Seismic retrofit of circular RC columns through using tensioned GFRP wires winding

The aim of this paper is to suggest a jacketing method using glass fiber reinforced polymer (GFRP) wires for reinforced concrete (RC) columns with lap splice of longitudinal reinforcement. For this study, four RC columns were prepared of 400 mm in diameter and 1400 mm in height with an aspect ratio of 3.5; two were lap spliced and the other two had continuous longitudinal reinforcement. One specimen of each of the two types was jacketed by GFRP wires that had a diameter of 1.0 mm. The GFRP wires were tensioned with small force during winding each column. The jacket comprised stepped layers along the variation of bending moment of the column. Cyclic lateral force was applied at the top of the columns, and the top displacement of the columns as well as corresponding force was measured during the bending tests.This study considered the failure of the four tested columns and analyzed their later force–displacement behavior. Additionally, the effective stiffnesses of the force–displacement curves were evaluated. The GFRP wire winding jacket prevented splitting of the lap-spliced reinforcement in the lap-spliced column and delayed buckling of the longitudinal reinforcement. The jacket protected the continuous reinforcement column against steel buckling and concrete spalling off and, thus, induced shear failure in the column. The GFRP wire winding jacket increased the failure drifts of both jacketed columns compared with those of the references.