The Arch Bridge Mystery

by Rafail Veksler, P.E., (M.ASCE), Chf. Struct. Engr.; Parsons Brinckerhoff Quade & Douglas, Inc., Philadelphia,
Abhay P. Thorat, P.E., (M.ASCE), Sr. Structural Engr.; Parsons Brinckerhoff Quade & Douglas, Inc., Philadelphia,

Serial Information: Civil Engineering—ASCE, 1999, Vol. 69, Issue 9, Pg. 48-51

Document Type: Feature article


For some years, concrete from the Manayunk Bridge�a long-idle, spandrel-arch railroad bridge in Philadelphia�had been spalling toward the streets and river below. While a system of nets caught the falling concrete, it did nothing to stop the deterioration. A study released in 1992 was inconclusive as to the cause, but since the Manayunk neighborhood has experienced a commercial and residential revival, the regional transportation authority decided to restore the historic bridge in preparation for the possible return of railroad traffic. Engineers conducted extensive investigations and concluded that a lack of waterproofing on the deck and a poor drainage system had allowed an alkali-silica reaction to damage the concrete. The solution included replacing concrete on the arch fascias and the spandrel arch surfaces, and adding waterproofing and a perforated piping collector system.

Subject Headings: Railroad bridges | Arch bridges | Rail transportation | Concrete | Drainage systems | Arches | Transportation studies

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