It would be visually perfect if the new McCormick Place annex were out on the prairie somewhere, its cable suspension pylons looming up to make it a kind of high-tech Chartres rising above the horizon.
Unfortunately, the annex is instead on a site that renders much of it invisible unless one happens to be in a helicopter or standing on the roof of another building nearby.
Yet for all that, the annex is still one of the most impressive construction accomplishments of the decade in a city where structural engineers have long given many buildings their muscular good looks and put more faith in mathematics than esthetics.
Certainly, the annex has a special sort of highstrung grace, but it is basically a workhorse building. In the old Chicago design tradition, it pretends to be nothing more than it is. That is particularly refreshing at a time when Postmodernists are adorning their buildings with a surfeit of frou frou.
The team of architects and engineers who put the McCormick annex together was drawn from Skidmore, Owings & Merrill (SOM) and Lester B. Knight & Associates, Inc. The full credit list of personnel is long, indeed, but in its most abbreviated form must include SOM`s Bruce Graham as design partner and Hal Iyengar as structural partner.
SOM`s mission was to create a huge two-level building for trade shows and other events requiring spaces interrupted by as few columns as possible. It was important to avoid functional shortcomings of the sort that still trouble the older McCormick Place to the east. First-rate fire safety was another essential, given the still vivid memory of the blaze that destroyed the original McCormick Place 20 years ago.
SOM and its client–the Metropolitan Fair and Exposition Authority–had no range of choices about where to locate the annex. The building had to make pedestrian connections with the older hall on the lakefront and with Donnelly Hall, immediately to the south on 23rd Street. Given that, it was clear that the new annex would have to straddle several sets of Illinois Central Gulf Railroad tracks alongside Lake Shore Drive.
Structural engineer Iyengar and his colleagues explored six basic schemes of supporting the building with a minimum number of columns that could be aligned without requiring railroad track relocation. Some of the options called for conventional truss systems, some for cable suspension.
More specifically, the challenge was to find the most efficient, cost-effective and visually attractive way of supporting the building`s gigantic steel roof, which measures 780 by 480 feet and weighs 4,500 tons. (Supporting the walls of the structure presented no problem at all, given their low height and lightweight aluminum siding.)
In the end, hanging the roof from cables affixed to concrete pylons turned out to be the best solution, although hardly a commonplace one. To better appreciate this engineering triumph, it is worth noting the rather limited history of earlier building suspension systems in the U.S.
Cables have been used to support bridges with a considerable degree of sophistication for well over a century, but it was not until Chicago`s 1933 Century of Progress exposition that the nation`s first cable-suspended building was created. It was the Travel and Transport pavilion, designed by architects Edward Bennett, Hubert Burnham and John Holabird and by engineers B.M. Thorud and Leon S. Moissieff. Its domed roof hung from cables slung from 12 steel towers 150 feet tall.
A lot of theorizing about cable systems went on at the Illinois Institute of Technology in the 1960s, but very little cable construction occurred anywhere until 1975, when SOM designed the Baxter Laboratories central facilities building in Deerfield. The metal roof of that long, low structure is hung from dozens of cables slanting downward from two pylons. The Baxter suspension system was the largest of its kind in the world at the time of its completion. Today, the McCormick Place annex is believed to hold the record.
In designing the annex, SOM drew on its Baxter experience, of course, and also on knowledge gained in its design of a suspended fabric roof structure for an immense airport terminal in Jeddah, Saudi Arabia. Such tent-like fabric tops are becoming quite common, however, and are certainly not in the same league as metal roofs weighing thousands of tons.
Engineers at SOM ultimately decided to hang the annex roof from 72 cables in groups of six attached to 12 concrete pylons. Each cable is four inches in diameter and composed of 450 strands of wire. The suspension system is
”overdesigned” in the sense of providing a generous margin of extra strength for unusual conditions of stress.
In addition to supporting the weight of the roof itself, the system is designed to withstand high winds, radical differences in temperature and heavy snow loads. It can also maintain its integrity if one of the cables snaps under the impact of, say, a light airplane that drifts off course while approaching Meigs Airport.
SOM`s engineers ran computer checks on all such types of weather and accident-related events in 180 different combinations before declaring themselves satisfied. Wind tunnel tests on mock-ups of the building were also employed.
Another clearly visible element of the system deserves explanation. Running along the east and west sides of the building are 12 vertical, freestanding pipes attached to ”ears” that project from just below the roofline. Under some weather conditions, it is routine for the roof to move up and down an inch or two. The rigid vertical tubes, anchored at their bottoms, stabilize the hanging roof under normal conditions and also ensure that it won`t move too far when upward suction is created by strong winds.
One might almost say that the roof of the annex is the only thing that makes the building an extraordinary work of architecture. The clearly expressed strength of the pylons and cables speaks not only for virtuoso engineering, but gives the annex a visual presence of taut elegance. Here is a carefully and tastefully detailed building that holds its own rather effortlessly against its darkly powerful companion structure across the street.
Yet there is more to the annex than that, and at least some of the highlights warrant comment.
The light gray aluminum skin of the building changes to a patterning of dark gray triangular panels along the top. This lighthanded ornamentation signals the presence of the 15-foot-deep roof trusses behind the skin and makes a quietly reverential bow to the look of an unbuilt Chicago exhibition hall designed by Mies van der Rohe in 1954.
Inside the main upper-level exhibition hall, one becomes aware that a single, shallow band of windows up near the ceiling gives visitors some sense of direction, time of day and the weather outside. The windows accomplish this without admitting too much daylight that would glare on computer screens used in displays and otherwise inconvenience exhibitors.
Sharp-eyed visitors may also notice that the ceiling 55 feet overhead is free from the ugly clutter of air conditioning ducts. Heated and chilled air rises through hidden channels in the hollow concrete pylons and is forced out through unobtrusive vents.
One problem at the old McCormick Place is the jumble of ugly and easily pilfered shipping crates that accompany each show and are stored haphazardly outdoors. SOM`s architects prevented that at the annex by providing two levels of crate storage in a low structure that is a northward extension of the exhibit building.
Fire safety at the annex is observable by the presence of 16,000 sprinkler heads, plenty of emergency exit doors and rows of small skylights that would pop open to allow the escape of smoke. Fire truck access is abundant.
One of the most frustrating design problems faced by SOM architect Bruce Graham was that of providing an enclosed pedestrian walkway crossing 14 highway and access ramp lanes between the new and old exhibition buildings at the 23rd Street viaduct. There was no elegant way to do this, partly because a combination of factors made it impossible to construct the walkway at a single level.
Graham`s solution was as tasteful as anyone might expect. The walkway parallels and abuts the two sections of the viaduct that pass over north and southbound lanes of Lake Shore Drive. At the center point, where auto ramps rise up to merge with 23rd Street, the walkway dips below 23rd, then rises again on the other side.
Making the best of a clumsy situation, Graham also flanked the elevated intersection of 23rd and Lake Shore Drive with a pair of limestone gazebos topped with copper-clad domes. Graham says the gazebos echo the form of Chicago`s many bridgetender towers and provide a certain sense of arrival
(although that is blunted by their ambiguous siting).
Construction cost overruns forced cutbacks in finishing materials that would have enhanced some areas in and around the annex. Terrazzo floors, granite paving and wood paneling were among the casualties. But while their absence will be detected by hardly anyone, some of the cutbacks are more conspicuous. At a couple of points, for example, you can ride an escalator going up, but must walk on a stairway coming back down.
Still, the greatest pity is that the new annex–like its forerunner across the street–is on such a dismally inappropriate site. Motorists speeding down Lake Shore Drive see little of either building as they pass between the grim retaining walls that flank the highway at that point. Choosing the lakefront as the location for the original McCormick Place was a mistake for which the city continues to pay a price.
SOM and Lester B. Knight & Associates carry no blame for the grossly inappropriate site handed them, of course. It is thus not inconsistent to say they deserve credit for a building sustaining Chicago`s worldwide reputation for bold architecture that speaks of structural clarity, efficiency and no small amount of elan. This is still a town where the Miesian architecture of muscle has not been forgotten.
THE PARENT MCCORMICK PLACE BUILDING SPARKED IRE–AND FIRE
The new McCormick Place annex is a reminder that variously good, bad and controversial architecture has been integral to Chicago`s exhibition hall scene for more than 25 years.
From the beginning, many conservation groups were opposed to using lakefront land for a commercial facility, regardless of its appearance. By 1960, however, even a court challenge had failed to prevent construction of the first hall on the shoreline.
The original McCormick Place completed in that year was designed by the firm of Shaw, Metz & Dolio, with assistance from Holabird & Root & Burgee and Edward D. Stone. The building they turned out was a graceless, hulking affair with precast concrete walls and absolutely no redeeming qualities.
Officials began talking about expanding McCormick Place along the lakefront in 1966. When conservationists again protested, Mayor Richard J. Daley proposed a compromise: The hall would be extended westward on air rights above Lake Shore Drive and the Illinois Central Railroad tracks, where it would not intrude further on park land.
That idea became moot when the exhibition hall burned down in January 1967. It was no esthetic tragedy.
When it came time to rebuild McCormick Place on the same lakeside site, the design commission went to the firm of C.F. Murphy Associates. The first Murphy scheme called for a building sheathed in marble or granite. It was rejected for functional and financial reasons. A second plan, also rejected, envisioned a structure with a cable-suspended roof.
A third design was drafted by Gene Summers, who had just joined the Murphy firm after several years in the office of Mies van der Rohe. Completed in 1971, the building by Summers was the tautly elegant, thoroughly Miesian glass and steel structure we see today. And now it has a fresh, sleek companion just across Lake Shore Drive: the McCormick Place annex designed by Skidmore, Owings & Merrill.
The annex generated controversy, too, largely because of cost over-runs and construction delays. Architecturally, however, the new building has drawn little attention from the public despite its vast size and unusual roof suspension system. That is hardly a surprise, since there are few accessible outdoor vantage points for seeing it.
