Building Construction Handbook, Eighth Edition

The tendency for a column to buckle depends on its slenderness as

determined by the ratio of its effective length to the radius of

gyration about the weaker axis.

Effective lengths of columns and struts in compression ~

L l = 0.7L

Position and direction fixed is location at specific points by

beams or other means of retention. Position fixed only means

hinged or pinned.

Position and

direction fixed

both ends Position and

direction fixed

at one end,

direction only

fixed at the

other end

Position

and

direction fixed

one end only

Position fixed

both ends,

direction fixed

at one end

Position

fixed

both ends

l = 0.85L l =L

l = 1.5L l = 2L

The effective lengths shown apply to the simplest of structures,

for example, single storey buildings. Where variations occur such as

cross braced support to columns, corrective factors should be

applied to the effective length calculations. This data is available

in BS 5950-1: Structural use of steelwork in building. Code of

practice for design. Rolled and welded sections.

End conditions Effective length relative

to actual length

Restrained both ends in position and

direction

0.70

Restrained both ends in position with one

end in direction

0.85

Restrained both ends in position but

not in direction

1.00

Restrained one end in position and

direction. The other end restrained

in direction only

1.50

Restrained one end in position and

direction. The other end unrestrained

2.00

Structural Steelwork -- Effective Column Length