Slender concrete beams (ACI 318)
Spacing of lateral supports for a beam shall not exceed 50*b1
In the program the lateral supports are taken as the distance between the faces of the supports, and for simplification, b is taken as the web width bw
If the above check fails then a 'Slender span' warning is displayed.
Effects of lateral eccentricity of load are considered in determining spacing of lateral supports.
Footnotes
1 ACI 318-08 and ACI 318-11 Section 10.4