Cyclic Lateral Load Response of Bridge Column-Foundation-Soil Systems in Freezing Conditions

The potential effects of seasonal freezing on seismic response of integrated bridge column-foundation systems were investigated using three outdoor large-scale test units installed in glacial till soil. Two of these test units had identical dimensions and reinforcement details and consisted of 0.61 m diameter columns and foundation shafts. These units, which were tested during summer and winter at ambient temperatures of 23°C and -10°C, respectively, revealed the impact of the effects of seasonal freezing. When compared to the test at 23°C, the identical unit tested at -10°C showed 170% increase in effective elastic stiffness, 44% increase in average lateral force resistance, a 0.84 m upward shift to the maximum moment location, and a 64% reduction in the length of the plastic region in the foundation shaft. The third test unit had a 0.61 m diameter column with a 0.91 m diameter foundation shaft. The use of the oversized foundation minimized the effects of frozen condition on the response of the column although the construction of this column-shaft system was relatively complex. A summary of this experimental investigation is presented in this paper.