Seismic performance of circular hollow RC bridge columns

A column test under cyclic lateral loads with a constant axial load was performed to investigate seismic performance of circular hollow reinforced concrete columns. Twenty-one test specimens with the following dimensions were tested: column lengths of 4,000 and 5,400 mm; outside cross-sectional diameters of 1,000 and 1,400 mm; inside cross-sectional diameters of 500, 750, and 980 mm; and therefore hollow ratios of 0.5, 0.7, and 0.75 defined by the inside diameter divided by the outside diameter. The test variables were the transverse steel ratio, arrangement of the transverse steel, longitudinal steel ratio, existence of the longitudinal steel near the inside wall face, hollow ratio, and axial force ratio. Test results showed that the outside transverse steel confined the concrete effectively, which resulted in decreasing neutral axis at failure, increasing ductility, and decreasing damaged area of the inside wall face. It was also found that, for the columns with compression-controlled section, the existence of the inside transverse steel could reduce the damaged area, even though significant confinement effect and displacement ductility were not achieved by the inside transverse steel.