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Nonlinear static analyses based on either inelastic or elastic spectra with equivalent viscous damping: A parametric comparison Enzo Martinelli, , Ciro Faella Highlights • The paper proposes a systematic comparison between CS Method and the N2 Method. • A dimensionless formulation is firstly derived for making both methods comparable. • A systematic parametric comparison in terms of predicted ductility demand is proposed. • The general trends of predictions deriving from the two methods are pointed out. • NLTH analyses are proposed to assess the accuracy of the two aforementioned methods. Abstract In the last decade, nonlinear static procedures emerged as the reference practice-oriented analysis method for structures under seismic actions. These procedures are generally based upon two key steps: (i) performing a nonlinear static (pushover) analysis under lateral forces and (ii) evaluating the seismic demand through the so-called capacity spectrum obtained at the end of the previous step. This paper specifically deals with the latter and proposes a parametric comparison between two wide classes of methods formally based on conceptually alternative approaches for defining the demand spectra in nonlinear static analyses of dissipative structures. First of all, the paper outlines the main conceptual aspects of such alternative methods and reports their key operational details. Particularly, it proposes a dimensionless formulation of their relationships and demonstrates that both methods are based upon a small and almost common set of dimensionless parameters. Therefore, a wide parametric analysis is proposed to compare the ductility demand obtained by means of these two alternative methods with the aim of describing and quantifying the different predictions obtained by applying such methods. Finally, the results of nonlinear time-history analyses are proposed for assessing the two aforementioned methods. Keywords Capacity spectrum; Hysteretic dissipation; Viscous damping; Parametric comparison ES2015_PrePrint.pdf

An Investigation of Efficiency and Accuracy of Energy-Based Capacity Spectrum in Estimating the Seismic Demands of Buildings Original Article, C40 Vakili H, Shakeri K, Seyyedi Viand S.M, Azadi Hir M. Journal. Civil Eng. Urban. 3(5):251-259. 2013 ABSTRACT:In the conventional methods of pushover analysis, the capacity spectrum is obtained with linking roof displacement to base shear, while this relationship only is meaningful in pushover analysis with load pattern that is proportional to the first mode. In the higher modes, changes of the roof displacement is not proportional to the changes of other stories displacement, and even in some cases roof displacement is decreased with increasing base shear and reverses. Therefore, using the roof displacement for establishing the capacity spectrum in the higher modes is faced with ambiguities. Using the energy method for establishing the capacity spectrum of structure is one of the proposed methods to eliminate these ambiguities. In this method, not only the amount of the roof displacement, but also the amount and the sign of other stories displacements participate in the establishment of capacity spectrum of structure. In this research, the accuracy and efficiency of energy-based capacity spectrum has been studied on two steel moment-frame buildings under different earthquakes for using in different pushover analysis with various load patterns. The results show that using the energy method for establishing the capacity spectrum not only eliminate the existent ambiguities and problems in establishment of capacity spectrum, but also the responses of the different nonlinear static analysis by using the energy-based capacity spectrum instead of the conventional capacity spectrum (based on roof displacement) have better accuracy and efficiency. Keywords: Seismic Demands, Modal Pushover Analysis, Higher Modes, Capacity Spectrum, Energy Method منبع: [Hidden Content] دانلود: [Hidden Content].,40-251-259.pdf J. Civil Eng. Urban.,40-251-259.pdf