Civil Engineering Association

Analysis of machine foundation vibrations: state of the art

The paper reviews the state-of-the-art of analysing the dynamic response of foundations subjected to machine-type loadings. Following a brief outline of the historical developments in the field, the concepts associated with the definition, physical interpretation and use of the dynamic impedance functions of foundations are elucidated and the available analytical/numerical methods for their evaluation are discussed. Groups of crucial dimensionless problem parameters related to the soil
prot~ile and the foundation geometry are identified and their effects on the response are studied. Results are presented in the form of simple formulae and dimensionless graphs for both the static and dynamic parts of impedances, pertaining to surface and embedded foundations having circular,strip, rectangular or arbitrary plan shape and supported by three types of idealized soil profdes: the halfspace, the stratum-over-bedrock and the layer-over-half space. Consideration is given to the effects of inhomogeneity, anisotropy and non-linearity of soil. The various results are synthesized in a case study referring to the response of two rigid massive foundations, and practical recommendations are made on how to inexpensively predict the response of foundations supported by actual soil deposits.