The NRCB, which broke ground in August 2006 and is scheduled for completion in summer 2008, is comprised of two separate areas split by an expansion joint; a five story lab/office area and a 30,000 square foot, tri-level cleanroom. Approximately 20,000 square feet of cleanroom space is dedicated to nanotechnology physical sciences and engineering, adjacent to a 10,000 square foot a biological and biomedical nanotechnology research facility.
A unique waffle slab design optimizes airflow and utility (gas/water) exhaust services throughout the flooring system. The design’s end result provides cleanroom filtering by pushing air through the building with uniform velocity and minimum turbulence. Additionally, the dome configuration was specified very deep to ensure the slab’s load per square foot strength to support the cleanrooms’ end use equipment load requirements. Dome Design The general contractor, The Whiting-Turner Contracting Company, Baltimore, Maryland, enlisted the project’s concrete trade contractor Untied Forming, Austell, Georgia, to source the unique formwork solution for the waffle slab. After eliminating wood and steel options, United Forming awarded the bid to Molded Fiber Glass Construction Products (MFG: Independence, Kansas) who manufactures a complete range of custom one-piece fiberglass reinforced plastic (FRP) forms. The unique requirement for the domes design was the depth of the forms: they had to be very deep and narrow compared to the size of void required for the floor. MFG produced three rectangular forms ranging from 44 inches deep by 18 inches wide by 38 inches long and smaller.
One characteristic of the forms helped win the bid. There is a lot of contact surface, so the stripping would normally be difficult. However the FRP forms release easily due to the physical properties of the forming material. Additionally, Whiting-Turner planned to finish the concrete two inches below the top of dome. With these forms workers could simply knock down the bottom with a sledge hammer rather than use blow-plug air devices. Pour Specs and Assembly A total of six floors of slab required dome forms. On the first elevated deck, 22,980 square feet will consist of the open top waffle slab with a 16.5-foot clear story height, while the other 19,875 square feet will be a traditional beam and slab with a 20-foot clear story height. On the first level, the traditional beam and slab design (four sections) alternate with waffle slab design (six sections). This alternating format allows for optimal concrete pours as the waffle slab pours are made first, then allowed to cure while the beam and slab pours are made. After the domes are stripped and the completed slab is in place, a heavy duty computer floor will cover the open waffle slab.
Since concrete dome pours were finished 2 inches below the top of the form, they created multiple voids in the slab once the forms were removed. This dome-next-to-dome (open-top vs. concrete slab on top) slab features beams intersecting east-west which, once dome forms are pulled out, leaves a 2-foot by 4-foot void where the dome form once was. “This unique floor design has more holes than floor as the majority of it is forms!” says Georgia Institute of Technology building owner Bob Rose. With over 3,000-plus holes in the floor it’s like a big grate that will facilitate the airflow process, he says. “This will create a laminar flow (vs. turbulent flow) that will streamline the uniform air velocity for the center’s research productivity,” he says.
Issued: May 10, 2007
Copyright: 2007 R.W. Nielsen Company