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Never mind the drizzle, the hurrying cars. It's barely 9 a.m. and already Alan J.

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Lutenegger and two of his students from the University of Massachusetts at Amherst are visiting their second wrought-iron truss bridge of the day, a 130-foot-long, single-lane span erected over the Mill River here sometime before 1884. It's called the Hotel Bridge or Hotel Street Bridge, and it is, as Mr. Lutenegger says, "in rough shape."

Painted a dull red, the bridge is battered and in places rusty. The road surface, or deck, consists of wood planks covered with an old layer of asphalt that is crumbling at the edges. The eastern approach is awkward -- a short, steep incline from a "T" intersection. Signs at either end warn of a three-ton load limit. That's as low as load limits go, too low for firetrucks or school buses. The students, Jason Pisano and Nathan Roy, try jumping up and down on the bridge to see if they can make it move. They can.

An old bridge that some drivers might shy away from is a bridge Alan Lutenegger will go out of his way to visit. By training he's a foundation engineer, an expert in soil testing and ground anchors. But gradually his interests have worked their way upward. While the students measure tie rods and trusses for drawings they plan to make for a local bridge inventory, Mr. Lutenegger is peering at the thick pins that hold the trusses together and speculating about whether the handsome lattices on either side of the deck are original. He's delighted to point out the builder's plate on the west end of the bridge: "Wrought Iron Bridge Co., Canton O., Builders, Patented Nov. 21st 1876."

"These were all catalog companies," he says of the Canton firm and its competitors. County engineers seeking a new bridge would describe the site and traffic needs to a company, and it would reply with a proposal -- usually one based on a model in the company's line. "The lighter you could make the bridge, the cheaper you could sell it," Mr. Lutenegger notes. A lighter bridge used less iron and cost less to ship, so it could be delivered at a more competitive price.

What was an advantage in the 1880s, however, became a disadvantage as decades passed and vehicles got heavier. Thousands of 19th-century truss spans have been replaced by heavier bridges at the behest of highway engineers. Others have been taken down because approaches that were fine in horse-and-buggy days are dangerous when traffic is moving at 35 or 40 miles an hour. Still others have been destroyed when vehicles slammed into their end posts and caused the trusses to collapse.

Which is why Mr. Lutenegger has become, of all things, a bridge collector.

So far three truss bridges have been delivered, in pieces, to the university's campus, and he has promises of five more. Mr. Lutenegger, who is the head of the department of civil and environmental engineering, has persuaded university officials to let him and a group of engineering students refurbish the spans and install them where campus footpaths cross streams or depressions, creating what he says will be a living-history museum of bridges. Other institutions, he says, may boast of having one historic bridge -- Merrimack and Central Pennsylvania Colleges, for instance -- but the University of Massachusetts will have an entire collection.

What's more, he says, the bridges will be a boon to students, as refurbishment projects in which they can learn by doing and later as a collection for on-site study of historic structures. One of the donated bridges, he says, will be set aside for use by engineering classes studying load testing and similar topics. While trusses aren't used as much in bridges now as they once were, they remain ubiquitous, particularly in roofs. Mr. Lutenegger also plans to create a walking tour of the bridge collection.

The eight bridges represent a mix of truss types. A truss -- bridges typically have one on either side of the deck -- consists of a top chord and a bottom chord connected by a series of triangles, which distribute the load through the structure. A bridge can be a deck truss (the deck sits on top of the trusses), a through truss (the deck sits between tall trusses, which are connected by cross-members above the roadway), or a pony truss (the deck sits between short trusses, which are not connected above). The trusses themselves come in a variety of designs.

The first span, a 42-foot pony truss built in 1906, is almost ready. Mr. Pisano, who graduated this spring, has been overseeing the bridge's refurbishment for two years now and has continued to work on it this summer. He and Mr. Lutenegger expect to move it from the engineering department's on-campus project yard to its new location within the next few months.

The bridge "was just a mangled mess" when it was delivered, Mr. Pisano recalls. "Everything was curved and buckled and bent out of shape." The two trusses had each been cut in half, and there was no sign of the deck structure. He and other members of the campus chapter of the American Society of Civil Engineers measured what remained, drew a set of plans, and then set about deciding how to proceed.

The work was done by hand, outdoors, in all kinds of weather. Mr. Pisano says about 100 rusted rivets had to be ground down and then popped out so that homemade replacement parts could be attached with high-strength bolts. Some parts could be reused but needed straightening, which was sometimes accomplished with the help of heavy equipment lent by the university grounds crew. It was often difficult to get bolt holes aligned, he says, because some large parts had to fit to within one-sixteenth of an inch.

"All we have left is putting on a few more bolts and a wood deck, and adding some lateral bracing underneath," says Mr. Pisano, who leaves later this month for graduate school at Stanford University. When all is said and done, the bridge should be as good as new, if not better. "In some places we've beefed up some of the thicknesses," he says. "I believe we've used a pretty big factor of safety."

As pedestrian spans, Mr. Lutenegger says, the heaviest loads the bridges will carry are the university's miniature snowplows. Even so, state bridge inspectors will check each crossing before it is opened to the public. He notes that the bridge project requires no university support beyond occasional assistance from the grounds crew -- he's been able to talk alumni and other friends into donating services and supplies, and engineering students will maintain the spans. The bridges themselves are being donated by the Vermont and Massachusetts highway departments as well as by a private owner and a local historical commission.

The second span, Mr. Pisano says, is in much better shape than the first and will be easier to refurbish. Mr. Lutenegger adds that if anyone has a large shed to donate so work could go on under cover, he -- and the students -- would welcome the gift.

One of the other spans is an 1880 pony truss from none other than the Wrought Iron Bridge Company of Canton, Ohio. Another is a rare truss that uses pipe for the main members, rather than girders. But the showpiece, according to Mr. Lutenegger, is sure to be a 90-foot lenticular through truss in North Adams, Mass., that is currently scheduled for replacement.

Lenticular trusses -- so called because their top and bottom chords come together in a graceful curve shaped like a lens -- are among the rarest and most attractive of truss designs. About 1,200 were built, almost all by the Berlin Iron Bridge Company of East Berlin, Conn. Mr. Lutenegger, whose love of bridges was sparked by lenticular trusses and who is now writing a book about them, says that only 56 are believed to survive in the United States, and that he will soon have visited and documented them all. The North Adams bridge, he says, could be put up in the quadrangle right in front of the engineering building.

The bridge project, Mr. Lutenegger says, will take at least 10 years. And that's good, he adds, becauseit means exposing a decade's worth of engineering students to invaluable hands-on instruction. Besidesrivet-grinding, "we're teaching teamwork, management, organization, materials, structures, and history -- all kinds of facets of engineering."

In the meantime, he sends a visitor off through the drizzle to visit a nearby lenticular truss, the 1882 Bardwell's Ferry Road bridge over the Deerfield River. It's a single 198-foot span, one lane wide, whose latticed posts and elegant curves make it one of the handsomest bridges that almost no one has ever heard of. It has a 10-ton weight limit but appears to be lovingly maintained. Its wood deck rumbles reassuringly when cars cross, and its trusses rattle gently with excitement. Even on a rainy afternoon, it's enough to make a bridge enthusiast out of anyone.