Columns, sway frames and BS 5950-1:2000

BS 5950-1:2000 introduced major changes to column design, particularly in sway frames. Some of the new clauses are badly draughted and contain anomalies. The new requirements for columns in sway frames make design more complicated and also more conservative. However analysis of the stability of columns in sway frames demonstrates that the second order analysis and notional lateral forces now required for load Combination 1 are unnecessary, as adequate allowances for buckling and initial imperfections are already included in standard column design stresses. Revisions to rectify these problems are proposed.

Alasdair N. Beal, BSc, CEng, MICE, FIStructE
Thomasons LLP