Seismic performance and retrofit of reinforced concrete bridge bents

The University of Nevada, Reno is currently developing a study on the seismic behavior of two-column bents with drop cap beams built prior to the 70's. Three 1/4 scale models were built with typical geometric and reinforcement properties and using the same construction details used at the time. One specimen was tested as built under the Sylmar record (Northridge 1994). The other two identical specimens were retrofitted, using carbon fibers wraps and longitudinal fibers on one bent, and an infill wall between the columns in the other. Both retrofitted specimens were tested under the same conditions as those of the as built. The fragile shear failure mode of the as built specimen was successfully modified with the retrofits, enhancing the performance and ductility. Overall performance and the effectiveness of the retrofit methods implemented used are discussed. The results indicate that the retrofits used are effective, however there are some concerns on the failure modes and excessive increase of strength.