Model reduction for structures subjected to blast loading by use of dynamic substructuring

In the present study, strategies are developed to enable time-efficient models for structures subjected to blast loading, appropriate for use in a structural design process. Dynamic sub structuring is employed to obtain reduced models with localized nonlinearities, such as predefined plastic hinges in a beam column structure. The parts of the substructures that remains linear elastic are modeled by Ritz-vectors whereas parts with a nonlinear response are retained as physical degrees-of-freedom. Furthermore, a time-stepping method is presented that is shown to be suitable for reduced models including local and predefined rigid-plastic behavior. The proposed methodology is applied and demonstrated in a numerical example of a concrete frame structure. Both the well-established Craig-Bampton method and reduction bases enriched by so-called correction modes are evaluated. For the load case studied, it is shown that the standard Craig-Bampton technique is suitable for reducing the substructures. Furthermore, it is shown that only a few Ritz-vectors are needed to sufficiently describe the deformation of the structure. However, additional modes are needed to ensure an accurate representation of the interface forces between the substructures.