An improved substructuring approach for dynamic modelling – The example of the ITER vacuum vessel

This study deals with the substructuring method that is adopted for treating complex structures, such as the ITER Tokamak, as an assembly of different components or substructures. This method uses basic mass and stiffness matrices combined with conditions representative of the geometrical compatibility along the substructure boundaries. This approach makes it possible to simulate the dynamic behaviour of the (complex) ITER Vacuum Vessel (VV), subjected to dynamic loading (e.g. seismic), by means of a simplified model (finite element discretization) with little loss of accuracy. In this framework, a simplified model of the ITER VV for use in global seismic analyses has been developed and implemented. In order to minimize the wavefront (and hence computational time), the simplified model is made of multiple superelements, each representing a part of the VV. Moreover, in order to reduce the number of Degrees of Freedom (DoFs) needed along the boundaries of the different substructures, a new approach has also been developed for the breakdown of the benchmark model.