Formulas: Required Strengths

Equation A-7-3

(a) All load combinations shall include an additional lateral load, $N_{i}$, applied in combination with other loads at each level of the structure:

where

$\alpha=1.0$ (LRFD); $\alpha=1.6$ (ASD)

$Y_{i}=$ gravity load applied at level $i$ from the LRFD load combination or ASD load combination, as applicable, kips (N)

$\Delta / L=$ maximum ratio of $\Delta$ to $L$ for all stories in the structure

• $\Delta$ = first-order interstory drift due to the LRFD or ASD load combination, as applicable, in. (mm). Where $\Delta$ varies over the plan area of the structure, $\Delta$ shall be the average drift weighted in proportion to vertical load or, alternatively, the maximum drift.
• $L \quad$ = height of story, in. (mm)

Found in

• FIRST-ORDER ANALYSIS METHOD