Abstract
The vibration response of equipment foundation structures is not only affected by the structural stiffness and mass, but also greatly influenced by the degree of a soil-foundation structural interaction. Furthermore, the vibratory performance of equipment foundation structures supported by pile systems largely depends on the soil-pile dynamic stiffness and damping, which are variable in nature within the speed range that machines operate at. This paper reviews a method for evaluating effective soil-pile stiffness and damping that can be computed by Novak’s method or by commercial software (DYNA6, University of Western Ontario). A series of Finite Element (FE) time history and steady-state analyses using SAP2000 have been performed to examine the effects of dynamic soil-pile-foundation interaction on the vibration performance of equipment foundations, such as large compressor foundations and steam/gas turbine foundations. Frequency-dependent stiffness is estimated to be higher than frequency-independent stiffness, in general, and, thus, affects the vibration calculation. This paper provides a full-spectrum steady-state vibration solution, which increases the reliability of the foundation’s structural design.
Highlights
The importance of foundational dynamic stiffness and damping in the vibration’s assessment has been addressed in many literatures such as Novak’s method [1], Kausel’s approach [2], and Roesset’s research [3].The conventional method for evaluating soil stiffness and damping is based on the classical theory of vibrations of a disk supported on top of an elastic half-space [4]
This paper proposes several state-of-the-art methods for evaluating effective soil damping that could be modelled in FE (Finite Element) software i.e., SAP2000 and GTSTRUDL
The frequency-dependent interaction effect [6,7] is accomplished by numerical simulations utilizing DYNA6 [8] and is incorporated in the frequency domain steady-state vibration analysis in this paper
Summary
The importance of foundational dynamic stiffness and damping in the vibration’s assessment has been addressed in many literatures such as Novak’s method [1], Kausel’s approach [2], and Roesset’s research [3]. The conventional method for evaluating soil stiffness and damping is based on the classical theory of vibrations of a disk supported on top of an elastic half-space [4]. This theoretical solution is limited to few simple foundation configurations and soil profiles. Field experiences show that the beneficial effects of radiation damping in mitigating foundational vibrations, as predicted by the elastic half-space vibration theory, may not always be effective [5] Such cases include large compressor foundations, combustion turbine generator/steam turbine generator (CTG/STG) table-top foundations, and other large foundational structures that support high-speed (30 Hz or higher) vibratory equipment. The frequency-dependent interaction effect [6,7] is accomplished by numerical simulations utilizing DYNA6 [8] and is incorporated in the frequency domain steady-state vibration analysis in this paper
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