Experimental Half‐Space Dynamic Stiffness

Experiments determining the dynamic stiffness of footings attached to or embedded in the model half‐space were conducted. The footings, both circular and rectangular, were forced into vertical vibration, and the dynamic stiffnesses were measured by use of a mechanical impedance measurement technique. The results of the experiments are given by graphs for dimensionless frequencies smaller than eight. The measured results may be approximated with adequate accuracy by second‐degree polynomials in terms of dimensionless frequency. The coefficients of the polynomials for each footing are presented. The polynomial expressions for an elastic case estimated from the results of the experiments are also presented. The model half‐space was made of RTV (room temperature vulcanizing) silicone rubber. The material of the model half‐space has small hysteretic damping; the Poisson's ratio of the material is close to 0.5. The footing‐model half‐space interface can be regarded as bonded.