Bellows Falls Arch Bridge (USA)
The Bellows Falls Arch Bridge was a three-hinged steel bridge of impressively light and economical construction. It was a through-arch bridge with a suspended deck, crossing the Connecticut River between Bellows Falls, Vermont and North Walpole, New Hampshire. With a span of 540 ft, it was the longest arch bridge in the United States when it was completed in 1905. It was demolished in 1982.
The designer was J. R. Worcester.
Construction started in November 1904, using falsework made of spruce. Assembly of the main superstructure began in December 1904. The steelwork was made by Louis A. Shoemaker and Company (Philadelphia). The total construction time was just four months.
The following information is condensed from Historic American Engineering Record - Bellows Palls Arch Bridge[1]:-
'In what may have been an effort to make the bridge more aesthetically pleasing, Worcester did not allow the top and bottom chords of the arch to converge at the top of the span as they would in a conventional three-hinged design. Instead, Worcester replaced the center hinge in each arch with a compression joint by inserting a horizontal strut between the chords and connecting it to the chords by diagonal steel members. Through this design feature the compressive stresses were transferred through the joints to the trusses comprising the arches and, consequently, the outline of the top and bottom chords of the arches appeared continous throughout their entire length. ..... Construction of the bridge began in November 1904. The first task was the erection of four wooden towers to serve as falsework. This was performed by Joseph A. Ross and Sons, a Boston contracting firm which was hired to drive the piles for the falsework and build the masonry abutments. In keeping with the economy of the project, the supporting piles were spruce, later sold to the local pulp mill. .... Each connection was temporarily bolted together rather than riveted so that adjustments could be made if the two halves of the arch did not meet properly. .... The final procedure involved the riveting of all the steel members together and was intended to be done with a pneumatic riveter. However, a fire in the tool shed the day before the process was to begin destroyed the compressor, and, consequently, all the riveting was performed by hand. Total construction time for the bridge was 4 months, and a total of forty- five men were employed.
In 1936 the Arch Bridge suffered extensive damage when a major ice jam on the river broke apart and sent large blocks of ice floating downstream. These ice blocks struck both ends of the upstream side of the bridge and bent some of the lower steelwork. The impact left the structure leaning slightly upstream. Major repairs were required, involving raising the entire structure through a complex jacking procedure, and placing it on specially designed falsework. Wire bridge cables were fastened to the ends of each arch to resist the horizontal thrust once the bridge had been detached from the abutments. The damaged steelwork was removed from both ends, thus shortening the length of the trusses. New steel beams were then attached to the ends of each chord and connected to new hinges. To compensate for the decreased length, the abutments that supported the hinges had to be re-designed and enlarged. With the new components in place, the arch was lowered into position and re-aligned. During reconstruction, the original timber decking was removed, and a new 3-inch thick steel grid deck, infilled with concrete, was installed.