Save Our Span!

Todd Milano, the president of Central Pennsylvania College, in Summerdale (a suburb of Harrisburg), recently accomplished the extraordinary feat of rescuing a doomed 133-year-old iron span, transporting it across the state, rebuilding it, and installing it on his campus. The story began in 1999, when Milano got a call from a retired engineer named Harolld Stahle, Jr., who had gone to Central Pennsylvania College. Stahle said the state had some old bridges it needed to get rid of. The college was planning to build a bridge across a small creek and ravine to connect its dormitories with its new technology center. Why not see if it could acquire an existing bridge and save a historic structure in the process?

The idea of rescuing something old appealed to Milano, whose office is in an early-nineteenth-century farmhouse. “When you’re the college president, you can get away with a few crazy things,” he says. He got in touch with the Pennsylvania Department of Transportation, where Kara Russell, a specialist in cultural resources, printed him out a list of unused and abandoned spans. She highlighted one in Lehigh County that was known as Henszey’s Bridge. It was just the right size for the campus crossing.

Next Milano got in touch with the civil and environmental engineering department at nearby Bucknell University. He persuaded Professor Jai Kim to direct four students in conducting a feasibility study on Henszey’s Bridge. The students found that moving it 70 miles and rehabilitating it would cost slightly more than building a new span. Either way the cost would be in the area of $250,000. (Actual rehabilitation costs, including engineering fees, came to $550,000.) Milano decided to go ahead. He bought the bridge from the state for $22, his lucky number, in an auction in which he was the only bidder.

According to Kara Russell, the state attempts to improve and reuse its historic bridges before seeking new homes for them but often can’t do so. Pennsylvania has about 400 bridges listed on the National Register of Historic Places and about 600 more eligible for listing, including 240 covered bridges, more than in any other state. “If it can be rehabilitated, we’ll rehabilitate it,” she says. “That’s our preference, especially from a historic preservation perspective. Historically, these truss bridges were made to be moved, so it’s still in keeping with their historic nature to move them.” Henszey’s Bridge couldn’t be kept where it was, because it was too frail to carry modern traffic, so it had to be either relocated or scrapped.

Henszey’s is an early example of an all-wrought-iron bowstring truss, or tied-arch, bridge. It is 92 feet long, 14 feet wide (originally 18), and 9 feet high, with a gently curved arch, or upper chord, rising above either side of the roadway. The arches, the heaviest part of the bridge, are in compression—that is, a load on the bridge pulls down on the arch and pushes it against its ends. There are also straight straps along the bottom of the span—the bottom chord—that act in tension, being stretched by the same strains that compress the upper chord. The two chords together are shaped like an archer’s bow and string: hence the name of the design.

The space between the top and bottom chords is called the web, and the members that connect them are called vertical posts and diagonals. It’s all held together by rivets, or pins, and rests on masonry piers and abutments. It was designed for nineteenthcentury traffic, mainly horses, carriages, and the occasional farm wagon filled with hay, but for nearly 80 years, ending in 1986, it carried the far heavier loads of automobiles and milk trucks.

Henszey’s occupies a special niche in the history of American bridges. The nation’s first ones were made of wood or stone. By 1850 high-quality iron could be produced cheaply enough for bridges, and it became especially valuable for spans that had to carry locomotives. The first iron bridges generally used cast iron for members in compression and wrought iron, which was stronger and more expensive, for those in tension. After the Civil War wrought iron came to dominate in both uses because cast iron sometimes had flaws that made it fail catastrophically. Wrought iron became the main material for bridges until the 1890s, when it was supplanted by steel.

Henszey’s is one of the earliest all-wrought-iron bridges. It was the creation of Joseph G. Henszey, a Philadelphia hardware merchant who patented his design in 1869. He is not known to have had any formal engineering education. The span was fabricated by his own Continental Bridge Company, which he founded to sell and assemble his patented designs. The company’s effusively worded catalogue copy described this design (of which the bridge now at Central Pennsylvania College is one of only two known surviving examples) as “so put together that while handsome in appearance in STRENGTH it is BEYOND QUESTION ,” with “parts arranged as to be easily reached for painting,” “no nuts or bolts REQUIRING CONSTANT attention,” “DURABILITY,” “neatness of appearance,” and “for the real value furnished, the CHEAPEST .”

The bridge’s first home, from 1869 to 1900, was in Slatington, in the northeast corner of Lehigh County, where it carried Main Street over a creek and a railroad line. There it was two spans long. A photograph from the time shows that there was a pier (a stone support tower) under the middle of each span, as well as one in the center where they met, and a curious castiron bracing system, not part of the original design, along the bottom chord.

Increasing traffic caused the county commissioners to replace the Slatington bridge in 1900. One span may have been scrapped; the other went to Wanamakers, 25 miles southeast of Allentown, where it carried a farm road over Ontelaunee Creek. A stone pier was installed under the center of the span there too, thus “reversing all the stresses in the top chord and web members,” according to an engineer who examined it in 1932. The pier was removed later in the 1930s. The bracing pieces remained, and the bridge stayed in service until 1986.

In 2001 the team from Bucknell began visiting the old bridge to study it and take measurements, building on research done in the early 1990s by the Historic American Engineering Record, a documentation program of the National Park Service. The Bucknell researchers had to hack away at vegetation and move rocks with crowbars to get at the span and find out how its members were connected to one another. They analyzed their findings by computer, designed a way to reinforce the chords to safely carry the projected load of pedestrian traffic, and wrote up a set of specifications for the restoration job. (Later it was determined that the existing trusses, supplemented with new floor beams, would be sufficient.)

The engineering contract was won by Clough, Harbour & Associates, a firm based in Albany, New York. Nicholas Demos, P.E., of Clough, Harbour concluded that the diagonal stays that were added when the central supporting pier was built had effectively changed the bridge from a simple arch structure (with the lower chord tying the ends of the arch together) into a truss (with a network of crisscrossed rods stiffening the whole structure). The Bucknell students’ computer software was flummoxed by this structural shift and insisted that the bridge was unstable, but Clough, Harbour’s engineers calculated that the span would be sound for pedestrian traffic as either an arch or a truss.

On January 22, 2002, the move began. A crew from Greiner Industries, a metal-fabrication and construction firm in Mount Joy, Pennsylvania, arrived with a 130-foot-high crane and a 90-foot-long flatbed trailer. The rotting oak flooring and its supporting structure had been removed over the preceding few days, leaving only the two separate bowstring arches along either side of the bridge. An I-beam was dangled horizontally above the upstream arch from the company’s towering crane, and straps hung from the beam were then tied to the arch. The beam was gently lifted, one end of the arch rose—and the lower chord of the bridge began to buckle. The forces on the arch were reversing as it was lifted, making the bottom warp. The crew set the bridge back down, got hold of some steel, and welded it alongside the bottom chord to stiffen it. After that the span was lifted again; the end that hadn’t risen still stayed put until it was rocked free like a loose tooth. Then the span rose through the air, was carefully maneuvered past a nearby tree, and was laid on the flatbed. The second arch followed without incident.

By February 15 rehabilitation work was under way at Greiner’s engineering shop. Decades of rust were sand-blasted off the trusses, which were then primed with a rustproof coating. New floor beams and stringers made the bridge four feet narrower for pedestrian use, and brackets angled several feet outward from the tops of the arches to the floor, to keep them vertical. Then came the trickiest part of the renovation: The diagonal rods between the vertical truss members had to be delicately tightened in a job something like tuning a piano.

On May 6 the now sturdy bridge was moved out of the Greiner engineering complex and down 40 miles of highway to the Central Pennsylvania campus. The next day it was eased into place. This time the site was open enough so that two cranes could be used, one lifting each end.

The dedication ceremony was held on May 10, a beautiful spring afternoon, with a gathering on the terrace outside the new Advanced Technology Center, which had itself been dedicated the day before. This juxtaposition of old and new echoed the way old-fashioned initiative, organization, and hard work can be brought together with Internet-based fundraising and computerized stress analysis to rescue historic bridges.

Todd Milano is one of a growing number of people who realize that saving pieces of our historic surroundings helps us understand and appreciate our built world and what we have done in and with it. Bridges are the single most visible examples of the engineer’s art, and while no one thinks every historic bridge can or should be saved, it would be a terrible loss if we ran out of all the most significant and representative ones. Keeping them around isn’t easy. Buying a bridge for $22 may sound like a neat idea, but that was only the beginning. All the shoring up, lifting, moving, repairing, strengthening, and reinstalling—and all the encounters with bureaucracy that those things entailed—paid off handsomely, though, in the case of Henszey’s Bridge. Lit at night and interpreted with markers, it is now the heart of the campus. Bridge aficionados and scholars travel from around the world to see it. Cambridge University may have its famous Mathematical Bridge, but Central Pennsylvania College can be just as proud of its counterpart.

Work started in August 2004 to restore the S-shaped 1828 Blaine Bridge, the oldest bridge in the state. It is scheduled for completion in June, with dedication planned for September 2005. The $1.3 million project is funded by the Federal Highway Administration. The reason for the shape is simple: Often the National Road, which this bridge originally crossed, and the stream did not intersect at 90-degree angles. By zigzagging the structure, engineers were able to build abutments perpendicular to the river but cross the stream at an angle. The 1828 Blaine Bridge, which crosses Wheeling Creek, is 345 feet long, with three segmental arches of 30-, 40-, and 50-foot spans. Its savior is Sue Douglass, a former schoolteacher turned community activist. For information, see www.blainebridge.org .

Jay Harding, along with other Erie Canal enthusiasts from western New York, rehabilitated this bridge after it collapsed into Ganargua Creek during ice storms in the winter of 1996. Sessler Excavating & Wrecking pulled the bridge’s remains from the creek for free. At the town of Macedon’s highway maintenance yard, volunteers cleaned and sorted the parts while they raised money to put them back together.

A change bridge serves to carry the towpath from one side of a canal to the other. The path looped under one end of the bridge, so that a mule could cross over without being unhitched from its barge. The one in Macedon is the only surviving example, a truss designed by the prolific Squire Whipple (the first American to analyze mathematically the structural mechanics of bridge building). The cast- and wrought-iron structure, 74 feet long and 14 feet wide, is Whipple’s oldest surviving bridge. It crossed the Erie Canal in two separate locations before being bought by a farmer and moved to Ganargua Creek. Restored and placed on new abutments in Wayne County’s Aqueduct Park, it was dedicated on July 10, 2004. The estimated cost of the restoration was $232,000. For further information, e-mail Jay Harding at jhardin2@rochester.rr.com.

This bridge’s setting is dramatic, high above the Sacandaga River in the southern Adirondacks just north of Albany. Equally dramatic to scholars is its design, in which the road is, quite unusually, situated at the middle of the lenticular (lensshaped) truss instead of at the bottom. In 2002 it was awarded highly competitive federal transportation enhancement funding of $1.2 million allocated by the New York State Department of Transportation. Tom Ryan (a retired structural engineer and artist who has painted many canvases depicting Bow Bridge), his colleagues at the Ryan-Biggs engineering consulting firm, Adirondack Architectural Heritage, the Preservation League of New York State, and the state’s Historic Preservation Office all contributed to its preservation.

At a rally in June 2004, more than 300 citizens walked across the bridge to show their support for saving this pin-connected, multiple-span truss set on cylindrical piers high above the Staunton River. The Clarkton Bridge Alliance has convinced state transportation officials that the 674-foot-long structure, fabricated by the Virginia Bridge & Iron Company, of Roanoke, can be part of a regional network of recreational trails linking up a number of historic and natural sites. The bridge will stay in place now that funding to repair, maintain, and insure it has been raised from private donors and local government. For more information on the alliance’s efforts, see www.clarktonbridge.com .

Hojack Bridge is a rare surviving swing span. Of all the movable bridge types— swing, bascule, retractile, and vertical lift—swings are the least common besides retractile, of which only two are known to survive. Two proposals for saving it have been brought forward: Using the Hoj ack as a distinctive symbolic gateway to the port of Rochester or as part of a light-rail system that would link the new Toronto-Rochester ferry terminal with downtown (the bridge carried trains over the Genesee River for most of a century). Richard Margolis, a professional photographer, is championing the effort to save the Hojack Bridge; he estimates the first round of renovation would cost $500,000. See www.savehojack.org and www.thebridgeproject.com for further information.

In 2003 Preservation Cascade, Inc., of Great Falls—a nonprofit preservation group based in Cascade County—was awarded $250,000 by the federal government’s highly competitive Save America’s Treasures program for a bridge that is indeed a treasure. Its design includes eight double-ribbed concrete arches resting on piers, and when they are lit by lateafternoon sun, their reflection in the Missouri River makes the bridge appear to be skipping across the water like a thrown stone. The bridge came precariously close to perishing, but as highway officials prepared to demolish it, residents banded together. Arlyne Reichert, a former state legislator, has led the preservation effort, most dramatically winning a court order to stay demolition just six days before the wrecking ball was scheduled to swing. Although close to a million dollars’ worth of repairs have already been performed, the span is still imperiled, and an additional $2 million will be needed to finish the job. For more information, see www.montanas-archbridge.org .

When bridges cross the Atlantic Intracoastal Waterway (a navigational channel running along the East Coast from Key West to Boston), they must allow boats to pass underneath. The type of bridge most commonly used is the bascule, or ordinary drawbridge. Of the many combinations of causeway and bascule in Florida, the Bridge of Lions, with 23 approach arches, is the most architecturally distinctive. In the 1990s the bridge looked likely to be demolished so that the navigable channel of the waterway could be widened and a new bridge with wider spans could be built to modern standards. A citizens’ campaign led by Theresa Segal, Nancy Sikes-Kline, and T. J. Tremmel showed that it could be kept in place with minor modifications, and rehabilitation started in February 2005. It should be completed in 2010. For one of the most sophisticated bridgepreservation Web sites, which was a major factor in the effort to save the bridge, see www.thebridgeoflions.org .

The only bridge park in the United States, if not the world, is located just south of Battle Creek, on 14 acres along the KaIamazoo River. The park currently contains six beautifully restored steel truss bridges that have been converted to pedestrian use. Hands-on workshops train workers in the skills needed to breathe new life into old truss bridges, such as riveting and flame-straightening of bent members, and the park has raised public awareness through numerous newspaper and television stories. The creation of the park was initiated in 1996 by Dennis Randolph, the managing director of the Calhoun County road commission. For more information, write Calhoun County Historic Bridge Park, 13300 Fifteen Mile Road, Marshall, MI 49068, 800-781-5512.

Professor Alan J. Lutenegger, head of the department of civil and environmental engineering at the University of Massachusetts, has become a bridge collector. In 2001 he persuaded university officials to let him and his students refurbish old bridges and install them on the campus. The work gives students hands-on experience in structural engineering and construction, and the results can be studied by future students. While pin-connected trusses aren’t the solution for modern spans, they are instructive, particularly when trying to understand the subtleties of load testing and analyzing structural dynamics. At present the site contains 10 bridges. Professor Lutenegger expects to have a Warren truss rescued from southern Vermont completed by May 2005 and two more in place this summer. The Web site for the UMass project is www.ecs. umass.edu/cee/adaptivebridge .