• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.9 no.3
• /
• pp.31-38
• /
• 1989

This paper concentrates on the analysis of reinforced concrete(R/C) structures subjected to monotonic loading, from zero to ultimate loads. Tensile cracking, the nonlinear stress-strain relationship for concrete and reinforcement are taken into account the concrete is assumed to be elastic in tension region and elasto-hardening plastic in compression region. The Kupfer's failure criteria and associated flow rule are adopted to govern the plastic behavior of the concrete. The reinforcing bar is considered as a elasto-hardening platic material. The tension stiffening effect of the concrete between cracks is also considered. The numerical error depends on the used finite element mesh size is reduced by correcting the slope of strain softening region of the concrete according to the developed energy criteria.

• Computers and Concrete
• /
• v.2 no.2
• /
• pp.97-110
• /
• 2005

Rheological behaviour of fresh concrete is an important factor in controlling concrete quality. It is recognized that the measurement of the slump is not a sufficient test method to adequately characterize the rheology of fresh concrete. To further understand the slump measurement and its relationship to the rheological properties, an elasto-viscoplastic, 2-D axisymmetric finite element (FE) model is developed. The FE model employs the Bingham material model to simulate the flow of a slump test. An experimental program is carried out using the Slump Rate Machine (SLRM_II) to evaluate the finite element simulation results. The simulated slump-versus-time curves are found to be in good agreement with the measured data. A sensitivity study is performed to evaluate the effects of yield stress, plastic viscosity and cone withdrawal rate on the measured flow curve using the FE model. The results demonstrate that the computed yield stress compares well with reported experimental data. The flow behaviour is shown to be influenced by the yield stress, plastic viscosity and the cone withdrawal rate. Further, it is found that the value of the apparent plastic viscosity is different from the true viscosity, with the difference depending on the cone withdrawal rate. It is also confirmed that the value of the final slump is most influenced by the yield stress.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.9 no.5
• /
• pp.564-571
• /
• 1985

The estimation of fracture toughness in inhomogeneous material is still insufficient because it is difficult to get information of fracture initiation at the crack tip. Therefore, martensite-ferrite dual phase steel was prepared for a model material and micro-fracture behavior was investigated in the region of pre-fatigue crack in order to understand the characteristic of fracture resistance in inhomogeneous materials. In the case of severely inhomogeneous state, micro-fracture appearance is not distributed homogenously so that the estimation of fracture toughness is hardly possible. On the other hand when the grain size is refined or the strength of martensite is lowered, micro-fracture appearance is distributed homogenously and fracture toughness remarkably increases.

• Communications of the Korean Mathematical Society
• /
• v.20 no.3
• /
• pp.589-602
• /
• 2005

We present the numerical algorithm for the model for high-strain rate deformation in hyperelastic-viscoplastic materials based on a fully conservative Eulerian formulation by Plohr and Sharp. We use a hyperelastic equation of state and the modified Steinberg and Lund's rate dependent plasticity model for plasticity. A two-dimensional approximate Riemann solver is constructed in an unsplit manner to resolve the complex wave structure and combined with the second order TVD flux. Numerical results are also presented.

• Journal of the Korean Society of Safety
• /
• v.14 no.1
• /
• pp.19-24
• /
• 1999

A two dimensional thermo elasto-plastic finite clement stress analysis was performed to study stress distributions in functionally gradient material. The upper $ZrO_2$ surface is heated at 1200K until a steady state is established and cooled at 300K. The influences on the thermal stress distributions due to the difference of compositional gradient exponent p were investigated. In this study, we obtained the thermal stresses are low for p=1.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.03a
• /
• pp.93-100
• /
• 2002

Vertical reinforcement of soft soils using the deep mixing method has received increasing applications. In this study, the theory of elasticity and plasticity including the upper bound theorem of limit analysis were used to derive the equations for obtaining composite elastic properties and shear strength parameters. The developed equations were validated using the finite element computer program SAGE CRISP. The analysis involved 4 different cases-two different type of soil and replacement ratios. Tile results of the analysis show that the proposed equations could determine the properties of composite material for practical applications.

• Steel and Composite Structures
• /
• v.24 no.3
• /
• pp.287-296
• /
• 2017

The buckling capacity of a radially retractable hybrid grid shell in the closed position was investigated in this paper. The geometrically non-linear elastic buckling and elasto-plastic buckling analyses of the hybrid structure were carried out. A parametric study was done to investigate the effects rise-to-span ratio, beam section, area and pre-stress of cables, on the failure load. Also, the influence of the shape and scale of imperfections on the elasto-plastic buckling loads was discussed. The results show that the critical buckling load is reduced by taking account of material non-linearity. Furthermore, increasing the rise-to-span ratio or the cross-section area of steel beams notably improves the stability of the structure. However, the cross section area and pre-stress of cables pose negligible effect on the structural stability. It can also be found that the hybrid structure is highly sensitive to geometric imperfection which will considerably reduce the failure load. The proper shape and scale of the imperfection are also important.

• Journal of Welding and Joining
• /
• v.17 no.1
• /
• pp.104-115
• /
• 1999

There have been many studies on the two dimensional thermo-elasto-plastic analysis in welding process, mostly from viewpoint of residual stresses. In this study, the temperature distribution, transient thermal stress, and angular distortion during bead-on-plate gas metal arc welding of rectangular plates were analyzed by using the finite element method. A nonlinear heat transfer analysis was first performed by taking account of the temperature-dependent material properties and convection heat losses on the surface. This was followed by a thermo-elasto-plastic stresses and distortion analysis that incorporates the constrained boundary condition of the two dimensional solution domain to get the three dimensional size effect of the plate. The constrained boundary conditions adopted in this study were the constant displacement condition over the whole two dimensional section for axial movement in the welding direction, and the force boundary condition for rotational movementof the domain around the axis of the welding direction. It could be revealed that the theoretical predictions of the angular distortion have an improved agreement with the experimentally obtained data presented in the previous study.

• Journal of Advanced Marine Engineering and Technology
• /
• v.41 no.3
• /
• pp.222-229
• /
• 2017

High manganese steel exhibits excellent mechanical properties with respect to strength and durability at low temperatures. Recently, high manganese steel has been considered as an alternative to existing materials, such as nickel steel and SUS304L for application as tank material for Liquefied Natural Gas (LNG) cargo containment systems. In the present study, tensile tests were performed at room and cryogenic temperatures in order to investigate the mechanical properties and non-linear tensile behavior of high manganese steel. In addition, elasto-plastic damage model was applied using the finite element analysis software ABAQUS via a user defined material subroutine (UMAT) to describe the material behavior. Finally, the results of the finite element simulations using the UMAT were compared to those of the tensile tests in order to validate the proposed UMAT. It has been demonstrated that the UMAT can effectively describe the non-linear tensile behavior of high manganese steel.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.7 no.2
• /
• pp.69-77
• /
• 1987

A finite element method has been developed to study the material nonlinear analysis of reinforced concrte structures. Concrete behavior under the biaxial state of stress is represented by a nonlinear constitutive relationship which incorporates tensile cracking, tensile stiffening effect between cracks and the strain-softening phenomenon beyond the maximum compressive strength. The concrete model used is based upon nonlinear elasticity by assuming concrete to be an orthotropic material and modeled as equivalent uniaxial stress-strain constitutive relationship using equivalent uniaxial strain. The streel reinforcement is assumed to be in a uniaxial stress state and is modeled as a bilinear, elasto-plastic material with strain hardening approximating the Bauschinger effect. In plane stress state, R.C. beams is modeled as a quadratic element that has two degrees of freedom in each node. And this results of finite element analysis are compared with the experimential results of midspan deflection, stresses and strains.