Konstantinos Kalfas: The dynamics of utility poles by considering soil-structure interaction (SSI)

Motivated from the large number of transmission and distribution utility poles that experience excessive vibrations during wind storms, this work sheds light to the eigenvalue analysis of a partially embedded flexural, prismatic column with embedded length, L, and exposed length, h, and accounts for the interaction with the soil of its embedded portion. The presentation will show that the dynamics of a partially embedded prismatic column depend solely on the embedment ratio, ε = L/h and a dimensionless stiffness that expresses the relative stiffness between the soil surrounding the embedded length (level of fixity) and the exposed portion of the flexural column. A partially embedded prismatic column exhibits a finite number of eigenmodes that are lower than its rigid-body mode; while, the associated eigenfrequencies are lower than the corresponding eigenfrequencies of the fixed-end cantilever. For a typical value of the embedment ratio ε = L/h = 0.15, the study uncovers that for any eigenmode n > 3, of the fixed-end cantilever, the partially embedded, prismatic column exhibits n + 1 eigenmodes. These rich dynamics result from soil-structure interaction and are associated with the way that the flexural patterns of the partially embedded column emerge from the ground.