There are bridges that get you from here to there. And there are bridges that transport you to a higher plane.
These bridges don’t look like one of those uglier-than-thou structures that an engineer slapped together and that span countless expressways and interstates. They’re landmarks in the true sense of the word — they mark, rather than mar, the land.
Many of these spans are as visually striking as a sculpture or a painting signed by an artist. That’s why they’re called “signature bridges.” They bring art into the equation of engineering, demonstrating that even the most utilitarian structures can have enormous imagemaking power.
One of these new bridges is making heads turn in the Will County suburb of Frankfort, about 40 miles southwest of Chicago. It’s an airy A-frame that has a million-dollar presence even though the price tag — about $600,000, according to state officials — was a lot less than many of the single-family homes being built these days.
Designed by structural engineer Shankar Nair of the Chicago architecture and engineering firm of Teng & Associates, the elegant pedestrian bridge confounds the idea that public works have to be eyesores — or that they should look cheap, just to make sure that taxpayers don’t feel like they’re getting fleeced.
Instead, the bridge is part of a growing trend that rejects the sterile, functionalist designs of the postwar years and is renewing the tradition represented by such beloved historic spans as the Golden Gate and Brooklyn Bridges.
That trend is global as well as local. It’s making itself felt in Spain, home to bridges by architect-engineer Santiago Calatrava that resemble giant harps, to St. Petersburg, Fla., where the steel cables and concrete pylons of the Sunshine Skyway Bridge have been likened, respectively, to sails and masts.
It’s there, too, in Alton, Ill., where there’s a twin-towered, cable-stay bridge made famous by the television program “Nova,” which documented its construction. The trend also has left its stamp on Chicago’s Northwest Side, where the red, tube-like arches of the Damen Avenue Bridge spring across the Chicago River, forming a gateway to a rapidly gentrifying neighborhood to the north.
“Bridges are points of connection between two communities and people want to celebrate those connections,” says Stan Kaderbek, deputy commissioner of the Chicago Department of Transportation and the city’s chief bridge engineer. “Why not do something that stands out?”
Even older bridges are part of the trend. For a year and a half, as part of an effort to attract people to the Loop at night, Chicago has been showcasing its downtown river bridges with bold nighttime lighting, bathing the aging spans in the frisky hues of blue, purple and magenta.
The city’s effort builds on a 1987 one in Philadelphia that celebrated the 200th anniversary of the signing of the U.S. Constitution. The firm of celebrated architect Robert Venturi devised a lighting plan that highlights the suspension cables of the Benjamin Franklin Bridge, which joins Philadelphia and Camden, N.J., over the Delaware River.
To be sure, anything that stands out — especially anything unconventional — represents an easy target. When Frankfort held a naming contest for its unconventional new bridge, for example, one citizen opined that it should be called “the Acorn Bridge” because its designer must have been a nut. The name Arrowhead Bridge was eventually selected, relates village administrator, Jerald Ducay.
Similarly, a pedestrian bridge designed for Chicago’s Grant Park by California architect Frank Gehry drew fire last year from Mayor Richard M. Daley, who fretted that Gehry’s snaking span would take up too much green space. Daley eventually approved the bridge after Gehry made it narrower, allowing for more shrubs and grass.
Some signature bridges have encountered safety problems. Last spring, the Millennium Bridge, Lord Norman Foster’s futuristic footbridge across the Thames in London, wobbled when hordes of pedestrians marched across it on opening day. It had to be closed for re-engineering. Underscoring the importance of safety in bridge design, more than 60 people were killed Sunday when a 116-year-old bridge in Portugal collapsed and a bus and two cars plunged into the water.
But the greatest hurdle to signature bridges is cost. In St. Paul, for example, an artist’s design for a twin-towered $50 million bridge across the Mississippi River was rejected in 1995 after city officials deemed it extravagantly expensive.
That was the sort of mindset that held sway in the mid-1990s, when the nation was still emerging from a recession and cost-cutters led by then-House Speaker Newt Gingrich (R., Ga.) had seized the reins of power in Congress. At that time, federal bureaucrats turned skittish about building bridges that even looked expensive.
Midway through the construction of one bridge in another part of the country, for example, a U.S. official ordered Nair to alter the design so the bridge would look plain. “It really cost more to make it plain,” says Nair, who declined to specify the location of the bridge. “The public client was afraid it would convey the wrong image.”
Since then, the signature bridge phenomenon has grown in force — driven by a booming economy that has swelled the coffers (and the confidence) of city and state governments. The trend also has been fueled by the recognition that signature bridges, like signature buildings (Frank Gehry’s Guggenheim Museum in Bilbao, Spain, being the prime example), can be a powerful lure for tourists.
As a result, many communities are throwing out old bridge design manuals and joining the rush to build signature bridges, according to Henry Petroski, a professor of civil engineering at Duke University and author of “Engineers of Dreams: Great Bridge Builders and the Spanning of America.”
While signature bridges typically cost 10 to 15 percent more than a standard bridge, the added costs are well worth it, in the view of many public officials.
“The community that is footing the bill feels that they’re getting more than a bridge,” Petroski says. “They’re getting something that they can put on T-shirts and souvenir spoons.”
Indeed, a likeness of Frankfort’s signature bridge is proudly splashed across a village T-shirt. Officials of the suburb, which was settled in 1855 by German immigrants and named for the German city of Frankfurt, also show images of the bridge at the opening of their computer presentations.
“The public agencies have realized that the public will pay for design,” Nair says. “They’re not afraid of being called extravagant if they build something beautiful. Even public clients say, `Can you give us a bridge like Calatrava’s?'”
Actually, it was Nair who proposed the idea of a signature bridge to the Illinois Department of Transportation, the state agency that commissioned the bridge. Agency officials only went along after they determined that the unusual design was doable and that it wouldn’t cost more than a conventional bridge. Frankfort officials also had to give their OK.
The $600,000 project was part of a larger road improvement effort in Frankfort that cost roughly $10 million, according to Nair and Ralph Anderson, the transportation department’s bridge and structures engineer.
Located on Frankfort’s southern outskirts, about five miles south of Interstate Highway 80, the bridge is a deceptively simple solution to a complex and widespread problem: How to build a span that crosses a road or river not on a right angle, but on a diagonal.
Typically, when confronted with such crossings, engineers design diagonal versions of bridges that cross obstacles at a right angle. But because a diagonal bridge must span a greater distance than a right-angled bridge, its supporting beams must be bulkier and more costly. Inevitably, as the many diagonal bridges over Chicago’s Kennedy Expressway show, the result is structurally inefficient and aesthetically inelegant — a visual blight.
Nair brought a more creative approach to the Frankfort bridge, which replaces an old railroad bridge that used to cross U.S. Highway 45. The new bridge carries the Old Plank Road Trail, a bicycle path and pedestrian walkway that occupies an abandoned railroad right-of-way, on a diagonal over the highway.
The most striking feature of the bridge is an 82-foot-tall, A-frame pylon whose legs straddle the highway at right angles. A 180-foot-long deck is suspended from the apex of the pylon by four steel cables. The deck slices over the highway on a 43-degree angle.
The whole thing resembles a giant letter “A.” Indeed, after the bridge went up last year, wags wondered if large-scale versions of the letters “R” and “Y” would appear on either side of the bridge. The reason: the first name of Frankfort’s first citizen.
“We’re still working on the `R’ and the Y,'” cracks Village President Ray Rossi.
Jokes aside, there is an elegant structural logic to the design; it actually turns the troublesome diagonal crossing to its advantage.
Because the pylon spans the shortest possible distance across the highway, it is both less bulky and less expensive. The diagonal deck, in turn, braces the pylon, helping to ensure that it doesn’t get blown over by the wind.
From both the highway and the pedestrian path that leads to it, the bridge is a startling sight, a welcome shift from the bland, generic environment of the suburban commercial strip. Part of the reason it succeeds so well is the district profile it etches against the sky — that big white “A” looks like a weightless pyramid, thin and elegant, with the blue of the sky behind it.
Equally important is the ribbonlike appearance of the pedestrian deck that hangs from the pylon. Because the pylon does the heavy lifting, the deck can be trim looking too. In addition, no central column is needed to support the deck from below, thus eliminating a safety hazard for drivers. Curving handrails designed by Teng architect Tom Hoepfenhance the bridge’s open feel.
The span is hardly perfect. The concrete blocks that anchor the legs of the pylon to the ground disrupt the bridge’s otherwise smoothly flowing lines. And while the pylon itself relates well to the vast scale of the highway, there is nothing to bridge the gap between it and the more intimately scaled deck. As a result, from some vantage points the bridge looks like two separate structures in somewhat awkward tension with each other, rather than a single, synthesized whole.
Still, the overall result demonstrates the kind of punch a well-designed signature bridge can pack.
Not only has the bridge put Frankfort on the map, replaced an old water tower as the suburb’s most prominent landmark and formed a new southern gateway to the town.
It has changed the town’s perception of itself.
Frankfort (pop: 10,000) has long prided itself on being a town with “1890s charm.” Even many of the new buildings there are supposed to have a vaguely Bavarian, half-timbered look. But the bridge has stirred things up, making many people in the town realize there’s a value in embracing the future rather than imitating the past.
Now people talk about “unique designs” as well as “1890s charm.”
In other words, Rossi says, the bridge didn’t simply meet the village’s expectations. “It changed those expectations,” he says, “for generations to come.”
Could such creative thinking be applied to other bridges?
Anderson says it might happen, though he cautions that it’s easier for the Frankfort bridge to look light and airy because it supports pedestrians and cyclists rather than cars and trucks.
Kaderbek adds the further caveat that signature bridges only are appropriate for sites where they can be seen from all points on the compass. Nevertheless, he envisions the day when some of those eyesore bridges that span Chicago’s highways might be replaced with something more appealing.
“Each one of those is a link for a community,” he says. “They need to be something more than the poor orphan that goes over the expressway.”
