• Magazine of the Korea Concrete Institute
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• v.6 no.4
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• pp.102-112
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• 1994

The drying shrinkage of concrete has a close relation to the water movement. Since the diffusion process of water in concrete is strongly dependent on the temperature and the pore humidity, the process is highly nonlinear phenomena. This study consists of two parts. The first is the development of a finite element program which is capable of simulating the rnoisture distri- ,bution in concrete, and the other is the estimation of the differential drying shrinkage and stress considering creep by using the modified elastic modulus due to inner temperature change and maturity. It is shown that the analytical results of this study are in good agreement with experlimental data in the literatures, and results calculated by BP-KX model. The internal stress caused by moisture distribution which was resulted from the diffusion process, was calculated :quantitatively. The tensile stress which occured in the drying outer zone mostly exceeded the tensile strength of concrete, and necessarily would result in crack formation.

• Journal of Korean Society of Steel Construction
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• v.20 no.3
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• pp.421-435
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• 2008

This paper presents an investigation on the ultimate behavior of a transmission tower using nonlinear analyses inconsideration of residual stress and initial imperfection. Main members, such as main post, horizontal member and diagonal member of the transmission tower were modeled using beam element. Moreover, submembers of the transmission tower were modeled using truss element. ABAQUS (2004) program was used to perform finite element analyses. Initial condition options of the ABAQUS program considering initial stress and imperfection were used in this study. Before performing the analysis of the total transmission tower, simple angle section models using beam or plate/shell element w ere investigated to verify the appropriateness of ABAQUS analysis models and options. According to the verification results, the beam element was used for nonlinear analyses of the transmission tower. From nonlinear analyses results, buckling failure was in the main member of the leg part because of ${P-{\triangle}}$ effect at that point. Also, this paper includes significant results to define real structural failure modes and quantitative values. This study should be used in the development of a reasonable and economic design method for transmission towers.

• Transactions of Materials Processing
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• v.28 no.1
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• pp.5-14
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• 2019

In order to reduce the weight of automobile parts, automobile parts using aluminum alloy are being developed. Aluminum alloy for automobile parts is mainly made of Al6xxx (Al-Mg-Si) type alloy, which is excellent in hot forming property, and it can increase mechanical properties by the use of heat treatment. In this study, hot forming was performed using Al6082. Before the hot forming, the forming analysis was performed using the DEFORM-3D finite element analysis program in this case. For the forming analysis, the heat transfer coefficient was derived from the experiment, and the forming analysis was performed by applying it. At the forging analysis, the temperature of Al6082 material was set to 813K and that of the mold was set to room temperature. After the forging analysis, the experiment was performed, and the forging analysis and the experimental results were compared.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.467-474
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• 2007

In this paper, a total of 13 beams with bonding, anchorage system, amount of prestressing and span length as variables of experiment were tested in flexural test and analyzed in finite element analysis; one control beam, two simplified FRP-boned beams, four prestressed FRP-unbonded beams and four prestressed FRP-bonded beams. Also, a nonlinear finite element analysis of beams in the flexural test is performed by DIANA program considered material nonlinear of concrete, reinforcement and the interfacial bond-slip model between concrete and CFRP plates. The failure mode of prestressed CFRP plated-beams is not debonding but FRP rupture. RC members strengthened with external bonded prestressed CFRP plates occurred 1st and 2nd debonding of the composite material. After the debonding of CFRP plates occurs in bonded system, behavior of bonded CFRP-plated beams change into that of unbonded CFRP-plated beams due to fix of the anchorage system. Also, It was compared flexural test results and analytical results of RC members strengthened with CFRF plates. The ductility of beams strengthened by CFRP plates with the anchorage system is considered high with the ductility index of above 3. Analysis results showed a good agreement with experiment results in the debonding load, yield load and ultimate load.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.33-42
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• 2003

This paper deals with the FEM analysis of nonlinear sloshing of incompressible, invicid and irrotational flow in two dimensional rectangular tank. We use laplace equation based on potential theory as governing equation. For large amplitude sloshing motion, kinematic and dynamic free surface conditions derived from Bernoulli equation are applied. This problem is solved by FEM using 9-node elements. For the time integration and accurate velocity calculation, we introduce predictor-corrector time marching scheme and least square method. Also, numerical stability in tracking of free surface is obtained by direct calculation of free surface location to time variation. Numerical results of sloshing induced by harmonic excitations, while comparing with those of linear theory and references, prove the accuracy and stability. After verification of our program, we analyze sloshing response characteristics to the fluid height and the excitation amplitude.

• Steel and Composite Structures
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• v.10 no.1
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• pp.23-43
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• 2010

In this paper, a nonlinear model is developed using the component method in order to represent the response of steel connections under various loading conditions and temperature variations. The model is capable of depicting the behaviour of a number of typical connection types including endplate forms (extended and flush) and angle configurations (double web, top and seat, and combined top-seat-web) in both steel and composite framed structures. The implementation is undertaken within the finite element program ADAPTIC, which accounts for material and geometric nonlinearities. Verification of the proposed connection model is carried out by comparing analytical simulations with available results of isolated joint tests for the ambient case, and isolated joint as well as sub-frame tests for elevated temperature conditions. The findings illustrate the reliability and efficiency of the proposed model in capturing the stiffness and strength properties of connections, hence highlighting the adequacy of the component approach in simulating the overall joint behaviour at elevated temperature.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.5
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• pp.538-546
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• 2008

In this paper, the constitutive equation is developed to analyze the characteristics of strain-induced plasticity in the range of low temperature of 316 stainless steel. The practical usefulness of the developed equations is evaluated by the comparison between experimental and numerical results. For 316 stainless steel, constitutive equations, which represent the characteristics of nonlinear material behavior under the cryogenic temperature environment, are developed using the Bodner's plasticity model. In order to predict the material behaviour such as damage accumulation, Bodner-Chan's damage model is implemented to the developed constitutive equations. Based on the developed constitutive equations, 3-D finite element analysis program is developed, and verified using experimental results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.103-113
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• 1996

Two-dimensional finite element hydrodynamic models for long wave simulation usually adopt fixed land boundary. However moving boundary treatment is strongly required in the simulation of tidal flats for west and south coast of Korea. In this study very efficient and realistic moving boundary treatment is applied by considering incident long wave surface slope. Developed STEP-CM (Superior Two-step Explicit Program for Coastal Modeling) ,shows numerically stable results in comparative study for idealized one-dimensional channel. Real application of the model is done for Chonsu Bay where tidal flats are distributed along the coast. Nonlinear tidal current and tidal flat effects are easily simulated in STEP-CM and resulting circulations are detected around headland of Wonsan Island.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.103-106
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• 2005

The material properties of membrane for stratospheric airship is experimentally investigated. Mechanical tensile properties of the membrane material at room, high and low temperature are measured using instron with thermal chamber. Experimentaly, material non-linearity is observed at room and high temperature. In order to simulate material non-linearity caused by the uniaxial extension curve of a woven fabric, the nonlinear hyperelastic problem is considered with finite clement program of ABAQS. Numerical results are compared with experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.260-265
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• 1997

Large dynamic loads act on the rotor in rotary compressors. There are unbalance forces due to eccentric rotation parts and gas forces induced by the difference in pressure between compression and suction gases6 Rotor-journal bearing system is nonlinear since the stiffness and damping coefficients of the lubricating oil film are not constant in the bearings. In this paper, the program for predicting the behaviors of rotor-journal bearing system of rotary compressor is developed. Finite element modeling is used to analyze the flexible rotor. The numerical results are compared with experimental results. The location of balancer weight are suggested for reducing rotor whiring displacement.