seismic site response
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GeoHazards ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 430-441
Author(s):  
Gaetano Falcone ◽  
Giuseppe Naso ◽  
Federico Mori ◽  
Amerigo Mendicelli ◽  
Gianluca Acunzo ◽  
...  

The effects induced by the choice of numerical base conditions for evaluating local seismic response are investigated in this technical note, aiming to provide guidelines for professional applications. A numerical modelling of the seismic site response is presented, assuming a one-dimensional scheme. At first, with reference to the case of a homogeneous soil layer overlying a half-space, two different types of numerical base conditions, named rigid and elastic, were adopted to analyse the seismic site response. Then, geological setting, physical and mechanical properties were selected from Italian case studies. In detail, the following stratigraphic successions were considered: shallow layer 1 (shear wave velocity, VS, equal to 400 m/s), layer 2 (VS equal to 600 m/s) and layer 3 (VS equal to 800 m/s). In addition, real signals were retrieved from the web site of the Italian accelerometric strong motion network. Rigid and elastic base conditions were adopted to estimate the ground motion modifications of the reference signals. The results are presented in terms of amplification factors (i.e., ratio of integral quantities referred to free-field and reference response spectra) and are compared between the adopted numerical models.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sparsha Sinduri Nagula ◽  
Yu-Wei Hwang ◽  
Shideh Dashti ◽  
Jürgen Grabe

AbstractA numerical model based on the finite element framework was developed to predict the seismic response of saturated sand under free-field conditions. The finite element framework used a non-linear coupled hypoplastic model based on the u-p formulation to simulate the behaviour of the saturated sand. The u-p coupled constitutive model was implemented as a user-defined routine in commercial ABAQUS explicit 6.14. Results of centrifuge experiments simulating seismic site response of a layered saturated sand system were used to validate the numerical results. The centrifuge test consisted of a three-layered saturated sand system subjected to one-dimensional seismic shaking at the base. The test set-up was equipped with accelerometers, pore pressure transducers, and LVDTs at various levels. Most of the constitutive models used to date for predicting the seismic response of saturated sands have underestimated volumetric strains even after choosing material parameters subjected to rigorous calibration measures. The hypoplastic model with intergranular strains calibrated against monotonic triaxial test results was able to effectively capture the volumetric strains, reasons for which are discussed in this paper. The comparison of the numerical results to centrifuge test data illustrates the capabilities of the developed u-p hypoplastic formulation to perform pore fluid analysis of saturated sand in ABAQUS explicit, which inherently lacks this feature.


Author(s):  
Yen-Hsiang Chang ◽  
Chi-Chin Tsai ◽  
Chien-Chia Huang ◽  
Duhee Park

2021 ◽  
Vol 284 ◽  
pp. 106031
Author(s):  
Giovanna Vessia ◽  
Giovanna Laurenzano ◽  
Alessandro Pagliaroli ◽  
Marco Pilz

2021 ◽  
Author(s):  
Stefania Fabozzi ◽  
Stefano Catalano ◽  
Giuseppe Naso ◽  
Alessandro Pagliaroli ◽  
Edoardo Peronace ◽  
...  

<p>The seismic subsoil response in terms of amplification or attenuation of the ground motion is the result of a complex combination of factors, including the vertical and horizontal subsoil heterogeneities (Fabozzi et al., 2021). In volcanic areas in particular, the vertical subsoil heterogeneities are well identified by characteristic superposition of stiffer volcanic horizons on softer levels, giving rise to stiff-soft alternating layers, also in the form of multiple Vs inversions with the depth. This condition is typical of sheet-like blankets of lava or pyroclastic deposits, extensively covering the sedimentary substratum, frequent in the peripheral areas of large basaltic stratovolcanos or in areas adjacent to large explosive acidic volcanic edifices. The aim of the present work is to study the effect of such vertical heterogeneities on the seismic site response. With this end, in correspondence of volcanic areas identified by means of a preliminary geological screening in the Italian territory, subsoil properties relevant for seismic site response analyses were extracted from the Italian database of the seismic microzonation studies (DB-SMs in DPC, 2018), which is available at www.webms.it and is developed and maintained by CNR IGAG (National Research Council of Italy, Institute of Environmental Geology and Geoengineering, www.igag.cnr. it). The collection of input data was used for an extensive one-dimensional equivalent linear numerical site response analyses, in order to evaluate the influence of stiffness inversions on ground motion at surface. In particular, different idealized subsoil 1D models of the identified geological areas were defined in terms of variation of layers thickness, shear wave velocity and nonlinear properties. The effect of the variability of these parameters on the seismic site response in terms of amplification factors (ICMS, 2008) was studied parametrically.</p><p><strong>References </strong></p><ul><li>DPC, Dipartimento della Protezione Civile, 2018. Commissione tecnica per il supporto e monitoraggio degli studi di Microzonazione Sismica (ex art.5, OPCM3907/10), (2018) WebMs; WebCLE. A cura di: Maria Sole Benigni, Fabrizio Bramerini, Gianluca Carbone, Sergio Castenetto, Gian Paolo Cavinato, Monia Coltella, Margherita Giuffrè, Massimiliano Moscatelli. In: Giuseppe Naso. Andrea Pietrosante, Francesco Stigliano.</li> <li>Fabozzi S., Catalano S., Falcone G., Naso G., Pagliaroli A., Peronace E., Porchia A., Romagnoli G., Moscatelli M. (2021) Stochastic approach to study the site response in presence of shear wave velocity inversion: application to seismic microzonation studies in Italy. Engineering Geology https://doi.org/10.1016/j.enggeo.2020.105914.</li> <li>ICMS, 2008. Indirizzi e Criteri per la Microzonazione Sismica. In: Gruppo di lavoro ICMS. Conferenza Delle Regioni E Province Autonome - Dipartimento Della Protezione Civile. https://www.centromicrozonazionesismica.it/it/download/category/7-indi rizzi-e-criteri-per-lamicrozonazione-sismica (In Italian).</li> </ul>


2021 ◽  
Author(s):  
Gaetano Falcone ◽  
Gianluca Acunzo ◽  
Amerigo Mendicelli ◽  
Federico Mori ◽  
Giuseppe Naso ◽  
...  

<p>Estimation of site effects over large areas is a key-issue for land management and emergency system planning in a risk mitigation perspective. In general, site-conditions are retrieved from available global datasets and the ground-shaking estimation is based on ground motion prediction equations.</p><p>An advanced procedure to estimate site effects over large areas is here proposed with reference to the Italian territory. Site-condition were defined for homogenous morpho-geological areas in accordance to the borehole logs and the geophysical data archived in the Italian database for seismic microzonation (https://www.webms.it/). Ground motion modifications were determined by means of about 30 milion of one-dimensional numerical simulations of local seismic site response. Correlations between amplification factors (i.e. the ratio between free-field and outcrop response spectra), AF, and site-condition (i.e. harmonic mean of the shear wave velocity in the upper 30 m of the deposit, V<sub>S30</sub>) were determined for each morpho-geological homogeneous area depending on the reference seismic intensity (i.e. referred to the outcropping stiff rock characterised by V<sub>S30</sub> ≥ 800 m/s). The AF-V<sub>S30</sub> correlations were proved to satisfactory forecast the site effects when compared with the results of site specific estimation of local seismic site response.</p>


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