Railway Track & Structures - April 2008 - (Page 39)

Bridge inspection Inspecting four prominent bridges Little Hell Gate Bridge in New York City. Inspecting four prominent railroad bridges, each nearly a century old, involved unique access challenges and some tricky analyses methods. by Craig J. Rolwood, PE, Robert Drew, PE, Hardesty & Hanover, LLP T he period from the mid-1890s through World War I was a “golden age” of railroad bridge engineering in North America. Hardesty & Hanover, LLP, had the privilege between mid-2005 and mid-2006 to inspect four prominent railroad structures that date to the first 20 years of the 20th Century. The bridges are: Little Hell Gate Bridge in New York, N.Y., owned by Amtrak. Tunkhannock Viaduct in Nicholson, Pa., owned by Canadian Pacific Railway. Martin’s Creek Viaduct near Kingsley, Pa., owned by Canadian Pacific Railway. Connecticut River Bridge in Old Saybrook, Conn., owned by Amtrak. In addition to inspection, three out of four of the structures were completely analyzed for load-rating capacity (seismic excluded). Specialized ultrasonic pin testing and concrete testing were performed. Little Hell Gate Bridge The Little Hell Gate Bridge was designed by Othmar Ammann as part of the New York Extension of the Pennsylvania Railroad. While the Little Hell Gate Bridge is a significant structure in its own right, it is overshadowed by its nearby sibling structure, www.rtands.com the famous Hell Gate Bridge designed by Ammann’s boss on the project, Gustav Lindenthall. The Little Hell Gate bridge construction was completed in 1917 and has carried passenger and freight trains ever since. The Little Hell Gate Bridge is a four span, inverted bowstring truss bridge over the former Little Hell Gate between Randall’s and Ward’s Islands. The structure was originally designed to carry four tracks, but the southernmost set has been taken out of service and removed. The bridge carries both eastbound and westbound trains between Boston and Penn Station. In its history, the Little Hell Gate Bridge has seen little maintenance or rehabilitation. The bridge was painted in 1939 and 1995 and a rehabilitation contract was performed in 1992 for minor steel repairs. Approximately 20 years after the bridge was constructed, the Little Hell Gate waterway below was filled in. Randall’s and Ward’s Islands are now a single land mass bordered by the East River to the west, the Bronx Kill to the east and the Hell Gate to the south. The main challenge for testing of the pins at the Little Hell Gate Bridge was not testing pins, but accessing the face of the pins. For nearly 90 years, the pins at Little Hell Gate Bridge had been retained and protected by cast iron caps. Temporarily removing these caps for access to the faces proved much more difficult than anticipated. It was initially planned that the access equipment supplier would remove the caps as part of their scope. The supplier could not remove the rust-frozen bolts that retained the caps. The solution was to hire a small ironwork contractor, who employed a specialized hydraulic torque wrench to loosen the through bolts, remove the caps and then reinstall the caps and bolts. After breaking the first bolt head while trying to figure out how to do the work, the contractor was able subsequently to successfully remove and reinstall the remainder of the caps. Through very tight scheduling and coordination of the access equipment usage, the ironwork contractor and the testing technician, budget and schedule were maintained. An unusual result occurred from the initial load and capacity analysis of the Little Hell Gate Bridge. Detailed research provided an interesting explanation. For Normal Rating per AREMA Chapter 15 Section 7.3, all structural members were found to have capacity in excess of Cooper E-60, except for a few members that were found to have a Railway Track & Structures April 2008 39 http://www.rtands.com

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Railway Track & Structures - April 2008 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Railroads Seeking More Advanced Systems to Handle Materials SKOL Bounces Back From Summer Flood Landmark Railroad Bridges Need Inspection, Too Products and Literature People Calendar Sales Representatives Advertisers Index Website Directory Professional Directory Classified Advertising Chicago Perspective

Railway Track & Structures - April 2008

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