Dynamic analysis and optimisation using morphological indicators

This paper presents a basic analysis methodology to predict if a structure meets the design requirements concerning dynamic behaviour at conceptual design stage, combining a single degree of freedom model and morphological indicators (MI). MI are dimensionless numbers allowing to represent a structural property (volume, displacement, eigenfrequency,…) with a limited numbers of variables. The theory of MI is based on the use of a fully stressed design and optimisation from the point of view of resistance (Ultimate Limit State). Achieving satisfying vibration behaviour of a structure is a serviceability constraint (Serviceability Limit State) and is therefore not necessarily met by ULS-optimised solutions, especially in lightweight design. If the vibration behaviour is not acceptable the possibilities offered by a tuned mass damper, topology modification and stress level reduction are discussed. In this case, the use of MI as a design tool is no longer advantageous.