ABSTRACT
Power generating sets, comprising large diesel engines and alternators, are often mounted on mass concrete foundation blocks which distribute the load over the base area to the supporting soil or rock. Piled foundations would be preferred where the ground conditions are poor. The block may be anything from twice to
five times the mass of the machinery. The performance of block foundations was discussed fully by Smith (1989). The idealized structural system consists of a large rigid mass resting on a semi-infinite elastic medium with dynamic forces and moments applied to the mass. This is an example of ground structure interaction for which the mathematical analysis is relatively advanced and inconvenient for general design practice (Arnold eta/. 1955). Various attempts have been made to derive simplified formulae including Hsieh (1962) who proposed an equivalent mass restrained by elastic elements, the system having an appropriate amount of damping derived from semi-infinite elastic theory. The theory of ground structure interaction is discussed briefly in Section 9.3.2.
