Performance of Precast Concrete Bearings on Steel Stringers for an Elevated Light Rail

Le résumé fourni par la source

Reconstruction of the Frankford elevated light rail line, originally constructed beginning in 1915, was completed in 1997. As part of the reconstruction, removal of portions of the existing structure and installation of new structural elements was performed. The original foundation, steel columns and cross girders remained while the deck and its support substructure were replaced. The new rail deck consisted mainly of precast concrete panels. Those portions of the precast concrete deck panels, which bear on and are attached to the supporting structural steel stringers, are referred to as haunches. The intent of certain connection details was to allow the concrete deck panels to be free to move or slip when loaded. In 1997, Southeastern Philadelphia Transit Authority (SEPTA) identified several haunch locations where concrete spalled at the bearings. By 2007, it was found that the number of distressed haunches had grown to over 5,000. An investigation was performed to review existing haunch conditions, investigate the precast concrete haunch distress, identify the cause of distress and recommend repairs. This work consisted of a document review of previous studies, field investigation and testing, laboratory testing, haunch distress inspection, and repair prototype constructability and testing. The investigation, testing, and analysis of data were performed to determine the extent and cause(s) of haunch distress, and determine options for repairing delaminated and spalled haunch concrete. This paper will describe the observed behavior of the haunch connections in the field and the lab in order to understand the causes for the precast concrete spalling. The haunch reinforcement repair to resist the unintentional partial composite action is described.

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