If a first order analysis is performed, the user can designate either the effective length method or the amplified sway method be performed. For the amplified sway method either a specific k_amp value is assigned or the program can calculate k_amp per load combination. Similar to the case of second order design is performed as follows. For each load combination, design moments will be calculated for the gravity (non-sway), and lateral (sway) load cases independently. That is, the sum of all gravity load case moments is stored separately from those of the lateral load cases in the combination.

• Per 4.8.3.3.4 the factors mx, my and myx, are only applied to the non-sway (gravity) moments. That is terms of the form mM are replaced by kampMsway + mMnonsway.
• If the effective lengths are calculated per Annex E then RAM Frame will use the non-sway mode in-plane effective length factors.
• No lower limit of 0.85 will be placed on the magnitude of mx, my and myx.

Where designated to be calculated per load combination the amplified sway factor k_amp is calculated assuming cladding, architectural walls etc are not considered in the lateral stiffness and thus:

K_amp = λcr / (1.15 λcr – 1.5)

Refer to the section Calculating λcr per Load Combination (BS5950-1:2000) for an explanation of how the program calculates λcr for each load combination.