A simplified approach that reduces the size of the problem to a more viable size is presented for estimating straining actions and drift values for preliminary design against lateral loads. The proposed technique does not dispense any of the main features that affect the structural behavior. The idea is an extension of the sub-frame method proposed by ACI for analysis against gravity loads. A one-story three-dimensional model of the actual building is proposed in order to provide estimates of forces, moments, and drift values for multi-story buildings. The results of a statistical study are used to develop analysis charts for framed systems with
and without shear walls. Different cases of torsion eccentricities are considered. The study is conducted for up to 20-story buildings with different height-width ratios. Equations resulting
from nonlinear regression analyses are presented in order to provide simplified expressions for preliminary analysis of multi-story buildings. Five cases are used to validate that the
method provides good approximations that are adequate for design of multi-story buildings.
Keywords: structures; lateral; seismic; analysis; approximate; model.