Advanced Steel Construction

Vol. 1, No. 1, pp. 105-128 (2005)



Rodrigo Gonçalvesand Dinar Camotim2

1ESTB, Polytechnic Institute of Setúbal, R. Stinville 14, 2830-114 Barreiro, Portugal

2Civil Engineering Department, ICIST/IST, Technical University of Lisbon,

Av. Rovisco Pais, 1049-001 Lisbon, Portugal.

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Some concepts and results dealing with the design and safety checking of members integrated in plane steelframes are presented and discussed. Initially, attention is paid to the identification and clarification of a number ofambiguities related to the application of the buckling length concept to frame members. Then, the safety checking ofcolumns integrated in frames is addressed and it is shown that, if their buckling lengths are “correctly determined”, only oneparticular column, designated as “critical column”, needs to be checked −a finding which leads to the proposal of a “frameoptimisation procedure”. Next, the safety checking of beam-columns integrated in frames is dealt with: the application ofthe interaction formulae appearing in the upcoming EN version of Eurocode 3 is addressed and particular attention is paidto the appropriate choice of the buckling length and “equivalent moment factor” values, both in terms of safety and accuracy. Inaddition, one proposes an alternative approach to use the beam-column interaction formulae, which is based on the results ofgenuine second-order elastic analyses. In order to illustrate the application and assess the validity and advantages of theconcepts and procedures presented throughout the paper, one presents numerical results concerning simple (two-bar)structural systems and these results are compared with “exact” frame ultimate (collapse) load values, yielded by second-orderplastic zone analyses that incorporate member initial imperfections. On the basis of the above comparative study, it ispossible to draw several conclusions and, in particular, it is shown that the proposed approaches consistently yield accurateand conservative frame strength estimates.



Steel frames, columns, beam-columns, buckling length, equivalent moment factors, non-dimensional slenderness, frame slenderness, Eurocode 3.


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