Effect of the Damping Ratio of the Non-Structural Components on Floor Acceleration Demands in Torsionally Irregular Buildings

Abstract

To investigate the effect of damping ratio of non-structural components on floor acceleration demands in torsionally irregular buildings, reinforced-concrete moment-resisting frame buildings resting on flat ground (regular), and on hill slopes (irregular) are analyzed. Bidirectional linear dynamic analyses are conducted, by applying a suite of far-field ground motions, along two orthogonal axes, to obtain the floor response of the investigated frames. From the obtained floor acceleration response of the investigated buildings, the elastic floor response spectra are derived at two different floor levels: (i) the floor with maximum eccentricity in the irregular building, and the corresponding floor in the reference regular building; and (ii) at the roof levels, for both the regular and irregular buildings, for NSC's damping ratios of 1%, 2%, 5%, and 10%. The effect of damping ratio of the NSCs is studied in terms of damping modification factors, at three different locations on each of the considered floor levels, i.e. (i) at the flexible edge, (ii) at the center of rigidity, and (iii) at the stiff edge. The derived median damping modification factors, as obtained from the time-history analyses are compared with the recommendations of EC 8 and other existing models available in the literature. It is observed that the recommendations of EC 8 underpredict damping modification factors significantly, for non-structural components, tuned to structural modes of vibration, especially, for low damping ratios of the non-structural components, and also for relatively flexible non-structural components, for high damping ratio of the non-structural components.