BS 5950

The effective length of a beam can be controlled by setting the criteria from the Beam Design Defaults dialog. The effective length, Le, of the unbraced segment depends on the end conditions of the segment.

The following assumptions are used unless overridden in the Beam Design Defaults dialog:

Loads are assumed to be normal loads (applied at the shear center).
For a segment continuous through brace points, Le is equal to the unbraced length.
Where a beam is continuous through a column or supporting girder an effective length factor of 0.7 is assigned to that end of the segment. This is indicative of the column providing the beam a measure of restraint for bending about the minor axis.
Where a beam is pinned at a support, or where a cantilever tip occurs, the effective length factor is taken as the value provided by the engineer in the Beam Design Defaults dialog.
The effective length factor for an entire segment is taken as the average of the factors at the segment ends.