Market-Frankford Line of Southeastern Pennsylvania Transportation Authority (SEPTA), with a daily ridership of more than 190,000 passangers plays an integaral role in transportation of the Philadelphia region. During routine inspections of the pedestrian overpass bridges on this line, it was noticed a few of the steel tube members were experiencing longitudinal cracks and blooming. SEPTA tasked Intelligent Infrastructure Systems to provide detailed analysis of these overpasses and recommend solutions.
As part of this project, the Intelligent Infrastructure Systems team reviewed the existing construction drawings and performed multiple site visits to document the location and level of the cracks and deterioration. In addition, finite element modeling and Demand to Capacity (D/C) analysis were performed for these bridges. In addition, a suite of NDE tests were performed on the steel members of these overpasses. The cracking phenomenon was attributed to water accumulation inside the steel tube members, and the overpasses were determined to have significant reserved capacity. Recommendations included methods for repairing the damaged members and for providing drainage for the structural members.