• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.3A
• /
• pp.447-455
• /
• 2006

A general purpose of 4-node co-rotational resultant shell element is developed for the solution of nonlinear problems of reinforced concrete, steel and fiber-reinforced composite structures. The formulation of the geometrical stiffness presented here is defined on the mid-surface by using the second order kinematic relations and is efficient for analyzing thick plates and shells by incorporating bending moment and transverse shear resultant forces. The present element is free of shear locking behavior by using the ANS (Assumed Natural Strain) method such that the element performs very well as thin shells. Inelastic behaviour of concrete material is based on the plasticity with strain hardening and elasto-plastic fracture model. The plasticity of steel is based on Von-Mises Yield and Ivanov Yield criteria with strain hardening. The transverse shear stiffness of laminate composite is defined by an equilibrium approach instead of using the shear correction factor. The proposed formulation is computationally efficient and versitile for most civil engineering application and the test results showed good agreement.

• Journal of the Korea Concrete Institute
• /
• v.22 no.5
• /
• pp.675-684
• /
• 2010

The reinforced concrete members are designed to fail in flexural to lead ductile fracture. In the building structures, the failure is typically imposed on beams to prevent damages in columns. However, progression of plastic collapse mechanism may ultimately develop, a plastic hinge at the bottem end of the first floor column, which then can be subjected to shear or bond finally due to large axial force and small shear span-to-depth ratio. In this study, 10 RC column specimens failed in shear after flexural yielding was investigated to determine the factors affecting the plastic hinge length. The findings of this study showed that the most effective factor affecting the plastic hinge length was an axial force. As an axial force increase, an axial strain and a ductility ratio were decreased obviously. The test also shows the observed plastic hinge length was about 0.8~1.2d and the this result has difference compared with forward research.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.4
• /
• pp.3-17
• /
• 1999

Torsion shear tests under various stress paths were performed to study the behavior of sand during large stress reversal. The stress paths can be classified into the clockwise and the counterclockwise according to torque applied to specimen, and the directions of plastic strain incremental on the stress paths including large stress reversal are compared with the direction of stress state and stress incremental. From test results, the isotropic hardening theory using the principle of St. Venant desirably showed that direction of plastic strain incremental coincided with stress state on primary loading part and nearby failure point, but it might result in a rough approximation on part of unloading and reloading by stress reversal.

• International Journal of Highway Engineering
• /
• v.10 no.2
• /
• pp.205-219
• /
• 2008

The polymers, low-density polyethylene (LDPE) and styrene-butadiene-styrene(SBS) -modified asphalt mixtures are advanced asphalt pavement materials in which $3{\sim}6%$ of them, and/or some other additive, by weight of total binder are added. The purpose of modifying asphalt material is to improve typical weakness such as rutting and cracking resistance of normal asphalt mixtures. These materials have been proved to show many advantages and practical applicability in the plant and field. Wet processed PMA binder and/or dry processed asphalt mixtures are developed as field products for many years. The objective of this paper is to show the characteristics of the LDPE and SBS-modified asphalt mixtures by comprehensive evaluation and comparison with those of normal asphalt mixtures.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.6
• /
• pp.675-683
• /
• 2011

When impacts by falling objects are applied to the structures, vertical resisting member(column or column group) results in progressive collapse. By knowing clearly load-deformation relationship of a structural frame, to prevent progressive collapse by absorbing potential energy of falling objects though column groups are lost by the impact of falling object accidently. If residual strength in vertical direction exceeds vertical load, which the sum of the weight of falling objects and usual supportive vertical load as the result of absorbing released location energy, it does not result in progressive collapse. On the other hand, in case when weight of falling objects is included in usual supportive vertical load. In this paper, 1-story 4-spans model is analyzed by non-linear FEM and to examine the level of deterioration, limit analysis of 1-story 4-spans plane frame was carried out.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.6
• /
• pp.1405-1415
• /
• 1994

The soil on the behavior of the nonlinear elastic work-hardening plasticity has a variety of stress paths due to the state of soil and the test conditions. The soil with a specific volume ${\upsilon}$ in principal stress space (${\sigma}_1$, ${\sigma}_2$, ${\sigma}_3$, and ${\upsilon}$v) displays the shape of an irregular hexagonal pyramid with an end cap. With variations of ${\upsilon}$ the size of the cap is changed but its shape remains unchanged and the movement of the cap is controlled by the increase or decrease of the plastic volumetric strain. By reflecting such a property of soil various cap models have been developed by researchers. In this thesis, a constitutive model of soil with a combination of the nonlinear elastic work-hardening plastic cap and the failure surfaces of Mohr-Coulomb (M-C cap model) has been developed. According to the the results of analyses using the work-hardening plastic cap model, the normally consolidated soil under shearing has experienced the work-hardening and plastic flow (movement of the cap). But in the shearing of the overconsolidated soil the elastic behavior is shown until the stress path has reached the failure surface and the cap does not move.

• Journal of the Korean Geosynthetics Society
• /
• v.11 no.3
• /
• pp.1-9
• /
• 2012

If the railways consisting of soil subgrade is applied to repetitive loading, elastic deformation and plastic deformation will occur at the same time. So the repeat traffic loading condition should be considered to predict the long-term deformation on railway roadbed. In this study, laboratory data from the repeated load triaxial tests and cylinder model test were used to predict accumulated settlement on railway foundation and results were analyed based on the nonliear models and stress state considered. It has proposed predict model using power function model on plastic settlement of roadbed materials.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.3
• /
• pp.323-331
• /
• 2010

In this study, we propose a 3D finite element (FE) model for the residual stress under oblique shot peening. Using the FE model for an oblique impact, we examine the effects of factors on the residual stress such as the Rayleigh damping in the material, dynamic friction, and the rate dependency of the material and systematically integrate the effects. The plastic deformation of the shot is also emphasized. Then, the FE model is used to study oblique multi-impacts. The results obtained using the FE model are compared with experimental x-ray diffraction (XRD) results; in contrast to the rigid and elastic shots, plastic shots are found to produce residual stresses similar to that shown in the XRD results. Thus, the 3D FE models with integrated factors and plastically deformable shots are validated. The proposed model will serve as a basis for the 3D FE model for multi-impacts with different impact angles to simulate the actual phenomenon of shot peening.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.6
• /
• pp.1-12
• /
• 2023

This paper assesses the suitability of existing standards for plastic material models and performance level evaluation methods in seismic performance evaluations of concrete dam piers during Maximum Credible Earthquakes (MCE). Dynamic plastic analysis was conducted to examine the applicability of the plastic material model under various conditions. As a result reveal that when the minimum reinforcement ratio is not met, the average stress-average strain method recommended in current dam seismic performance evaluation guidelines tends to underestimate pier responses compared to the predicted outcomes of dynamic elastic analysis. Consequently, the paper proposes an improvement plan that treats dam piers with an insufficient minimum reinforcement ratio as unreinforced and integrates fracture energy into concrete tensile behavior characteristics for performance level evaluation. Implementing these improvements can lead to more conservative evaluation outcomes compared to current seismic performance evaluation methods.

• Journal of Korean Society of Steel Construction
• /
• v.27 no.1
• /
• pp.31-42
• /
• 2015

The plastic stress distribution method and the strain compatibility method are the two representative methods to calculate the P-M interaction strength of RCFT (rectangular concrete filled tube) columns. The plastic stress distribution method is approximate while the stress compatibility method should approach the exact solution if accurate constitutive relations of the materials involved are used. Recent study by the authors pointed out that, because of lack of accurate constitutive model for the concrete confined by the rectangular steel tube, no strain compatibility method according to the current structural provisions provides a satisfactory prediction of the P-M interaction strength of RCFT columns under various material combinations. An empirical constitutive model which can capture the stress-strain characteristics of the confined concrete of RCFT columns is proposed based on analyzing extensive exisitng test database. The key idea was to define the concrete crushing strain as a function of steel-to-concrete strength ratio and width-to-thickness ratio of steel tube. It was shown that the proposed model leads to more accurate and more consistent prediction of the P-M interaction strength of RCFT columns under general design conditions.