Inelastic displacement ratio of near‐source pulse‐like ground motions

Abstract

Near-source pulse-like records resulting from rupture's directivity have been found to depart from so-called ordinary ground motions in terms of both elastic and inelastic structural seismic demands. In fact, response spectra may be strong if compared with what is expected from common ground motion prediction equations. Moreover, because not all spectral ordinates are affected uniformly, a peculiar spectral shape, with an especially amplified region depending on the pulse period, may follow. Consequently, inelastic seismic demand may show trends different to records not identified as pulse-like (i.e., ordinary). This latter aspect is addressed in the study reported in this short communication, where a relatively large dataset of identified impulsive near-source records is used to derive an analytical-form relationship for the inelastic displacement ratio. It is found that, similar to what was proposed in literature for soft soil sites, a double-opposite-bumps form is required to match the empirical data as a function of the structural period over the pulse period ratio. The relationship builds consistently on previous studies on the topic, yet displays different shape with respect to the most common equations for static structural assessment procedure

Near -Source Pulse-Like Seismic Demand for Multi-Linear Backbone Oscillators

“…Having as a starting point the dataset used in [9], the pulse identification approaches suggested in [10] and [11] were used to seek out additional directivity ground motions. This search mainly focused on more recent seismic events which provided a multitude of NS recordings, such as the Parkfield 2004 (California) event, the Darfield 2010 and Christchurch 2011 (New Zealand) events and the South Napa 2014 (California) event.…”

“…The effect of varying these parameters on the seismic response to pulse-like ground motions has already been the object of investigation [12]. An additional variable that must be included in the model is pulse period, by virtue of its demonstrable value as a predictor for the inelastic response of this type of ground motion [9], [13]. In this case, pulse period is included as the denominator of the normalized period ratio p TT, in a manner analogous to [9].…”

“…An additional variable that must be included in the model is pulse period, by virtue of its demonstrable value as a predictor for the inelastic response of this type of ground motion [9], [13]. In this case, pulse period is included as the denominator of the normalized period ratio p TT, in a manner analogous to [9]. Consequently, the ground motion IM adopted for the IDAs is strength reduction factor R, defined as per Equation (1).…”

Estimation of inelastic displacement demands of flexible-based structures on soft soils

“…Xu and Xie (2004) and Ziotopoulou and Gazetas (2010) proposed that the periods of an acceleration response spectrum should be normalised with respect to the spectral predominant period (corresponding to peak ordinate) in order to capture the peak spectral response. Similar suggestions have been made to improve the velocity (e.g., Mavroeidis et al, 2004;Xu and Xie, 2007) and displacement (Maniatakis and Spyrakos, 2012) response spectra, and also to modify the ductility reduction factor (e.g., Miranda and Bertero, 1994;Miranda and Ruiz-Garcia, 2002;Gillie et al, 2010), and inelastic displacement ratio (e.g., Miranda, 2000;Ruiz-García and Miranda, 2006;Iervolino et al, 2012) for nonlinear systems. However, all of these studies were restricted to fixed-base building systems and, therefore, the effects of soil-structure interaction (SSI) were not considered.…”

Inelastic Displacement Ratio Spectrum for Near-Fault Ground Motions

“…The categorization and analytical representation of near-fault earthquakes as well as the study of their effects on the seismic behavior of structures are very important research topics today. On e can mention here the works of Makris [8], Makris and Chung [9], Zhai et al, [10], Ruiz-Garcia [11] and Iervolino et al [12]. Although the development that has been accomplished so far, there is still a clear need to understand the behavior of structures subjected to near-source seismic ground motions.…”