Mitigating mass eccentricity effects on the rotational response of setbacks structures: An analytical solution for linear systems

Abstract

Stiffness irregularities induced by the curtailment of some of the lateral load resisting bents introduce serious complexities in the response of multi-story setback buildings under seismic excitations. The effect of floor mass eccentricities may substantially increase the analysis requirements and it may be challenging for practicing engineers to gain an insight into the overall dynamic behavior of setback structures. This paper addresses this issue on a theoretical basis and investigates the torsional response of setback multistory buildings for an arbitrary spatial combination of mass eccentricities. The influence of height-wise mass eccentricities is compared with the nominal no eccentricity case and a simple analytical solution is proposed for minimizing the rotational response of setback structures. The accuracy of the analytical solution is verified using the results of a parametric study on 12-story setback buildings comprising mixed-type curtailed lateral load resisting elements (wall, frame) and representative height-wise variations of accidental eccentricities.