Comparison of the Dynamic and Static Corner Frequencies in Ground Motion Simulation: Cases Study of Jiuzhaigou Earthquake and Northridge Earthquake

By using the stochastic finite-fault method based on static corner frequency (Model 1) and dynamic corner frequency (Model 2), we calculate the far-field received energy (FRE) and acceleration response spectra (SA) and then compare it with the observed SA. The results show that FRE obtained by the two models depends on the subfault size regardless of high-frequency scaling factor (HSF). Considering the HSF, the results obtained by Model 1 and Model 2 are found to be consistent. Then, similar conclusion was obtained from the Northridge earthquake. Finally, we analyzed the reasons and proposed the areas that need to be improved.

Physics-Based Ground Motion Simulations for the Prediction of the Seismic Vulnerability of Masonry Building Compounds in Mirandola (Italy)

The current paper aims at investigating the seismic capacity of a masonry building aggregate in the historical centre of Mirandola based on a reliable ground motion simulation procedure. The examined clustered building is composed of eleven structural units (SUs) mutually interconnected to each other, which are made of brick walls and are characterized by wooden floors poorly connected to the vertical structures. Non-linear static analyses are performed by adopting the 3Muri software to characterize the seismic capacity of both the entire aggregate and the individual SUs. In this framework, a multi-scenario physics-based approach is considered for the definition of the seismic input in terms of broadband seismic signals inclusive of source and site effects. Finally, the incidence of the seismic input variability is discussed for the prediction of the global capacity response of the case study building.

Assessment on the deflection amplification factor of steel buckling-restrained bracing frames

Researchers in the field of earthquake engineering are always looking for new ways to improve the seismic behavior of structures. The buckling-restrained brace (BRB) is one of these exciting innovations that are employed to increase the ductility capacity of traditional steel braced frames. Understanding the nonlinear response of these novel systems in estimating maximum displacements due to an earthquake has been of significant importance for structural designers. Accordingly, this research is carried out to study of deflection amplification factor ( C d) in BRBs, which have recently been presented in seismic design provisions as one of the seismic lateral-resisting systems. To this end, five 3-, 5-, 7-, 10-, and 15-story BRBs are modeled in the software framework of OpenSees. Ground motion simulation is performed by selecting several scaled earthquake records, and the values of elastic and ultimate displacements of structural systems are computed through pushover and nonlinear time-history analyses. The results showed that the deflection amplification factor suggested within famous building codes (such as ASCE-7-16) compared to the obtained values is, in some cases, for certainty; conversely, it is underestimated under some conditions. In fact, the findings indicate that the magnitude of C d in these systems is strongly related to the height of the building.

Embedding Spectral Decomposition Results in Broadband Simulation: Application to Rhine Graben Area

<p>Over the past decade, there is growing consensus that physics-based simulations can be utilized in engineering applications. However, for the simulations to be accepted, they need to be calibrated and validated. This study presents the results of ground motion simulation calibration and validation using earthquakes that occurred in the Upper Rhine Graben with a modified version of the Graves-Pitarka (GP) hybrid ground-motion simulation methodology implemented on the Southern California Earthquake Center Broadband Platform, which uses an improved high-frequency computation. To calibrate the HF simulation, we take advantage of the growth of seismological data (including weak motions) in the region and the ability to evaluate critical seismic parameters such as anelastic attenuation, stress drop, and site effects through spectral decomposition methods (separate site-source-propagation from the datasets).  Hence in the simulation, the adopted anelastic attenuation and stress parameter are defined based on the spectral decomposition results. The additional modification of the standard GP method is the incorporation of compressional wave in the HF motion.</p><p>Results are compared with observations and simulations from the unmodified GP approach; we also use a range of ground motion intensity measures as summary statistics. We found that in general, the modification in the HF part (e.g., incorporation of compressional waves) was necessary to improve the fit with observations. Our findings also validate the fact that parameters from the spectral decomposition are giving well-calibrated time-histories (in terms of frequency and amplitude) when used as input parameters of the broadband simulations. The findings in this study support the incorporation of scenario-based ground motion simulations for use in the characterization of seismic hazard and other engineering applications. For simulation of future earthquakes, instead of using event-specific stress-drops, we use the average stress-drops taken from the distribution of the stress drops derived from spectral decomposition.</p>