INFLUENCE OF DAMPING ON THE PREDICTION OF DYNAMIC RESPONSE OF MOMENT FRAMES BY NONLINEAR STATIC METHODS

摘要

Modern seismic codes allow nonlinear static methods of analysis for the prediction of the seismic response of existing buildings. These methods are mainly related to two approaches available in literature: N2 method proposed by Fajfar and Capacity Spectrum method proposed by Freeman. Bosco et al. carried out a numerical investigation on a wide set of steel moment frames and showed that the prediction of the displacement demand obtained by N2 method provides in most cases a conservative estimation of the maximum response obtained by nonlinear dynamic analysis. In this paper, the prediction obtained by Capacity Spectrum method, which takes into account the beneficial effect of the energy dissipation by an equivalent viscous damping, is compared to that of N2 method and to the actual displacement demand evaluated by nonlinear dynamic analysis. Different formulations available in literature are considered for the evaluation of the equivalent viscous damping.