Optimal design of long-span steel portal frames using fabricated beams

Ross McKinstray, James B.P. Lim, Tiku T. Tanyimboh, Duoc T. Phan, Wei Sha

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)
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This paper considers the optimal design of fabricated steel beams for long-span portal frames. The design optimisation takes into account ultimate as well as serviceability limit states, adopting deflection limits recommended by the Steel Construction Institute (SCI). Results for three benchmark frames demonstrate the efficiency of the optimisation methodology. A genetic algorithm (GA) was used to optimise the dimensions of the plates used for the columns, rafters and haunches. Discrete decision variables were adopted for the thickness of the steel plates and continuous variables for the breadth and depth of the plates. Strategies were developed to enhance the performance of the GA including solution space reduction and a hybrid initial population half of which is derived using Latin hypercube sampling. The results show that the proposed GA-based optimisation model generates optimal and near-optimal solutions consistently. A parametric study is then conducted on frames of different spans. A significant variation in weight between fabricated and conventional hot-rolled steel portal frames is shown; for a 50 m span frame, a 14–19% saving in weight was achieved. Furthermore, since Universal Beam sections in the UK come from a discrete section library, the results could also provide overall dimensions of other beams that could be more efficient for portal frames. Eurocode 3 was used for illustrative purposes; any alternative code of practice may be used.
Original languageEnglish
Pages (from-to)104-114
Number of pages11
JournalJournal of Constructional Steel Research
Early online date22 Oct 2014
Publication statusPublished - 1 Jan 2015


  • hot-rolled steel
  • fabricated beams
  • portal frames
  • genetic algorithms
  • serviceability limits
  • buckling limits


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