American Society of Civil Engineers


Optimizing Structures Subject to Multiple Deflection Constraints and Load Cases Using the Principle of Virtual Work


by Richard Walls, (Research Assistant, School of Civil and Environmental Engineering, Univ. of the Witwatersrand, Johannesburg, South Africa.) and Alex Elvin, (corresponding author), (Professor, School of Civil and Environmental Engineering, Univ. of the Witwatersrand, Johannesburg, South Africa E-mail: Alex.Elvin@wits.ac.za)

Journal of Structural Engineering, Vol. 136, No. 11, November 2010, pp. 1444-1452, (doi:  http://dx.doi.org/10.1061/(ASCE)ST.1943-541X.0000246)

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Document type: Journal Paper
Abstract: This paper presents an iterative automated method for optimizing structures with multiple deflection criteria and load cases. The method is based on the principle of virtual work. Discrete sections are selected for structures with fixed geometries. An optimal structure is one which meets all strength and deflection criteria using minimal material. Four case studies are considered in this paper. A simple portal frame is presented to show how the method works. A 60-story frame is optimized to demonstrate the effectiveness of the method for large structures. A warehouse designed by professional engineers is presented to show how the method can be used for structures subjected to complex loading conditions and deflection criteria. The automated method’s solution is 4.5% lighter than the engineers’. Finally, a stepped cantilever is optimized and compared to results in literature. Material savings of up to 14.4% are realized.


ASCE Subject Headings:
Optimization
Deflection
Load factors
Structural analysis

Author Keywords:
Virtual work optimization method
Automated member selection
Discrete sections
Design