Dynamical analysis and optimisation of statically determinate strusses at conceptual design stage

Thomas Vandenbergh, Benjamin Verbeeck, Willy De Wilde

Onderzoeksoutput: Conference paper

Samenvatting

Within the framework of sustainable development we strive for constructions with a minimum volume of material. When we only consider criteria on resistance and buckling, it is shown that even at the stage of conceptual design a clear hierarchy among the different truss topologies can be established with Morphological Indicators (MI). MI are dimensionless numbers that represent a characteristic performance of a structure (e.g. volume) and depend only on a small number of variables (in its most simple formulation only the slenderness of the structure). We define the slenderness as L/H, L being the horizontal and H the vertical dimension of the rectangle, which inscribes the structure. This allows us to compare the efficiency of structures objectively, with only a reduced number of variables to consider. The problem is formulated as follows: given a load case (e.g. distributed load), structural typology and geometry (e.g. Warren truss) and supports (e.g. hinge and roller), we seek the slenderness that minimises a MI (e.g. volume indicator). Up to now, dynamic effects -such as resonance- were not considered when designing constructions with MI. However, an optimum obtained by minimising the volume, and only considering strength performance, often results in solutions with a problematic dynamic behaviour. To avoid resonance the stiffness and/or the damping charac-teristics must be modified in order to shift the eigenfrequencies outside the range of possible excitation frequencies. This yields a volume increase, additional equipment and as a consequence a cost raise. With an optimisation process that considers dynamic behaviour at the stage of conceptual design, an optimum can be obtained without the necessity to alter the (strength-optimised) construction drastically afterwards. In this study the undamped solutions for statically determinate trusses are analysed.
Taking stiffness into account compares the different truss types on a new priority scale, gen-erating new optima. This implicates a significant change in the truss choice at conceptual de-sign stage. The solutions depend logically on the forbidden frequency range(s).
This approach forms a first step to a design philosophy that considers all the stiffness con-straints at conceptual design stage and is called design for stiffness.
Originele taal-2English
TitelProc. of the ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Rethymno, Creta, Greece, 13-16 June
RedacteurenM. Papadrakakis, D.c. Charmpis, N.d. Lagaros, Y. Tsompanakis
Pagina's253
Aantal pagina's1
StatusPublished - 13 jun 2007
EvenementUnknown - Stockholm, Sweden
Duur: 21 sep 200925 sep 2009

Publicatie series

NaamProc. of the ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Rethymno, Creta, Greece, 13-16 June

Conference

ConferenceUnknown
Land/RegioSweden
StadStockholm
Periode21/09/0925/09/09

Bibliografische nota

M. Papadrakakis, D.C. Charmpis, N.D. Lagaros, Y. Tsompanakis

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