# Moment capacity (section) (Columns: AS 4100)

The (section) moment capacity check is performed
according to AS 4100 clause 5.1 for the moment about the x-x axis (M_{x})
and about the y-y axis (M_{y}), at the point under consideration.

For (member) moment capacity refer to the section Lateral torsional buckling resistance (Member moment capacity).

Note that for all section types, the effective section modulus about the major axis
(Z_{ex}) will be based on the minimum slenderness ratio considering both
flange and web. Internally Tekla Structural Designer will calculate the following:

- flange slenderness ratio, z
_{f}= (λ_{ey}- λ_{ef}) / ( λ_{eyf}- λ_{epf}) - web slenderness ratio, z
_{w}= (λ_{eyw}- λ_{ew}) / ( λ_{eyw}- λ_{epw})

For sections which have flexure major class either Compact or Non-compact, the
effective section modulus about the major axis (Z_{ex}) will then be
calculated by:

- Z
_{ex}= Z_{x}+ [MIN(z_{f}, z_{w}, 1.0) * (Z_{c}- Z_{x})] where Z_{c}= MIN(S_{x}, 1.5 * Z_{x})

Note that for Channel sections under minor axis bending:

- if there is single curvature with the flange tips in compression then
Z
_{ey}will be based on Z_{eyR} - if there is single curvature with the web in compression then Z
_{ey}will be based on Z_{eyL} - if there is double curvature then Z
_{ey}will be based on the minimum of Z_{eyR}and Z_{eyL}

## Eccentricity Moments

Eccentricity moment will be added algebraically to the coincident real moment (at top or bottom of column stack) only if the resulting 'combined' moment has a larger absolute magnitude than the absolute real moment alone.

The resulting 'combined' design moment (major and/or minor) will be that used in moment capacity, combined bending & shear, LTB, and combined actions checks.