Sears Tower’s Innovative Viewing Modules

Starting this summer, sightseers visiting the Sears Tower’s glass-enclosed 103rd-floor skydeck will be able to see Chicago at all angles—including straight down—thanks to four laminated structural-glass modules that will extend more than 4 ft from the tower’s curtain wall.

Each “ledge,” measures 12 ft long and 10 ft tall, offers about 4.5 ft by 10.5 ft of floor space, and fits between existing columns. Structural frames hidden behind ceiling and drywall support the boxes, which hang from cantilevered steel frames with no structural elements other than fastening clips.

The result, says Terry McDonnell, principal at project engineer Halcrow Yolles, is “an unimpeded view of the city of Chicago and the street below your feet.”

The Sears Tower’s new movable glass observation boxes extend outside the building to provide spectacular views in many directions—including downward. (Rendering courtesy of SOM.)

During conception and design, local architect Skidmore, Owings and Merrill discovered that protruding viewing boxes would interfere with the tower’s unmanned window washer, which travels down the building from the roof. They eliminated the conflict by installing a linear oscillator that retracts the boxes as much as 4 ft inside the building and then pushes them back out for viewing. The boxes will slide along four steel beams.

The engineering team left a 1-in. gap in the facade around each box so a dual-gasket pneumatic seal could be deflated when the boxes were being moved, then reinflated when the boxes are in position. SOM project manager Charles Hasbrouck explains, “They’re like little bay windows that move in and out.” A motor helps retract the boxes, according to Tom Brooks, vice president of local general contractor Berglund Construction. “Ninety percent of the time, the box will be in the out position,” he notes.

The project team went to great lengths to ensure the ledges’ safety and security. Chicago had never permitted such a system, so extensive testing was required. A full-scale mock-up of half the glass floor and a full-wall panel—including connections—was load tested to 2½ times the code for pedestrian loads. Each box can hold nearly 5,000 pounds and wind pressures of 125 lb per sq ft. The glass floor features a sacrificial tempered “lite,” a coating separated by 7-mil protective fi lm, providing redundancy and easy maintenance of the walking surface. The glass walls and floor also feature redundant laminate for additional safety.

To protect against the elements, interior designer Environmental Design Services, San Francisco, directed air diffusers toward the boxes to increase airflow and decrease condensation. The firm also included heat elements in each box to prevent ice from forming on the roof. Ramps near the boxes provide wheelchair access.

Building owner American Landmark Properties and manager U.S. Equities say the project is part of an ongoing multimillion-dollar renovation of the skydeck.

AIA Wisconsin Honors Projects

Seven building projects have been recognized for architectural excellence by the 2009 Design Awards program of AIA Wisconsin, the state society of The American Institute of Architects.

This year’s award-winning architecture reflects a diverse mix of projects, including a sushi restaurant, a condo development welcome center, private residences, a hospital, a transportation center and a national headquarters building.

These projects are honored for their creative, contemporary, innovative and environmentally sensitive design solutions.

The common thread among all seven projects is that they were designed by architect members of AIA Wisconsin.

A jury of nationally distinguished architects from outside Wisconsin selected the award-winning projects.

Members of the 2009 Design Awards jury were Kathy Achelpohl, AIA, Kansas City, Mo.; Stephen Knowles, AIA, Minneapolis and Kevin Rice, AIA, New York.

“The projects selected for recognition add to the voice of Wisconsin,” according to this year’s awards jury. “Wisconsin architects should be proud that these are rising to the surface.”

The projects and architects selected to receive Honor Awards for overall design excellence include the following:

• Sushi Muramoto, Madison, Wis.: AroEberle Architects Inc., Madison;

• Palomar Welcome Center, Milwaukee: Johnsen Schmaling Architects, Milwaukee and

• Grand Itasca Clinic and Hospital, Grand Rapids, Minn.: Kahler Slater Inc., Milwaukee.

Projects and architects receiving Merit Awards for excellence in particular aspects of architectural design include the following:

• Milwaukee Intermodal Station, Milwaukee: Eppstein Uhen Architects Inc., Milwaukee;

• Blur Loft, Milwaukee: Johnsen Schmaling Architects, Milwaukee;

• National Conference of Bar Examiners, Madison, Wis.: Potter Lawson Inc., Madison and

• Private Single Family Residence, De Soto, Wis.: River Architects Inc., La Crosse, Wis.

The 2009 AIA Wisconsin Design Awards were presented to the architects, building owners and contractors at a ceremony on May 20 at the Monona Terrace Community and Convention Center in Madison.

The annual design awards program represents the highest recognition given for excellence in architectural design by AIA Wisconsin.

The co-chairs of AIA Wisconsin’s 55th annual design awards program are architects Katherine Schnuck, AIA, Whitefish Bay, and Mark Kruser, AIA, Middleton. AIA Wisconsin is a 1,500-member professional society representing architects in private practice, business, industry, government and education.