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Charles J. Arrigoni Bridge,
Bridge No. 524
• Routes 66 and 17 over Connecticut River
• Steel through arch
• Length: 3,428' overall, two 660' arch spans
• Built 1936-1938
• Bethlehem Steel Company, fabricator
At the time of its completion, the Arrigoni Bridge was the largest and most expensive bridge built in Connecticut, costing $3.5 million. Even today its two 600' arches have the longest span length of any bridge in the state. The choice of large steel through arches for this location, with the roadway suspended from the arches by cables, allowed wide navigation channels on the river, minimized pier construction, and provided a profile to the bridge that was aesthetically pleasing. By replacing a drawbridge with a high-level crossing (the bridge provides more than 90' of clearance above the river), the Arrigoni Bridge foreshadowed all subsequent major highway crossings of Connecticut's navigable rivers.
From a technical standpoint, the bridge exemplifies the long-span bridge engineering of the first half of the 20th century. Because of the growing need to provide uninterrupted highway passage over large bodies of water, engineers increasingly were called upon to design large cantilevered trusses, suspension bridges, and steel arches. Innovative erection methods, the availability of very large structural components, and special metals all contributed to the development of long-span bridge technology. For example, nearly a third of the Arrigoni Bridge utilized high-strength silicon steel, and the bridge was almost entirely erected by building the arches outward from the center pier, letting them balance each other as they were extended over the water. Another notable engineering feature are the chains of huge eyebars under the roadway that tie together the ends of each arch; the tied-arch technique resisted the outward horizontal thrust of the arches and thus allowed the piers to be much smaller and more economical.
The Arrigoni Bridge, named for the state legislator who promoted the project, was designed by Leslie G. Sumner of the State Highway Department and William G. Grove of the American Bridge Company. The eminent New York firm of Robinson and Steinman served as consulting engineers. The bridge won the American Institute of Steel Construction's First Prize in the large bridge category in 1938.