oa Civil Engineer in South Africa - Design consequences of variations in the effective length of slender columns in unbraced reinforced concrete frames

Volume 24, Issue 5
  • ISSN : 0009-7845



It was illustrated in a recent study that a variation in the effective-length value for columns in unbraced steel frames can be responsible for a considerable difference in the design of such columns. It was also shown that such variation in effective length can easily occur when comparing results of effective-length charts with solutions obtained from a rigorous elastic buckling analysis of the entire framework.

In this investigation a number of slender columns in symmetrical and unsymmetrical unbraced reinforced concrete frames have been evaluated wing effective-length values derived from the relevant formulae of the South African Code of Practice for the Structural Use of Concrete, SABS 010W. Subsequently, the same columns were analysed using a more accurate assessment of the effective length. A comparison of the results has shown that vast differences can occur in the prediction of the load carrying capacity of certain slender columns.

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