Revision 2 posted to RAM | STAAD Wiki by Seth Guthrie on 4/20/2017 4:01:31 PM
The following VBA enabled spreadsheet allows the user to produce the N-M interaction plots and strain diagrams for a given concrete rectangular column cross section. This was used in a recent column design verification post http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/17799.column-design-verification-as3600-09-ram-concrete.
The N/M values are obtained by resolving the forces and moments at each trial neutral axis depth.
Please see video below for demonstration:
(Please visit the site to view this video)
The tool can be downloaded from here (note that its a Macro Enabled Spreadsheet ): 
Tags: interaction diagram, RAM Structural System, Column Design, Ram Concrete