Some Examples of 1D, Fully Stochastic Site Response Analyses of Soil Deposits

2010 ◽  
pp. 15-26 ◽  
Author(s):  
Carlo G. Lai ◽  
Mirko Corigliano ◽  
Heidy Sanchez L
Keyword(s):  
Site Response ◽  
Soil Deposits

Simplified Criteria to Select Ground Response Analysis Methods for Seismic Building Design: Equivalent Linear versus Nonlinear Approaches

2021 ◽  
Author(s):  
Mauro Aimar ◽  
Sebastiano Foti
Keyword(s):  
Seismic Waves ◽  
Site Response ◽  
Building Design ◽  
Soil Conditions ◽  
Response Analysis ◽  
Depth Range ◽  
Ground Response Analysis ◽  
Equivalent Linear ◽  
Acceleration Time Histories ◽  
Soil Deposits

ABSTRACT The possible amplification of seismic waves in soil deposits is crucial for the seismic design of buildings and geotechnical systems. The most common approaches for the numerical simulation of seismic site response are the equivalent linear (EQL) and the nonlinear (NL). Even though their advantages and limitations have been investigated in several studies, the relative field of applicability is still under debate. This study tested both methods over a wide population of soil models, which were subjected to a set of acceleration time histories recorded from strong earthquakes. A thorough comparison of the results of the EQL and the NL approaches was carried out, to identify the conditions in which the relative differences are significant. This assessment allowed for the definition of simplified criteria to predict when the two schemes are or are not compatible for large expected shaking levels. The proposed criteria are based on simple and intuitive parameters describing the soil deposit and the ground-motion parameters, which can be predicted straightforwardly. Therefore, this study provides a scheme for the choice between the EQL and the NL approaches that can be used even at the preliminary design stages. It appears that the EQL approach provides reliable amplification estimates in soil deposits with thickness up to 30 m, except for very deformable soils, but this depth range may be extended at long vibration periods. This result reveals a good level of reliability of the EQL approach for various soil conditions encountered in common applications, even for high-intensity shaking.

Comparison of Invasive and Non-Invasive Methods in Site Response, Case Study: Soil Deposits of La Estrella

2021 ◽  
Vol 906 (1) ◽  
pp. 012119
Author(s):  
Daniel Largo ◽  
César Hidalgo ◽  
Juan Olarte
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Spectrum Analysis ◽  
Site Response ◽  
Response Spectrum ◽  
Response Spectrum Analysis ◽  
Non Invasive ◽  
Soil Deposits ◽  
Relative Differences

Abstract A great part of the Colombian territory is under medium to high seismic hazard due to the complex tectonic condition, which in turn affects, particularly, areas where the population density is highest. A response spectrum analysis of the ground is currently required by seismic design codes for site response analysis. For this, the shear wave velocity (Vs) profile must be established. The use of seismic invasive methods such as Down Hole or Cross Hole for the determination of the shear wave velocity (Vs), has been typically recommended. In recent years, significant progress has been made in non-invasive seismic methods such as MasW (Multichannel Analysis of Surface Waves) and ReMi (Refraction Microtremor), in order to estimate the Vs profile from surface waves analysis. Due to the accessibility and low cost, these methods represent a viable alternative to determine the profile of Vs. In this project, the seismic response of soil deposits was evaluated in the La Estrella municipality located in the south of The Aburrá Valley. One-dimensional (1D) models were simulated by characterizing the soil profile through the shear wave velocity with MasW and ReMi seismic tests. The results were compared with models based on shear wave characterization through Down Hole methods. The 1D response spectrums were determined with an equivalent linear model in DEEPSOIL and GTS NX software. The resulting spectra were compared through relative difference and correlation coefficient. Final results demonstrated that the spectra present low relative differences for long periods, moderate relative differences for moderate periods, and low to moderate relative differences for short periods. The general correlation coefficients were 0.6. This was evidence that non-invasive seismic methods allow an appropriate response spectrum analysis.

scholarly journals Geometrical Optics applied to 1D Site Response of Inhomogeneous Soil Deposits

2020 ◽  
Author(s):  
Joaquin Garcia-Suarez ◽  
Domniki Asimaki ◽  
Elnaz E. Seylabi
Keyword(s):  
Wave Propagation ◽  
Natural Frequencies ◽  
Site Response ◽  
Geometrical Optics ◽  
Ray Theory ◽  
Resonance Amplitude ◽  
Analytical Results ◽  
Soil Deposits ◽  
Open Question ◽  
As If

The technique referred as Geometrical Optics entails considering the wave propagation in a heterogeneousmedium as if it happened with infinitely small wavelength. This classic simplification allows to obtain useful approximate analytical results in cases where complete description of the waveform behavior is virtually unattainable, hence its wide use in Physics. This approximation is also commonly termed Ray Theory, and it has already been thoroughly applied in Seismology. This text presents an application of Geometrical Optics to 1D Site Response (1DSR): it is used herein to, first, explainand elucidate the generality of some previous observations and results; second, to partially settle an open question in 1DSR, namely “what are the equivalent homogeneous properties that yield the same response, in terms of natural frequencies and resonance amplitude, for a certain inhomogeneous site?”, provided few assumptions.

On the role of stiff soil deposits on seismic ground shaking in western Liguria, Italy: Evidences from past earthquakes and site response

2017 ◽  
Vol 226 ◽  
pp. 172-183 ◽  
Author(s):  
Roberto De Ferrari ◽  
Gabriele Ferretti ◽  
Simone Barani ◽  
Giacomo Pepe ◽  
Andrea Cevasco
Keyword(s):  
Site Response ◽  
Ground Shaking ◽  
Soil Deposits ◽  
Stiff Soil

A proposed dynamic foundation factor for the National Building Code of Canada

1991 ◽  
Vol 18 (6) ◽  
pp. 974-984 ◽  
Author(s):  
Kamel Elhmadi ◽  
Arthur C. Heidebrecht
Keyword(s):  
Parametric Study ◽  
Site Response ◽  
Site Amplification ◽  
Building Code ◽  
Dense Sand ◽  
Study Results ◽  
Soil Deposits ◽  
Class 1 ◽  
Soil Site ◽  
Strong Ground

Results of a parametric study on site response effects due to seismic strong ground motions are used in this paper to develop a new "dynamic foundation factor" for the National Building Code of Canada. In order to capture the effect of the site resonance, the proposed dynamic foundation factor, F*, is given as a function of the ratio between the fundamental period of the building and the site period, T/Ts (i.e., F* spectra in terms of T/Ts). The parametric study results suggested that the proposed F* spectra be dependent on four different classes of soil deposits. These classes are deep cohesive (class 1), deep cohesionless (class 2), shallow cohesive and cohesionless (class 3), and dense sand (class 4). For classes 1 and 2, the F* spectra are independent of the ratio of peak acceleration to peak velocity, av, of the seismic ground motion. For classes 3 and 4, however, the F* spectra are an increasing function of the ratio a/v. A scaling multiplier is introduced to take into account the influence of level of intensity, v. The proposed dynamic foundation factor is compared with the National Building Code of Canada 1990 foundation factor. Finally, actual sites are used to check the validity and consistency of the proposed dynamic foundation factor. Key words: seismic, foundation factor, soil, site, amplification, building, shear, force, period, spectra.

scholarly journals Linear One-dimensional Site Response Analysis in the presence of stiffness-less free surface for certain power-law heterogeneities

2020 ◽  
Author(s):  
Joaquin Garcia-Suarez ◽  
Domniki Asimaki
Keyword(s):  
Free Surface ◽  
Power Law ◽  
Site Response ◽  
Small Strain ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Physical Explanation ◽  
One Dimensional ◽  
Soil Deposits ◽  
Heterogeneous Soil

We revisit previous results in small-strain One-dimensional Site Response Analysis of heterogeneous soil deposits. Specifically, we focus on sites whose shear modulus distribution is described by means of a power law that yields zero stiffness at the free surface. First, we show that in some cases (which we characterize in detail) considerations of energy finitude should prevail over considerations of vanishingtractions at the free-surface, as these may pose acuter constrains. We re-evaluate previous contributions in light of this result. Second, we analyze the previously-reported occurrence of “energy accumulation in upper layers”, providing a physical explanation for it. In passing, we supply estimates of the natural frequencies, and compare these with our previous results.

Ground Motion Site Amplification Factors for Sites Located within the Mississippi Embayment with Consideration of Deep Soil Deposits

2015 ◽  
Vol 31 (2) ◽  
pp. 699-722 ◽  
Author(s):  
Mojtaba Malekmohammadi ◽  
Shahram Pezeshk
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Site Amplification ◽  
Sediment Depth ◽  
Deep Soil ◽  
Mississippi Embayment ◽  
Soil Response ◽  
Amplification Factors ◽  
Nonlinear Site Response ◽  
Soil Deposits

In this study, site amplification factors for the deep soil deposits of the Mississippi embayment are computed using a nonlinear site response analysis program first to develop a model for nonlinear soil response for possible use by ground motion developers and second to address site amplification estimation. The effects of geology, sediment depth, and average shear wave velocity at the upper 30 m of soil ranging 180–800 m/s, as well as the effect of peak ground acceleration at the bedrock on nonlinear ground motion amplification for the upper embayment, are investigated. The site response computations cover various site conditions, sediment depth of 70–750 m, and peak acceleration of input rock motions of 0.01–0.90 g. The amplification (or de-amplification) at various frequencies implied by the sediment depth is greater than that implied just by site classification of the top 30 m of soil.

scholarly journals On the fundamental resonant mode of inhomogeneous soil deposits

2019 ◽  
Author(s):  
Joaquin Garcia-Suarez ◽  
Domniki Asimaki
Keyword(s):  
Fundamental Frequency ◽  
Numerical Solutions ◽  
Ground Deformation ◽  
Site Response ◽  
Seismic Hazard Assessment ◽  
Resonant Mode ◽  
Single Degree Of Freedom ◽  
Shallow Layer ◽  
Soil Deposits ◽  
Definition Of

The problem of estimating seismic ground deformation is central to state-of-practice procedures of designing and maintaining infrastructure in earthquake-prone areas. Particularly, the problem of estimating the displacement field in a soft shallow layer overlying rigid bedrock induced by simple SH wave excitation has been favored by engineers due to its simplicity combined with inherent relevance for practical scenarios. We here derive analytical, accurate estimates for both the fundamental frequency and the amplitude of the first resonant mode of such systems by applying an intuitive argument based on resonance of single-degree-of-freedom systems. Our estimates do not presuppose a continuous velocity distribution, and can be used for fast assessment of site response in seismic hazard assessment and engineering design. On the basis of the said estimates of fundamental frequency and amplitude, we next propose a novel definition of ``equivalent homogeneous shear modulus’’ of the inhomogeneous deposit; and we show that the response of the fundamental mode of these systems is governed by the mechanical properties of the layers closer to the bedrock. We finally discuss the validity of our argument, and evaluate the accuracy of our results by comparison with analytical and numerical solutions.

Empirical Study of Sediment-Filled Basin Response: The Case of Taipei City

2000 ◽  
Vol 16 (3) ◽  
pp. 681-707 ◽  
Author(s):  
Vladimir Yu Sokolov ◽  
Chin-Hsiung Loh ◽  
Kuo-Liang Wen
Keyword(s):  
Site Response ◽  
Propagation Path ◽  
Reference Spectrum ◽  
Spectral Ratios ◽  
Taipei Basin ◽  
Soil Deposits ◽  
Source Scaling ◽  
Attenuation Models ◽  
Basin Response ◽  
Strong Ground

We analyze the site response of the Taipei basin using the records obtained by the Taiwan Strong Ground Motion Instrumentation Program (TSMIP) network. Records of 66 earthquakes of M=2.6-6.5 with a hypocentral depth varying from 1 km to 118 km and hypocentral distances of up to 150 km are studied for 35 stations located within this triangle-shaped alluvium structure. The site response is obtained in terms of spectral ratios calculated by dividing of the site spectrum by the reference spectrum estimated for a hypothetical “very hard rock” site. The recently developed empirical source scaling and attenuation models for the Taiwan region are used for the reference spectra calculation. This approach allows us to evaluate the variability of spectral ratios due to uncertainties introduced by source and propagation path effects and variability in the site response itself. The characteristics of site response in the Taipei basin depend on the properties of soil deposits and, in general, may be described by 1-D models. However, there are some peculiarities of spectral ratios that show the influence of subsurface topography.

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