Laroque Bridge, Spanning New Haven River at State Route 116, Bristol, Addison County, VT
Significance: This bridge is typical of the engineering practice of the early 20th Century. By that time, two basic truss designs Warren and Pratt had replaced the variety of types which characterized the 19th Century. Riveted construction was almost universal. In the heaviness of its members and concrete slab floor, the bridge reflects the growing use of automobiles and trucks in the 1920s. This truss is identical to the standard bridges built in the late 1920s except that it uses built-up members instead of rolled I-beams. These members cost more but were lighter than equivalent rolled sections. Like most flood-era bridges, built in late 1920s it has a curved top chord. Though more costly to fabricate, curved chords saved money in heavy-service bridges like this relatively long and wide concrete decked span, since the truss has extra depth only in the middle where it was needed to counter bending forces. McClintic-Marshall Company was a Pennsylvania based fabricator which advertised heavily for New England business in the 1920s. This Company built the Bath bridge in Maine as well as four other Vermont bridges.
Survey number: HAER VT-21
Building/structure dates: 1925 Initial Construction