Gorham Bridge Trusses Heading To NH After 2 Years in Ohio

By Karen Farkas
Northeast Ohio Media Group
October 28, 2014

CLEVELAND, Ohio - Two 13,000-pound trusses, resurrected from the charred ruins of a wooden bridge, are heading home to New Hampshire after spending more than two years at Case Western Reserve University.

Dario Gasparini, a civil engineering professor nationally known for his work on historic bridges, has been studying the strengths and weaknesses of what's known as a Howe truss bridge.  He and his students are still analyzing data but the trusses, which have sat outside Bingham Hall, were lifted to a flatbed truck Monday.

The trusses were rebuilt after an 86-year-old bridge in Gorham, N.H., was set on fire in 2004.  A truss bridge is a triangular assembly of members that act principally in tension or compression, Gasparini said in a 2012 interview. The design creates a very rigid structure that transfers the load to a wide area.

As part of the research about 45 sensors were attached to the trusses -- made of Douglas fir -- and the vertical steel rods that hold the wood in place. The sensors measured strain on the rods and the wood's moisture and temperature.

The bridge will be reconstructed in a place at Gorham where it will be safe and can be visited by the public. A wooden deck bridge replaced it at the original location.

A worker secures a bridge truss before it is lifted onto a flatbed truck at Case Western Reserve University.
(Case Western Reserve University Photo)

 

Related Story:

Rebuilt Bridge Trusses from 1918 Burned Gorham Bridge Transferred to
Case Western Reserve University in Ohio

By Karen Farkas
Northeast Ohio Media Group
August 11, 2012

CLEVELAND, Ohio - Two 13,000-pound trusses, resurrected from the charred ruins of a wooden bridge in New Hampshire, surely must be among the largest research specimens at Case Western Reserve University.

Dario Gasparini, a civil engineering professor nationally known for his work on historic bridges, had the wood and iron pieces trucked here to study the strengths and weaknesses of what's known as a Howe truss bridge.  Because of his interest, the trusses -- rebuilt after an 86-year-old bridge in Gorham, N.H., was set on fire in 2004 -- eventually will be returned to their home state and the historically significant structure will be reconstructed.

A truss bridge is a triangular assembly of members that act principally in tension or compression, Gasparini said. The design creates a very rigid structure that transfers the load to a wide area.  William Howe's design -- which he patented in 1840 -- introduced iron rods, which were tightened to pre-stress the bridge and held the wooden members in place without attaching them to other elements, Gasparini said.

The design resulted in a near monopoly for railroad bridges because they could be cheaply and quickly built since the rods and truss timbers could be prefabricated and the parts easily shipped.  Howe's brother-in-law, Amasa Stone, bought the rights to the truss design, moved to Cleveland and made a fortune building railroad bridges. Stone was a major donor to Western Reserve College, which eventually became CWRU. Amasa Stone Chapel on the campus was built in his honor.

Gasparini said his project is, "A nice connection between Howe, Stone, Western Reserve College and the history of Northeast Ohio."  The two 11-foot-high, 44-feet-long reconstructed trusses are from the Moose Brook Bridge, built in 1918. It is known as a boxed pony truss "pony" referring to its low height and "boxed" because the trusses were covered by wood.

It is considered a covered bridge even though there is no roof over the deck, according to the National Society for the Preservation of Covered Bridges Inc.  When the Boston & Maine Railroad tracks were removed, the right-of-way became a trail for off-road vehicles, snowmobiles and hikers.

But in 2004, the bridge -- one of only eight wooden pony truss bridges known to exist in North America -- was heavily damaged by an arsonist.  The covered bridge society was asked if it was interested in what was left, said president David Wright, of Westminster, Vt.  It was, so the group removed the charred trusses from the abutments and set them to the side until someone could do detailed drawings of them.

Wright said the society planned to salvage the metal parts of the bridge, including the original iron shoes, which hold the wooden braces and counter braces in place and the top chords of the trusses. Eventually, the group hoped to reconstruct the bridge.  "It is a very rare beast," Wright said.  But, lacking funding, the project stalled

In 2009, Gasparini, who is affiliated with the U.S. National Park Service's Historic Engineering Record Division, was involved in its extensive study of the Moose Brook Bridge, part of an ongoing project to document historically significant bridges.  Gasparini told federal officials that he was interested in studying the Howe truss and, with the support of the park service, submitted a request for money to restore, research and reconstruct the bridge.

The project received a $270,000 grant through the U.S. Federal Highway Administration's covered bridge preservation program. About $138,000 paid for the reconstruction of the trusses and transportation to Cleveland. The remainder is being used for research, including the instrumentation, Gasparini said.

It took longer than expected to get the trusses to Cleveland because four iron shoes, which had cracked in the fire, had to be repaired by an expert in Lansing, Mich. The wood, which cost about $35,000, had to be ordered from Oregon.  Tim Andrews of Barns and Bridges of New England built the trusses. They were disassembled, brought by truck from New Hampshire to CWRU and reassembled. The first arrived about a year ago and the second in March.

As part of Gasparini's research, about 45 sensors are attached to the trusses -- made of Douglas fir -- and the vertical steel rods that hold the wood in place. The sensors will measure strain on the rods and the wood's moisture and temperature for more than a year.

Students are studying the trusses in structural analysis courses and mathematical models will be created using the results of the tests, he said. The results will be important not only for rehabilitating existing Howe truss bridges, but also will help engineers improve designs of future truss bridges, Gasparini said.

In a few weeks, the trusses will be moved from his lab and placed outside Bingham Hall where they will be covered by a hoop and fabric tent.  Wright said Gasparini can have the trusses as long as he wants because his organization is thrilled that the bridge was saved.

"We heard about Dario's plan and said 'Hey we have the remnants of this particular bridge and it serves your interest and our interest,' " he said.  When the trusses are shipped back to New Hampshire, the bridge will be reconstructed in a place where it will be safe and can be visited by the public, Wright said. A wooden deck bridge replaced it at the original location.

Case Western Reserve University professor Dario Gasparini explains how a vertical rod, bolted to the top and bottom horizontal pieces
of a bridge truss, provides the tension to hold the wooden cross beams in place against the iron shoes.

 

The Moose Brook Bridge, built in 1918, was originally a railroad bridge in Gorham, New Hampshire. The tracks were later replaced by a trail.
The bridge, photographed in 1985, is considered a covered bridge because the side trusses were covered.

 

An arson fire destroyed the bridge in 2004. Only the iron components of the trusses could be salvaged.
The trusses have been rebuilt and are being studied at Case Western Reserve University.


 

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