This study was carried out to determine the cause of fatigue cracking in tie plates in a multi-span, non-redundant, steel plate-girder bridge. Repairs have been on-going. The goal was to provide additional information that could be used to explain the cause of cracking and provide guidelines to those responsible for designing the repairs to assure that there would be no further cracks. A review of the cracking history has shown that the cracks have been developing in the tie plates, at similar locations on the bridge. The plates are needed to provide continuity for the transverse floor beams. The designers expected that these bolted plates would act in simple tension, which is a reasonable assumption based on the plans and actual bridge. Initial field monitoring demonstrated however that the plates were acting as bending members, with bending occurring in the horizontal plane. Both the bending and the corresponding deformations were unexpected. As a result, additional field testing was carried out. It was necessary to develop a finite element model to finally explain the behavior causing bending and provide further information needed for the repairs.
Abstract