International Benchmark on Numerical Simulations for 1D, Nonlinear Site Response (PRENOLIN): Verification Phase Based on Canonical Cases

Abstract

PREdiction of NOn-LINear soil behavior (PRENOLIN) is an international benchmark aiming to test multiple numerical simulation codes that are capable of predicting nonlinear seismic site response with various constitutive models. One of the objectives of this project is the assessment of the uncertainties associated with nonlinear simulation of 1D site effects. A first verification phase (i.e., comparison between numerical codes on simple idealistic cases) will be followed by a validation phase, comparing the predictions of such numerical estimations with actual strongmotion recordings obtained at well-known sites. The benchmark presently involves 21 teams and 23 different computational codes.We present here the main results of the verification phase dealing with simple cases. Three different idealized soil profiles were tested over a wide range of shear strains with different input motions and different boundary conditions at the sediment/bedrock interface. A first iteration focusing on the elastic and viscoelastic cases was proved to be useful to ensure a common understanding and to identify numerical issues before pursuing the nonlinear modeling. Besides minor mistakes in the implementation of input parameters and output units, the initial discrepancies between the numerical results can be attributed to (1) different understanding of the expression "input motion" in different communities, and (2) different implementations of material damping and possible numerical energy dissipation. The second round of computations thus allowed a convergence of all teams to the Haskell-Thomson analytical solution in elastic and viscoelastic cases. For nonlinear computations, we investigate the epistemic uncertainties related only to wave propagation modeling using different nonlinear constitutive models. Such epistemic uncertainties are shown to increase with the strain level and to reach values around 0.2 (log 10 scale) for a peak ground acceleration of 5 m=s 2 at the base of the soil column, which may be reduced by almost 50% when the various constitutive models used the same shear strength and damping implementation.

Integration of Site Effects into Probabilistic Seismic Hazard Assessment (PSHA): A Comparison between Two Fully Probabilistic Methods on the Euroseistest Site

“…One set of time histories on soil is generated that is based on the SHAKE91 equivalent-linear (EL) code [42][43][44], while the second set was derived using the NOAH [45] fully non-linear code (NL). Both of the codes were used with the objective of incorporating somehow the code-to-code variability, which has been shown in all recent benchmarking exercises to be very important [46,47]. The final step in the SM method consists in deriving the site-specific hazard curve by simply calculating the annual rate of exceedance from the set of surface synthetic time series.…”

An accessible approach for the site response analysis of quasi-horizontal layered deposits

“…The damping ratio chosen for both sets of analyses is 3%, which results in a smooth transfer function where the effect of noise is minimized. The choice of this damping ratio (Regnier et al 2016), where a series of tests were conducted to determine the most appropriate damping value for viscous-elastic analysis. It is easy to fix the damping ratio in STRATA but more challenging in Abaqus because it treats damping in a different way (Volpini et al 2018).…”

“…Secondly, to make the soil profile considered more realistic than a single soil layer overlying a stiff bedrock layer, the analysis was repeated using an idealized shear wave velocity profile from the Prenolin project (Regnier et al 2016), described by this equation: . 9 Summary of the Pearson's sample correlation coefficient, r, for all analyses.…”

Soil–Structure Interaction Assessment of the 23 November 1980 Irpinia-Basilicata Earthquake

“…Recent earthquakes, such as the Athens (Greece, 1999) [9], the Kocaeli (Turkey, 1999) [10], the Haiti (2010) [11], and the Gorkha (Nepal, 2015) [12][13][14] earthquakes, showed the importance of taking into account soil amplifications. In the literature, several approaches have been applied to perform ground motion analyses including site effects: hybrid analyses that consist of a combination of probabilistic and deterministic methods (e.g., [15,16]), convolution approaches that provide modifications of the rocking hazard (e.g., [17,18]), and 1D seismic site response analyses (e.g., [19,20]).…”