Report No.: CCEER-99-1

Title: Seismic Retrofit of Flared Bridge Columns with Steel Jackets

Authors: C. Caywood, M. Saiidi, and D. Sanders

Date: February 1999

Sponsoring Agency: Nevada Department of Transportation (NDOT)

Performing Organization:
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557


This study was undertaken to provide a seismic retrofit design for flared bridge columns located in Reno, Nevada. Previous studies 20, 21 determined that the shear capacity of some of these columns is inadequate. This study investigates the behavior of two potential retrofit designs for these columns. Two specimens were tested as part of the experimental study, representing different retrofit designs using steel jackets. The experimental study concentrated on the behavior of the retrofitted specimens with respect to previously tested as-built specimens. Using the data and observed behavior of the specimens, the preferred retrofit design between the two specimens was chosen.

In addition to the experimental study, analytical studies were performed. The purposes of the analytical studies were to verify analytical procedures with the experimental results, and to optimize the retrofit design. The analysis included calculating the lateral load versus deflection envelopes for:

  1. Both specimens under the conditions of the experiment
  2. Different retrofit cases of the specimen which was determined to have the preferred retrofit design

Both specimens were determined to have adequate shear capacity, however, it was believed that by refining the preferred retrofit design, the displacement ductility could be increased. To accomplish this, the jacket gap location was varied and the location that yielded the maximum column displacement ductility was determined (Abstract by authors).