Abstract
An energy-based approach facilitates the explicit consideration of the damage associated with both maximum displacements and cumulative plastic deformations under earthquakes. For structural systems that can undergo pulse-like seismic ground motions close to causative faults, an energy-based approach is deemed especially appropriate with respect to well-established force- or displacement-based strategies. In such a case, in fact, most of the damage is attributable to the dominant pulse-like component, which usually occurs into the velocity time history of the seismic ground motion, thus implying high energy levels imparted to a structural system. In order to enable the implementation of an energy-based approach in the analysis and design of structures under near-fault pulse-like seismic ground motions, this study presents a comprehensive numerical investigation about the influence of seismological parameters and hysteretic behavior on the spectra of the following energy-related parameters: inelastic absolute and relative input energy; input energy reduction factor; hysteretic energy dissipation demand; hysteretic energy reduction factor; dimensionless cumulative plastic deformation ratio. Closed-form approximations are proposed for these spectra, and the numerical values of the corresponding parameters have been also calibrated (with reference to both mean and standard deviation values) as functions of earthquake magnitude, type of hysteretic behavior (i.e., non-degrading or degrading) and ductility level. The outcomes of this study are meant to support the derivation of design spectra for the energy-based seismic design of structures under near-fault pulse-like seismic ground motions.
Highlights
A significant number of strong ground motions recorded during recent earthquakes at sites close to the causative seismic fault is characterized by the presence of a dominant pulse-like and often high-amplitude component, which is especially evident in the fault-normal velocity waveform
The present study provides a systematic investigation about the seismic demand for inelastic structural systems subjected to the near-fault pulse-like seismic ground motion by focusing on energy-related parameters rather than on those expressed in terms of forces or displacements
The dataset of horizontal fault-normal pulse-like seismic ground motions employed in the present study was prepared by collecting relevant time histories from the Engineering Strong-Motion (ESM) database, the Italian Accelerometric Archive (ITACA), the Pacific Earthquake Engineering
Summary
A significant number of strong ground motions recorded during recent earthquakes at sites close to the causative seismic fault is characterized by the presence of a dominant pulse-like and often high-amplitude component, which is especially evident in the fault-normal velocity waveform. This kind of behavior is different from the one that typically occurs under high-frequency seismic motions; in such a case, the energy dissipation takes place over a relatively long time window, and the affected structures undergo to a higher number of reversals in their seismic response without experiencing too much damage if properly designed, since high spectral accelerations usually correspond to a moderate level of the energy transmitted by the earthquake [27] In this context, the present study provides a systematic investigation about the seismic demand for inelastic structural systems subjected to the near-fault pulse-like seismic ground motion by focusing on energy-related parameters rather than on those expressed in terms of forces or displacements. Closed-form approximations for these spectra are proposed in Section 6, where a regression analysis is carried out to estimate the numerical values of the corresponding parameters (with reference to both mean and standard deviation values) as a function of earthquake magnitude, type of hysteretic behavior (i.e., non-degrading or degrading) and ductility level
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