Following the dramatic failure of the flared column in the Mission Gothic overpass in Southern California during the Northridge earthquake, a multi-phase study of flared columns in bridges in Northern Nevada was undertaken. The study included analytical evaluation of representative bridges, cyclic testing of large-scale as-built and steel jacketed columns, and shake table testing of an as-built column and several columns retrofitted using fibrous composites. The shake table specimens were of 0.3 scale. The primary purpose of the retrofit was to enhance the shear capacity of the columns. Based on a comprehensive evaluation of different retrofit methods, glass composite fabrics were selected for field implementation. The bridge in which the composites are used consists of two parallel 16-span structures supported on three- or four-column bents. The total number of the columns is 94. All the columns have structural flares. Because the columns are flared and non-prismatic, a continuous wrap cannot be applied efficiently. A new method of composite installation was devised in the course of research and is being used in the field. Some of the shortcomings observed during the tests have been addressed in the field by slightly modifying the application of the composite fabrics. As a result of the research only approximately one-half of the columns were found to be in need of retrofit.
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