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Underground Research Labs Limit Vibrations

Exterior rendering of the William Eckhardt Research Facility on the campus of the University of Chicago, features its aluminum-and-glass curtainwall
The William Eckhardt Research Facility on the campus of the University of Chicago will include world-class molecular engineering and physical science research space. Its aluminum-and-glass curtainwall will admit light that will be channeled inward by clerestory windows and will enable passersby to view some of the research spaces. HOK

A research center at the University of Chicago will include underground space for a cleanroom, an imaging suite for electron microscopes, and high-performance optics labs.

April 29, 2014—Construction has topped out on the University of Chicago’s newest research center: the William Eckhardt Research Facility. The completed building—including two deep-underground levels housing low-vibration laboratories—will include world-class molecular engineering and physical science research space. While the exterior of the building boasts an aluminum and glass enclosure that appears to play with light and the barriers between interior and exterior space and, the lower levels will remain carefully isolated to provide a world-class, 10,000 sq ft low-vibration and acoustically quiet cleanroom, an imaging suite for electron microscopes, and high-performance optics laboratories.

The 270,000 sq ft research center will comprise seven stories, five of which are above ground and two extending a total of 45 ft below ground. Located on the intersection of East 57th Street and South Ellis Avenue—both busy routes used by passenger vehicles, buses, and fire trucks—the center is a concrete structure with a shear-wall lateral bracing system, and is encased by an aluminum-and-glass curtainwall. Pedestrian bridges will connect the center to nearby buildings. A structure framed in steel is located atop the roof to house mechanical equipment.

In addition to the programmatic needs of the new building, the university also wanted the project to create a new landscaped quadrangle behind the building, according to Mickey Collins, AIA, LEED-AP, a vice president of the global architecture firm HOK and the senior project manager for the project, working from the firm’s Chicago office. The underground laboratories extend beneath this quad, putting them as far from the vibrations introduced by traffic as possible, Collins says.

Creating a basement of such a significant size on such a tight site was further complicated by a high water table, starting a mere 10 ft below grade at the site. “The basement was too deep for sheet-pile earth retention, and the site is surrounded by existing buildings, so an open cut was not possible,” says Helen S. Torres, S.E., LEED-AP, a vice president of the global engineering firm Thornton Tomasetti, working from its Chicago office. (Carol Post, S.E., P.E., LEED-AP, was the project principal on the job for Thornton Tomasetti, and Mary Williams, S.E., P.E., LEED-AP BD+C, was the project engineer.)

So the design team chose to use slurry walls containing special “water-stop” joint details between the panels to create the two underground levels, Collins says. Slurry-wall construction uses the earth as the formwork for the concrete basement wall, Torres explains. Bentonite slurry added to the trench prevents the soil from caving in; a reinforcement cage and concrete is then added to the trench. Concrete is pumped into the bottom of the trench and the displaced slurry is pumped out. 

“The neighboring buildings did require some underpinning and jet grouting to stabilize their shallow foundations, but once that work was in place, the slurry-wall contractor was able to trench down 60 ft without disturbing the neighboring buildings,” Torres adds. A total of 45 slurry-wall panels were installed in a checkerboard pattern across the site, she says. A cap beam added to the top of the wall acted as a mechanical tie between all of the panels before the basement excavation began. The underground construction—encompassing the slurry wall construction, excavation of the basement, and three levels of floor framing—took 16 months to complete, according to Torres.

Construction site of the William Eckhardt Research Facility on the campus of the University of Chicago

Two deep basement levels will house vibration-controlled
laboratories. Slurry walls that use special “water-stop” joint details
between panels will create watertight basement walls.
H. Torres/Thornton Tomasetti

A walkable water-management zone was built on the interior side of the slurry walls to capture any moisture that might seep through and ensure that the labs will remain dry, Collins says.

The underground laboratories had large clear-height requirements: The clean room required 23 ft and the imaging suite required 22 ft, according to Torres. As a result, the research center’s typical basement depth is 45 ft, with a maximum depth of 51 ft beneath the imaging lab, she says.

To reduce the vibrations in the lower levels, HOK and Thornton Tomasetti worked with consultants Colin Gordon Associates, vibration and acoustics specialists located in Brisbane, California. “They have done a lot of studies of existing facilities around the world, and they finally came to the conclusion that the approach that’s been used often—isolated slabs—was actually not the best approach,” Collins says. “They advised that just mass and stiffness are most important in controlling vibration.”

Hal Amick, Ph.D, P.E., M.ASCE, the vice president of Colin Gordon Associates, who wrote in response to written questions posed by Civil Engineering online, said, “The problem of isolated slabs is that the decoupling—[the] joints, used to isolate them from their surroundings—actually make the slab system less stiff in the horizontal plane. The high mass also acts as an ‘impedance block’.”

Instead, a mat foundation measuring 2 to 4 ft thick (typically 3 ft) was used beneath the structure, according to Torres. Working with a foundation this thick, instead of a slab, presented some challenges of its own, Collins notes. “Plumbing for the labs had to be absolutely worked out in advance,” she says. “You can’t core into this at will.”

The upper basement slab uses a 30 in. to 36 in. deep waffle-slab floor construction to minimize vibrations, according to Torres. A tight column bay of 22 ft by 22 ft was used in the underground levels for vibration control. The standard column bay used in the upper levels, where vibration was not as much of a factor, was 22 ft by 33 ft, according to Torres. Waffle slabs of this size can span more than 40 ft in locations where vibration for sensitive equipment is not a concern, she notes.

“On the lower levels vibration really governed, and so everything else is secondary to that,” Collins says. In addition to vibration control, however, the lower levels also had to control acoustic noise and shield for electromagnetic interference, she says. For this reason, all the rebar used in the imaging area was coated in epoxy to avoid ground loops, in which metal objects conduct current and emit electromagnetic fields themselves, according to Amick.

Although extreme care had to be taken with the underground lab spaces, “the building really is quite different above grade, and in lot of respects much more flexible,” Collins says.

The upper floors will include lab spaces located in the center of the floor plates on levels two through five. While these labs are more flexible than the underground labs, they were also designed to stringent acoustic and clear-height specifications. All of the major mechanical systems and access valves are located in the corridors to keep the labs as acoustically quiet as possible, according to Collins. A larger-than-normal clear path had to be provided through the same corridors that contain the ductwork and into the center of each lab, where a so-called “high hat” area provides space for large experiments to be constructed. The upper two floors of the building will house physics labs, while the second and third floors will house chemistry and biology labs.

Faculty offices will line the exterior of each of these four floors along the east, west, and south sides, according to Collins. “Each office has one single window that’s quite a large [piece] of glass,” Collins says. “They’re very dramatic.” Daylight from the windows will be channeled through clerestories into the interior corridors of the building. “We’re taking the actual lighting as deep as possible into the building,” Collins says.

Light designer James Carpenter of New York City-based James Carpenter Design Associates Inc., was hired to consult on the design of the building’s exterior and the manner in which light reaches into the building. (Carpenter has taught at the university, including a course on the observable properties of light, which he taught with Sidney Nagel, Ph.D., a professor of physics at the university).

Carpenter’s vision “had a lot of influence on the exterior wall of the building,” Collins notes, including “the enclosure and how light was going to be handled, how it would be reflected, and how it would be brought into the center of the building.”

The aluminum-and-glass curtainwall developed by the design team will also work engage passersby, Collins notes. Although this will not be a public building, activity within the building and in a ground floor cafe will be visible from the street. “The campus architect and the president both wanted a strong relationship to the street, and they wanted to enliven the street facade so that when somebody walked by the building they could look in and see activity, rather than closed spaces,” Collins explains. “At the University of Chicago, [this] isn’t necessarily the case.”

“Because of the water table that’s as high as 7 feet below grade on campus, the older buildings are all a half story above grade…[so] that doesn’t make for the friendliest face of a building along a street front,” Collins says. The university is trying to change that with its newer buildings, she says.

The building topped out last month and is expected to officially open in fall 2015. The building is being constructed by the Chicago office of the national contractor W.E. O’Neil Construction.



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