Normalized Modulus Reduction and Material Damping Ratio Curves for Bay of Campeche Sand

2016 ◽  
Author(s):  
Victor M. Taboada ◽  
Vishal Dantal ◽  
Diego Cruz Roque ◽  
Francisco Flores Lopez ◽  
Procoro Barrera Nabor
Keyword(s):  
Damping Ratio ◽  
Material Damping ◽  
Modulus Reduction

Normalised Modulus Reduction and Material Damping Ratio Curves for Bay of Campeche Clay

2017 ◽  
pp. 457-463
Author(s):  
VM Taboada ◽  
V Dantal ◽  
D Cruz Roque ◽  
FA Flores Lopez ◽  
RE Vazquez Monroy ◽  
...  
Keyword(s):  
Damping Ratio ◽  
Material Damping ◽  
Modulus Reduction

Normalized Modulus Reduction and Damping Ratio Curves for Bay of Campeche Calcareous Clay to Carbonate Mud

2021 ◽  
Author(s):  
Victor Manuel Taboada ◽  
Shuang Cindy Cao ◽  
Francisco Alonso Flores Lopez ◽  
Diego Cruz Roque ◽  
Procoro Barrera Nabor
Keyword(s):  
Site Response ◽  
Damping Ratio ◽  
Laboratory Data ◽  
Confining Pressure ◽  
Carbonate Content ◽  
Large Strains ◽  
Material Damping ◽  
Ratio Curve ◽  
Shear Strains ◽  
Modulus Reduction

Abstract Equations to calculate the modulus reduction curve (G/Gmax-γ) and material damping ratio curve (D-γ) of calcareous clay and clayey carbonate mud of the Bay of Campeche and Tabasco Coastline are developed. This was achieved using a database of 156 resonant column tests and 468 strain-controlled cyclic direct simple shear tests performed in clays with 10 % ≤ CaCO3 ≤90 %. The effects of carbonate content (CaCO3), mean effective confining pressure (σ′m), plasticity index (PI), and overconsolidation ratio (OCR) on the shape of the modulus reduction and material damping ratio curves are shown based on the available laboratory data and the equations developed to calculate these curves. It is shown that as CaCO3 increases, the normalized shear modulus (G/Gmax) curve tends to shift downward and the damping ratio (D) curve tends to shift upward; as σ′m and PI increase, the G/Gmax curve tends to shift upward and the damping ratio curve tends to shift downward; and the value of OCR has practically no effect on the position of the curves. The validation of the calculated values of G/Gmax and D shows the best predictions are found at low shear strains for G/Gmax and at large shear strains for D, falling within ± 25 % of the measured values, and shows that due to limitations in the model at large strains (γ > 1 %) for G/Gmax and at low strains (γ < 0.05 %) for D, the calculated values fall within ± 50 % of the measured values. The equations developed to calculate the curves of G/Gmax-γ and D-γ of calcareous clay and clayey carbonate mud are recommended for preliminary or perhaps even final seismic site response evaluations. However, considering the scatter of the data points around the curves, the equations should be used with caution, and parametric and sensitivity studies are strongly recommended to assess the importance of this scatter. In large critical projects, direct experimental determinations of G/Gmax and D for the soils of interest are suggested to be more appropriate.

scholarly journals INFLUENCE OF MATERIAL DAMPING ON THE RESPONSE OF UNDERGROUND STRUCTURES SUBJECTED TO EARTHQUAKE

2020 ◽  
Vol 26 ◽  
pp. 64-70
Author(s):  
Veronika Pavelcová ◽  
Tereza Poklopová ◽  
Michal Šejnoha ◽  
Tomáš Janda
Keyword(s):  
Damping Ratio ◽  
Underground Structure ◽  
Eurocode 8 ◽  
Viscous Damping ◽  
Material Damping ◽  
Underground Structures ◽  
Fixed Boundary ◽  
Design Spectrum ◽  
Rayleigh Damping ◽  
Element Simulation

The paper describes a finite element simulation of the response of a real underground structure subjected to earthquake using GEO5 FEM program. It concentrates on the influence of material damping with respect to a specific type of boundary condition prescribed at the bottom of the analyzed domain. It is seen that considering material damping is inevitable particularly in case of so called fixed boundary conditions to arrive at meaningful results. This is demonstrated on an artificial earthquake generated according to a design spectrum defined in Eurocode 8. A viscous damping ratio combined with the results of eigenvalue analysis is used to derive parameters of Rayleigh damping for three specific scenarios promoting the approach based on the lowest natural frequency as sufficiently accurate for the present task.

Shear modulus reduction and damping ratio curves for earth core materials of dams

2019 ◽  
Vol 56 (1) ◽  
pp. 14-22 ◽  
Author(s):  
DongSoon Park ◽  
Tadahiro Kishida
Keyword(s):  
Shear Modulus ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Empirical Relationship ◽  
Embankment Dams ◽  
In Situ Data ◽  
Earth Core ◽  
Dynamic Analyses ◽  
Modulus Reduction ◽  
Core Materials

It is essential to obtain shear modulus reduction and damping ratio curves to perform dynamic analyses of earth-cored embankment dams. Many studies have been performed for dynamic properties of clayey soils, but they have been limited for earth core materials of dams. This study conducted resonant column tests to obtain shear modulus reduction (G/Gmax) and damping ratio (D) curves for 31 specimens (17 undisturbed and 14 remolded specimens) from 13 earth-cored embankment dams. Empirical G/Gmax and D curves are proposed for dynamic properties of clayey earth core materials. Fitting curves are provided by using the functional forms of the Ramberg–Osgood and Darendeli models. The observation shows that the undisturbed earth cores yield relatively higher G/Gmax and lower D curves than the remolded cores. G/Gmax curves of compacted earth cores are relatively higher than those of Vucetic and Dobry curves for a similar level of plasticity index. Uncertainty and bias are calculated by performing residual analysis, which shows that there is no clear bias in predicting G/Gmax and the uncertainties between undisturbed earth core materials and natural deposits are at a similar level. A proposed empirical relationship of G/Gmax and D curves for earth core materials can be utilized for dynamic analyses of embankment dams for cases where there is insufficient in situ data.

scholarly journals Novel Methods for the Computation of Small-Strain Damping Ratios of Soils from Cyclic Torsional Shear and Free-Vibration Decay Testing

Geotechnics ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 330-346
Author(s):  
Zhongze Xu ◽  
Yumeng Tao ◽  
Lizeth Hernandez
Keyword(s):  
Free Vibration ◽  
Ambient Noise ◽  
Damping Ratio ◽  
Small Strain ◽  
Material Damping ◽  
Viscous Material ◽  
Small Strains ◽  
Torsional Shear ◽  
Novel Methods ◽  
Decay Testing

This paper illustrates two novel methods for computing the small-strain hysteretic material damping ratio, λmin, of soils from the cyclic torsional shear (TS) and computing the small-strain viscous material damping ratio, Dmin, from the free-vibration decay (FVD) testing. Both λmin and Dmin are challenging to measure, due to the significant level of ambient noise at small strains (<10−4%). A two-step method is proposed combining the Fourier Transform and a phase-based data fitting method for torsional shear testing, and this method can effectively eliminate the ambient noise at small strains. A Hilbert Transform-based method is proposed for the free-vibration decay testing in order to achieve a more accurate measurement of the viscous material damping ratio, D, at different strain levels, especially at small strains. The improved λmin and Dmin at small strains are compared to data available in the literature. The two novel methods are shown to be accurate in computing the small-strain damping ratios.

Damping Identification and its Comparison for Various Types of Blade Couplings

2013 ◽  
Author(s):  
Zdenek Kubin ◽  
Vaclav Polreich ◽  
Vaclav Cerny ◽  
Petra Babkova ◽  
Lubos Prchlik
Keyword(s):  
Steam Turbine ◽  
Damping Ratio ◽  
Nonlinear Behavior ◽  
Mode Shapes ◽  
Material Damping ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Linear Behavior ◽  
Disc Rotation ◽  
Identification Technique

Regarding steam turbine blade vibrations, damping of blade as well as bladed disc mode shapes is one of the most important parameters in terms of steam turbine operation. A value of the parameter depends on properties of material used for manufacturing and construction elements of the blades and the discs such as blade roots, shrouds, tiebosses (snubbers) and dampers. This article deals with a comparison of damping of mode shapes for particular blade couplings and shows which methods are suitable for determination of the damping in individual cases. The whole identification procedure of the damping together with its specifics is also presented. At first, an identification technique of material damping ratio is introduced and its results are given for different materials. The material damping ratio is assessed as material strain dependent. Subsequently, damping ratio of bladed disc mode shapes under bladed disc rotation is identified taking into account two alternatives. The alternatives differ in such a way that blades have been free for the first time and then coupled with friction dampers. Outcomes presented in the article illustrate good agreement between damping ratio of bladed disc mode shapes with free blades and material used for manufacturing of the blades. On the other hand, damping ratio of bladed disc mode shapes with friction dampers is significantly different and strongly dependent on blade vibration amplitudes as well as nodal diameters of bladed disc mode shapes. Finally, nonlinear behavior of the bladed disc has been revealed along large blade vibration amplitudes and higher nodal diameters of the disc. The non-linear behavior manifests itself in such a way that values of natural frequencies of the disc have become dependent on blade vibration amplitudes.

The Effect of Temperature on the Material Damping of Graphite/Epoxy Composites in a Simulated Space Environment

1990 ◽  
Vol 112 (3) ◽  
pp. 277-279 ◽  
Author(s):  
G. T. Spirnak ◽  
J. R. Vinson
Keyword(s):  
Room Temperature ◽  
Damping Ratio ◽  
Theoretical Models ◽  
Space Environment ◽  
Effect Of Temperature ◽  
Time Cost ◽  
Material Damping ◽  
Temperature Dependent ◽  
Increasing Temperature ◽  
Free Beam

An experimental method for measuring material damping is described, which employs a free-free beam lightly supported at the nodes. A thermal space environment is simulated by measuring the material damping in air at temperatures ranging from −65°F to 225°F, and then subtracting out the effects of atmospheric damping. This method saves considerable time, cost and experimental difficulties associated with performing the experiments in a vacuum. Graphite/epoxy AS4/3501-6 composite beam specimens were tested. At room temperature, the [0°]12 composites were found to have an average damping ratio of 0.0556 percent. The [90°]12 composites were found to have an average material damping ratio of 0.55 percent. These data agree well with the theoretical models and experimental measurements performed in a vacuum. The material damping ratio is temperature dependent over the range −65°F to 225°F, increasing with increasing temperature. For the [0°]12 composite, the material damping ratio varies from 0.0397 percent at −65°F to 0.083 percent at 225°F. For the [90°]12 composite, the material damping ratio varies from 0.408 percent at −65°F to 0.860 percent at 225°F.

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