The optimisation of reinforced concrete beams (RCBs) is a multi-variable problem because of the different effects, such as bending and shear, as well as the reinforcement conditions that are required to resist these forces. The process becomes even more involved when the costs of each material are considered, as the ratio of steel volumes to concrete volumes affect the final solution.

The aim of this paper is to apply PSO to the design of RCBs under user defined loads and to investigate the sensitivity of the solution to the various PSO parameters. The optimisation process involves developing an objective function that is subject to a number of restraints. For the RCB, the objective function will be the total cost of the beam, and the constraints will be limitations of the bending strength, as well as practical size constraints. The development of the objective function has been done using Microsoft Excel Macros and Visual Basic for Applications (VBA).

The program developed for this research optimises the RCB design for cost. The final objective function used for optimisation includes the material cost for concrete, steel reinforcement and formwork along with penalty costs for moment capacity and ductility according to AS3600. The penalty function also includes practical dimension constraints on depth and width.

A series of tests where conducted to investigate the effect of different parameters of the particle swarm algorithm and some refinement of these parameters was conducted. The optimum solution was not heavily influenced by swarm size or acceleration coefficients. The value penalty coefficients had a significant effect on the results, causing non-convergence when very large penalty coefficients where used, and convergence on non-viable results when very small penalty coefficients where used.

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