New terrain

An asymmetrical "geode" is the signature feature of new 250,000-sq.-ft. building on the University of Minnesota campus in Minneapolis that has a dual role. The geode encloses 23,000 square feet of public space, while the remainder of McNamara Alumni Center houses 217,000 square feet of office space for university-related organizations and other support sites.

Albuquerque, N.M.-based Antoine Predock Architects was the design architect, collaborating with Minneapolis-based executive architect KKE Architects. Minneapolis-based M.A. Mortenson Co. was the general contractor.

"The geological realm in Minnesota is palpable," Predock says. "The architecture of the alumni center honors the university by expressing timeless qualities through the use of materials such as stone, wood and copper, and by creating a dynamic gathering place that looks adventurously to the future." Defining the geometry of Memorial Hall was the most challenging aspect of the project. It was developed with the aid of a clay model. "Split Rock," a major formation on the north shore of Lake Superior, helped him to develop a "geologic inspiration" for the design. "The McNamara Alumni Center seems to rise out of the land, not sit upon it," says Thomas Fisher, dean of the university's College of Architecture and Landscape Architecture.

The geode, which is covered with 40,000 square feet of pink granite and fissures of glass, encloses the 85-ft.-high Memorial Hall. McNamara Alumni Center has 4,200 square feet of skylights, including angled skylights in the geode that admit slanting rays of sunlight during the day and radiate beams of light at night. The office portion of the building is clad with 75,000 square feet of sheet copper panels.

The end wall of the office block, which faces into the Memorial Hall, is also clad with copper-20,000 square feet of it. The 30-in.-high flat panels, which vary from 1 foot to 5 feet in width, are randomly placed, according to KKE senior project architect Bill Beaupre.

Strips of hemlock wood cover the remaining walls of the hall. In addition to providing a contrasting appearance, the wood also helps to improve the acoustical properties of the space.

David Broesder, project principal with KKE, says that although Predock's design was "tweaked," his overall concept "was pretty much etched in stone." "For all intents and purposes," he adds, "we did a fast-track building." He notes that close teamwork, including the contractor's involvement beginning at the end of design development, made the execution of the complex project possible.

The contractor's involvement made possible an ongoing assessment of the project against the budget. As is the case with almost every project, modifications were made to keep costs on track. For example, the granite floor originally planned for Memorial Hall was changed to terrazzo. The hemlock strips on its inside wall were initially to be 4 inches wide, but 8-inch wide strips were used because of their lower cost. In retrospect, Broesder thinks the wider strips have a more pleasing appearance.

Differential settlement

Not surprisingly, the unusual nature of the building design created challenges for the contractors-starting from the ground up. Michael Smalley, Mortenson's project manager during its initial phase, notes that the potential for differential settlement between the concrete-framed office section and the steel-framed geode was addressed by supporting the entire structure on pipe piles. This also helped to improve the building's appearance by eliminating the need for a large expansion joint.

Because the inclined geode imposes lateral loads on the office portion, framing around an office elevator core was designed with greater than normal reinforcement.

The anchoring system for the granite panels that are attached to the exterior of the geode, which was designed to be totally concealed, extends even into blind corners. The patterning of the granite is interrupted by windows and skylights, and stone fabricator Granicor (U.S.A.) worked from CAD drawings to make accurate cuts. Although the granite panels were nominally 5 feet square, 60 percent of them were individually shaped-and few had right-angle cuts. Each full-size stone weighed about 750 pounds.

The secondary steel structure that provides support for the granite is a thermally exposed system that must accommodate the cyclic expansion and contraction of the steel. It consists of 4-in.-square galvanized hollow steel sections spaced every 5 feet, and connected to the primary steel structure by stub columns. The anchors for the secondary system had to accommodate the load not only of the stone, but also the weight of the scaffolding used to install it. A portable tower crane was used to place the stone. This equipment option gave the crane operator a better view and greater depth perception than if he had been working from ground level.

Waterproofing of the geode was "an incredible challenge." Before granite panels were installed, a roof deck with a rubberized asphalt coating was constructed. The stone was then anchored to tube steel supported on pedestals rising from hundreds of roof penetrations that had to be wrapped by hand. "It was like trying to roof a porcupine," Smalley observes.

Since the geode is not plumb, conventional surveying measures could not provide reference points for determining the location of anchor bolts. Three-dimensional coordinates were established instead by using a global positioning system.

Stadium arch reconstructed

A 50-ft.-high arch salvaged when the university's former football stadium was razed in 1992 was reconstructed inside Memorial Hall by Engineered Wall Corp. of Lindstrom, Minn. It serves as the entrance to a 2,500-sq.-ft. museum devoted to the university's 150-year history. The arch's original 7,300 bricks and 92 pieces of stone were backed with concrete and erected in sections. Owner University Gateway Corp. originally wanted the arch to be incorporated into the building façade, but was persuaded that an interior location would be preferable.

Predock wanted the copper to look aged-like a "dirty penny." Fortunately, the exterior copper aged substantially, much more quickly than anticipated. The architect wanted copper on the interior to have a similar appearance. The task of chemically aging interior walls fell to M.G. McGrath Architectural Sheet Metal.

James Ducharme, mechanical designer with the project's St. Paul-based mechanical/electrical engineer, Ericksen Ellison and Associates, notes that all outlets for conditioned air in Memorial Hall are along the hemlock-clad wall. As a result, discharged air must travel as far as 50 feet into the space. Extensive ductwork is concealed in a 4-ft. space behind the wall. To keep condensation on glass surfaces under control, baseboard-type radiation was installed to wash glass areas with a curtain of warm air.

The 16-in. space between the granite cladding and the roof deck of the geode is not only equipped with drains to remove any moisture that penetrates the granite skin. In addition, a closed-loop system moves air through this interstitial space to prevent the formation of condensation that could cause rust.

The nonprofit University Gateway Corp. was formed in 1997 to develop, own and operate the building. Owners and primary occupants of McNamara Alumni Center are the University of Minnesota Foundation, the University of Minnesota Alumni Association and the Minnesota Medical Foundation. Revenue bonds backed by rental income financed construction.

CONSTRUCTION COSTS