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1. Expanded Byrne model for evaluating seismic compression

   https://doi.org/10.1177/8755293020957350  

   Jiang, Yusheng; Green, Russell A.; Taylor, Oliver-Denzil (September 2020, Earthquake Spectra)

   Seismic compression is the accrual of contractive volumetric strain in unsaturated or partially saturated sandy soils during earthquake shaking and has caused significant distress to overlying and nearby structures. The phenomenon can be well characterized by load-dependent, interaction macro-level fatigue theories. Toward this end, the Byrne cyclic shear-volumetric strain coupling model is expanded and calibrated for evaluating seismic compression for several soil types. In addition, the model was transformed to allow it to be implemented in a “simplified” manner, in addition to the original “non-simplified” formulation. Both implementation approaches are used to analyze a site in Japan impacted by the 2007, M_w6.6 Niigata-ken Chuetsu-oki earthquake. The results from the analyses are in general accord with the post-earthquake field observations and highlight the sensitivity of predicted magnitude of the seismic compression to the input variables used and modeling assumptions (e.g. relative density of the soil, magnitude of the volumetric threshold strain, orientation of the ground motions, settlement of soils below the ground water table, and accounting for multidirectional shaking). Although additional studies are needed to further validate the findings presented herein, estimation of relative density and threshold shear strain of the soil and ground motion orientation individually have moderate-to-significant influence on the computed magnitude of seismic compression, but they have a significant influence when taken in combination. Also, the seismic compression models can seemingly be used to predict the settlement in fully saturated sand when the excess pore water pressures are limited. Finally, accounting for multidirectional shaking has a significant influence on the computed magnitude of seismic compression. 

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2. Influence of Ground Motion Orientation on Predicted Seismic Compression

   Green, R.A. and (April 2020, Proc. New Zealand Society of Earthquake Engineering Annual Conference 2020 (NZSEE 2020))

   null (Ed.)

   Seismic compression is the accrual of contractive volumetric strain in unsaturated or partially saturated sandy soils during earthquake shaking and has caused significant distress to overlying and nearby structures. The phenomenon can be well-characterized by load-dependent, interaction macro-level fatigue theories, which means that the nature of the accumulation of volumetric strain is a function of the absolute amplitude and sequencing of pulses in the loading function. One model that captures this behavior and that can be used to predict seismic compression is the expanded Byrne cyclic shear-volumetric strain coupling model. However, one potential implication of the load-dependent, interaction macro-level fatigue behaviour is that ground motion orientation will influence predicted settlements. To examine the significance of this, the seismic compression that occurred at the Kashiwazaki-Kariwa Nuclear Power Plant (KKNPP) site during the 2007, Mw6.6 Niigata-ken Chuetsu-oki, Japan, earthquake is analyzed using the expanded Byrne model. The horizontal motions recorded at the site by a down-hole array during this event are rotated in 5° increments and the predicted settlements due to seismic compression are computed. The predicted settlements range from 12.3 to 16.1 cm, with a geometric mean of the values for various orientations being 13.8 cm. These results are in general accord with the post-earthquake field observations and highlight the sensitivity of predicted magnitude of the seismic compression to ground motion orientation. 

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3. Hydrodynamic pressures on rigid walls subjected to cyclic and seismic ground motions

   https://doi.org/10.1002/eqe.4020  

   AlKhatib, Karim; Hashash, Youssef M. A.; Ziotopoulou, Katerina; Morales, Brian (September 2023, Earthquake Engineering & Structural Dynamics)

   Abstract Seismic design of water retaining structures relies heavily on the response of the retained water to shaking. The water dynamic response has been evaluated by means of analytical, numerical, and experimental approaches. In practice, it is common to use simplified code‐based methods to evaluate the added demands imposed by water sloshing. Yet, such methods were developed with an inherent set of assumptions that might limit their application. Alternatively, numerical modeling methods offer a more accurate way of quantifying the water response and have been commonly validated using 1 g shake table experiments. In this study, a unique series of five centrifuge tests was conducted with the goal of investigating the hydrodynamic behavior of water by varying its height and length. Moreover, sine wave and earthquake motions were applied to examine the water response at different types and levels of excitation. Arbitrary Lagrangian‐Eulerian finite element models were then developed to reproduce 1 g shake table experiments available in the literature in addition to the centrifuge tests conducted in this study. The results of the numerical simulations as well as the simplified and analytical methods were compared to the experimental measurements, in terms of free surface elevation and hydrodynamic pressures, to evaluate their applicability and limitations. The comparison showed that the numerical models were able to reasonably capture the water response of all configurations both under earthquake and sine wave motions. The analytical solutions performed well except for cases with resonance under harmonic motions. As for the simplified methods, they provided acceptable results for the peak responses under earthquake motions. However, under sine wave motions, where convective sloshing is significant, they underpredict the response. Also, beyond peak ground accelerations of 0.5 g., a mild nonlinear increase in peak dynamic pressures was measured which deviates from assumed linear response in the simplified methods. The study confirmed the reliability of numerical models in capturing water dynamic responses, demonstrating their broad applicability for use in complex problems of fluid‐structure‐soil interaction. 

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4. Spatial variability of site effects and its correlation with site response in Japan

   https://doi.org/10.3208/jgssp.v10.P2-25  

   Lorenzo-Velazquez, Cristina; Cabas, Ashly (January 2024, Japanese Geotechnical Society Special Publication)

   Local soil conditions depict an important role in regional seismic hazard assessments due to their influence on earthquake-induced ground shaking and deformation. The different levels of damage and site response at nearby locations correlate to site and geologic conditions variability, as has been reported after past earthquakes. Evaluating spatially variable ground motions (GMs) is key for earthquake reconnaissance efforts and regional seismic hazard assessments. This study focuses on the evaluation of spatial correlations in site parameters (e.g. time-averaged shear-wave velocity to a depth of 30 meters) at Kiban-Kyoshin Network (KiK-net), and their comparison to the observed spatial correlation residuals from ground motion intensity measures (IMs) from the Mw9.1 Tohoku earthquake. Current spatial correlation models treat site effects either as a fixed amplification factor or as randomized amplifications, but site effects are neither fixed nor random. Hence, geostatistical methods are used here to estimate spatial correlations between parameters that control site response and integrate their effects on resulting spatially variable ground motions. In this work, we evaluate the significance of the spatial correlation for different site parameters with respect to the GM amplification IMs residuals. 

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5. Evaluating Liquefaction Triggering Potential Using Seismic Input Parameters that Are Consistent with ASCE 7-16

   https://doi.org/10.1061/9780784482810.010  

   Green, R.A. and (February 2020, Geo-Congress 2020: Geotechnical Earthquake Engineering and Special Topics)

   J.P. Hambleton, R. Makhnenko (Ed.)

   ASCE 7-16 details how the peak ground acceleration (PGA) should be determined for evaluating liquefaction triggering, with this PGA reflecting the influence of a range of earthquake magnitudes on a site’s seismic hazard. Similarly, the Finn and Wightman magnitude-weighting scheme can be used to account for the full range of magnitudes influencing the seismic hazard at a site, where the weights are derived from a site’s seismic hazard deaggregation data. However, the deaggregation data for the seismic hazard maps for the Central/Eastern U.S. are only available for rock motions and not motions at the surface of the soil profile. The authors explore this issue by comparing the weighted average magnitude scaling factors (MSF) and depth-stress weighting factor (rd) values for multiple sites in the Western U.S. developed using deaggregation data for rock motions and for motions at the surface of the soil profiles. Based on these comparisons, the authors found that using the PGA deaggregation data for rock conditions yield similar weighted averages for MSF and rd as those computed using deaggregation data for the PGA at the surface of the soil profile. 

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