Chicago is a city of neighborhoods, and a brand new one is taking shape at University Village, a 20-square-block development located on the city's near West Side. Several all-precast structures are playing a key role in helping to bring the area back to live.

"The design goal is to create a new Chicago neighborhood in an area where there was vacant land," says Michael DeRouin, project manager for FitzGerald Associates Architects in Chicago. The firm has designed the four mid-rise condominium buildings that make up University Village. Two are nine-story structures featuring precast concrete frames, and the other two are reconstructed mid-rise buildings.

"We are very happy with our ability to use precast for the mid-rise buildings," said Larry Justice, project executive for the South Campus Development Team. The consortium of developers for the project's housing specified precast as its material of choice for the two buildings. "Precast gave us a good design, a no-hassle erection process and a cost-effective way to construct the buildings," Justice says.


No Small Plan

The four mid-rises are key elements in a $750-million, 10-year master plan being carried out by the University of Illinois at Chicago (UIC). The plan includes the expansion of both academic facilities and student housing at UIC along with 930 units of private-market housing. Land for the new housing is being sold by UIC to the South Campus Development Team. New residences include the four mid-rises plus town homes, walk-up condominiums and loft conversions of existing buildings, says Justice.

Green space plays an integral role at University Village. "We didn't remove and streets," says DeRouin. "There's a grid of parkways that run between all of the buildings. Green space is important. The parkways give everyone a larger front yard than they otherwise would have."

The two new nine-story mid-rises are located on the southern border of the site. "We wanted the buildings to emulate existing Chicago neighborhoods," says DeRouin. "The goal is to make the buildings look like they ad always been there."

The first of the two new mid-rises is complete, ante the second is expected to begin construction soon. Each of the mid-rises contains 98 units, in one-, two-, and three-bedroom homes. Sale prices range from $150,000 for a one-bedroom unit to more than $600,000 for a three-bedroom penthouse. Of the 930 units of housing, about 60 percent had been sold by mid-May, Justice said.


A $300,000 Savings

The first mid-rise building features an all-precast frame, using precast concrete hollowcore floor planks from Spancrete Industries in Waukesha, Wis. The only non-precast elements are the masonry bearing walls that frame the exterior of the lower three levels and steel columns that were used to frame inset porches (but not the cantilevered balconies).

"I have been very satisfied with Spancrete's ability to innovate and create a precast design that meets my cost objectives and produces the framework for a handsome building," says Pete Robinson, director of residential construction for New Frontier Companies, one of three developers in the South Campus Development Team. "The cost for this building's structural system was approximately $300,000 less than for conventional cast-in-place methods. And the ability to immediately work on the floors below the floor being constructed, without the impediment of shoring or re-shoring, was a major advantage."

Considerable savings were derived from the precast floor planks' ability to span longer distances, typically 29 feet, that cast-in-place could reach, DeRouin said. The precast planks are 8 inches thick in the residential floors and 12 inches thick for the lower three levels, which contain parking. At those thicknesses, cast-in-place slabs can span about 24 or 25 feet. Precast's longer spans enabled designers to eliminate an entire row of columns, as well as a row of foundations caissons.

The undersides of the precast planks required no additional finish coat to create an attractive ceiling finish for the lofts. In addition, precast provided excellent acoustical control, which was an important factor because a commuter railroad runs next to the building. The precast frame and floors also deliver good fire-resistance ratings.

"We initially designed the building schematics with cast-in-place," says DeRouin. "But Pete Robinson said ‘No.' He was looking toward construction during the winter, and he knew we could eliminate a row of columns. So we modified the structure to take advantage of the benefits of precast. It was a new experience for us, but once we understood the parameters of what precast can do, the design went very well. We ended up with a good, unique solution with a product developer can sell at a time when there are many loft condominiums on the market. The longer spans of precast allow us to have more open space in the units."

Precast construction enabled the building to go up quickly, before winter began. Erection began in late August 2002. Within about 80 days, Area Erectors Inc. of Rochelle, Ill., the erection contractor, had put up all nine floors and finished the process by mid-November. Linn-Mathes Inc., Chicago, was the general contractor for the first mid-rise.

The major precast components consisted of:

• Inverted T-beams (24 inches deep and averaging 24 feet long);
• Columns (35 feet high and 20 by 20 inches in cross-section);
• Shear walls (50,000 square feet at a typical thickness of 8 inches);
• Balcony beams (14,000 square feet of specially-designed members, in which the 12- by 6-foot balcony floors were cast as on piece with perimeter beams);
• Hollowcore plank (300,000 square feet).


One-Piece Balcony Beams

For the University Village mid-rise, the cantilevered balconies each were cast as one piece with the perimeter beam spanning between exterior columns. "We cast the balconies into the outsides of the beams," says Dick Winkowski of Spancrete, the building's precaster. "Those pieces looked like an airplane fuselage with a wing on one side."

Each balcony beam is 26 feet long, 20 inches deep and 25 inches wide. At a typical distance of 2 1/2 feet from one end of the beam, the balcony "wing" is attached to the beam, explains Terry Chung, general manager for Spancrete's Engineering Department. Each balcony juts out 6'5" from the building and is 12 feet long. Balcony thickness at the beam is 8 inches and at the outside edge is 7 inches, creating a downward drainage slope.

Casting a balcony in one piece with the beam has two advantages, say Roger Becker, vice president of Spancrete's Precast Division. First, lifting and erecting fewer pieces saves crane and erection time. Second, by making the balcony integral with the perimeter beam, special connection designs are avoided. "With one piece, there's no joint, and it can't leak," says Chung.

To prevent the balconies from overturning during erection, Area Erectors placed shoring under the balconies. Once the hollowcore planks rested on the inside ledge of the balcony beam, the planks' dead load was enough to counteract the overturning moment of the balconies' weight.

Two layers of mild steel reinforcing help hold the balcony slab to the beam, Chung says. Some of the rebar is L-shaped to pass from the beam into the balcony. The entire assembly can be made without the need of welding.