CSX TRANSPORTATION BR. A605.25, OVER THE ST. MARY'S RIVER, TRUSS COUNTER REMOVALS AND EYE-BAR CONVERSIONS WITHOUT DISRUPTION TO RAIL TRAFFIC

摘要

CSX Transportation (CSXT) Bridge A605.25 over St. Mary's River, near Folkston, GA, is a 1907 vintage structure measuring 1,405.67-ft total length, comprised of north and south steel approach viaducts, and the main river span consisting of a 160-ft pin-connected Camelback through truss, with counters. The counters had become worn and slack over their 112-year plus life, exhibiting significant oscillation under live loading. With the 160-ft truss being in generally good condition, CSXT was looking for a unique counter repair that could be achieved with CSXT field forces, under continuous rail traffic, performing the work using "natural" work windows. The unique repair was more of a truss reconfiguration than repair. Reconfiguration of the truss encompassed the removal of the counters and the conversion of the main diagonal eye-bars into stress reversal members. This conversion incorporated the installation of 4~L4x4x3/4 and 3/8" thick stay plates, transforming the existing eye-bars into boxed sections. The uniqueness of the project was the implementation of scaffolding, field-side and trackside of the trusses, the use of ATV winches, and no disruption to rail traffic. CSXT forces field drilled 1,088 ~ 15/16" diameter holes, 136 holes per eye-bar, between trains. Holes were left open until the installation of the angle components. Incorporating drilling jigs, ensured consistent drilled bolt hole locations in the eye-bars. ATV winches aided the movement of the drilling jigs, as well as the lifting and placement of the angles.