• Computers and Concrete
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• v.7 no.4
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• pp.303-315
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• 2010

In this paper, we present a new finite Timoshenko beam element with a model for ultimate load computation of reinforced concrete frames. The proposed model combines the descriptions of the diffuse plastic failure in the beam-column followed by the creation of plastic hinges due to the failure or collapse of the concrete and or the re-bars. A modified multi-scale analysis is performed in order to identify the parameters for stress-resultant-based macro model, which is used to described the behavior of the Timoshenko beam element. The micro-scale is described by using the multi-fiber elements with embedded strain discontinuities in mode 1, which would typically be triggered by bending failure mode. A special attention is paid to the influence of the axial force on the bending moment - rotation response, especially for the columns behavior computation.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.1
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• pp.92-99
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• 2011

In this study, new multi-axial, critical plane based, fretting fatigue crack initiation parameter is developed by the addition of a new term into the Modified Shear Stress Range(MSSR) parameter. The newly developed parameter (MSSR') is then used to evaluate fretting fatigue life of titanium alloy, Ti-6A1-4V with various contact conditions. Finite element analysis is also used in order to obtain stress distribution on the contact surface during fretting fatigue test, which is then used for the calculation of fretting fatigue parameter. The MSSR' parameter shows better performance in predicting fretting fatigue lives from the conventional fatigue data, and less scattering within fretting fatigue data with different contact geometries.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.591-594
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• 2005

Concrete structure that has been constructed in real field is on multi-axial stress state condition. After placing of concrete, hydration heat and shrinkage of concrete can cause various stress conditions with respect to the restraint level and condition. So, to predict the early age behavior of concrete structure, multi-axial material model is required and microplane model is acceptable. Recently, many studies have been performed on the microplane model, but the model developed up to now has been related to hardened concrete that material property is constant with concrete age. So, it is inappropriate to apply this model immediately to analyze the early age behavior of concrete. In this study, microplane model that can predict early age behavior of concrete was developed and cracking analysis using that was performed to describe cracking behavior for massive concrete sturucture.

• Fibers and Polymers
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• v.7 no.2
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• pp.123-128
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• 2006

The present study aims at characterizing and modeling the anisotropic creep behavior of coated textile membrane, a class of flexible textile composites that are used for moderate span enclosures (roofs and air-halls). The objective is to develop a creep model for predicting the lifetime of coated textile membrane. Uniaxial creep tests were conducted on three off-axis coupon specimens to obtain the directional creep compliance. A potential with three parameters is shown to be adequate for modeling the anisotropic creep behavior of coated textile membrane. Furthermore, a possibility of predicting the creep deformation of coated textile membrane in a multi-axial stress state is discussed using the three-parameter potential.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.193-200
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• 2008

Cohesive and frictional materials such as concrete and soil are pressure dependent. In general, failure criterion for such materials inclined with respect to positive hydrostatic axis in Haigh-Westergaard stress space. Consequently, inelastic volumetric strain always positive with associated flow rule. In this study, to overcome this shortcoming, non-associated flow rule which controls volumetric component of plastic flow is adopted. Numerical analysis based on a constitutive model using nonuniform hardening plasticity with five parameter failure criterion and non-associated flow rule has conducted to predict concrete behavior under multi-axial stress state and verified with experimental result.

• Computers and Concrete
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• v.9 no.5
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• pp.341-355
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• 2012

Numerical studies are performed to predict the stress-strain behavior of rectangular RC columns confined by multi-spiral hoops under axial and eccentric compressions. Using the commercial finite element package ABAQUS, the Drucker-Prager criterion and the yield surface are adopted for damaged plasticity concrete. The proposed finite element models are compared with the published experimental data. Parametric studies on concrete grades, confinement arrangement, diameter and spacing of hoops and eccentricity of load are followed. Numerical results have shown good agreements with experimental values, and indicated a proper constitutive law and model for concrete. Cross-sectional areas and spacing of the hoops have significant effect on the bearing capacity. It can be concluded that rectangular RC columns confined by multi-spiral hoops show better performance than the conventional ones.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1043-1044
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• 2011

This paper discusses the electromagnetic and mechanical design considerations to improve the design accuracy and power to mass ratio of multi-stack axial flux permanent magnet synchronous generator (AFPMSG). Design accuracy of multi-stack AFPMSG for direct drive wind turbine application is improved by considering magnetic flux leakages and fringing effect. FEM structural analysis is utilized to increase power to mass ratio of three-stack AFPMSG by reducing the rotor yoke thickness considering magnetic and centrifugal forces and Von Mises stress distribution.

• Ocean Systems Engineering
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• v.12 no.1
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• pp.1-22
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• 2022

The majority of tubular joints commonly found in offshore jacket structures are multi-planar. Investigating the effect of loaded out-of-plane braces on the values of the stress concentration factor (SCF) in offshore tubular joints has been the objective of numerous research works. However, due to the diversity of joint types and loading conditions, a number of quite important cases still exist that have not been studied thoroughly. Among them are internally ring-stiffened two-planar TT-joints subjected to axial loading. In the present research, data extracted from the stress analysis of 243 finite element (FE) models, verified against available numerical and experimental data, was used to study the effects of geometrical parameters on the chord-side SCFs in two-planar tubular TT-joints reinforced with internal ring stiffeners subjected to two types of axial loading. Parametric FE study was followed by a set of nonlinear regression analyses to develop six new SCF parametric equations for the fatigue analysis and design of axially-loaded two-planar TT-joints reinforced with internal ring stiffeners.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.423-433
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• 2012

The axial load on the concrete-filled steel tube (CFT) column produces confinement stress, which enhances strength of the core concrete. The amount of strength increase in concrete depends on the magnitude of produced confinement stress. From nonlinear analyses, the ultimate resisting capacity of the CFT columns subjected to axial loads was calculated. Nonlinear material properties such as Poisson's ratio and stress-strain relation were considered in the suggested model, and the maximum confining stress was obtained by multi axial yield criteria of the steel tube. This proposed model was verified by comparing the analytical results with experimental results. Then, regression analyses were conducted to predict the maximum confining stress according to D/t ratio and material properties without rigorous structural analysis. To ensure the validity of the suggested regression formula, various empirical formulas and Eurocode4 design code were compared.

• Journal of Korean Society of Steel Construction
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• v.13 no.4
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• pp.327-335
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• 2001

The characteristics and production mechanism of residual stress generated by multi-pass welding of the steel pipe were elucidated from the results of three-dimensional thermal elastic-plastic FEM analysis. When the steel pipe was jointed by multi-pass welding, the stress components of circumferential direction and radial direction near welded joints on the inner surface and the outer surface of the pope were tensile. The stress component of axial direction on the inner surface was tensile and on the outer surface was compressive. On the other hands, the production mechanism of residual stress generated by multi-pass welding of the steel pipe was investigated. Residual stress generated by welding of the steel pipe was investigated not only by the thermal history but also by geometrical shape. Then, the generality of the production mechanism of residual stress generated by multi-pass welding was confirmed.