EVALUATION OF SEISMIC RETROFIT METHODS FOR REINFORCED CONCRETE BRIDGE COLUMNS

The objective of this task was to collect and review information on the current state-of-the-art for seismically upgrading vulnerable concrete bridge columns. Over 200 (national and international) references were collected. A questionnaire was developed and disseminated to obtain information on the column retrofitting activities of the various states (and Canadian provinces). The survey had a response rate of over 77%. The majority of published information is on one of the two most commonly used column retrofit techniques: steel jacketing and composite fiber jacketing. Several other techniques such as infilled walls in multi-column piers, external prestressing using high strength bars, and internal column strengthening, among others, were examined. The majority of research completed to date has been on reduced-scale laboratory specimens subjected to lateral loads. These tests have shown that column jacketing can substantially improve the ultimate ductility and lateral load capacity of reinforced concrete columns. Jacketing can arrest the two common column failure modes: loss of confinement with subsequent slip in column lap splices, and premature brittle shear failure of columns with inadequate shear capacity. The structural performance of steel and composite jacketed specimens is similar. An evaluation technique for assessing the relative merits of dissimilar was developed. Included in this technique are the following four parameters: structural performance, cost, environmental performance, and design process. To date, there is insufficient data available to use the technique developed. Areas requiring further investigation have been presented in the final chapter of the report. A classification chart which assists the reader in determining the type of information a particular reference contains is presented in an appendix. Also included is a cross-reference list which assists the reader in locating where a specific reference is cited in the report.