• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.465-471
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• 2006

To describe hysteretic behavior of steel structures under dynamic loading such as earthquake, the dynamic cyclic plasticity model considering stress-strain relationship and characteristics of used steel materials under static-dynamic deforming is required. In this paper, mechanical characteristics and stress-strain relationship of SM490 was clarified by carrying out static-dynamic monotonic and cyclic loading test. A dynamic cyclic plasticity model of SM490 was proposed based on the test results and applied 3-dimensional finite element analysis using finite deformation theory. An analytical method developed by the authors was verified validity and accuracy by comparing both analysis and test results. The comparison result shows that the analytical method developed by the authors can predict static-dynamic hysteretic behavior of steel structures with accuracy.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.735-746
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• 2002

The task of plastic theory is twofold: first, to set up relationships between stress and strain that adequately describe the observed plastic deformation of metals, and second, to develop techniques for using these relationships in studying of the mechanics of metal forming processes, and the anlaysis and design of structures. One of the major problems in the theory of plasticity is to describe the behavior of work-hardening materials in the plastic range for complex loading histories. This can be achieved by formulating constitutive laws either in the integral or differential forms. To adequately predict the response of steel members during cyclic loading, the hardening rule must account for the features of cyclic stress-strain behavior. Neithe of the basic isotropic and kinematic hardening rules is suitable for describing cyclic streess-strain behavior, although a kinematic hardening rule describes the nearly linear portions of the stabilized hystersis loops. There is also a limited expansion of the yield surface as predicted by the isotropic hardening rule. Strong ground motions or wind gusts affect the complex and nonproportional loading histories in the inelastic behavior of structues rather than the proportional loading. Nonproportional loading is defined as externally applied forces on the structure, with variable ratios during the entire loading history. This also includes the rate of time-dependency of the loads. For nonproportional loading histories, unloading may take place along a chord instead of the radius of the load surface. In such cases, the shape of the stress-strain curve has to be determined experimentally for all non-radial loading conditions. The plasticity models including two surface models ae surveyed based on a yield surface and a bound surface that represent a state of maximum stress. This paper is concerned with the improvement of a plasticity models of the two-surface type for structural steel. This is follwed by an overview of plasticity models on structural steel. Finally the need for further research is identified.

• Structural Engineering and Mechanics
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• v.78 no.5
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• pp.545-556
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• 2021

The present experimental study evaluated the seismic performance of six engineered cementitious composite (ECC) columns strengthened with carbon fiber reinforced polymer (CFRP) laminates under cyclic lateral loading. The ECC columns damaged and crushed in the first stage of cyclic tests were repaired using the ECC with a certain polyvinyl alcohol (PVA) fiber and strengthened with flexural and sheer CFRP laminates and then re-assessed under the cyclic loading. The effects of some variables were examined on lateral displacement, energy absorption and dissipation, failure modes, crack patterns, load bearing capacity and plasticity, and the obtained results were compared with those of the first stage of cyclic tests. The results showed that retrofitting the ECC columns can improve their performance, plasticity and load-bearing threshold, delayed the concrete failure, changed the failure modes and increased the energy absorbed by the strengthened columns element by over 50%.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.451-454
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• 1999

An existing plasticity model using multiple failure criteria is modified to describe the behavior of reinforced concrete planar members under cyclic load. Multiple failure criteria are used to define both isotropic damage of compressive crushing and anisotropic damage of tensile cracking. A numerical method is developed to define multi-directional and non-orthogonal crack directions. The material model is implemented in the finite element analysis and verified by comparison with existing experiments of reinforced concrete shear wall.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.469-476
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• 2023

Soil plasticity models for cyclic and dynamic loads are essential in non-linear numerical analysis of geotechnical structures. While a single yield surface model shows a linear behavior for cyclic loads, J₂-bounding surface plasticity model with zero elastic region can effectively simulate a nonlinearity of the ground response with the same material properties. The radius of the yield surface inside the boundary surface converged to 0 to make the elastic region disappear, and plastic hardening modulus and dilatancy define plastic strain increment. This paper presents the stress-strain incremental equation of the developed model, and derives plastic hardening modulus for the hyperbolic model. The comparative analyses of the triaxial compression test and the shallow foundation under the cyclic load can show stable numerical convergence, consistency with the theoretical solution, and hysteresis behavior. In addition, plastic hardening modulus for the modified hyperbolic function is presented, and a methodology to estimate model variables conforming 1D equivalent linear model is proposed for numerical modeling of the multi-dimensional behavior of the ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.529-536
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• 2005

Based on an estimating method for post-cyclic strength and stiffness with cyclic triaxial tests, Direct Simple Shear (DSS) tests were carried out to confirm whether the method can be adapted to DSS test on fine-grained soils: silty clay, plastic silt, and non-plastic silt. Results from post-cyclic DSS tests were interpreted by a modified method as adopted for post-cyclic triaxial tests. In particular, influence of plasticity index for fine-grained soils was emphasised. Findings obtained from the present study are: (i) the higher the plasticity index of fine-grained soils is, the less not stiffness ratio but strength ratio decreases with increment of a normalised excess pore water pressure; and (ii) post-cyclic strength and stiffness results from DSS tests agree well with those predicted by the method modified from a procedure used for triaxial test results.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.239-248
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• 2002

A constitutive model unifying plasticity and crack damage mode)s was developed to address the cyclic behavior of reinforced concrete planar members. The stress of concrete in tension-compression was conceptually defined by the sum of the compressive stress developed by the strut-action of concrete and the tensile stresses developed by tensile cracking. The plasticity model with multiple failure criteria was used to describe the isotropic damage of compressive crushing affected by the anisotropic damage of tensile cracking. The concepts of the multiple fixed crack damage model and the plastic flow model of tensile cracking were used to describe the tensile stress-strain relationship of multi-directional cracks. This unified model can describe the behavioral characteristics of reinforced concrete in cyclic tension-compression conditions, i.e. multiple tensile crack orientations, progressively rotating crack damage, and compressive crushing of concrete. The proposed constitutive model was implemented to finite element analysis, and it was verified by comparison with existing experimental results from reinforced concrete shear panels and walls under cyclic load conditions.

• Journal of Korean Association for Spatial Structures
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• v.6 no.4 s.22
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• pp.53-61
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• 2006

In th is paper, to predicting the large deformation and cyclic plastic behavior of steel members under loading, 3-Dimensional elastic-plastic FE analysis method is developed by using finite deformation theory and proposed cyclic plasticity model. finite deformation theory, described the large deformation, is formulated by using Updated-lagrangian formulation and Green's strain tensor, Jaumann's derivative of Kirchoff stress. Also, cyclic plasticity model proposed by author is applied to developed analysis method. To verification of developed analysis method, analysis result of steel plate specimen compare to the analysis result using infinitesimal deformation theory and test result. Also, load-displacement and deflection shape, analysis result of pipe-section steel column, compare to test result. The good agreement between analysis result and experiment result shown that developed 3-dimensional finite element analysis can be predict the large deformation and cyclic plastic behavior of steel members.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.225-231
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• 2005

In this paper, to prediction of large deformation behavior of steel structures under loading, 3-Dimensional elastic-plastic FE analysis method is developed by using finite deformation theory and proposed cyclic plasticity model. The accuracy of developed analytical method was verified by comparison of experiment result and analysis results using infinitesimal deformation theory. The good agreement between analysis result by developed analytical method and experiment result is shown. Proposed 3-dimensional FE analysis using finite deformation theory and cyclic plasticity hysteresis model can be predict the large deformation of steel members under cyclic loading.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.476-479
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• 2005

In this study, the process parameters in powder compaction are optimized for getting high relative densities. To find optimized parameters, the analytic models of powder compaction are firstly prepared by 2-dimensional rod arrays with random green densities using a quasi-random multi-particle array. Then, using finite element method, the changes in relative densities are analyzed by varying the size of the particle, the amplitude of cyclic compaction, and the coefficient of friction, which influence the relative density in cyclic compactions. After the analytic function of relative density associated process parameters are formulated by aid of the response surface method, the optimal conditions in powder compaction process are found by the grid search method.