When a loading on a structure is uniform, it is common to assign to each structural member a "tributary area" that the member (alone) supports. This assignment is typically performed by a simplistic visual analysis. The assigned area is not truly supported by only the member to which it is assigned. The effects of the (true) uniform loading on the member are similar to the effects if the entire load of the tributary area was applied to the member. Most design codes use the tributary area as the primary parameter in the live load reduction calculations.

RAM Concept calculates tributary areas by applying a unit uniform load to the entire slab and analyzing the flow of the vertical forces. The tributary areas for the following members are calculated from the unit load as follows:

Columns - the vertical reaction, but not less than zero.

Walls - (not currently reduced).

Punching Checks - the vertical reaction, but not less than zero.

Design Strip Segments - the absolute value of the difference between the vertical shears at both ends. When multiple segments make up a span, the segments combined tributary areas are used in calculations.

Design Sections - the absolute value of the shear.

With the above calculations, it is possible (but not common) for the sum of the tributary areas of walls and columns to exceed the total floor area. This happens when one or more of the support reactions are negative.