• Architectural research
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• v.14 no.4
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• pp.153-161
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• 2012

This paper presents an integrated procedure to predict the temperature and moisture distributions in hardening concrete considering the effects of temperature and aging. The degree of hydration is employed as a fundamental parameter to evaluate hydro-thermal-mechanical properties of hardening concrete. The temperature history and temperature distribution in hardening concrete is evaluated by combining cement hydration model with three-dimensional finite element thermal analysis. On the other hand, the influences of both self-desiccation and moisture diffusion on variation of relative humidity are considered. The self-desiccation is evaluated by using a semi-empirical expression with desorption isotherm and degree of hydration. The moisture diffusivity is expressed as a function of degree of hydration and current relative humidity. The proposed procedure is verified with experimental results and can be used to evaluate the early-age crack of hardening concrete.

• Structural Engineering and Mechanics
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• v.9 no.3
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• pp.215-226
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• 2000

Computational procedure within the framework of return mapping technique has been presented to integrate the constitutive behavior of a concrete model. Developed by Ohtani and Chen, this concrete model is based on multiple hardening concept, and is rate-independent and associative. Consistent tangent operator suitable for finite element analysis is derived to preserve the rate of convergence. Accuracy of the integration technique is verified and compared with available experimental data. Computational efficiency is demonstrated by comparing with results based on elasto-plastic tangent.

• Structural Engineering and Mechanics
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• v.2 no.1
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• pp.35-48
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• 1994

A plasticity-based concrete model is proposed. The failure surface is elliptic in the ${\sigma}-{\tau}$ stress space. Independent hardening as well as softening is assumed in tension, compression, and shear. The nonlinear inelastic action initiates from the origin in the ${\sigma}-{\varepsilon}$(${\tau}-{\gamma}$) diagram. Several parameters are incorporated to control hardening/softening regions. The model is incorporated into a nonlinear finite element program along with other classical models. Several examples are solved and the results are compared with experimental data and other failure criteria. "Reasonable results" and stable solutions are obtained for different types of reinforced concrete oriented structures.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.1
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• pp.106-117
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• 1998

The nature of stress-path dependency, the principle that governs deformations in granular soil, and the use of Lade's double work-hardening model for predicting soil response for a variety of stress-paths have been investigated, and are examined The test results and the analyses presented show that under some conditions granular soils exhibit stress-path dependent behavior. For stress-paths involving unloading or reloading, the stress-path with the higher average stress level produces the larger strains, whereas all stress-paths having the same intial states of stress, and involving only primary loading conditions, produce strains of similar magnitudes. Experimental evidence indicates that the stress- path dependent response obtained from the double work-hardening model is also observed for real soils. It is concluded that the influence of stress history on the friction angle is negligible and the strains increment direction is uniquely determined from the state of stress but is not perpendicular to the yield surface. The strains calculated from Lade's double work-hardening model are in reasonable agreement with those measured.

• Geomechanics and Engineering
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• v.36 no.4
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• pp.355-366
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• 2024

The original elastoplastic Hardening Soil model is formulated actually partly under hexagonal pyramidal Mohr-Coulomb failure criterion, and can be only used in specific stress paths. It must be completely generalized under Mohr-Coulomb criterion before its usage in engineering practice. A set of generalized constitutive equations under this criterion, including shear and volumetric yield surfaces and hardening laws, is proposed for Hardening Soil model in principal stress space. On the other hand, a Mohr-Coulumb type yield surface in principal stress space comprises six corners and an apex that make singularity for the normal integration approach of constitutive equations. With respect to the isotropic nature of the material, a technique for processing these singularities by means of Koiter's rule, along with a transforming approach between both stress spaces for both stress tensor and consistent stiffness matrix based on spectral decomposition method, is introduced to provide such an approach for developing generalized Hardening Soil model in finite element analysis code ABAQUS. The implemented model is verified in comparison with the results after the original simulations of oedometer and triaxial tests by means of this model, for volumetric and shear hardenings respectively. Results from the simulation of oedometer test show similar shape of primary loading curve to the original one, while maximum vertical strain is a little overestimated for about 0.5% probably due to the selection of relationships for cap parameters. In simulation of triaxial test, the stress-strain and dilation curves are both in very good agreement with the original curves as well as test data.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.5
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• pp.498-509
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• 2009

Present study is concerned with the simulation of plasticity models for the cyclic stressstrain behavior of aluminum alloy AC4C-T6 that can be used for primary materials of LNG cargo pump. Material model of cyclic hardening and plasticity for aluminum alloy AC4C-T6 was investigated through experiments and numerical simulations. Monotonic tensile and cyclic tension-compression test under symmetric load cycles was performed at both room temperature and cryogenic temperature of $-165^{\circ}C$. Based on the experimental data plastic hardening models were evaluated for isotropic/kinematic/combined hardening. FEA (Finite Element Analysis) models which describe the cyclic stress-strain relationship were evaluated for the simulation of plasticity. An appropriate hardening model is proposed comparing the results of FEA with those of experiments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.7 s.250
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• pp.757-764
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• 2006

Isothermal cyclic stress-strain deformation and thermomechanical deformation (TMD) of 429EM stainless steel were analyzed using a rheological model employing a bi-linear model. The proposed model was composed of three parameters: elastic modulus, yield stress and tangent modulus. Monotonic stress-strain curves at various temperatures were used to construct the model. The yield stress in the model was nearly same as 0.2% offset yield stress. Hardening relation factor, m, was proposed to relate cyclic hardening to kinematic hardening. Isothermal cyclic stress-strain deformation could be described well by the proposed model. The model was extended to describe TMD. The results revealed that the hi-linear thermomechanical model overestimates the experimental data under both in-phase and out-of-phase conditions in the temperature range of $350-500^{\circ}C$ and it was due to the enhanced dynamic recovery effect.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.65-73
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• 2000

An elasto-plastic constitutive model was proposed, in which the behavior at small-to-large strain level can be modeled. The proposed model is based on the anisotropic hardening description with the generalization of isotropic hardening rule and the total stress concept. From a mathematical approach it was proved that the model includes the previous successful models. The model was verified by a series of resonant column tests, torsional shear tests and triaxial tests, and the proposed model predicted small-to-large strain behavior more consistently and accurately than the hyperbolic model and the Ramberg-Osgood model for a weathered granitic soil. In addition, the nonlinearity under small strain condition was predicted appropriately for the torsional shear test results.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.75-83
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• 2004

This study is focused on the constitutive model in order to represent brittleness and dilatancy of cohesionless soils. The constitutive model was proposed on the basis of an anisotropic hardening rule with generalized isotropic hardening rule. The shape of yield surface is a simple cylinder type in stress space and it makes the model practically useful. Flow rule was approximated by a concrete function on dilatancy. A peak stress ratio was defined to model brittle stress-strain relationships. The proposed model was formulated and implemented to calculate the stress-strain relationship from triaxial tests. In the companion paper the proposed model will be verified by comparison with the triaxial test results.

• Earthquakes and Structures
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• v.17 no.5
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• pp.489-499
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• 2019

Elastic-plastic behavior of nuclear power plant elbow piping under seismic loads has been conducted in this study. Finite element analyses are performed using classical Bilinear kinematic hardening model (BKIN) and Multilinear kinematic hardening model (MKIN) as well as a nonlinear kinematic hardening model (Chaboche model). The influence of internal pressure and seismic loading on ratcheting strain of elbow pipe is studied by means of the three models. The results found that the predicted results of Chaboche model is maximum, closely followed by the predicted results of MKIN model, and the minimum is the predicted results of BKIN model. Moreover, comparisons of analysis results for each plasticity model against predicted results for a equivalent cyclic loading elbow component and for a simplified piping system seismic test are presented in the paper.