Development of dynamic test for analyzing free vibrations of bridge piers

A quick release test on piles was designed to aid in the understanding of the soil-pier interface of bridge piers under seismic loads. All facets of the test were designed and proof tested in the laboratory before field tests were performed. The test was specifically for use in loess soil, but was designed to be applied to tests in any type soil.

The results of the preliminary field tests demonstrate the acceptability of the design as a quick release test to determine the dynamic characteristics of the soil-pile interface. The tests resulted in a static stiffness of 66.67 kips per inch in loess soil. The tests also provided a frequency of 15 hertz for a unit mass pile. This frequency should be reduced considerably by attaching a lumped mass to the system. A damping ratio of 13.9 percent of critical damping also was recorded. This quick release test demonstrated the acceptability of the procedure for future tests.