scholarly journals Effects of relative density and accumulated shear strain on post-liquefaction residual deformation

2013 ◽  
Vol 1 (2) ◽  
pp. 1579-1617
Author(s):  
J. Kim ◽  
M. Kazama ◽  
Y. Kwon
Keyword(s):  
Cyclic Loading ◽  
Relative Density ◽  
Shear Strain ◽  
Axial Strain ◽  
Residual Deformation ◽  
Volumetric Strain ◽  
Lateral Spreading ◽  
Monotonic Loading ◽  
Test Method ◽  
Lateral Strain

Abstract. The damage caused by liquefaction, which occurs following an earthquake, is usually because of settlement and lateral spreading. Generally, the evaluation of liquefaction has been centered on settlement, that is, residual volumetric strain. However, in actual soil, residual shear and residual volumetric deformations occur simultaneously after an earthquake. Therefore, the simultaneous evaluation of the two phenomena and the clarification of their relationship are likely to evaluate post-liquefaction soil behaviors accurately. Hence, a quantitative evaluation of post-liquefaction damage will also be possible. In this study, the effects of relative density and accumulated shear strain on post-liquefaction residual deformations were reviewed through a series of undrained K0 control cylindrical torsional tests. In order to identify the relationship between residual shear and residual volumetric strains, this study proposed a new test method that integrates monotonic loading after cyclic loading, and K0 drain after cyclic loading-in other words, the combination of cyclic loading, monotonic loading, and the K0 drain. In addition, a control that maintained the K0 condition across all the processes of consolidation, cyclic loading, monotonic loading, and drainage was used to reproduce the anisotropy of in-situ ground. This K0 control was performed by controlling the axial strain, based on the assumption that under undrained conditions, axial and lateral strains occur simultaneously, and unless axial strain occurs, lateral strain does not occur. The test results confirmed that the restoration behaviors of effective stresses, which occur during monotonic loading and drainage after cyclic loading, respectively, result from mutually different structure restoration characteristics. In addition, in the ranges of 40~60% relative density and 50~100% accumulated shear strain, relative density was found to have greater effects than the number of cycles (accumulated shear strain).

scholarly journals Effects of relative density and accumulated shear strain on post-liquefaction residual deformation

2013 ◽  
Vol 13 (10) ◽  
pp. 2567-2577
Author(s):  
J. Kim ◽  
M. Kazama ◽  
Y. Kwon
Keyword(s):  
Cyclic Loading ◽  
Relative Density ◽  
Shear Strain ◽  
Axial Strain ◽  
Residual Deformation ◽  
Volumetric Strain ◽  
Monotonic Loading ◽  
Test Method ◽  
Lateral Strain ◽  
Undrained Conditions

Abstract. The damage caused by liquefaction, which occurs following an earthquake, is usually because of settlement and lateral spreading. Generally, the evaluation of liquefaction has been centered on settlement, that is, residual volumetric strain. However, in actual soil, residual shear and residual volumetric deformations occur simultaneously after an earthquake. Therefore, the simultaneous evaluation of the two phenomena and the clarification of their relationship are likely to evaluate post-liquefaction soil behaviors more accurately. Hence, a quantitative evaluation of post-liquefaction damage will also be possible. In this study, the effects of relative density and accumulated shear strain on post-liquefaction residual deformations were reviewed through a series of lateral constrained-control hollow cylindrical torsion tests under undrained conditions. In order to identify the relationship between residual shear and residual volumetric strains, this study proposed a new test method that integrates monotonic loading after cyclic loading, and K0-drain after cyclic loading – in other words, the combination of cyclic loading, monotonic loading, and the K0 drain. In addition, a control that maintained the lateral constrained condition across all the processes of consolidation, cyclic loading, monotonic loading, and drainage was used to reproduce the anisotropy of in situ ground. This lateral constrain control was performed by controlling the axial strain, based on the assumption that under undrained conditions, axial and lateral strains occur simultaneously, and unless axial strain occurs, lateral strain does not occur. The test results confirmed that the recovery of effective stresses, which occur during monotonic loading and drainage after cyclic loading, respectively, result from mutually different structural restoration characteristics. In addition, in the ranges of 40–60% relative density and 50–100% accumulated shear strain, relative density was found to have greater effects than the number of cycles (accumulated shear strain).

Residual Deformation Behavior of Reinforced Rock-Fill Materials

2010 ◽  
Vol 150-151 ◽  
pp. 1495-1499
Author(s):  
Yong Liang Lin ◽  
Meng Xi Zhang ◽  
Xin Xing Li
Keyword(s):  
Cyclic Loading ◽  
Deformation Behavior ◽  
Residual Deformation ◽  
Volumetric Strain ◽  
Test Results ◽  
Rock Fill ◽  
Triaxial Apparatus ◽  
Deformation Behaviors ◽  
Confining Pressures ◽  
Fill Materials

Reinforcement technology is widely used in rock-fill dams in high seismic hazard zones. The evaluation of reinforcement on deformation and safety is concerned and it is one of the major study objectives in rock-fill engineering. The residual deformation behaviors of reinforced rock-fill materials were experimentally studies by use of a triaxial apparatus. The effects were analyzed of intervals of reinforcement layers, confining pressures and the conditions of cyclic loading on residual deformation. Results show that reinforcement improves the residual deformation behaviors of rock-fill materials. Both the residual shear strain and the residual volumetric strain are deduced. Based on the test results, the mechanism of the influence of reinforcement on residual deformation is proposed tentatively.

Noise Performance and Signal-to-Noise Ratio of Shear Strain Elastograms

2005 ◽  
Vol 27 (3) ◽  
pp. 145-165 ◽  
Author(s):  
Arun Thitai Kumar ◽  
Jonathan Ophir ◽  
Thomas A. Krouskop
Keyword(s):  
Shear Strain ◽  
Signal To Noise Ratio ◽  
Axial Strain ◽  
Center Frequency ◽  
Theoretical Expression ◽  
Lateral Strain ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Theoretical Results ◽  
Phantom Experiments

In this paper, we develop a theoretical expression for the signal-to-noise ratio (SNR) of shear strain elastograms. The previously-developed ideas for the axial strain filter (ASF) and lateral strain filter (LSF) are extended to define the concept of the shear strain filter (SSF). Some of our theoretical results are verified using simulations and phantom experiments. The results indicate that the signal-to-noise ratio of shear-strain elastograms ( SNRsse) improves with increasing shear strain and with improvements in system parameters such as the sonographic signal-to-noise ratio ( SNRs) beamwidth, center frequency and fractional bandwidth. The results also indicate that the amount of axial strain present along with the shear strain is an important parameter that determines the upper bound on SNRsse. The SNRsse will be higher in the absence of additional deformation due to axial strain.

Characterization of permanent axial strain of granular materials subjected to cyclic loading based on shakedown theory

2019 ◽  
Vol 198 ◽  
pp. 751-761 ◽  
Author(s):  
Wen-Bo Chen ◽  
Wei-Qiang Feng ◽  
Jian-Hua Yin ◽  
Lalit Borana ◽  
Ren-Peng Chen
Keyword(s):  
Cyclic Loading ◽  
Granular Materials ◽  
Axial Strain ◽  
Shakedown Theory

scholarly journals Optical Coherence Elastography Techniques for Carotid Arterial Wall Imaging

2021 ◽  
Author(s):  
Felix Nolte
Keyword(s):  
Axial Strain ◽  
Image Correlation ◽  
Arterial Blood Flow ◽  
Lateral Strain ◽  
Optical Coherence ◽  
Phantom Experiment ◽  
Arterial Blood ◽  
Speckle Patterns ◽  
Imaging Mode

In this thesis, elastography is evaluated in combination with optical coherence tomography (OCT). Two approaches to OCT based elastography, Digital image correlation (DIC) and Doppler optical coherence elastography (DOCE), are evaluated for an intravascular setup using in vivo images from a porcine carotid model. DIC tracks the displacement of speckle patterns in consecutive frames, allowing the calculation of axial and lateral strain. Rapid speckle decorrelation was observed in preprocessed structural images, affecting the tracking and limiting the feasibility of this algorithm. DOCE measures axial strain based on relative tissue velocities. Rotational movement of the imaging optical fibre was the biggest source of artefacts in this imaging mode, but could be removed with a newly developed algorithm, based on the phase change induced in a surrounding catheter. The standard deviation of phase after artefact removal, measured in a stationary phantom experiment, was ~0.2 rad, corresponding to a minimum detectable velocity of 792 μm/s at a Doppler angle of 20°. The sensitivity allowed the detection of arterial blood flow velocity and pattern and the detection of adjacent veins, but did not allow direct elastography.

scholarly journals EVOLUTION OF THE CARBON NANOTUBE BUNDLE STRUCTURE UNDER BIAXIAL AND SHEAR STRAINS

2020 ◽  
pp. 525
Author(s):  
Leysan Kh. Rysaeva ◽  
Dmitry V. Bachurin ◽  
Ramil T. Murzaev ◽  
Dina U. Abdullina ◽  
Elena A. Korznikova ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Shear Strain ◽  
Cross Sections ◽  
Degrees Of Freedom ◽  
Shear Bands ◽  
Volumetric Strain ◽  
Structural Evolution ◽  
Biaxial Compression ◽  
Chain Model ◽  
Nanotube Bundle

Close packed carbon nanotube bundles are materials with highly deformable elements, for which unusual deformation mechanisms are expected. Structural evolution of the zigzag carbon nanotube bundle subjected to biaxial lateral compression with the subsequent shear straining is studied under plane strain conditions using the chain model with a reduced number of degrees of freedom. Biaxial compression results in bending of carbon nanotubes walls and formation of the characteristic pattern, when nanotube cross-sections are inclined in the opposite directions alternatively in the parallel close-packed rows. Subsequent shearing up to a certain shear strain leads to an appearance of shear bands and vortex-like displacements. Stress components and potential energy as the functions of shear strain for different values of the biaxial volumetric strain are analyzed in detail. A new mechanism of carbon nanotube bundle shear deformation through cooperative, vortex-like displacements of nanotube cross sections is reported.

scholarly journals Mechanical response and pore pressure generation in granular filters subjected to uniaxial cyclic loading

2018 ◽  
Vol 55 (12) ◽  
pp. 1756-1768
Author(s):  
Jahanzaib Israr ◽  
Buddhima Indraratna
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Pore Water ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Axial Strain ◽  
Water Pressure ◽  
Internal Erosion ◽  
Excess Pore Water Pressure ◽  
Excess Pore

This paper presents results from a series of piping tests carried out on a selected range of granular filters under static and cyclic loading conditions. The mechanical response of filters subjected to cyclic loading could be characterized in three distinct phases; namely, (I) pre-shakedown, (II) post-shakedown, and (III) post-critical (i.e., the occurrence of internal erosion). All the permanent geomechanical changes such, as erosion, permeability variations, and axial strain developments, took place during phases I and III, while the specimen response remained purely elastic during phase II. The post-critical occurrence of erosion incurred significant settlement that may not be tolerable for high-speed railway substructures. The analysis revealed that a cyclic load would induce excess pore-water pressure, which, in corroboration with steady seepage forces and agitation due to dynamic loading, could then cause internal erosion of fines from the specimens. The resulting excess pore pressure is a direct function of the axial strain due to cyclic densification, as well as the loading frequency and reduction in permeability. A model based on strain energy is proposed to quantify the excess pore-water pressure, and subsequently validated using current and existing test results from published studies.

Exterior RC joints subjected to monotonic and cyclic loading

2020 ◽  
Vol 37 (7) ◽  
pp. 2319-2336 ◽  
Author(s):  
Yasmin Murad ◽  
Haneen Abdel-Jabar ◽  
Amjad Diab ◽  
Husam Abu Hajar
Keyword(s):  
Shear Strength ◽  
Cyclic Loading ◽  
Axial Load ◽  
Monotonic Loading ◽  
Concrete Compressive Strength ◽  
Joint Shear Strength ◽  
Content Type ◽  
Loading Case ◽  
Joint Shear ◽  
Test Points

Purpose The purpose of this study is to develop two empirical models that predict the shear strength of exterior beam-column joints exposed to monotonic and cyclic loading using Gene expression programming (GEP). Design/methodology/approach The GEP model developed for the monotonic loading case is trained and validated using 81 data test points and that for cyclic loading case is trained and validated using 159 data test points that collected from different 9 and 39 experimental programs, respectively. The parameters that are selected to develop the cyclic GEP model are concrete compressive strength, joint aspect ratio, column axial load and joint transverse reinforcement. The monotonic GEP model is developed using concrete compressive strength, column depth, joint width and column axial load. Findings GEP models are proposed in this paper to predict the joint shear strength of beam-column joints under cyclic and monotonic loading. The predicted results obtained using the GEP models are compared to those calculated using the ACI-352 code formulations. A sensitivity analysis is also performed to further validate the GEP models. Originality/value The proposed GEP models provide an accurate prediction for joint shear strength of beam-column joints under cyclic and monotonic loading that is more fitting to the experimental database than the ACI-352 predictions where the GEP models have higher R2 value than the code formulations.

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