Abstract

ELVIN, A; WALLS, R  and  CROMBERGE, D. Optimising structures using the principle of virtual work. J. S. Afr. Inst. Civ. Eng. [online]. 2009, vol.51, n.2. ISSN 2309-8775.

This paper presents a method for optimising structures with a given geometry and loading based on the principle of virtual work. The Virtual Work Optimisation Method, or VWOM, that was developed minimises the mass of the structure while meeting building code strength requirements, and flexibility (or deflection) criteria. The optimisation can be readily constrained by grouping together members with the same sectional properties. The VWOM automates most of the design process, obviating the requirement of experience and expertise in stiffening a structure. Three case studies were conducted using the VWOM: (i) the benchmark optimisation ten-member truss; (ii) a truss frame designed by professional engineers; and (iii) a 24-storey frame. The results of the VWOM were compared with published or available solutions. The VWOM produced structures that were 0,9 to 15,1% lighter than those produced by the methods used in the comparisons. If every member was allowed to have its own sectional properties, the VWOM found even lighter structures (by as much as 19,5%). The VWOM is less computationally expensive than the comparison methods, requiring two or three orders of magnitude fewer iterations to converge to the solution.

Keywords : automated member selection; discrete sections.

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