Rebuilding Philadelphia's El

by C. Milton Zuras, Deputy Manager and Chief Engr.; Philadelphia Transit Consultants,
E. Bruce Garber, Lead Structural Engr.; Philadelphia Transit Consultants,

Serial Information: Civil Engineering—ASCE, 1989, Vol. 59, Issue 2, Pg. 52-54

Document Type: Feature article


In reconstructing an urban transit system, the challenge in Philadelphia was to do it without disrupting peak hour commuter traffic or disturbing activities on the street and sidewalks below. The Frankford Elevated, one leg of Philadelphia's Subway Elevated System, carries 50,000 commuters daily to and from the central business district. Built in 1925, the double-track structure being renovated is 5¼ miles long; its three major bridges and 11 stations are also being rebuilt. The need to keep the El in operation from 6 a.m. to 9 p.m. Monday through Friday governs both design and construction. The design incorporates new continuous steel stringer units supporting floor beams encased in a cast-in-place concrete deck. Precast concrete track beams carry new direct fixation continuous welded rail track. A separate structure on precast beams carries the walkway, handrail and cables for power and signals. It also serves as a noise barrier. In special construction areas (curves and crossovers) precast concrete deck slabs with integral haunches and track beams are substituted for the cast-in-place concrete. This reduces the time needed for track alignment. The contractor, working section by section, schedules extensive preparation between weekend and weeknight shutdowns. This includes preliminary demolition, substructure repairs and stringer placement.

Subject Headings: Concrete beams | Precast concrete | Cables | Commute | Walkways | Bridge design | Steel decks | Cast in place | Philadelphia | Pennsylvania | United States

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