• Title/Summary/Keyword: shear stress-strain

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Behaviour of laminated elastomeric bearings

  • Mori, A.;Moss, P.J.;Carr, A.J.;Cooke, N.
    • Structural Engineering and Mechanics
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    • v.5 no.4
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    • pp.451-469
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    • 1997
  • Experimental work undertaken to investigate the behaviour of laminated elastomeric bridge bearings under compression and a combination of compression and shear or rotation has been reported on elsewhere. However, it is difficult to determine the state of stress within the bearings in terms of the applied forces or the interaction between the steel shims and the rubber layers in the bearings. In order to supply some of the missing information about the stress-strain state within the bearings, an analytical study using the finite element method was carried out. The available experimental results were used to validate the model after which the analyses were used to provide further information about the state of stress within the bearing.

A new size-dependent shear deformation theory for wave propagation analysis of triclinic nanobeams

  • Karami, Behrouz;Janghorban, Maziar
    • Steel and Composite Structures
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    • v.32 no.2
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    • pp.213-223
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    • 2019
  • For the first time, longitudinal and transverse wave propagation of triclinic nanobeam is investigated via a size-dependent shear deformation theory including stretching effect. Furthermore, the influence of initial stress is studied. To consider the size-dependent effects, the nonlocal strain gradient theory is used in which two small scale parameters predict the behavior of wave propagation more accurately. The Hamiltonian principle is adopted to obtain the governing equations of wave motion, then an analytic technique is applied to solve the problem. It is demonstrated that the wave characteristics of the nanobeam rely on the wave number, nonlocal parameter, strain gradient parameter, initial stress, and elastic foundation. From this paper, it is concluded that the results of wave dispersion in isotropic and anisotropic nanobeams are almost the same in the presented case study. So, in this case, triclinic nanobeam can be approximated with isotropic model.

Stress-Strain Characteristics of Weathered Granite Soil in Plane Strain Test (평면변형시험을 이용한 화강풍화토의 응력-변형률 특성)

  • Kim, You-Seong;Lee, Jin-Kwang;Kim, Jae-Hong
    • Journal of the Korean Geotechnical Society
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    • v.30 no.5
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    • pp.37-46
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    • 2014
  • Geotechnical structures have been analyzed and constructed in various geometry conditions to maintain their stability in accordance with the characteristics of construction design. Shear strengths are generally obtained from triaxial test to apply to design analysis. Geotechnical structures under strip loading, such as earth dam, embankment, and retaining wall, have the strain in a direction, and plane strain condition. Thus, an approximate shear strengths should be applied for stability analysis suitable to ground condition. When applying shear strengths obtained from triaxial tests for slope stability analysis, the evaluation of it may underestimate the factor of safety because the implementation is not suitable for geometry condition. The paper compares shear strengths obtained from triaxial test and plane strain test based on various relative densities using weathered granite soils. Additionally, yield stress is determined by maximum axial strain 15% in triaxial test because of continuous kinematic hardening, but plane strain test can determine a failure point in critical state to evaluate the shear strengths of soils at the second plastic hardening step. This study proposes to perform an appropriate test for many geotechnical problems with plane strain condition.

Unidirectional cyclic shearing of sands: Evaluation of three different constitutive models

  • Oscar H. Moreno-Torres;Cristhian Mendoza-Bolanos;Andres Salas-Montoya
    • Geomechanics and Engineering
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    • v.35 no.4
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    • pp.449-464
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    • 2023
  • Advanced nonlinear effective stress constitutive models are started to be frequently used in one-dimensional (1D) and two-dimensional (2D) site response analysis for assessment of porewater generation and liquefaction potential in soft soil deposits. The emphasis of this research is on the assessment of the implementation of this category of models at the element stage. Initially, the performance of a coupled porewater pressure (PWP) and constitutive models were evaluated employing a catalogue of 40 unidirectional cyclic simple shear tests with a variety of relative densities between 35% and 80% and effective vertical stresses between 40 and 80 kPa. The authors evaluated three coupled constitutive models (PDMY02, PM4SAND and PDMY03) using cyclic direct simple shear tests and for decide input parameters used in the model, procedures are recommended. The ability of the coupled model to capture dilation as strength is valuable because the studied models reasonably capture the cyclic performance noted in the experiments and should be utilized to conduct effective stress-based 1D and 2D site response analysis. Sandy soils may become softer and liquefy during earthquakes as a result of pore-water pressure (PWP) development, which may have an impact on seismic design and site response. The tested constitutive models are mathematically coupled with a cyclic strain-based PWP generation model and can capture small-strain stiffness and large-strain shear strength. Results show that there are minor discrepancies between measured and computed excess PWP ratios, indicating that the tested constitutive models provide reasonable estimations of PWP increase during cyclic shear (ru) and the banana shape is reproduced in a proper way indicating that dilation and shear- strain behavior is well captured by the models.

Effect of Duration of Confinement and Its Affecting Factors on the Low-Amplitude Shear Modulus ($G_{max}$) of Soils (토질 최대전단탄성계수($G_{max}$)에 미치는 시간지속효과 및 그 영향요소에 관한 연구)

  • 박덕근
    • The Journal of Engineering Geology
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    • v.9 no.2
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    • pp.135-145
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    • 1999
  • Dynamic Shear modulus (G) is one of the imfortant dynamic soil properties to estimate the response of soil to dynamic loading. Problems in engineering geo1ogy practice the require the knowledge of soil properties subjected to dynamic loadings include soil-structure interaction during earthquakes, bomb blasts, construction operations, and mining. Although the dynamic shear modulus (G) is a time-dependent property, G change with time is often neglected. In this study, the effect of duration of confinement and its affecting factors (previous stress and strain, particle size and sustained pressure, and plasticity index) on the low-amplitude shear modulus ($G_{max}$) of soils are reviewed, and some empirical correlations based on mean particle diameter and plasticity index are proposed.

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Debonding of microbially induced carbonate precipitation-stabilized sand by shearing and erosion

  • Do, Jinung;Montoya, Brina M.;Gabr, Mohammed A.
    • Geomechanics and Engineering
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    • v.17 no.5
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    • pp.429-438
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    • 2019
  • Microbially induced carbonate precipitation (MICP) is an innovative soil improvement approach utilizing metabolic activity of microbes to hydrolyze urea. In this paper, the shear response and the erodibility of MICP-treated sand under axial compression and submerged impinging jet were evaluated at a low confining stress range. Loose, poorly graded silica sand was used in testing. Specimens were cemented at low confining stresses until target shear wave velocities were achieved. Results indicated that the erodibility parameters of cemented specimens showed an increase in the critical shear stress by up to three orders of magnitude, while the erodibility coefficient decreased by up to four orders of magnitude. Such a trend was observed to be dependent on the level of cementation. The treated sand showed dilative behavior while the untreated sands showed contractive behavior. The shear modulus as a function of strain level, based on monitored shear wave velocity, indicated mineral debonding may commence at 0.05% axial strain. The peak strength was enhanced in terms of emerging cohesion parameter based on utilizing the Mohr-Coulomb failure criteria.

Useful Guide to Solve Herschel-Bulkley Model in a Flow Mode Damper (유동 모드 댐퍼에서의 Herschel-Bulkley 모델의 유용한 해법)

  • 이덕영;박성태
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.11a
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    • pp.784-787
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    • 2003
  • Electrorheological(ER) and magnetorheological(MR) fluid-based dampers are typically analyzed using Bingham-plastic shear model under quasi-steady fully developed flow conditions. A Herschel-Bulkley constitutive shear flow relationship is that the linear shear stress vs. strain rate behavior of Bingham model is replaced by a shear stress that is assumed to be proportional to a power law of shear rate. This power is called the flow behavior index. Depending on the value of the flow behavior index number, varying degrees of post-yield shear thickening or thinning behavior can be analyzed. But it is not practical to analyze the damping force in a flow mode damper using Herschel-Bulkley model because it is needed to solve a polynomial equation. A useful guide is suggested to analyze the damping force in a damper using the Herschel-Bulkley model.

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Predicting the Nonlinear Behavior of Reinforced Concrete Membrane Elements Subjected to Reversed Cyclic Loading (반복하중을 받는 철근콘크리트 막요소의 비선형거동에 대한 예측)

  • 이정윤
    • Journal of the Earthquake Engineering Society of Korea
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    • v.6 no.4
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    • pp.7-13
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    • 2002
  • The behaviors of the reinforced concrete membrane elements are expected by Navier's three principles of the mechanics of materials. The adopted cyclic stress-strain curves of concrete consist of seven different unloading and loading stages in the compressive zone and six other stages in the tensile zone. The curves took into account the softening of concrete that was influenced by the tensile strain in the perpendicular direction of cracks. The stress-strain relationships for steel bar embedded in concrete subjected to reversed cyclic forces considered the tension stiffening effect and Baushinger effect. The predicted results of the analysis based on Navier's principles were in good agreement with the observed shear stress-strain relationships as well as transverse and longitudinal strains.

Rheological Behavior of Semi-Solid Ointment Base (Vaseline) in Steady Shear Flow Fields (정상전단유동장에서 반고형 연고기제(바셀린)의 레올로지 거동)

  • Song, Ki-Won;Kim, Yoon-Jeong;Lee, Chi-Ho
    • Journal of Pharmaceutical Investigation
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    • v.37 no.3
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    • pp.137-148
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    • 2007
  • Using a strain-controlled rheometer [Rheometrics Dynamic Analyzer (RDA II)], the steady shear flow properties of a semi-solid ointment base (vaseline) have been measured over a wide range of shear rates at temperature range of $25{\sim}60^{\circ}C$. In this article, the steady shear flow properties (shear stress, steady shear viscosity and yield stress) were reported from the experimentally obtained data and the effects of shear rate as well as temperature on these properties were discussed in detail. In addition, several inelastic-viscoplastic flow models including a yield stress parameter were employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models was examined by calculating the various material parameters (yield stress, consistency index and flow behavior index). Main findings obtained from this study can be summarized as follows : (1) At temperature range lower than $40^{\circ}C$, vaseline is regarded as a viscoplastic material having a finite magnitude of yield stress and its flow behavior beyond a yield stress shows a shear-thinning (or pseudo-plastic) feature, indicating a decrease in steady shear viscosity as an increase in shear rate. At this temperature range, the flow curve of vaseline has two inflection points and the first inflection point occurring at relatively lower shear rate corresponds to a static yield stress. The static yield stress of vaseline is decreased with increasing temperature and takes place at a lower shear rate, due to a progressive breakdown of three dimensional network structure. (2) At temperature range higher than $45^{\circ}C$, vaseline becomes a viscous liquid with no yield stress and its flow character exhibits a Newtonian behavior, demonstrating a constant steady shear viscosity regardless of an increase in shear rate. With increasing temperature, vaseline begins to show a Newtonian behavior at a lower shear rate range, indicating that the microcrystalline structure is completely destroyed due to a synergic effect of high temperature and shear deformation. (3) Over a whole range of temperatures tested, the Herschel-Bulkley, Mizrahi-Berk, and Heinz-Casson models are all applicable and have an almostly equivalent ability to quantitatively describe the steady shear flow behavior of vaseline, whereas the Bingham, Casson,and Vocadlo models do not give a good ability.

Strain-Based Shear Strength Model for Prestressed Beams (프리스트레스트 콘크리트 보를 위한 변형률 기반 전단강도 모델)

  • Kang, Soon-Pil;Choi, Kyoung-Kyu;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.21 no.1
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    • pp.75-84
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    • 2009
  • An analytical model for predicting the shear strength of prestressed concrete beams without shear reinforcement was developed, on the basis of the existing strain-based shear strength model. It was assumed that the compression zone of intact concrete in the cross-section primarily resisted the shear forces rather than the tension zone. The shear capacity of concrete was defined based on the material failure criteria of concrete. The shear capacity of the compression zone was evaluated along the inclined failure surface, considering the interaction with the compressive normal stress. Since the distribution of the normal stress varies with the flexural deformation of the beam, the shear capacity was defined as a function of the flexural deformation. The shear strength of a beam was determined at the intersection of the shear capacity curve and the shear demand curve. The result of the comparisons to existing test results showed that the proposed model accurately predicted the shear strength of the test specimens.