Crack Repairs to a Fracture-Critical Cross-Girder on the I-476 Bridge over the Schuylkill River - IBC 08-91

摘要

Cracks were recently discovered in the web of a cross-girder on the I-476 Southbound Bridge over the Schuylkill River approximately 12 miles west of Philadelphia, Pennsylvania. The damaged cross-girder, a transverse fracture-critical member, supports the Pier 11 end of the Span 12 main longitudinal stringers. The cracks originated at the base of a connection plate connecting the west fascia girder to the cross girder web. The cracks resulted from out-of-plane distortion of the web at the base of the connection plate. A field testing program using strain gages and LVDT's was implemented by the ATLSS Center of Lehigh University to assess the behavior of web sections at cracked and uncracked connection plate locations. Complementing the field testing, a finite element model was developed for a cross-girder retrofit design. A high-priority repair contract was implemented by the Pennsylvania Department of Transportation, repairing the cracked cross-girderrnweb and ensuring that no new cracks would occur at other cross girder web locations. Finally, ATLSS executed a post-repair testing program, measuring the post-repair performance of the cross girder retrofit. This paper will illustrate the cause of the cracking, outline the objectives and results of the field testing program and retrofit design, and present the results of the retrofit repairs and post-repair monitoring program.