Dynamic Response Analysis Of Turbine-generator Foundation Considering Soil-structure Interaction

This dissertation systematically explores the soil-structure interaction (SSI) andits impact on the dynamic behavior of turbine-generator foundation. To consider theSSI effect and the facility vibration, a sophisticated finite element model isconstructed. The theory of viscous-spring artificial boundary and the equivalentground motion input method are investigated and successfully applied to thethree-dimensional dynamic analys is of a large machine foundation under excitationsfrom both rotor unbalance forces and earthquake inputs. The influence of the SSI onthe response of the system is thus explored by contrasting the results of with andwithout the soil medium and piles. Major findings are as follows:(1) Essential characteristics of the soil-structure interaction is examinedanalytically by formulating the compatibility and equilibrium constraints on thecontact surface between the structure and the soil. Consequently, the transmittingartifical boundary, inlcuding the kinematic interaction and the inertia interaction, isdeveloped. Additionally, the theory of viscous-spring artificia l boundaries andequivalent ground motion input method are introduced, the accurcy of which isverified by several computational examples.(2) A sophisticated finite element model is constructed to consider thesoil-structure interaction effect. All major components of the system, including shaft,rotor, journal bearings, deck, piers, foundation mat, piles, soil mediu m, and artificialboundaries, are considered. The finite element models of rebar and concrete areintroduced and the interaction between them is depicted. Modal information of thesophisticated finite element model has been compared by a simplified model, whichdemonstrates the validity of the sophisticated model.(3) Dynamic responses of the turbine-generator-foundation assembly areobtained through explicit time integration algorithm. Both facility unbalanced forceintroduced by the rotor eccentricity and seismic input are considered. It is found thatthe soil-structure interaction has siginficant influence on the seis mic responses,specifically, displacements and internal forces because of the flexib ility offered bythe soil. When considering the facility excitation, the structural responses, however,are mitigated because of the rediation damping provided by the soil.