Turbo Generator Machine Foundations Subjected to Earthquake Loadings

Abstract eng:
For industrial partners, actual simplified design rules in line with the growth of knowledge regarding earthquake engineering are essential for competitiveness. As turbo generators are placed all over the world, i.e. in different seismic hazard zones, not only machine sets but also the foundations have to be standardised and able to resist certain earthquake loading levels. Prior to the release of new or revised turbo generators (foundations), extensive static and dynamic calculations are carried out to confirm the foundation outline and basic dimensions, and also verifying the resistance against unfavourable load combinations. Based on gained knowledge of detailed seismic analyses, practical design approaches have been elaborated for different kind of foundation types (mainly spring mounted, table mounted and raft foundations); and, for some machine manufacturers, summarised in specific design criteria. This paper focuses on the a.m. investigations and studies, proposes simplified design principles for large machine foundations and will show specific requirements for turbo generators, which are sometimes in contradiction to seismic design demands. For practicable design of pedestals, foundation supports and machine anchorages, it is preferred to transfer seismic loads to static equivalent forces. Here, apart from local parameters such as ground acceleration and soil amplifications, the main concern is the load distribution over the height. Especially for compact raft foundations, the soil-structure-interaction is an eminent attribute, as first eigenfrequencies are in strong dependence to the bedding situation, and are often situated within the critical earthquake frequency range with regard to the soil amplification.

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