The foundation module uses the provisions of ACI 318 for rigid foundations. The foundation is determined to be rigid by length to width ratio values. The warning acknowledges that this is a flexible foundation. The engineer will need to either change the footing dimensions to be within guidelines OR do some additional checks based on ACI flexible foundation design.
The following equations are used to determine rigid footing classification:
In order to assign a spread footing to a model the following conditions must be met:
Additionally, in order to assign a continuous footing, the user must select exactly two nodes with supports. The program does not strictly enforce the requirement that the nodes have the same elevation (Y coordinate), but that is the best practice since the continuous footing design assumes a flat foundation.
Ram Elements Modules