Seismic performance of lap-spliced columns with glass FRP

The present paper represents experimental studies on the seismic performance of reinforced concrete circular columns with lap-splice details using glass fibre reinforced polymer (FRP) wrapping. Five full-scale model columns of 1200 mm diameter and 6550 mm height were classified into one column with no lap-splice, one column with lap-splice and three glass FRP retrofitted columns with lap-splice; those models were conducted by quasi-static cyclic loading test. The prototype structure is an existing circular reinforced concrete bridge pier designed by the following pre-seismic codes and constructed in South Korea in 1979. The lap-spliced column was expected to have a brittle failure owing to the bond-slip of lap-spliced longitudinal reinforcement. The retrofitted columns using glass FRP wrapping showed a significant improvement of seismic performance and developed the stable hysteretic loops. However, from the strain gauge readings, the unyieldingness of lap-spliced longitudinal bars was observed regardless of glass FRP thickness. It is concluded that the displacement ductility factor cannot be defined owing to the unyieldingness of longitudinal bar and the estimated displacement ductility factor should be introduced in order to evaluate the performance of the columns with lap-spliced longitudinal bars. Glass FRP retrofit design methods suggested by other researchers were verified in the experiment and a new modified design method was proposed.