned concrete support beams (prior to stressing the cables) would damage the pool deck below. To reduce the total weight, the 13-foot-deep support beams were installed in three steps: first, the lower eight feet of the beams were formed, then the cables were stressed, and finally the remaining five feet of support beams were formed. The structure required more than 2,680 cubic yards of concrete weighing 5,434 tons, and it incorporated 60 miles of post-tension cables in the floor slab.
Forming the post-tensioned concrete floor slab proved equally complicated. Because the roof couldn't be touched, the Building Team could not use conventional hoisting to erect the concrete formwork. Instead, the team erected a custom, 76,000-sf scaffolding deck 55 feet above the pool deck. The system incorporated an elaborate lagging system to distribute the weight of the system and avoid puncturing the pool deck below.
Controlling cost overruns was another headache. The design-build team brought several key subcontractors on board during design and pre-construction to help with constructability issues. For instance, when it was a determined that the building required a chiller nearly twice the size (and cost) of the unit initially specified, mechanical engineer Lee Company, Franklin, Tenn., swapped the corrosion-resistant stainless steel ductwork originally specified for the facility with fabric ducts, saving more than $250,000.
The recreation center, which was completed last fall, includes a 50-meter competition pool, a six-court gymnasium space, a fitness center, racquetball courts, a climbing wall, a leisure pool, offices, locker rooms, and a 500-car, three-level parking garage. Seating was reduced from 20,000 to 1,800.
In the end, the project came in within budget and two months ahead of schedule, and had zero change orders—a feat that speaks to the close collaboration of the Building Team.
"Many people told us it could not be done," said Michael Edwards, Georgia Tech's director of recreation. "I'm glad that our team was not affected by conservative thinking."
|Sitework, demolition, foundations||$3,800,000|
|Roofing, waterproofing, sealants||980,000|
|Doors, frames, hardware||465,000|
|Drywall, acoustical ceilings||1,900,000|