Vincent P. Drnevich

Bio: Vincent P. Drnevich is an academic researcher from University of Kentucky. The author has contributed to research in topics: Mercalli intensity scale & Urban seismic risk. The author has an hindex of 11, co-authored 47 publications receiving 2940 citations.

Shear modulus and damping in soils: design equations and curves

Abstract: Equations and graphs for the determination of shear modulus and damping of soils, for use in design problems involving repeated loading or vibration of soils, are presented. These equations and graphs are based on numerous laboratory tests on both remolded and undisturbed cohesive soils and on clean sands. Comparison of the measured and computed values shows good agreement. An example problem showing how these equations and curves are used is given.

Shear modulus and damping in soils: measurement and parameter effects

Abstract: BASED ON NUMEROUS TESTS ON A SPECTRUM OF DISTURBED AND UNDISTURBED SOILS, THE SHEAR MODULUS DECREASES AND THE DAMPING RATIO INCREASES VERY RAPIDLY WITH INCREASING STRAIN AMPLITUDE. THE RATE OF INCREASE OR DECREASE DEPENDS ON MANY PARAMETERS: EFFECTIVE MEAN PRINCIPAL STRESS; DEGREE OF SATURATION; VOID RATIO; AND NUMBER OF CYCLES OF LOADING. AMBIENT STATES OF OCTAHEDRAL SHEAR STRESS, OVERCONSOLIDATION RATIO, EFFECTIVE STRENGTH ENVELOPE, FREQUENCY OF LOADING, AND TIME EFFECTS HAVE A LESS IMPORTANT INFLUENCE ON THESE PROPERTIES. COHESIVE SOILS ARE AFFECTED DIFFERENTLY THAN CLEAN SANDS. THE APPARATUS USED TO MEASURE SHEAR MODULUS AND DAMPING MUST BE CAPABLE OF MAKING ACCURATE MEASUREMENTS AT VERY SMALL SHEARING STRAINS, THE RANGE BEING DEFINED BY PRACTICAL PROBLEMS IN EARTHQUAKE AND FOUNDATION VIBRATIONS. A PSEUDO STATIC SIMPLE SHEAR APPARATUS AND TWO DIFFERENT RESONANT COLUMN APPARATUS WERE USED. /AUTHOR/

Shear Modulus and Damping in Soils: Measurement and Parameter Effects (Terzaghi Leture)

Abstract: Based on numerous tests on a spectrum of disturbed and undisturbed soils, the shear modulus decreases and the damping ratio increases very rapidly with increasing strain amplitude. The rate of increase or decrease depends on many parameters: (1) Effective mean principal stress; (2) degree of saturation; (3) void ratio; and (4) number of cycles of loading. Ambient states of octahedral shear stress, overconsolidation ratio, effective strength envelope, frequency of loading, and time effects have a less important influence on these properties. Cohesive soils are affected differently than clean sands. The apparatus used to measure shear modulus and damping must be capable of making accurate measurements at very small shearing strains, the range being defined by practical problems in earthquake and foundation vibrations. A pseudo static simple shear apparatus and two different resonant column apparatus were used.

Modulus and Damping of Soils by the Resonant-Column Method

Abstract: The resonant-column method, a relatively nondestructive test employing wave propagation in cylindrical specimens, is used to obtain modulus and damping of soils as functions of vibratory strain amplitude and other factorssuch as ambient confining stress and void ratio. Descriptions of the apparatus, calibration procedures, testing procedures, and aids for data reduction are given for apparatus which propagate either rod compression waves or shear waves or both. Data reduction aids include graphs for a wide range of apparatus conditions and include a computer program that covers all admissable boundary conditions.

Dynamic prestraining of dry sand

Abstract: Dynamic prestraining is the application of vibratory shearing strains to soil that is acted upon by static confining pressure. Tests on hollow, cylindrical Ottawa sand specimens, in a torsional resonant column apparatus, demonstrate that material behavior may be significantly changed by prestraining. In general, prestraining at shearing strains between 0.001% and 0.01% can double the dynamic shear modulus and damping, strikingly reduce the static compressibility, and cause fatigue failures. Density changes cannot account for this. No changes occur for prestraining at shearing strains less than 0.001%. The effects are dependent on confining pressure, void ratio, shearing strain amplitude, and cycles of vibration. Millions of cycles may be necessary to produce these changes. Test results indicate that density or void ratio measurements may not reveal the total change in these parameters imparted to dry sands by vibratory loading. This is important in determining the dynamic response of foundations and the compaction improvement of sand soils.

Effect of Soil Plasticity on Cyclic Response

Abstract: A study on the influence of the plasticity index (PI) on the cyclic stress‐strain parameters of saturated soils needed for site‐response evaluations and seismic microzonation is presented. Ready‐to‐use charts are included, showing the effect of PI on the location of the modulus reduction curve G/Gmax versus cyclic shear strain γc, and on the material damping ratio λ versus γc curve. The charts are based on experimental data from 16 publications encompassing normally and overconsolidated clays (OCR=1-15), as well as sands. It is shown that PI is the main factor controlling G/Gmax and λ for a wide variety of soils; if for a given γc PI increases, G/Gmax rises and λ is reduced. Similar evidence is presented showing the influence of PI on the rate of modulus degradation with the number of cycles in normally consolidated clays. It is concluded that soils with higher plasticity tend to have a more linear cyclic stress‐strain response at small strains and to degrade less at larger γc than soils with a lower PI. ...

NGA Ground Motion Model for the Geometric Mean Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra for Periods Ranging from 0.01 to 10 s

Abstract: We present a new empirical ground motion model for PGA, PGV, PGD and 5% damped linear elastic response spectra for periods ranging from 0.01– 10 s. The model was developed as part of the PEER Next Generation Attenuation (NGA) project. We used a subset of the PEER NGA database for which we excluded recordings and earthquakes that were believed to be inappropriate for estimating free-field ground motions from shallow earthquake mainshocks in active tectonic regimes. We developed relations for both the median and standard deviation of the geometric mean horizontal component of ground motion that we consider to be valid for magnitudes ranging from 4.0 up to 7.5–8.5 (depending on fault mechanism) and distances ranging from 0 – 200 km. The model explicitly includes the effects of magnitude saturation, magnitude-dependent attenuation, style of faulting, rupture depth, hanging-wall geometry, linear and nonlinear site response, 3-D basin response, and inter-event and intra-event variability. Soil nonlinearity causes the intra-event standard deviation to depend on the amplitude of PGA on reference rock rather than on magnitude, which leads to a decrease in aleatory uncertainty at high levels of ground shaking for sites located on soil. DOI: 10.1193/1.2857546

Moduli and Damping Factors for Dynamic Analyses of Cohesionless Soils

Abstract: Data are presented concerning the shear modulus and damping ratios of sands and gravelly soils as determined by laboratory and field tests. A simple relationship is proposed to relate the shear modulus of a cohesionless soil to a modulus stiffness coefficient, which is a soil property and depends on the characteristics of the soil, and the effective mean principal stress at any point in the soil. Values for the modulus coefficient at low strains are suggested, and it is shown that these values for sands can be estimated from the standard penetration resistance of the sand. Values for gravels are generally greater than those for sands by factors ranging from 1.35–2.5. Suggestions are also made for determining the variation of shear modulus with shear strain and the damping ratios for both sandy and gravelly soils.

Liquefaction resistance of soils from shear-wave velocity

Abstract: A simplified procedure using shear-wave velocity measurements for evaluating the liquefaction resistance of soils is presented. The procedure was developed in cooperation with industry, researchers, and practitioners and evolved from workshops in 1996 and 1998. It follows the general format of the Seed-Idriss simplified procedure based on standard penetration test blow count and was developed using case history data from 26 earthquakes and >70 measurement sites in soils ranging from fine sand to sandy gravel with cobbles to profiles including silty clay layers. Liquefaction resistance curves were established by applying a modified relationship between the shear-wave velocity and cyclic stress ratio for the constant average cyclic shear strain suggested by R. Dobry. These curves correctly predicted moderate to high liquefaction potential for >95% of the liquefaction case histories and are shown to be consistent with the standard penetration test based curves in sandy soils. A case study is provided to illustrate application of the procedure. Additional data are needed, particularly from denser soil deposits shaken by stronger ground motions, to further validate the simplified procedure.