Six reinforced concrete columns were tested at the University of Washington to evaluate the effects of cyclic loading on damage progression in lightly confined reinforced concrete circular bridge columns. The six columns, which were nominally identical, were typical of those built by the Washington State Department of Transportation until the mid-1970s.
The columns were subjected to a variety of lateral-deformation histories. These tests showed that increasing the number of cycles from 1 to 15 at each deformation level resulted in an approximately 30% reduction in the maximum column deformation at the three final damage states: 20% and 50% loss of lateral load, and the loss of axial load.
Three damage models (Park-Ang, modified Park-Ang, and cumulative plastic deformation) were used to evaluate the effect of cycling on damage accumulation. There was no clear correlation between the e ffect of cycling and damage accumulation for the six columns using the Park-Ang damage model because of the model’s sensitivity to the yield displacement. Better correlations were obtaine d when using the cumulative plastic deformation damage model because it is relatively insensitive to small changes in the yield displacement. This model is also convenient because it does not require estimates of the column’s force-displacement relationship.
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