Cold-formed steel portal frames are a popular form of construction for low-rise commercial, light industrial and agricultural single-storey buildings of spans of up to 30 m. Such buildings typically use cold-formed steel channel-sections for the columns and rafters, with joints formed through back-to-back gusset plates bolted to the webs of the channel-sections. This chapter investigates effects of frame topography on the frame weight and cost per metre length of building. An optimisation technique that uses a real-coded genetic algorithm is applied to search for the optimum topography of steel portal frame for a building, to minimise the cost of the main frame of such buildings. The key decision variables considered in this algorithm consist of both the spacing and pitch of the frame as continuous variables, as well as the discrete section sizes. A routine taking the structural analysis and frame design for cold-formed steel sections is embedded into the genetic algorithm. The real-coded genetic algorithm handles effectively the mixture of design variables, with high robustness and consistency in achieving the optimum solution. All wind load combinations according to Australian code are considered in this research. Also, frames with knee braces are included for which the optimisation achieved even larger savings in cost.
KeywordsFrame Spacing Load Combination Exhaustive Enumeration Portal Frame Knee Brace
- AS/NZS1170-0 (2002) Structural design actions—part 0: general principles. Australian/New Zealand Standard. Australian Institute of Steel Construction, SydneyGoogle Scholar
- AS/NZS1170-1 (2002) Structural design actions—part 1: permanent, imposed and other actions. Australian/New Zealand Standard. Australian Institute of Steel Construction, SydneyGoogle Scholar
- AS/NZS1170-2 (2002) Structural design actions—part 2: wind actions. Australian/New Zealand Standard. Australian Institute of Steel Construction, SydneyGoogle Scholar
- AS/NZS 4600 (2005) Cold-formed steel structures. Australian/New Zealand Standard. Australian Institute of Steel Construction, SydneyGoogle Scholar
- Eid MA, Elrehim MA, El-kashef F, Swoboda G (2010) Optimization of ground improvement techniques in tunnelling using genetic algorithms. In: IV European Conference on Computational Mechanics (ECCM 2010), ParisGoogle Scholar
- Phan DT, Lim JBP, Sha W, Siew CYM, Tanyimboh TT, Issa HK, Mohammad FA (2013) Design optimization of cold-formed steel portal frames taking into account the effect of building topology. Eng Optim 45. doi: 10.1080/0305215X.2012.678493