Retrofit of slender square reinforced concrete columns with glass fiber-reinforced polymer for seismic resistance



This paper explains an experimental research program on the use of GFRP (Glass Fiber- Reinforced Polymer) for retrofitting small-scale slender R/C columns to enhance seismic performance. An important deficiency in many existing nonductile reinforced concrete frames is the inability of the columns to undergo significant deformations while maintaining their load-carrying capacity. As a result, relatively brittle modes of column failure, accompanied by soft storey structural failure mechanisms, are possible. Providing additional confinement to the columns allows them to behave in a more ductile manner.
In this study, six 1/2-scale columns were constructed and tested under cyclic loading to examine the effectiveness of the retrofitting technique for improving the seismic resistance of slender concrete columns. Three columns were tested after being retrofitted with GFRP wraps at the potential plastic hinge zone, while three others were tested in the “as-built” condition. One of the “as-built” specimens was constructed according to ACI (318-02) detailing and five others were built in accordance with ACI (pre.1971). In general, the common mode of failure for the “as-built” samples was a brittle failure due to bond deteriorationof the lap-spliced longitudinal reinforcement. Test results suggest that GFRP wraps can significantly increase the flexural strength and ductility of slender rectangular reinforced concrete columns.