Seismic retrofit of lap splices in nonductile square columns using carbon fiber-reinforced jackets

Many reinforced concrete frame structures built prior to the 1970s were designed only for gravity and wind loads. Compression-only reinforcing details used in the columns of these structures are often associated with nonductile lap splice failures when subject to lateral load. The objective of this study is to investigate the use of carbon fiber-reinforced polymer.(CFRP) jackets as a seismic retrofit measure for deficient lap splices. Three full-scale building column specimens with lap spliced longitudinal reinforcing bars were tested under combined axial and cyclic lateral load. The columns were intentionally designed such that the lap splices would fail prior to achieving the flexural capacity of the column. One column was tested without retrofit as a control specimen, while the others were retrofitted with CFRP jackets. Comparisons are also made with results of tests of similar columns without lap splices. It is shown that with a CFRP jacket retrofit, the nominal flexural capacity of the column may be achieved. The ductility of the repaired column, however is limited by slip of the spliced bars, resulting in a splitting failure in the lap splice region. Additionally, the behavior of the lap splice is accurately modeled and predicted using existing lap splice behavior models regardless of the presence of the retrofit jacket.