This study investigated retrofitting measures applied to 2/5-scale shear-deficient columns representative of rectangular bridge columns in the Puget Sound area of Washington state. The retrofit methods studied included external hoops applied over the height of the column and full-height rectangular steel jacketing. Test specimens consisted of a single column connected at the base to a rectangular footing. The specimens were subjected to increasing levels of cycled inelastic displacements under constant axial load. The performance of the specimens was evaluated in terms of load capacity and ductility.
Tests on the as-built column resulted in a brittle shear failure at the calculated yield displacement, i.e., at a displacement ductility factor of 1. Both retrofit methods improved the behavior of the deficient column.
With the external hoop retrofit, performance of the retrofitted columns was only moderately improved over that of the as-built column. Brittle fracture of the retrofit hoops limited the load-carrying capability and ductility enhancement, and displacement ductility factors of 2 and 4 were achieved.
With the rectangular steel jacket retrofit, performance was significantly improved over that of the as-built column. The jacket retrofit resulted in a ductile column response with good load-carrying capability through a displacement ductility factor of 8. When this retrofit was applied over the full height of the column, the steel jacket increased the column shear strength enough that flexural failure resulted. Although buckling of the steel jacket and longitudinal reinforcement occurred near the maximum moment section, sufficient confinement to the hinging region was provided by the buckled steel jacket to maintain load-carrying capability.