Plan Irregular Structures: Simplified Approach

Abstract

A proposed simplified method (called) SESA is used to estimate the displacement amplification due to general torsion. The SESA method uses modal response spectrum analysis and takes into account the inelastic behavior by applying the capacity spectrum method. For single-story structures, the single degree of freedom inelastic system is equated to an elastic one, equivalent in translation. The resulting linear equivalent system is defined by the secant to maximum displacement stiffness, and the viscous damping properties are set through equivalence with the hysteretic damping properties of the initial system. Regular modal analysis is applied to the linear equivalent system by using over damped response spectra. This is how the displacement amplification due to torsion (compared to translational only behavior) is determined. A large parametric study was conducted on single-story structures comparing results from the SESA method and from dynamic nonlinear analysis. For the multistory inelastic structure analyzed in this chapter, a force–displacement relationship was determined by static nonlinear analysis. The corresponding single degree of freedom inelastic system was defined by an idealized force–displacement curve. The response of a “real” multistory plan irregular structure was computed by dynamic nonlinear analysis (target of results), by dynamic nonlinear analysis on the single-story model, and by the simplified SESA method. By applying the SESA method, results give a better estimation of the structural response of irregular structures (influenced by general torsion) than engineers can obtain by using code provisions for the most cases (Köber and Zamfirescu, Sci J Math Model Civ Eng 5(2):32–51, 2009).KeywordsGround MotionDynamic Nonlinear AnalysisSeismic InputUltimate Limit StateCode ProvisionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.