DYNAMIC BEHAVIOUR OF TURBO-GENERATOR FOUNDATIONS

Abstract

Turbo-generator foundations are large.three dimension-al framed structures built for thermal power plants. Main requirement of these structures is that they should be able to transmitthe dynamic loads to soil keeping the amplitude of vibrations within safe limits. Faulty designs may cause excessive vibrations affecting the performance of the tur-bo-generator and may even lead to closure of the power plant for long periods. The loss of production and cost of corrective measures in such cases may be much more than the cost of structure itself. The current trend of designing foundations as undertuned structures has further necessi-tted the study of dynamic behaviour of these foundations in the entire range,of machine speed.. In the present study an actual foUndation structure of a 110 MW T.G. unit has been selected for analysis. The structure is idealised as an assemblage of space beam ele-ments with six degrees of freedom per node.. Consistent mass matrix approach As been adopted to account for self weight of the structure. Damping is incorporated in the system by using dayleight type damping matrix. Dynamic analysis has been carried out for dynamic loads viz. (i) due to harmonic ground motion and (ii) due to centrifugal forces generated,by revolving eccentric rotor mass. . For both the cases the peak structural responses have been found in the entire range of machine speed