Experimental study of as-built and composite materials retrofitted reinforced concrete columns

Four full-size reinforced concrete columns as used in school buildings were cast and tested under reversed cyclic loading. Test results of the two as-built columns confirm that the hysteresis behaviours of a column are considerably improved if special seismic design provisions are used in addition to general design requirements instead of using general design requirements only. Although lateral strength and stiffness are not increased, ductility increases and pinching decreases in hysteretic loops. It is also found that the column conformed to general design requirements can be effectively retrofitted by wrapping with either carbon fibre fabrics or carbon fibre reinforced polymer (CFRP) L-shaped plates if its lateral confinement is upgraded to the same level as that designed based on special seismic design provisions. This retrofitting of lateral confinement is effective at improving the ductility of a column and mitigating the strength degradation, stiffness degradation, and pinching in the hysteretic loops, although the strength and stiffness of the column are not increased.Key words: CFRP L-shaped plate, carbon fibre fabric, retrofit, cyclic loading test.