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Author: RM. Chung Publisher: ISBN: Category : Damping Languages : en Pages : 10
Book Description
Torsional resonant column tests were performed on Monterey No. 0 sand of 60% relative density under confining pressures ranging from 10 to 300 kPa to evaluate the dynamic properties of the sand. Both solid and hollow cylindrical specimens were used in testing, and shear moduli and damping ratios were determined for cyclic shear strain amplitudes from 10-4 to 5 × 10-2%. The test results indicated that the type of specimen, that is, solid or hollow cylinder, had no significant effect on the calculated shear moduli and damping ratios, except that at very low strain amplitudes (?
Author: RM. Chung Publisher: ISBN: Category : Damping Languages : en Pages : 10
Book Description
Torsional resonant column tests were performed on Monterey No. 0 sand of 60% relative density under confining pressures ranging from 10 to 300 kPa to evaluate the dynamic properties of the sand. Both solid and hollow cylindrical specimens were used in testing, and shear moduli and damping ratios were determined for cyclic shear strain amplitudes from 10-4 to 5 × 10-2%. The test results indicated that the type of specimen, that is, solid or hollow cylinder, had no significant effect on the calculated shear moduli and damping ratios, except that at very low strain amplitudes (?
Author: Soheil Moayerian Publisher: ISBN: Category : Languages : en Pages : 112
Book Description
Dynamic properties of soils (shear stiffness and damping ratio) are critical for the design of structures subjected to vibrations. The dynamic properties of a benchmark standardized laboratory sand (Ottawa silica sand) were evaluated with two different resonant column devices, utilising software with different analytical approaches for the evaluation of soil properties. The dynamic properties (shear modulus and damping ratio) are evaluated as a function of the shear strain level. The results are compared to evaluate the effect of the type of equipment and the form of the data analysis on the measured dynamic properties of the samples. The results are discussed in light of the applicability of the procedures in practice, the ease of the testing methods, and the errors they introduced into analysis and design. In general, the shear wave velocities obtained from the two different devices are in good agreement. However, the damping ratios they give show considerable differences as strains increase. Dynamic properties are typically measured by curve fitting of the transfer function between the excitation and the response using the resonant column device. However, the force function generated by sinusoidal sweep or random noise excitations induce different shear strain levels at different frequencies. Consequently, the shape of the measured transfer function is distorted and differs from the theoretical transfer function for an equivalent single-degree-of-freedom system. The difference between the measured and theoretical transfer functions as well as the bias in the computed dynamic properties becomes more pronounced with the increase in shear strain. This study presents a new methodology for the evaluation of dynamic properties from an equivalent constant-strain transfer function. The soil specimen is excited simultaneously using a sinusoidal excitation (carrier signal) at the required strain level and a small amplitude, narrow band random noise. The strain level induced by the fixed sine is shown to control the resonant frequency of the specimen; whereas the random noise introduces the required frequency bandwidth to determine the transfer function and hence the dynamic properties at a constant strain level. The new methodology also shows a good potential for the evaluation of frequency effects on the dynamic properties of soils in resonant column testing.
Author: Boonam Shin Publisher: ISBN: Category : Languages : en Pages : 188
Book Description
This study was motivated by the fact that many times intact specimens with a number of oversized particles are dynamically tested in the laboratory and the impact of the particles on the dynamic properties is unknown. The effects of oversized particles represented by gravel particles on the shear modulus (G) and material damping ratio (D) of a uniform sand were evaluated in the linear ([gamma] ≤ 0.001%) and nonlinear ([gamma] > 0.001%) ranges of shear strain with combined resonant column and torsional shear (RCTS) equipment. The sand used in this investigation is a uniform sand as a reference, well-characterized material on the dynamic properties. Sand-gravel specimens were constructed using the undercompaction method. A variety of rounded gravel particles was used in building the specimens. Dynamic tests on the sand-gravel specimens were performed, and the tests results are presented. Among the findings of this investigation are that, compared to uniform sand: (1) oversized gravel particles symmetrically located along the longitudinal axis in uniform sand generally decreased slightly the small-strain shear modulus (Gm̳a̳x̳), (2) oversized gravel particles asymmetrically located away from the longitudinal axis of rotation resulted in slight increases in Gm̳a̳x̳ and the small-strain material damping ratio (Dm̳i̳n̳), (3) the G - log [gamma] relationships of sand-gravel specimens with asymmetrically located gravel particles are generally above those with gravel particles symmetrically located along the longitudinal axis, and (4) the G/Gm̳a̳x̳ - log [gamma] relationships of all specimens were reasonably close for the nonlinear ranges covered in these tests ([gamma] 0.05 % and G/Gm̳a̳x̳ 0.6). As long as the oversized particles were near the axis of rotation, the particles had little effect on the dynamic properties (Gm̳a̳x̳, Dm̳i̳n̳ and G - log [gamma] relationships) regardless of sizes and numbers of particles. However, once the oversized particles were located away from the axis of rotation and closer to the perimeter of the specimen, the oversized particles influenced the dynamic properties. Finally, the additions of oversized particles located both symmetrically and asymmetrically in the uniform sand specimens have little impact on the nonlinear dynamic properties (G/Gm̳a̳x̳ - log [gamma] and D - log [gamma] relationships) which compared well with uniform sand.
Author: Yaning Wang (Ph. D.) Publisher: ISBN: Category : Languages : en Pages : 324
Book Description
The study of the dynamic properties of two specific kinds of granular soils is performed using torsional resonant column testing. The sandy soils are: (1) liquefiable sand from Christchurch, New Zealand, and (2) calcareous sand from Puerto Rico. The effects of isotropic effective confining pressure, shear strain amplitude, void ratio, and total unit weight on the small-strain and nonlinear dynamic properties of both types of sand are presented and discussed. Empirical models from previous studies are examined to determine how well the models fit the test results.
Author: Z. X. Yang Publisher: ISBN: Category : Soil dynamics Languages : en Pages : 26
Book Description
The shear modulus and damping ratio of soils at low to medium strains are essential input parameters in dynamic response analysis of soils. As soil elements in the field always have a history of being subjected to vibrations due to earthquakes, construction works, and vehicle motions, etc., the previbration effect on the dynamic properties of soils needs to be addressed appropriately. This study presents a series of tests performed by a newly developed resonant column system that enables the assessment of the dynamic properties of soils that have only undergone dozens of vibration cycles to investigate the impact of the vibration history on the dynamic properties of dry sand. Both the shear modulus and damping ratio of sand under different confining pressures (p′) are measured after the application of a previbration with a wide range of vibration amplitudes (?pre) and number of cycles (N). The results show that an elastic threshold strain exists for the dynamic properties of sand, beyond which the effect of the vibration history can be identified from the shear modulus reduction and damping ratio curves. The results also confirm that the effect of the vibration history on dry sand depends on the test variables of?pre,N, andp′. In addition, a new interpretation method is proposed to quantify the combined effects of?preandNon the signature of the vibration history, which could potentially be useful for interpreting the dynamic properties of the in situ soils that may experience previbration.
Author: T. G. Sitharam Publisher: Springer Nature ISBN: 9813340010 Category : Science Languages : en Pages : 421
Book Description
This volume presents select papers presented at the 7th International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. The papers discuss advances in the fields of soil dynamics and geotechnical earthquake engineering. A strong emphasis is placed on connecting academic research and field practice, with many examples, case studies, best practices, and discussions on performance based design. This volume will be of interest to researchers and practicing engineers alike.
Author: RM. Chung
Author: RM. Chung
Author: Soheil Moayerian
Author: Deron J. Van Hoff
Author: Boonam Shin
Author: Sheng-Huoo Ni
Author: Yaning Wang (Ph. D.)
Author: Z. X. Yang
Author: Frank Edwin Richart
Author: Dugkeun Park
Author: T. G. Sitharam