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Keywords: optimisation, computational heuristics, plane trusses.

Summary

Nowadays the use of truss structures is very common in different architectural concepts. Such structures can be easily found in a number of usual places and allows the human ingenuity to be freely exercised. A truss consists of bars whose ends are connected at pinjoints. Truss structures are light and very strong.

This paper is focused on demonstrating the application of computational methods, known as heuristics, in search of good solutions for plane truss structural analyses. The main idea is to reduce the overall costs of truss structural projects by means of material reduction and, therefore, by decreasing their weight, subjected to the limitations imposed by the project.

There are several ways to optimise a structure. Some use standard mathematical methods; however, in this work different computational heuristics are used. Moreover, due to the inherent characteristics of the heuristics, there must be a primer necessity for experimentation or calibration because most of the heuristics that are suitable to a given problem, might not always work well for a different class of problem. Consequently, parametric adjustments are essential and a considerable number of tests are imperative, so that better results can be obtained.

It is important to emphasise that in this paper only a parametric optimisation is considered. Hence, the project variables are dimensions or geometric features. The shape of the structure is not modified. In the present context, the cross-sectional area is the only variable used to minimise the weight and the costs of the plane structures studied.

The heuristics tested and, more importantly, customised, in this paper were: genetic algorithms, variable neighbourhood search (VNS), grasp, simulated annealing, tabu search and ant colony optimisation. The details of the implementation of each heuristic can be found in [1].

The algorithms were implemented in conjunction with the finite element software INSANE [2], developed in Java. Three different examples are shown in the paper. They demonstrate the suitability of the use of heuristics to minimise the weight of such structures. The advantages and drawbacks of each method are presented and discussed, including the analysis of the results obtained in the different structural problems, and also compared to the results of the different methods applied to the examples.

References

1: J.P.G. Pereira, "Computational Heuristics Applied to Optimisation of 2-dimensional Trusses", M.Sc. Dissertation, CEFET-MG, Belo Horizonte, Brazil, 2007. (In Portuguese.)
2: F.T. Fonseca, R.L. Pitangueira, "An Object Oriented Class Organization for Dynamic Geometrically Non-Linear FEM Analysis", Proceedings of the Iberian Latin American Congress on Computational Methods in Engineering CMNE/CILAMCE, CD-ROM, Oporto, 2007.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 89 PROCEEDINGS OF THE SIXTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: M. Papadrakakis and B.H.V. Topping Paper 82 Computational Heuristics and their Use in Optimisation of Two-Dimensional Trusses G.F. Moita and J.P.G. Pereira Federal Centre for Technological Education of Minas Gerais, Belo Horizonte MG, Brazil doi:10.4203/ccp.89.82 purchase the full-text of this paper Full Bibliographic Reference for this paper G.F. Moita, J.P.G. Pereira, "Computational Heuristics and their Use in Optimisation of Two-Dimensional Trusses", in M. Papadrakakis, B.H.V. Topping, (Editors), "Proceedings of the Sixth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 82, 2008. doi:10.4203/ccp.89.82 Keywords: optimisation, computational heuristics, plane trusses. Summary Nowadays the use of truss structures is very common in different architectural concepts. Such structures can be easily found in a number of usual places and allows the human ingenuity to be freely exercised. A truss consists of bars whose ends are connected at pinjoints. Truss structures are light and very strong. This paper is focused on demonstrating the application of computational methods, known as heuristics, in search of good solutions for plane truss structural analyses. The main idea is to reduce the overall costs of truss structural projects by means of material reduction and, therefore, by decreasing their weight, subjected to the limitations imposed by the project. There are several ways to optimise a structure. Some use standard mathematical methods; however, in this work different computational heuristics are used. Moreover, due to the inherent characteristics of the heuristics, there must be a primer necessity for experimentation or calibration because most of the heuristics that are suitable to a given problem, might not always work well for a different class of problem. Consequently, parametric adjustments are essential and a considerable number of tests are imperative, so that better results can be obtained. It is important to emphasise that in this paper only a parametric optimisation is considered. Hence, the project variables are dimensions or geometric features. The shape of the structure is not modified. In the present context, the cross-sectional area is the only variable used to minimise the weight and the costs of the plane structures studied. The heuristics tested and, more importantly, customised, in this paper were: genetic algorithms, variable neighbourhood search (VNS), grasp, simulated annealing, tabu search and ant colony optimisation. The details of the implementation of each heuristic can be found in [1]. The algorithms were implemented in conjunction with the finite element software INSANE [2], developed in Java. Three different examples are shown in the paper. They demonstrate the suitability of the use of heuristics to minimise the weight of such structures. The advantages and drawbacks of each method are presented and discussed, including the analysis of the results obtained in the different structural problems, and also compared to the results of the different methods applied to the examples. References 1 J.P.G. Pereira, "Computational Heuristics Applied to Optimisation of 2-dimensional Trusses", M.Sc. Dissertation, CEFET-MG, Belo Horizonte, Brazil, 2007. (In Portuguese.) 2 F.T. Fonseca, R.L. Pitangueira, "An Object Oriented Class Organization for Dynamic Geometrically Non-Linear FEM Analysis", Proceedings of the Iberian Latin American Congress on Computational Methods in Engineering CMNE/CILAMCE, CD-ROM, Oporto, 2007. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £95 +P&P)
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