Limitation of effective length method and codified second-order analysis and design

Siu Lai Chan, Y. P. Liu, Z. H. Zhou

Research output: Journal article publicationJournal articleAcademic researchpeer-review

8 Citations (Scopus)


The effective length method for flexural (column) buckling has been used for many decades but its use is somewhat limited in various contemporary design codes to moderately slender structures with elastic critical load factor (λcr) less than 3 to 5. In pace with the use of higher grade steel in recent years, the influence of buckling in axial buckling resistance of a column becomes more important and the over-simplified assumption of effective length factor can lead to an unsafe, an uneconomical or a both unsafe and uneconomical solution when some members are over-designed while key elements are under-designed. Effective length should not normally be taken as the distance between nodes multiplied by an arbitrary factor like 0.85, 1.0, 2.0 etc. Further, the classification of non-sway and sway-sensitive frames makes the conventional design procedure tedious to use and, more importantly, limited to simple regular frames. This paper describes the practical use of second-order analysis with section capacity check allowing for P-δ and P-ΔA effects together with member and system imperfections. Most commercial software considers only the P-Δ effect, but not member and frame imperfections nor P-δ effect, and engineers must be very careful in their uses. A verification problem is also given for validation of software for this type of powerful second-order analysis and design. It is a trend for popular and advanced national design codes in using the second-order analysis as a norm for analysis and design of steel structures while linear analysis may only be used in very simple structures.
Original languageEnglish
Pages (from-to)181-192
Number of pages12
JournalSteel and Composite Structures
Issue number2-3
Publication statusPublished - 1 Apr 2005


  • Buckling
  • Imperfections
  • Steel structures

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Metals and Alloys


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