SEISMIC PERFORMANCE OF A DUCTILE RETROFITTED

Seismic evaluations of many existing deck-truss bridges have revealed the vulnerability of their substructure and members of their superstructure. An innovative retrofit strategy developed by the authors includes replacement of the existing non-ductile end and lower-end bracing with ductile panels by incorporating energy dissipating devices to act as fuses, which can yield and dissipate energy while protecting both superstructure and substructure. A 27-ft long deck-truss bridge model was designed and constructed at the University of Ottawa, and was pseudo-dynamically tested in its as-built as well as retrofitted conditions. Two configurations of Eccentrically Braced Frames, EBF, and Vertical Shear Links, VSL, were used as ductile retrofits, and both performed well. The ductile retrofit devices exhibited a robust hysteretic behavior, dissipated the seismic induced energy and prevented damage in other structural members of the model bridge when it was subjected to scaled El Centro earthquake. This paper describes the retrofit concept, the innovative seismic testing procedure, and the performance of the steel ductile retrofits