Optimization of single-span single-storey portal frame buildings

Abstract

Many structural designs are done without comprehensive consideration for achieving optimum design. To achieve minimum mass optimization, a mathematical model was developed in this study and subjected to British Standard (BS 5950) code requirements for structural integrity as constraints. Visual basic application (VBA) codes were written into a spreadsheet environment to implement the model. The developed optimization model was validated using different sample shed structures of same volume (729m?) but of different height to span to length (H: b: L) ratios which were obtained using the Ratio method and the Step size method. The best parameter ratio of height to length to breadth obtained was 1:1:1 which is similar to what was obtained by other authors. Parametric design case study analysis was also performed for three different design situations with a given span b, heights H and h and frame spacing S. The minimum masses of steel for a fixed plan area of the buildings were obtained for each of the three scenarios. It is recommended that design engineers should consider varying major frame parameters such as frame spacing and heights at pre-design stages in order to obtain optimal values of parameters which will ensure economical structures.