Seismic performance of bond controlled RC columns

An experimental investigation was carried out to examine the enhancement of seismic performances of reinforced concrete (RC) columns such as shear strength and ductility by controlling the bond of longitudinal reinforcements. Four 300×300 mm square RC columns with ordinary bonded reinforcements and completely unbonded reinforcements were tested under reversed cyclic loading. The test results showed that this method is very effective in completely altering the failure mode at the ultimate state from an undesirable shear to a ductile flexural one. The hysteretic load–displacement behavior of the columns with unbonded reinforcements, however, greatly differs from those of the ordinary ones. A restoring force model capable of capturing the hysteretic behavior of the unbonded columns was therefore proposed. The proposed model was then experimentally verified by conducting pseudo-dynamic tests. The restoring force model was finally applied to conduct seismic response analysis by using input earthquake waves from Hyogoken Nanbu earthquake and El Centro earthquake.