Finite element modeling for floating raft isolation systems

Floating raft isolation equipment is a kind of mixed dynamic system which includes springs, dampers, rigid and elastic substructures. It is difficult to construct a reasonable dynamic model for it A highly accurate superelement modeling method for the system is proposed in this paper. In this method, the finite element models of the elastic substructures in the system are firstly reduced in physical space to formulate their superelements respectively. Then they are added to the general finite element model of the floating raft isolation system directly just like usual clements. The reduced finite element model obtained from the proposed method is much smaller than the general in dimension and can retain all the dynamic characteristics in the low and middle frequency range of the general model. Another advantage of this method is that the reduced model is still defined in the physical space. Numerical example shows that the proposed superelement modeling method is an efficient one for floating raft isolation systems.