Capacity Reserves in the Global Buckling Analysis of Steel Columns

In steel skeleton multi-storey buildings the global buckling analysis of columns is very often carried out on basis of individual single span members regarded as cut out of the system. With continuous columns and similar heights between the floors the section in the bottom storey will be governing due to the highest compressive load. In order to be on the safe side and to receive quick results it is common practice to have this section analysed with pinned ends.

Capacity reserves result from the fact that both, the stepped compressive load and the actual restraints at the column base, shorten the buckling length of the column and thus increase the buckling load. These effects are investigated in the present paper for practical column dimensions. It is shown, in which cases it is worthwhile to undertake a higher effort in structural analysis.