Title:
Cumulative Seismic Damage of Circular Bridge Columns: Variable Amplitude Tests
Author(s):
Ashraf El-Bahy, Sashi Kunnath, William Stone, and Andrew Taylor
Publication:
Structural Journal
Volume:
96
Issue:
5
Appears on pages(s):
711-719
Keywords:
bridges (structures); cyclic loads; damage; ductility
DOI:
10.14359/724
Date:
9/1/1999
Abstract:
The findings from an experimental study to investigate cumulative seismic damage in reinforced concrete circular bridge piers is pre-sented. Twelve identical quarter-scale bridge columns, designed in accordance with current AASHTO specifications, were fabricated and tested to failure. Results from Phase I testing, which included constant amplitude tests to determine the low-cycle fatigue character-istics of the bridge column, were presented in a companion paper. This paper summarizes results of variable amplitude testing that focused on the effects of load path on cumulative damage. The imposed displacement histories were obtained from analytical simu-lations of the model column subjected to a sequence of earthquakes of varying duration and magnitude. Test observations indicate that failure is generally initiated by confinement inadequacy and the rup-ture of the transverse spiral reinforcement. The tests also demon-strated the potential for low-cycle fatigue fracture of the main longitudinal steel when the specimen was subjected to relatively larger displacement amplitudes, typically in excess of 4% lat-eral drift. A fatigue-based damage model, derived from the constant-amplitude tests completed in Phase I testing, was applied to the observed response of the six specimens tested in this phase. Findings from the study indicate that the energy capacity of members is ductility-dependent and that fatigue-based damage models offer a reliable means of assessing seismic structural performance.