• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.39-53
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• 2019

Bi-directional pile load test (briefly called 'BDH PLT') cannot be performed at loading levels where ultimate bearing capacity could be assessed in field, it is not possible to precisely determine both ultimate load and yield load and under loading. Since the load is transmitted separately to the skin and the end unlike the static pile load test (briefly called 'SPLT') and the direction of loading on the skin is opposite, such methods could have a result different from actual movements of shafts. In this study, three-dimensional finite element method (briefly called '3D FEM') analysis was conducted from results of the BDH PLT, made with barret piles, which were large-diameter cast-in-place concrete piles, and the calculated design constants were applied to the 3D FEM analysis of the SPLT to interpret them numerically and then, actual behaviors of cast-in-place concrete piles were estimated. First, using the results of the BDH PLT with cast-in-place concrete piles, behaviors of the piles made by loading upwards and downwards were analyzed to calculate load-displacement. Second, the design constants, calculated by the 3D FEM analysis and the back analysis, were applied on the 3D FEM analysis for the SPLT, and from these results, behaviors of the SPLT through the BDH PLT was analyzed. Last, the results of the 3D FEM analysis of the SPLT through the BDH PLT was expressed in relationships as {A ratio of bearing capacity of the SPLT and of the BDH PLT (y)} ~ {A ratio of reference displacement and pile circumference (x)}, and they were all classified by reference displacement at 10.0 mm, 15.0 mm, and 25.4 mm.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.57-68
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• 2020

In the case of two-dimensional analysis generally applied in the analysis of Earth Retaining Wall, mutual interference occurs due to earth pressure, when the excavation width is small, and in the section where the excavation width is small, and the resulting influence makes it difficult to secure reliability in the horizontal displacement of the retaining wall when performing 2-dimensional analysis in a section with a small excavation width. This study performed two-dimensional and three-dimensional finite element analyses on excavation depth (H) and excavation width (B) under various conditions for the H-pile earth wall, in the geological conditions of clayey soil, sandy soil, and weathered rock, and examined the relationship between excavation width and horizontal displacement according to each condition, to identify the boundary of the excavation width, which is the range of mutual interference caused by earth pressure. As a result, it was possible to clearly distinguish the analytical boundary according to the excavation width only in the clayey soils with relatively large horizontal displacement. It is concluded that it is reasonable to perform a 3D finite element analysis, which is similar to the actual behavior, if the excavation scale (B/H) is 2.0 or less, with the digging width less than 12 m at a digging depth of 10 m or less, and with the the one less than 24 m at a digging depth of 10 m or more, and that 2-dimensional finite element analysis may be used in cases where the excavation width is greater than 12 m when the excavation scale (B/H) is 2.0 or more and the excavation depth is 10 m or less, and the excavation width is greater than 24 m at an excavation depth of 10 m or more.

• Structural Engineering and Mechanics
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• v.5 no.5
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• pp.625-634
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• 1997

Reinforced concrete (RC) interior beam-column joints with high-strength materials: concrete compressive strength of 100 MPa and the yield strength of longitudinal bars of 685 MPa, were analyzed using three-dimensional (3-D) nonlinear finite element method (FEM). Specimen OKJ3 of joint shear failure type was a plane interior joint, and Specimen 12 of beam flexural failure type was a 3-D interior joint with transverse beams. Though the analytical initial stiffness was higher than experimental one, the analytical results gave a good agreement with the test results on the maximum story shear forces, the failure mode.

• Computers and Concrete
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• v.1 no.4
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• pp.401-416
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• 2004

This paper presents investigation of a three-dimensional (3-D) nonlinear finite element model analysis to examine the behavior of reinforced concrete beams strengthened with Carbon Fiber Reinforced Polymer (CFRP) composites to enhance the flexural capacity and ductility of the beams. Three-dimensional nonlinear finite element models were developed between the internal reinforcement and concrete using a smeared relationship. In addition, bond models between the concrete surface and CFRP composite were developed using a smeared bond for general analyses and a contact bond for sensitivity analyses. The results of the FEA were compared with the experimental data on full-scale members. The results of two finite-element bonding models showed good agreement with those of the experimental tests.

• Journal of the Korean Geosynthetics Society
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• v.15 no.4
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• pp.25-32
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• 2016

The two-dimensional (2D) analysis is widely used in geotechnical engineering for slope stability analysis assuming a plane-strain condition. It is implicitly assumed that the slip surface is infinitely wide, and thus three-dimensional (3D) end effects are negligible because of the infinite width of the slide mass. The majority of work on this subject suggests that the 2D factor of safety is conservative (i.e. lower than the 'true' 3D factor of safety). Recently, the 3D finite element method (FEM) became more attractive due to the progress of computational tools including the computer hardware and software. This paper presents the numerical analyses on rotational mode and translational mode slopes using the 2D and 3D FEM as well as 2D limit equilibrium methods (LEM). The results of the parametric study on the slope stability due to mesh size, dilatency angle, boundary conditions, stress history and model dimensions change are analysed. The analysis showed that the factor of safety in 3D analysis is always higher than that in the 2D analysis and the discrepancy of the slope width in W direction on the factor of safety is ignored if the roller type of W direction conditions is applied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.11
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• pp.3454-3462
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• 1996

Compared to a full three dimensional FEM, the Slab-FEM hybrid method reduces the required computation time distinctly and it can be applied to the analysis of a shape rolling process. However, the method is somewhat approximate and predictions by the method contain certain inaccuracies. In the present investigation a parameter called T-factor was introduced to compensate the inaccuracies of the method and proper values of the parameter were estimated for different widths of bars and reduction ratios. Then, the method was applied to analyze cold and hot rollings of rectangular bars and predicted results were compared to those of experiments. Nonuniform distributions of temperature in the bars were predicted by utilizing the temperature equation obtained for a semi-infinite solid under radiation and convection boundary conditions. It was found out that accuracies of spread and roll separating force predictions could be enhanced by using proper values of the T-factor.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.263-266
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• 1997

Three dimensional numerical model based on the finite element method(FEM) were developed to predict the mechanical behavior of hip implants. The purpose of this study is to investigate the stress distribution of two types of cementless total hip replacement femoral component -a straight stem and a curved stem, and to compare their effect on the stress shielding between two types by three dimensional finite element method. The authors analyzed von Mises stress in the cortex & stem and compared the stress between the straight and the curved stem. In comparison of stresses between two different design of femoral stem, there was 25% more decrease of stress in straight stem than curved stem in the medial cortex at proximal region. The straight stem had consistently much lower stresses than the curved stem throughout the whole medial cortex with maximum 70% reduction of stress. However, there was little change in stress between nature and 2 implanted femur throughout the lateral cortex. Stress of femoral stem was much higher in the straight stem than the curved stem up to 60%. The straight stem had more chance of stress shielding and a risk of fatigue fracture of the stem compared with the curved stem in noncement hip arthroplasty. In design of femoral stem still we have to consider to develop design to distribute more even stress on the proximal medial cortex.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.592-597
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• 2001

An automobile lower arm has been fabricated in a prototype form by hydroforming with the aids of numerical analysis and experiments. For the numerical process design, a program called HydroFORM-3D developed here on the basis of a rigid-plastic model, has been applied to the lower arm hydroforming. The friction calculation between die and workpiece has been dealt carefully by introducing a new scheme in three-dimensional surface integration. To accomplish successful hydroforming process design, thorough investigation on proper combination of process parameters such as internal hydraulic pressure, axial feeding, and tool geometry has been performed. Results obtained from numerical simulation for a lower arm in hydroforming process are compared with a series of experiments. The comparison shows that the numerical analysis successfully provides the manufacturing information on the lower arm hydroforming, and it predicts the geometrical deformation and the thinning.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.201-204
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• 2006

A three-dimensional finite element (FEM) model has been developed to simulate the deformation due to bead on plate welding of curved plates with curvature in the weld direction. By using traditional method such as thermal-elastic-plastic FEM, the weld-induced deformation can be predicted accurately. However, this method is not practical approach to analyze the deformation of large and complex structures such as ship hull structures in view of time and cost. This study is classified from the aspect of equivalent load based on inherent strain near the weld line. Therefore, the residual deformation can be simply computed by elastic analysis. Further more, a practical solution is proposed to consider the contact between the plate and the positioning jig by judging the reaction forces of the jig at calculation step and the effect of the longitudinal curvature is closely considered.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.207-210
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• 2004

The deformation behavior of copper during equal channel angular pressing (ECAP) was calculated using a three-dimensional version of a constitutive model based on the dislocation density evolution. Finite element simulations of the variation of the dislocation density and the dislocation cell size with the number of ECAP passes are reported. The calculated stress, strain and cell size are compared with the experimental data for Cu deformed by ECAP in a modified Route C regime. The results of FEM analysis were found to be in good agreement with the experiments. After a rapid initial decrease down to about 200 nm in the first ECAP pass, the average cell size was found to change little with further passes. Similarly, the strength increased steeply after the first pass, but tended to saturate with further pressings. The FEM simulations also showed strain non-uniformities and the dependence of the resulting strength on the location within the workpiece.