• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.55-62
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• 1999

When stress is beyond elastic limit or cracks occur in a reinforced concrete member subjected to axial force and biaxial bending, curvature about each principal axis of uncracked section is influenced by axial force and bending moments about both major and minor principal axes. It is mainly due to the translation and rotation of principal axes of the cross section after cracking. Recently, by considering these effects, a numerical method predicting the behavior of concrete columns subjected to axial force and biaxial bending was proposed. In this study, in order to verify the proposed numerical method and investigate the effects of cracking on the behavior of reinforced concrete columns, a series of tests were carried out for 16 tied reinforced concrete columns with 100×100 mm square and 200×100 mm rectangular sections under various loading conditions. The angle between the direction of eccentricity and the major principal axis of uncracked section were 0, 30, 40° for the square section and 0, 30, 45, 60, 90° for the rectangular section, respectively. A comparison between numerical predictions and test results shows good agreements in ultimate loads, axial force-lateral deflection relations, and lateral deflection trajectories. It is also found, in this limited investigation, that the ACI's moment magnifier method is conservative in both uniaxial and biaxial loading conditions.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.6
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• pp.419-427
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• 2018

In case high strength steels are applied for press-formed automotive parts, it is very difficult to secure forming accuracy due to large springback compared to moderate strength steels. In this study, a repetitive step-wise forming analyses based on secant method was proposed as the die design method for mandrel(bending tool) for the 2-axis bending equipments. A bending die with circular mandrel was designed for the DP780 blow motor case of which diameter and thickness are 70.8mm and 2.0mm respectively. Forming tests were performed to verify the validity of established die design and the results were compared with that of conventional HGI(Hot galvanized iron steel) blow motor case. For additional improvement in forming accuracy, an elliptical mandrel was proposed and its validity was verified using forming analyses based on secant method.

• Steel and Composite Structures
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• v.38 no.6
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• pp.637-656
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• 2021

The component-based method is widely used to analyze the initial stiffness of joint in steel structures. In this study, an analytical component model for determining the column face stiffness of square or rectangular hollow section (SHS/RHS) subjected to tension was established, focusing on endplate connections. Equations for calculating the stiffness of the SHS/RHS column face in bending were derived through regression analysis using numerical results obtained from a finite element model database. Because the presence of bolt holes decreased the bending stiffness of the column face, this effect was calculated using a novel plate-spring-based model through numerical analysis. The developed component model was first applied to predict the bending stiffness of the SHS column face determined through tests. Furthermore, this model was incorporated into the component-based method with other effective components, e.g., bolts under tension, to determine the tensile stiffness of the T-stub connections, which connects the SHS column, and the initial rotational stiffness of the joints. A comparison between the model predictions, test data, and numerical results confirms that the proposed model shows satisfactory accuracy in evaluating the bending stiffness of SHS column faces.

• Korean Journal of Applied Biomechanics
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• v.20 no.1
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• pp.57-65
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• 2010

Korean traditional martial arts Taekkyon has a unique stepping method, Poombalbki. The purpose of this study was to investigate kinematic factors and ground reaction forces on two types of Poombalbki, one of which use knee bending and the other use chiefly hip bending. Six male taekkyoners who are the students of Y University participated in this study. Positions and velocities of CoM, the elapsed times of each phase, angles and angular velocities of low limb joints, and GRFs were analyzed for this study. The results were as follows; CoMs of whole body, trunk, and head were more posteriorly positioned in performing hip bending Poombalbki than knee bending one. Horizontal velocities of those were slower in performing hip bending Poombalbki. A player stayed more shortly within range of his opponent in performing hip bending Poombalbki. The vertical and horizontal components of GRF of forward-stepping foot were smaller in performing hip bending Poombalbki(p<.05). In conclusion hip bending is useful strategy, because A player is farther from his opponent, he stayed more shortly within range of his opponent, and the smaller weight is loaded on his front foot in performing hip bending Poombalbki than knee bending one.

• Structural Engineering and Mechanics
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• v.30 no.4
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• pp.387-402
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• 2008

The Integrated Force Method (IFM) has been developed in recent years for the analysis of civil, mechanical and aerospace engineering structures. In this method all independent or internal forces are treated as unknown variables which are calculated by simultaneously imposing equations of equilibrium and compatibility conditions. The solution by IFM needs the computation of element equilibrium and flexibility matrices from the assumed displacement, stress-resultant fields and material properties. This paper presents a general purpose code for the automatic generation of element equilibrium and flexibility matrices for plate bending elements using the Integrated Force Method. Kirchhoff and the Mindlin-Reissner plate theories have been employed in the code. Paper illustrates development of element equilibrium and flexibility matrices for the Mindlin-Reissner theory based four node quadrilateral plate bending element using the Integrated Force Method.

• Journal of the Korean Wood Science and Technology
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• v.28 no.4
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• pp.61-71
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• 2000

The effect of the treatment with CCFZ, FR-4, and PEG400 from butt end on the dimensional stability and bending properties was examined. Three softwood species such as red pine, Korean white pine and Japanese larch and three hardwood species such as poplar, alder and oak were investigated in this research. Shrinkage of red pine, Korean white pine, poplar, and alder treated with PEG400 decreased. However, there was no significant decrease of shrinkage in Japanese larch and oak. The decrease of shrinkage when moisture content changed from about 20% to 10% was larger than that at any other phase. In regard to the effect of treatment on bending properties, bending MOE and MOR of all specimens treated with PEG400 decreased significantly. Especially in the case of red pine, poplar, and alder treated with PEG400, bending MOR reduced 9%, 14%, and 12%, respectively. Reductions of MOR of the hardwood was also much larger than that of the softwood. However, in all species, treatment with CCFZ and FR-4 did not affect the change of bending MOE and MOR significantly. Comparing the large specimen which also included heartwood with the small specimen which included only treated sapwood, there was a difference in the change of bending MOE and MOR between them. The large specimens of Korean white pine, alder and Poplar, which had a relatively low proportion of sapwood(18~22%), showed the decrease of MOR by 11~13% more than that of small specimens, while red pine, Japanese larch and oak, which had a relatively high proportion of sapwood(35~40%), showed little decrease. It means that bending MOE and MOR of structural wood treated from butt end should be considered in terms of sapwood proportion as well as effect of treated chemicals.

• Journal of Technologic Dentistry
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• v.33 no.1
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• pp.55-61
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• 2011

Purpose: In this study, FEM(Finite Element Method) and bending strength test was conducted using normal implant and porous implant for the mechanical estimation of porous dental implant made by SLM method. Methods: Mechanical characteristics of PI(porous implant) and NI(normal implant) applied distributed loads(200N, 500N) were observed through FEM analysis. And each bending strength was gotten through bending test using MTS(Mechanical Test System, Instron 8871). Results: The result of FEM analysis was observed that stress difference between upper and surface of PI was 12 times, while NI was 2 times. The result of bending test was observed that bending strength of PI was lower than NI. we made a decision about this result that cross-sectional area of NI was larger than the PI. Conclusion: The stress shielding ability of porous implant was better than normal implant through result of FEM analysis. And bending strength of porous implant was lower than NI. We think that cause of this result was difference of cross-sectional area.

• Advances in nano research
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• v.16 no.3
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• pp.265-272
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• 2024

In this paper, the problem of static bending of axially functionally graded (AFG) nanobeam is formulated with the local stress(Lσ)- and strain-driven(εD) two-phase local/nonlocal integral models (TPNIMs). The novelty of the present study aims to compare the size-effects of nonlocal integral models on bending deflections of AFG Euler-Bernoulli nano-beams. The integral relation between strain and nonlocal stress components based on two types nonlocal integral models is transformed unitedly and equivalently into differential form with constitutive boundary conditions. Purely LσD- and εD-NIMs would lead to ill-posed mathematical formulation, and Purely εD- and LσD-nonlocal differential models (NDM) may result in inconsistent size-dependent bending responses. The general differential quadrature method is applied to obtain the numerical results for bending deflection and moment of AFG nanobeam subjected to different boundary and loading conditions. The influence of AFG index, nonlocal models, and nonlocal parameters on the bending deflections of AFG Euler-Bernoulli nanobeams is investigated numerically. A consistent softening effects can be obtained for both LσD- and εD-TPNIMs. The results from current work may provide useful guidelines for designing and optimizing AFG Euler-Bernoulli beam based nano instruments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.822-829
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• 2015

A transfer matrix method has been developed to determine the more accurate natural frequencies for the bending vibration of Bernoulli-Euler beam with linearly reduced width and a concentrated tip mass. The proposed method can be computed an infinite number of the natural frequencies using a single element. Using the differential equation, shear force, and bending moment in which can be deduced by the diverse variational principles, a transfer matrix is formulated. The roots of the differential equation are computed by the Frobenius method. The effect of the concentrated mass for the natural frequencies of width-tapered beams is examined through a parametric study, and to show the accuracy of the proposed method, the computed results compared with those obtained from commercial finite element analysis program(ANSYS).

• International Journal of Automotive Technology
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• v.7 no.2
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• pp.209-216
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• 2006

A study has been conducted for an optimal processing and an apparatus for manufacturing a laser welded tube for one-body formed bumper beam. The tube dimensions used in calculation were the thickness of 1.4 mm, the diameter of 105.4 mm and the length of 2000 mm. The tube was formed of a cold rolled high strength steel plate(tensile strength of 600 MPa). The two-roll bending method was the optimal tube forming process in comparison with the UO-bending method, the bending method on the press brake, the multi-step continuous roll-forming method and the 3-roll bending method. Monitoring of the welding quality was conducted and the seam tracking along the butt-joint lengthwise to the tube axis was also examined. The longitudinal butt-joint was welded by using a $CO_2$ laser welding machine equipped with a seam tracker and a plasma sensor. The $CO_2$ laser tube welding machine could be used for precise seam tracking and real-time monitoring of the welding quality. As a result, the developed laser welded tube could be used for a one-body formed automobile bumper beam.