Nationwide Children’s Hospital (NCH) in downtown Columbus, Ohio — ranked as one of the best hospitals in the United States — is currently undergoing a re-birth of sorts, with the construction of a new, 12-storey, 65,000m2 (700,000-sq.-ft). main hospital building into which precast figures prominently.
“We were looking for something durable,” explains Paul Saphos, Lead Senior Project Architect for FKP Architects, “and that would also give us some contrast and provide some character. We provided some horizontal accent banding, introducing a rib pattern that was cast in with these 26-foot wide by 7-foot high panels that make up the head and the system below the windows. We also have a roughly 9 m (30-foot) column base facing on a single building radius point, for which we provided spandrel precast pieces that were connected to the columns.”
International Precast Solutions supplied a total of 487 of these architectural spandrel panels — accounting for approximately 5843 m2 (62,896 square feet) of curved, precast limestone coloured panels, with a sandblasted finish, erected using two tower cranes and two crews.
Precast panels provide a cost-effective balance to the complex curtain walls on other facades, but crucial visual balance as well. The project includes a very large exterior wall, which would have seemed even larger and busier with facets or segments, so the scale of the panels was reduced through the use of a radius precast, resulting in a simple and elegant visual.
The exposed surfaces are fluted below the windows, creating a louver effect on the panels, which are supported on six levels of cast-in-place concrete frame and seven upper floors of structural steel.
Given the unique shapes involved, designers faced a challenge at the drawing board in figuring out how to hang the panels. “In one bay on the back side,” notes FKP Technical Coordinator Tho Ngo, “there was only 150 mm (six inches) of clearance above the floor, which is not much room, so the structural engineers included a little reset pocket on the slab to add a little support. At the column line, we didn’t hang the panels to the floor line, but rather to the column itself, which is not typical, so the structural engineer came up with several details by which to hang these panels and to keep them in place.”
The anchoring of our punched window system in the precast façade also proved a challenge for the design team. “If you were dealing with a more traditional material — plaster and metal panels, for example — you would have to have some type of a structural metal stud-type framing system to clip off of,” notes Saphos. With the precast, he says, one of the things that the subcontractor in charge of the window wall and curtain wall system came up with was a T-anchor system that actually anchored to the back of the precast, and which they could then adjust right there out in the field for tolerance. “Using that anchoring system versus a rigid structural opening gave a little more flexibility,” Saphos explains, “at least for the installation of the windowsill system.”
The sandblasted finish of the precast panels offers another noteworthy example of how industry technique is evolving to meet the demands of sustainability. “Rather than actually using sand,” notes International Precast Vice President Mark Fusani, “we started using recycled glass to blast our panels. We actually take a glass bead and shoot that against our panels to get that sandblast look. It’s a recyclable waste product, and we have found that, of all of the products we’ve tried, this one gives us a finish that is closest to what we used to get with the sand.”
Fusani says that NCH was the first large project for which his firm switched techniques to what he jokingly refers to as “glass-blasting”, and is understandably elated that it was so successful. “We got a very consistent finish,” he says. “The customer was happy with it and we’re very proud of this project in that regard. We’ve used it quite a bit since, and there is so little difference between glass and this sand that no one notices.”
The job was so successful that Fusani’s firm has been retained to produce the precast for a research building right across the street that will become the next addition to the NCH campus. “We’re just getting ready to get started,” he declares proudly, “so clearly, everybody was happy with the work that we did on this project.”
Owner: Nationwide Children’s Hospital
Architect: FKP Architects
Engineer: Jezerinac Geers & Associates
Contractor: Turner Construction
Precaster: Prestressed Systems Group