Abstract
ABSTRACTA.comprehensive experimental program has been conducted to evaluate the use of advanced composite materials for the repair and the retrofit of substandard squat bridge columns in California. In an earlier phase of this program, twelve half-scale squat circular and rectangular reinforced concrete columns were tested for shear enhancement in a fixed-fixed condition. Three columns were tested in the as-built condition whereas nine columns were tested after being retrofitted with different composite jacket systems. Recently, second phase of the experimental program has been completed by testing five half-scale circular columns in shear. The emphasis of this paper is on experimental results for three representative column samples from the second phase. These samples include one as-built column that failed in brittle shear without even reaching a ductility of 1.0. This column was re-tested after being repaired and wrapped with a carbon fiber/epoxy jacket. The third column sample was retrofitted with carbon fiber/epoxy jacket. Both the repaired and retrofitted columns underwent flexural failure modes with a significant improvement in their displacement ductility.INTRODUCTIONRecent destructive earthquakes such as Whittier 1987, Loma Prieta 1989, Northridge 1994, have demonstrated the vulnerability of older reinforced concrete bridge columns to fail under seismic attacks. Particularly vulnerable are bridge columns designed prior to the 1971 San Fernando earthquake, since before that time the transverse column reinforcement was only nominally provided, typically #4 bars placed at 12 inch (30.48 cm) on center, independent of column size, strength, or deformation demands. Even after 1971, substandard transverse reinforcement and inadequate seismic reinforcement detailing can be encountered in some of the existing reinforced concrete bridge columns. Due to the insufficient transverse reinforcement and/or seismic detailing in short reinforced concrete bridge columns, different potential failure modes can be observed under seismic actions.