Search

This study develops new equations for predicting the constant-strength inelastic displacement ratio (CR) by considering nonlinear single-degree-of-freedom systems subjected to near-fault ground motions. To this aim, an energy-based parameter, the MEA/MEV ratio, is firstly considered for characterizing the properties of pulse-like records. "MEA" and "MEV" represent the Maximum Energy of the half-cycle pulse in Acceleration and Velocity time histories, respectively. The effects of the MEA/MEV ratio on the CR spectra are investigated in terms of elastic-perfectly plastic hysteretic behavior. Finally, a simplified equation for estimating the CR spectra is developed, and its accuracy is evaluated by calculating the error measures. [ABSTRACT FROM AUTHOR]

Summary: Near‐fault ground motions can impose particularly high seismic demands on the structures due to the pulses that are typically observed in the velocity time‐histories. The velocity pulses can be further categorized into either a distinct acceleration pulse (acc‐pulse) or a succession of high‐frequency, one‐sided acceleration spikes (non‐acc‐pulse). The different characteristics of velocity pulses imply different frequency content of the ground motions, potentially causing different seismic effects on the structures. This study aims to investigate the characteristics of the two types of velocity pulses and their impacts on the inelastic displacement ratio (CR) of single‐degree‐of‐freedom systems. First, a new method that enables an automated classification of velocity pulses is used to compile a ground motion dataset which consists of 74 acc‐pulses and 45 non‐acc‐pulses. Several intensity measures characterizing different seismological features are then compared using the two groups of records. Finally, the influences of acc‐pulses and non‐acc‐pulses on the CR spectra are studied; the effects of pulse period and hysteretic behavior are also considered. Results indicate that the characteristics of the two types of velocity pulses differ significantly, resulting in clearly distinct CR spectral properties between acc‐pulses and non‐acc‐pulses. Interestingly, mixing acc‐pulses and non‐acc‐pulses can lead to local "bumps" that were found in the CR spectral shape by previous studies. The findings of this study highlight the importance of distinguishing velocity pulses of different types when selecting near‐fault ground motions for assessing the nonlinear dynamic response of structures. [ABSTRACT FROM AUTHOR]

Abstract: Structures located in seismically active regions may be subjected to mainshock–aftershock sequence-type ground motions, which are characterized by the presence of strong aftershock ground motions after the mainshock and separated by short intervals of time. This manuscript investigates the damage of inelastic SDOF structure with four hysteretic models and three response demand parameters. The relative intensity of the aftershock ground motion to the mainshock ground motion is defined, denoted by PGA as/PGA ms. The aftershock ground motions are scaled to have different levels of PGA as/PGA ms. The results indicate that the effect of aftershock on ductility demand is slight for PGA as/PGA ms≤0.5 and can be ignored in engineering practice. The aftershock ground motion has more significant influence on the normalized hysteretic energy and damage index than on ductility demand. The effect of aftershock ground motion with larger PGA as/PGA ms on the response demand is generally more obvious for non-degrading system than for degrading system. [Copyright &y& Elsevier]