Automatic calculation of the effective flange width of composite beams is one of the major functions of RAM Steel Beam. For certain framing configurations, the steel design codes are not specific regarding the determination of the effective flange width; for example, the solution for skewed beams or penetrations is not specifically addressed. Determination of effective flange width in such cases has not been the subject of clear and precise guidelines.

Traditionally, for complex beam configurations the Engineer uses "engineering judgment" and a scale to determine the value to be used for distance to adjacent member in calculating the effective flange widths and accepts an educated guess as "close enough". The computer, on the other hand must operate on definite numerical rules. A rational method has been developed and employed by RAM Steel Beam to determine the effect of adjacent beams and/or penetrations on the effective flange width, and select the single distance in any given framing configuration that represents the "distance to adjacent beam." For regular (orthogonal) beam layout configurations it will produce exactly the correct results, while for complex configurations it results in values of effective flange width that may be slightly conservative.

It is important to note that any "error" associated with the program's approach is not likely to be critical, since reasonable differences in the value of effective flange width will generally only have a minor impact on the results.

It should be emphasized that for regular orthogonal framing the algorithm is exact, while for skewed conditions and penetrations it rationally and conservatively approximates the value to use for distance to adjacent member or edge when calculating the effective flange width; it is likely to be at least as accurate as traditional methods.

When calculating the effective flange width for BS 5950 for a simple beam with a cantilever, L_z = L₃ - 0.3L₄, but L_z ≥ 0.7L₃ (see Figure 3 therein). When the slab spans at an angle with respect to the beam, b_e is based on a interpolation which is a function of sin²θ and the values from Clause 4.6(a) and Clause 4.6(b).

When calculating the effective flange width for the Eurocode for a simple beam with a cantilever, L_e = 0.85L when there is a cantilever on one end, and L_e = 0.70L when there is a cantilever on both ends (see Figure 5.1 in EC 4).