Improved evaluation of inelastic displacement demands for short‐period masonry structures

Abstract

Summary This work discusses the simplified estimation of earthquake‐induced nonlinear displacement demands as required by nonlinear static procedures, with particular attention on short‐period masonry structures. The study focuses on systems with fundamental periods between 0.1 and 0.5 s, for which inelastic amplification of the elastic displacement demand is more pronounced; hysteretic force‐displacement relationships characteristic of masonry structures are adopted, because these structures are more commonly found within the considered period range. Referring to the results of nonlinear dynamic analyses of single‐degree‐of‐freedom oscillators, some limitations of the Eurocode 8 and Italian Building Code formulations are first discussed, then an improved equation is calibrated that relates inelastic and elastic displacement demands. Numerical values of the equation parameters are obtained, considering the amount of hysteretic energy dissipation associated with various damage mechanisms observed in masonry structures. Safety factors are also calculated to determine several percentiles of the displacement demand. It is shown that the proposed equation can be extended to more dissipative systems. Finally, the same formulation is adapted to the estimation of seismic displacements when elastic analysis procedures are employed. Copyright © 2017 John Wiley & Sons, Ltd.

Rintc Project: Nonlinear Dynamic Analyses of Italian Code-Conforming Urm Buildings for Collapse Risk Assessment

“…The first deals with the design parameters (in particular the drift limits associated with shear failure) recommended in NTC08, which are too large for the considered modern masonry typologies (as highlighted by the evidences provided by the increasing number of experimental tests available in the literature) and whose reduction is already foreseen in the draft of revision of NTC. The second deals with the tendency of the N2 method -which is embedded in the nonlinear static assessment procedure -to underestimate the displacement demand for masonry buildings, in case of high values of required ductility [12]. The ongoing research is already addressed to widen all these issues.…”

Investigation of the seismic performance of modern masonry buildings during the Emilia Romagna earthquake series

“…The seismic demand is described by damped spectra [6], [7] as well as inelastic spectra [8], [9] and [10]. The latter one can be determined with a pushover analysis by means of an inelastic static load-deformation curve (pushover curve) calculated under monotonously increasing horizontal loads.…”

“…The damped spectra are calculated by means of an effective damping as the sum of equivalent viscous damping of 5 % according to Eurocode 8 [3] and hysteretic damping based on a comprehensive evaluation of cyclic shear wall tests by Norda [11]. Furthermore, inelastic spectra for intermediate failure of shear and bending are applied as proposed by Guerrini et al [8]. The inelastic spectra are calculated according to the N2 method [3] and a modified version of the N2 method [9].…”

“…Der notwendige seismische Verformungsbedarf wird durch gedämpfte Spektren [6], [7] sowie inelastische Spektren [8], [9] und [10] beschrieben. Letztere kann mithilfe einer Pushover-Analyse mittels einer inelastischen statischen Lastverformungskurve (Pushover-Kurve) unter monoton ansteigenden Horizontallasten ermittelt werden.…”

“…Die gedämpften Spektren werden mittels einer effektiven Dämpfung als Summe aus äquivalenter viskoser Dämpfung von 5 % nach Eurocode 8 [3] und hysteretischer Dämpfung auf Basis einer umfassenden Auswertung von zyklischen Schubwandscheiben-Versuchen durch Norda [11] berechnet. Darüber hinaus werden inelastische Spektren für ein kombiniertes Versagen aus Biegung und Schub angewendet, wie von Guerrini et al [8] vorgeschlagen. Die inelastischen Spektren werden nach der N2-Methode [3] und einer modifizierten Version der N2-Methode [9] berechnet.…”