Abstract:
The current South African Steel design code, SANS 10162-1, has a set of effective length factors
for overhang beams which is independent of the geometrical properties of the beam and the
lengths of the backspan and cantilever. This simple approach is consistent with several other
international steel design codes and design guidelines. These effective length factors make no
allowance for the stiffness of the adjacent span, but in reality warping at the supports allows
interaction buckling between the cantilever and beam segments.
In the research presented in this paper the backspan-to-overhang-segment ratio was
investigated with the view of refining the calculations for determining the critical buckling
moment of overhang beams. The scope was limited to beams with lateral and torsional
restraints at the supports, and to shear centre and top flange loading applied at the free
overhang end. Physical experiments and finite solid element analyses were used to determine
the relationship between the critical moments and the beam buckling parameters. A simplified
design calculation procedure was formulated, which includes a buckling parameter to include
warping at the supports and allows interaction buckling between the beam segments. The
buckling parameter is dependent on the size of the beam, the length of the overhanging
segment and the ratio of backspan-to-overhang length.
