Reduced-order model for nonlinear dynamical structures having a high modal density in the low-frequency range

Abstract : This research is devoted to the construction of a reduced-order computational model for nonlinear dynamical structures which are characterized by the presence of numerous local elastic modes in the low-frequency band. Therefore these structures have a high modal density in the low-frequency band and the use of the classical modal analysis method is not suited here. We propose to construct a reduced-order computational model using a small-dimension basis of a space of global displacements, which is constructed a priori by solving an unusual eigenvalue problem. Then the reduced-order computational model allows the nonlinear dynamical response to be predicted with a good accuracy on the stiff part of the structure. The methodology is applied to a complex industrial structure which is made up of a row of seven fuel assemblies with possibility of collisions between grids and which is submitted to a seismic loading.