Capacity of Circular Bridge Columns Subjected to Base Excitation

Fourteen single-stem cantilever columns with various aspect ratios and axial-load ratios were tested on a shaketable. Test results are compared with state-of-the-art methods used to calculate the strength and displacement capacity of columns. It was concluded that large displacement and curvature ductilities were achieved, even though some of the columns had much less spiral reinforcement than required by modern codes; buckling of the longitudinal reinforcing steel initiated failure in all columns; low-level displacement cycling, less than that which causes buckling of the longitudinal steel, softens the column but does not affect ductility capacity; the effective plastic hinge length is not consistently predicted by present methods, but the calculated displacement capacity using the predicted plastic hinge length is conservative; and a possible increase in flexural strength from dynamic excitation was observed.