## Design moments

The design bending moment is illustrated in Figure 4 and defined as:

Mo, = Min {|Mtop|, |Mbottom|} + ei NEd M02 = Max {|Mtop|, |Mbottom|} + ei Na ei = Max {/o/400, ft/30, 20} (units to be in millimetres). Mtop, Mbottom = Moments at the top and bottom of the column M 0e = 0.6 M02 + 0.4 M01 > 0.4 M02 M2 = NEd e2 where NEd is the design axial load and e2 is deflection due to second order effects

M0, and M02 should be positive if they give tension on the same side.

A non-slender column can be designed ignoring second order effects and therefore the ultimate design moment, MEd = M02.

The calculation of the eccentricity, e2, is not simple and is likely to require some iteration to determine the deflection at approximately mid-height, e2. Guidance is given in Figure 3.

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