There is a significant difference in the strength design of axial/flexural members according to the 318-02 Code. Axial/flexural members are classified as "compression controlled" or "tension controlled" in accordance with 10.3.3 and 10.3.4 depending upon the tensile strain in the extreme tension reinforcement at the ultimate strain conditions (when the concrete compressive strain reaches 0.003). When the tensile strain is sufficiently large as to provide ample ductility, the section is defined as "tension controlled" and a strength reduction factor of 0.9 is used. When the tensile strain is at or below the balanced strain condition, the member is defined as "compression controlled" and a strength reduction factor of 0.65 is used. Between these tensile strain values a linear transition between 0.65 and 0.9 is used.

RAM Concept uses the ratio of neutral axis depth to the depth of the resultant tensile force (rather than the depth of the extreme tension steel) to calculate the strength reduction factor. For singly reinforced sections, the results will be identical to using the depth of the extreme tension steel. For sections with multiple layers of reinforcement (including post-tensioning), this implementation will provide a smoother transition and will be conservative. In determining the compression-controlled strain limit, RAM Concept uses the maximum of 0.002 and f_y / E_s. The tension-controlled strain limit is 0.005.

Reinforcement areas are not deducted from the concrete area.

Strain compatibility design is used.

RAM Concept ’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an over-reinforced section. See "Ductility" for more information on applying ductility requirements.

Post-tensioning Tendon forces are ignored

Axial forces (loads) on the section are either considered or ignored based on the settings in the design section of design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force.

At "T", "L" and "Z" beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design.

User E_s values are used

For sections with multiple values of f ’_c, the f ’_c of each concrete block is used appropriately.

For cross sections with very small moments, the amount of reinforcement calculated by RAM Concept may exceed the amount necessary. This is because RAM Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement RAM Concept selects is that necessary for axial force equilibrium in the cross section.