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: a) large displacement and curvature ductilities were achieved, even though some of the columns had much less spiral reinforcement than required by modern codes; b) buckling of the longitudinal reinforcing steel initiated failure in all columns; c) lowlevel displacement cycling, less than that which causes buckling of the longitudinal steel, softens the column but does not affect ductility capacity; d) 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 e) a possible increase in flexural strength from dynamic excitation was observed.