The eight-span, 803'-long, steel stringer bridge has a four-span continuous main span (116.7'-154'-154'-116.7') flanked by a single 65'-long approach span to one side and three 65'-long simply supported spans to the other side. The builtup, all-welded continuous beams of the main span have a minimum 5' depth and are shaped over the piers. The curved lower-flange profile of the beams over the interior piers is to accommodate where the stress moments are greatest in the continuous design – it is not an aesthetic detail, but it does have pleasing lines over the piers. The web stiffeners are also welded. There are welded angle crossbraces between beams. The bridge has standard two-rail high on high-curb column railings on a cantilevered deck section. The concrete deck is made composite with shear connectors. The bridge is supported on two-column and cap beam bents with partial web walls for the spans in the stream. The end posts have the date inscription “1956" and a commemorative metal plaque, "Alva J. Hopkins Jr. Bridge." Mr. Hopkins was a politician and business leader from Folkston.
The 1956 steel stringer bridge is technologically significant as Georgia’s first long-span, continuous, "all-welded" beam bridge (Criterion C). As such it represents an important advance in the long-lived steel stringer technology and the transition from riveted to welded beams as the dominant fabrication technology. The beams with their variable depth, curved profile over the piers illustrate the savings in material and fabrication achievable with welding technology. The economical design was "state-of-the-art" for its time, including the use of composite deck to make the deck do useful work in supporting the loads and minimizing the amount of steel required. Bridges with similar characteristics have been standard fare in the state and throughout much of the nation for the past 50 years, and thus this bridge is significant as a design prototype.
Since the mid-19th century, when bridge builders wanted beams of greater depth than the available rolled beams, they have turned to built-up beams. The technique of building up beams by riveting plates, angles, and channels had been used by the railroads prior to the Civil War, and riveting continued to be most common method of building up beams through the first half of the 20th century. With improvements in arc-welding, engineers increasingly turned to fabricated welded beams after WWII. These beams, in depths of up to 5' or more, became available in the early to mid 1950s, and were increasingly used during the 1960s, particularly with the availability of structural steel alloys developed specifically for welding. Bridge engineers made expanded use of welded beams citing material and fabrication savings over riveted built-up beams, which according to one 1960 study could weigh 25-30% more than similar welded beams for span lengths from 90' to 140'.
Georgia was a national follower, not a leader, in the use of welded beams, but Doug Hudson, who began his career as an engineer in the bridge division during the 1950s, recalls the SR 252 over Satilla River bridge as being the first major welded bridge designed by the state bridge division, a recollection confirmed by the 1956 SHD Annual Report. The SR 252 bridge set the precedent for the steadily increased use of welding, such that by the mid 1960s welding had largely replaced riveting as the technique for building up beams for state highway bridges. Georgia was slower than some states to adopt welding because trained welders and fabricators were difficult to find in many areas of the state, and inspecting the quality of the welds required considerable experience or expensive testing equipment. As an illustration of the growing confidence in welding from the mid 1950s to 1960s, the 1956 edition of the SHD’s Specifications conservatively stated that “welding will not be permitted except where it is specified or to remedy minor defects where its use is approved by the engineers.” In 1958, State Bridge Engineer Charles Marmelstein reported that there had been an increase in the use of welding for shop and field work, and the bridge department was working to ensure that it was being done only by “qualified, tested” welders. It was not until the 1966 edition of the Specifications that the SHD dropped the restrictive language and greatly expanded its directions on the proper design, fabrication, and inspection of welded beams and connections. Much of the language was borrowed directly from national guidance issued by the American Welding Society.
James G. Clark, ed. Comparative Bridge Designs (Cleveland: James F. Lincoln Arc Welding Foundation, 1954), pp. 24-40
Omer W. Blodgett, “Welded Plate Girders,” SASHO Proceedings (1960), pp. 32-35.
SHD, Biennial Report (1955-56), p. 109, (1957-58), p. 107; Specifications (1956), pp, 389, 416; (1966), pp. 489-98.
Doug Hudson, Personal Communication with P. Harshbarger (July 1, 2007)