[en] The response of thin walled subassembly ducts of hexagonal cross section to an internal pulse of arbitrary shape is studied. A typical reactor core configuration consists of an array of such constituents, each containing an array of fuel elements whose failure may expose the duct to an internal pressure pulse, causing permanent deformation that can reach the order of the wall thickness and cause contact between adjacent elements. Recently a number of papers have tackled the problem of estimating the permanent duct deformation, under various simplifying assumptions. The purpose of this study is to consider the possibility of application of bounding techniques developed in the dynamics of elastoplastic structures, which permit to bound from above total or permanent displacement under given dynamic actions, with a computational effort moderate with respect to a step-by-step evolutive dyanamic analysis. The duct is conceived as a hexagonal frame and the effects of interaction between bending and membrane forces is accounted for, both in the plasticity condition and in its geometric consequences. (Auth.)