Railway Track & Structures - April 2008 - (Page 41)

structural elements of each span are the east and west reinforced concrete arch ribs (the spandrel walls separate in an archway at varied elevations above the ribs) that spring from each pier 125 feet below the top of deck. The Martin’s Creek Viaduct is a 10-span reinforced concrete arch bridge, built in conjunction with the Tunkhannock Viaduct (nine miles distant) as part of the Hallstead Cutoff project. The Martin’s Creek Viaduct is 1,600 feet long with 150-foot-high arches. The structure was completed in 1914 and was originally constructed with three tracks. Today it carries a single center track, which services both northbound and southbound trains on the rail line. The geometric makeup of the bridge varies for the first three spans. Spans 1 and 2 are short single-arch spans that directly support the railway deck. Spans 3 through 10 are similar to the visible spans of the Tunkhannock Viaduct. Each span consists of two arch ribs that support a series of spandrel walls, which in turn support the spandrel arches and deck above. Reinforced concrete parapets extend the length of the bridge along each fascia. Span 3 is shorter than Spans 4 through 10. The span supports seven spandrel walls, five of which rest directly on the arch ribs. Spans 4 through 10 each support eleven spandrel walls, nine of which rest directly on the arch ribs. The two end walls comprise a portion of the tower at each support pier. The ten piers supporting the structure are buried deep below grade. The north abutment span similarly consists of two reinforced concrete arch ribs supporting four spandrel walls, which, in turn, support the deck above. Concrete sidewalls block in CPR’s Martin’s Creek Viaduct in Pennsylvania. the span along the east and west fasciae. A significant portion of the north abutment span is buried under fill material. Concrete testing Limited concrete investigations were performed for the viaducts, the overall purpose being to sample the concrete to check compressive strength against rating analysis assumptions, and to verify some of the mechanisms causing deterioration for estimating the repair quantities and costs. After initial examination of core samples indicated evidences of Alkali-Silica Reactivity, petrographic analysis was performed on two of the core samples to check the extent and the activity of the ASR. It was found that the concrete, while having suffered the effects of freeze-thaw and ASR, was generally in a stable state. It was recommended that a rehabilitation that addresses the visually observed areas of surface deterioration would likely suffice to repair the structure for continuous, acceptable service. www.rtands.com Railway Track & Structures April 2008 41 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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