Structural optimisation using the principle of virtual work
Date
2011-05-24
Authors
Walls, Richard Shaun
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Abstract
This dissertation presents a new method for the automated optimisation of
structures. The method has been developed to: (1) select sections to satisfy
strength and deflection requirements using minimum material, and (2) efficiently
group members.
The member selection method is based on the principle of virtual work, and is
called the Virtual Work Optimisation (VWO) method. It addresses multiple
deflection and load case constraints simultaneously. The method determines
which sections provide the highest deflection and strength resistance per unit
mass. When compared to several other methods in the literature, and designs from
industry, the VWO method produced savings of up to 15.1%.
A parametric investigation of ungrouped, multi-storey frames is conducted using
the VWO method to determine optimal mass and stiffness distributions. Unusual
mass patterns have been found. Diagonal paths of increased stiffness are formed
in the frames, which suggests truss behaviour.
A grouping algorithm is presented which determines how efficiently to create a
specified number of groups in a structure. The VWO method has been
incorporated into the automated algorithm to optimise the grouped structures.
Members are grouped according to their mass per unit length. In the algorithm an
exhaustive search of all feasible grouping permutations is carried out, and the
lightest structure selected. Results produced are up to 5.9% lighter than those
obtained using ad hoc grouping configurations found in the literature and based
on experience.
Description
MSc(Eng),School of Civil and Environmental Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, 2010
Keywords
Virtual Work Optimisation, structural optimisation, virtual work