Capacity of circular bridge columns subjected to base excitation

Fourteen single-stem cantilever columns with various aspect ratios and axia l-load ratios were tested on a shaketable. Test results are compared with s tate-of-the-art methods used to calculate the strength and displacement cap acity of columns. It was concluded that: a) large displacement and curvatur e ductilities were achieved: even though some of the columns had much less spiral reinforcement than required by modern codes; b) buckling of the long itudinal reinforcing steel initiated failure in all columns; c) low-level d isplacement cycling, less than that which causes buckling of the longitudin al steel, softens the column but does not affect ductility capacity; d) the effective plastic hinge length is not consistently Predicted by present me thods, but the calculated displacement capacity using the predicted plastic hinge length is conservative; and e) a possible increase in flexural stren gth from dynamic excitation was observed.