Effect of serviceability limits on optimal design of steel portal frames

Duoc Phan, James Lim, Tiku Tanyimboh, Mark Lawson, Yixiang Xu, S Martin, Wei Sha

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)
889 Downloads (Pure)


The design of hot-rolled steel portal frames can be sensitive to serviceability deflection limits. In such cases, in order to reduce frame deflections, practitioners increase the size of the eaves haunch and / or the sizes of the steel sections used for the column and rafter members of the frame. This paper investigates the effect of such deflection limits using a real-coded niching genetic algorithm (RC-NGA) that optimizes frame weight, taking into account both ultimate as well as serviceability limit states. The results show that the proposed GA is efficient and reliable. Two different sets of serviceability deflection limits are then considered: deflection limits recommended by the Steel Construction Institute (SCI), which is based on control of differential deflections, and other deflection limits based on suggestions by industry. Parametric studies are carried out on frames with spans ranging between 15 m to 50 m and column heights between 5 m to 10 m. It is demonstrated that for a 50 m span frame, use of the SCI recommended deflection limits can lead to frame weights that are around twice as heavy as compared to designs without these limits.
Original languageEnglish
Pages (from-to)74–84
Number of pages11
JournalJournal of Constructional Steel Research
Publication statusPublished - Jul 2013


  • optimization
  • hot-rolled steel
  • serviceability limits
  • portal frames
  • real coded niching GA


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