• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
• /
• pp.219-222
• /
• 2003

Substantial experimental and theoretical work exists on the bond characteristics of FRP-concrete adhesive joints. Experimental studies show that the bond strength cannot always increase with an increase in the bond length, and that the ultimate strength is strongly influenced by the concrete strength. To solve this feature, analytic solutions based on fracture mechanics are widely used, and the local shear stress-slip curve with a softening branch is known as more rational model. The analytic solution, however, cannot describe various shapes of model curve. In this study, numerical method using interface element is introduced to express various shapes of model curve. Characteristics of adhesive joint is investigated for the shapes of the model curve and their parameters. And the numerical solutions are compared with the test results of CFRP sheet adhesive joints.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2000년도 가을 학술발표회 논문집
• /
• pp.201-208
• /
• 2000

In this study, the behavior of saturated sandy soils under dynamic loads - pore water pressure and effective stress - was investigated using Disturbed State Concept(DSC) model. The model parameters are evaluated from laboratory test data. During the process of loading and reverse loading, DSC model is utilized to trace strain-hardening and cyclic softening behavior. The procedure of back prediction proposed in this study are verified by comparing with laboratory test results. From the back prediction of pore water pressure and effective mean pressure under cyclic loading, excess pore water pressure increases up to initial effective confining pressure and effective mean pressure decrease close to zero in good greement with laboratory test results. Those results represent the liquefaction of saturated sandy soils under dynamic loads. The number of cycles at initial liquefaction using the model prediction is in good agreement with laboratory test results. Therefore, the results of this study state that the liquefaction of saturated sandy soils can be explained by the effective tress analysis.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1998년도 춘계학술대회논문집
• /
• pp.94-99
• /
• 1998

In bulk metal forming processes prediction of tool life is very important for saving production cost and achieving good material properties. Generally the service life of tools in metal forming process is limited to a large extent by wear, fracture and plastic deformation of tools. In case of hot and warm forging processes, tool life depends on wear over 70%. In this study finite element analyses are applied to warm forging and hot forging by adopting suggested wear model. By comparision of simulation and real profile of die, suggested model is verified

• Computers and Concrete
• /
• 제5권3호
• /
• pp.195-216
• /
• 2008

This paper presents a new hypoelasticity model which was implemented in a nonlinear finite element formulation to analyze reinforced concrete (RC) structures. The model includes a new hypoelasticity constitutive relationship utilizing the rotation of material axis through successive iterations. The model can account for high nonlinearity of the stress-strain behavior of the concrete in the pre-peak regime, the softening behavior of the concrete in the post-peak regime and the irrecoverable volume dilatation at high levels of compressive load. This research introduces the modified version of the common application orthotropic stress-strain relation developed by Darwin and Pecknold. It is endeavored not to violate the principal of "simplicity" by improvement of the "capability" The results of analyses of experimental reinforced concrete walls are presented to confirm the abilities of the proposed relationships.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1992년도 가을 학술발표회 논문집
• /
• pp.97-102
• /
• 1992

To predict the shear strength of low - rise reinforced concrete shear walls with boundary elements, truss model theory considering the Vecchio - Collins stress - strain curve for softened concrete is applied. The model transforms cracked shear walls with a truss which consists of vertical bar. horizontal bar and diagonal concrete strut, and is based on equilibrium and compatibility conditions among three truss components, as well as stress - strain relationship considered for softening in diagonal concrete strut. In barbell specimens(M/VD = 0.75. fc = 420 kg/$\textrm{cm}^2$), the ratio of experimental to analytical maximum shear strength was within 0.83 ν$_{exp}$. / ν$_{cal}$. 1.25 with a relatively good agreement. As a result, the truss model was observed to be capable of predicting the maximum shear strength wi th a reasonable accuracy.acy.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
• /
• pp.375-382
• /
• 1997

In this paper, a unified micromechanics-based model which can be applied to both tensile and compressive member of concrete is suggested and to the analysis of the strain-localization in concrete. From the comparison of the analysis results obtained from different size of concrete members with experimental data, it id shown that the model in this paper can be applied to the analysis of the strain localization concrete. For the finite element analysis of the strain-localization in concrete, the localized zone in concrete under strain localization is modeled as ad plastic model which can consider nonlinear strain softening and the non-localized zone is modeled as a nonlinear elastic-damage model. Using developed finite element analysis program. strain localization behaviors under compressive force for the different sizes of concrete having different sizes of the localized zone are simulated.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
• /
• pp.406-412
• /
• 1997

This paper presents the newly developed model for the stress-strain relationship of ultra high- strength concrete on the basis of the more refined statistical to analysis the various test results available in the literature to be more rigorous in accuracy and generalized scheme. Through the comprehensive analysis of the previously existing equations for each model, multiple curves equation has turned out to be most appropriate to simulate the linearly varying ascending branch and brittle type of descending one. The principal variables to model the stress-strain relationship such as the modulus of elasticity, ultimate strain and deformation characteristics due to stress softening phenomenon were extensively studied to be simplified in the function of the concrete compressive strength.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
• /
• pp.155-158
• /
• 2005

Damage and fracture of concrete is characterized as the degradation of strength and stiffness. There can be modeled as the so-called homogenized crack model which can overcome the mesh sensitivity. But the plasticity and damage modeling for damage behavior before the fracture of concrete should be combined with the crack model. In this study, a damage function and an unified hardening-softening function are applied to the homogenized crack model to develope a 3-dimensional FEM program for nonlinear damage and fracture analysis of concrete. The comparison of numerical results and experimental data show that the combined modeling in this study can simulate the damage and fracture of concrete without the mesh-sensitivity. It is also shown that the behavior of the so-called Engineering Cementitious Composite(ECC) characterized by strain-hardening and multiple cracks can be well simulated using the modeling.

• Structural Engineering and Mechanics
• /
• 제72권1호
• /
• pp.71-81
• /
• 2019

The objective of this paper is to develop a size-dependent nonlinear model of beams for fluid-conveying nanotubes with an initial deflection. The nonlinear frequency response of the nanotube is analysed via an Euler-Bernoulli model. Size influences on the behaviour of the nanosystem are described utilising the nonlocal strain gradient theory (NSGT). Relative motions at the inner wall of the nanotube is taken into consideration via Beskok-Karniadakis model. Formulating kinetic and elastic energies and then employing Hamilton's approach, the nonlinear motion equations are derived. Furthermore, Galerkin's approach is employed for discretisation, and then a continuation scheme is developed for obtaining numerical results. It is observed that an initial deflection significantly alters the frequency response of NSGT nanotubes conveying fluid. For small initial deflections, a hardening nonlinearity is found whereas a softening-hardening nonlinearity is observed for large initial deflections.

• Computers and Concrete
• /
• 제23권3호
• /
• pp.171-188
• /
• 2019

This study proposed a new and efficient 2D damage-plasticity model within the framework of Isogeometric analysis (IGA) for the geometrically nonlinear damage analysis of concrete. Since concrete exhibits complicated material properties, two internal variables are introduced to measure the hardening/softening behavior of concrete in tension and compression, and an implicit gradient-enhanced formulation is adopted to restore the well-posedness of the boundary value problem. The numerical results calculated by the model is compared with the experimental data of three benchmark problems of plain concrete (three-point and four-point bending single-notched beams and four-point bending double-notched beam) to illustrate the geometrical flexibility, accuracy, and robustness of the proposed approach. In addition, the influence of the characteristic length on the numerical results of each problem is investigated.