Torsional Instability in Hysteretic Structures

Abstract

The occurrence of inelastic instability in the response of idealized eccentric building structures exhibiting various forms of bilinear hysteretic behavior is investigated. The Kryloff‐Bogoliuboff method of averaging provides the response to harmonic ground excitation, with results examined in amplitude‐frequency parameter space. The variables involved in the parametric portion of the work are the bilinearity coefficient, the degree of viscous damping, the torsional‐to‐translational frequency ratio and the magnitude of the eccentricity. It is found that pinched elastoplastic behavior representing steel frames with diagonal tension bracing leads to a high degree of instability, whereas ductile moment resisting frames possess full hysteresis loops and thus remain torsionally stable.