Input Notes

• As2, As3 and As4 reinforcement (and associated d-dimensions) are optional, except As4 is required for cases with tensile axial load;

• Positive (+)P - compressive force;
  Negative (-)P - tension force;

• Moment causes tension at the bottom of the section and is always positive;

• Provide Material and Strength Data only if strength analysis is desired;

• Provide Working Stress Data only if stress analysis is desired;

Output Notes

• (T) denotes tension;
  (C) denotes compression;

• In strength analysis, if an axial load is in tension (Pu<0) and a center of gravity of the reinforcement is not coincidental with the center of gravity of the concrete section then ‘C’ and strain are not calculated (see last design note);

Design Notes

• Strength analysis is based on an equilibrium and stress/strain compatibility as outlined in the ACI and ASHTO Codes;

• The tensile strength of the concrete is neglected;

• In strength analysis stress in reinforcement = 29000ε ≤ Fy;

• β1 = 0.85 for F'c ≤ 4.0 ksi;
  β1 = 0.85 - 0.05(F'c-4) ≥ 0.65 for F'c > 4.0 ksi;

• If an axial load is in tension (Pu<0) and a center of gravity of the reinforcement is not coincidental with the center of gravity of the concrete section then the moment resistance (Mr) is calculated equal to Mo(1-Pu/Po), where
  Mo – moment resistance corresponding to Pu=0
  Po - axial tensile resistance corresponding to Mu=0 (Po is based on a portion of the specified reinforcement with the center of gravity at the center of gravity of the concrete section;

© 2009-2010 Anatoly Klevitsky