ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/439391
PROJECT Paducah & Louisville Railway Bridge J23.7 New railroad bridge pushes the limits of typical rail construction to replace a 120-year-old, 120-ft-tall trestle structure by Scott Wojteczko and Michael O’Connor, Alfred Benesch & Company Paducah & Louisville (P&L) Railway Bridge J23.7 was originally constructed in the 1880s as a curved, 700-ft-long, 120-ft-tall steel trestle structure. It was built along land that would eventually become the Fort Knox Army Base. Less than ½ mile down the track is P&L Railway Bridge J23.3, a structure of similar age and construction to P&L Railway J23.7, though shorter and on a tangent. These two historic freight rail bridges, known together as the Muldraugh bridges, allow the P&L to • transport commodities across Kentucky, and • maintain rail access for military shipments to Fort Knox Army Base (as the only rail line servicing the base). The age and condition of the existing trestle structures had necessitated numerous repairs and strengthening measures over the past 20 years to maintain continual rail service. With repair costs mounting each year and both structures beyond their expected service lives, P&L made the decision in 2009 to move forward with the replacement of both P&L Railway Bridge J23.3 and P&L Railway Bridge J23.7. The P&L initiated a two-phase program that would commence with the replacement of P&L Railway Bridge J23.3 and culminate with the replacement of P&L Railway Bridge J23.7. After the financial commitment that had been made in replacing P&L Railway Bridge J23.3, the P&L was awarded a Transportation Investment Generating Economic Recovery (TIGER) Grant in 2011 towards the replacement of the more-complex P&L Railway Bridge J23.7. Construction on P&L Railway Bridge J23.7 began in the fall of 2012 and was completed in the summer of 2014. Railway Re-Alignment The original P&L Railway Bridge J23.7 was built on a 5-degree horizontal curve spanning a valley that contained a creek, hiking trail, and Fort Knox private-access road. A large fill had been constructed on the west side of the valley to minimize the overall bridge length. Reconstruction of P&L Railway Bridge J23.7 on the existing alignment would have been highly constrained by the location of the existing steel trestle towers, with rail closures required to systematically remove and replace sections of the existing structure. The project team elected to construct P&L Railway Bridge J23.7 offset north of the existing structure, with span lengths maximized to minimize the number of substructure units required. Piers could not be located within the existing creek, trail, and roadway. Additionally, the topography of the region is highly irregular through the valley, with vertical exposed rock faces in some locations and 50 ft of overburden material in others. The final bridge layout includes 14 spans, with maximum span lengths of 85 ft and an overall bridge length of 1031 ft. Piers reach elevations 120 ft above grade in the deepest portions of the valley. The horizontal curve across the bridge has been reduced from 5 to 4 degrees to reduce track maintenance and enhance sight distances. The bridge is within a vertical curve, with a maximum grade of 1.3%. PROFILE PADUCAH & LOUISVILLE RAILWAY BRIDGE J23.7 / WEST POINT, KENTUCKY BRIDGE DESIGN ENGINEER: Alfred Benesch & Company, Chicago, Ill. CONSTRUCTION ENGINEER: GEM Engineering Inc., Louisville, Ky. PRIME CONTRACTOR: Haydon Bridge Company, Springfield, Ky. PRECASTER: Prestress Services Industry LLC, Lexington, Ky.—a PCI-certified producer OTHER MATERIAL SUPPLIERS: Reinforcement: Gerdau, Muncie, Ind.; and Bearings: D.S. Brown, North Baltimore, Ohio