Structure Type:
7 span, reinforced-concrete deck rib arches (river spans), with a 9 span reinforced concrete slab viaduct (railroad spans). Each of the river spans is made up of 5 Melan-type, two-hinged, reinforced-concrete arch ribs of parabolic profile. The longest (channel span) ribs have a center to center span of 209 feet and a rise of 29.71 feet; the ribs of the other spans vary from 176.5 feet to 121 feet in length, with rises from 29.2 feet to 19.1 feet. The three interior ribs in each span are grouped together near the center of the roadway (where a street railway line was originally located), the two outer ribs are more widely spaced and carry thin concrete fascia walls (concealing what is otherwise an open-spandrel design). The reinforcing in each rib consists of a pair of riveted steel parallel-chord Warren-type trusses, connected by transverse bracing to form a self-supporting arch rib. A crown hinge, which allowed each rib to function as a 3-hinged arch during construction, was riveted fixed before the encasing concrete was poured. Reinforced-concrete spandrel columns carry the reinforced-concrete roadway deck. The 9 viaduct spans over the rail yard consists of a reinforced concrete slab deck carried by transverse bents of either concrete-encased structural steel or standard, reinforced concrete. The piers are granite-faced reinforced-concrete.
By the 1990's, the concrete above the arches was suffering from advanced ASR (Alkali-Silica Reactivity) attack. The 1996 rehabilitation project replaced the entire deck system. The decorative architectural elements were replaced either in kind using cast stone or replaced with architectural fiberglass reproductions. The viaduct over the railroad was replaced with adjacent precast/prestressed deck beams made continuous.
History of Bridge:
The Connecticut River was first bridged at Springfield in 1805, by an open wooden bridge said to have been "mongrel in style." This collapsed in 1814 and was replaced by a covered wooden Burr arch-truss bridge built by Isaac Damon of Northampton. Partly rebuilt after a spring freshet in 1818, Damon's bridge survived into the 20th century, and was the structure which the present concrete arch bridge was built to replace. In 1915, the Hampden County Commissioners opened hearings to discuss construction of a new bridge, but it wasn't until the winter of 1918/19 that the location and overall design of the present concrete arch bridge were finally agreed upon. The main construction contract (at $3,254,883) was let to H.P. Converse on April 3, 1920; the completed bridge was opened to traffic on August 3, 1922. At the ceremonies held that day, the bridge was dedicated as a memorial to "those who had died as pioneers, and soldiers in the Revolutionary, Civil and Foreign Wars."
Significance of Bridge
One example of the 158 concrete arch bridges (of at least a 20 foot span) currently identified in the MassHighway database. It is one of only three known examples of Melan-type reinforced concrete arch construction, and one of only 7 open-spandrel rib arches (as opposed to filled-spandrel barrel arches) in the database; it includes the longest single concrete arch span in the database. Its self-supporting steel rib arches represent an uncommon refinement of Melan's original idea - by making the steel arches self-supporting, and using them to support their own dead load plus the weight of the formwork and the wet concrete during construction, an initial compressive stress was developed in the steel prior to the setting of the concrete. This prestressing of the steel allowed a much higher proportion of its ultimate strength to be utilized, allowing, in turn, the use of smaller and lighter arch ribs and a less massive substructure.
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