• Journal of Korean Association for Spatial Structures
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• v.5 no.2 s.16
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• pp.81-87
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• 2005

The Space structures may have large freedom in scale and form. And especially Hybrid structures are received much attention from the view points of their light weight and aesthetics. Hybrid systems are stable structures which are reticulated spatial structures composed of compressive straight members, struts and cables and Membranes. In this paper, The Hybrid Unit System are suggested using the Membrane and Cable elements based on the Tensegrity Unit system. Also, The Hybrid System of double-layered single curvature is presented. We analyze the force density method allowing form-finding for Tensegrity systems. And We analyze the shape analysis by the LARSH which is the program for nonlinear analysis.

• Journal of Korean Association for Spatial Structures
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• v.2 no.2 s.4
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• pp.69-76
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• 2002

The basic systems of spatial structures such as shells, membranes, cable-nets and tensegrity structures have been developed to create the large spaces without column. But there are some difficulties concerning structural stability, surface formation and construction method. Tensegrity systems are flexible structures which are reticulated spatial structures composed of compressive members and cables. The rigidification of tensegrity systems is related to selfstress states which can be achieved only when geometrical and mechanical requirements are simultaneously satisfied. In this paper, the force density method allowing form-finding for tensegrity systems is presented. And various modules of unit-structures are investigated and discussed using the force density method. Also, a model of double-layered single curvature arch with quadruplex using supplementary cable is presented.

• Structural Engineering and Mechanics
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• v.33 no.4
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• pp.447-484
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• 2009

The spatially coupled buckling, in-plane, and lateral bucking analyses of thin-walled Timoshenko curved beam with non-symmetric, double-, and mono-symmetric cross-sections resting on elastic foundation are performed based on series solutions. The stiffness matrices are derived rigorously using the homogeneous form of the simultaneous ordinary differential equations. The present beam formulation includes the mechanical characteristics such as the non-symmetric cross-section, the thickness-curvature effect, the shear effects due to bending and restrained warping, the second-order terms of semitangential rotation, the Wagner effect, and the foundation effects. The equilibrium equations and force-deformation relationships are derived from the energy principle and expressions for displacement parameters are derived based on power series expansions of displacement components. Finally the element stiffness matrix is determined using force-deformation relationships. In order to verify the accuracy and validity of this study, the numerical solutions by the proposed method are presented and compared with the finite element solutions using the classical isoparametric curved beam elements and other researchers' analytical solutions.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.2
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• pp.194-201
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• 2005

For engineers in the industry, this study considers a reliable and practical finite element modeling technique to estimate the behavior of closed thin-walled members with spot weldings. Dynamic and static experiments confirm that the technique - modeling the spot weldings with solid elements which have the adjusted rotational freedoms and fill the welding space - Yields satisfactory results. Numerical studies on the double hat-shaped members. adopting this modeling technique. show the effect of the spot welding Pitch and the spot welding location in the flange on the stiffness of the members Using the principal stiffness and newly proposed GSPI(global stiffness performance index), we also carefully examine how the spot welding curvature, and sectional shape, etc.. synthetically influence the stiffness of a real excavator pillar in the field.

• Steel and Composite Structures
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• v.24 no.6
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• pp.741-751
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• 2017

A steel slit shear wall has vertical slits and when it is under lateral loads, the section between these slits has double-curvature deformation, and by forming a flexural plastic hinge at the end of the slit, it dissipates the energy on the structure. In this article, Experimental, numerical and analytical analyses are performed to study the effect of slit shape and edge stiffener on the behavior of steel slit shear wall. Seismic behavior of three models with different slit shapes and two models with different edge stiffener shapes are studied and compared. Hysteresis curves, energy dissipation, out of plane buckling, initial stiffness and strength are discussed and studied. The proposed slit shape reduces the initial stiffness, increases the strength and energy dissipation. Also, edge stiffener shape increases the initial stiffness significantly.

• Steel and Composite Structures
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• v.24 no.6
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• pp.659-670
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• 2017

In the present work, an analytical solution for the static analysis of laminated composites, functionally graded and sandwich singly and doubly curved panels on the rectangular plan-form, subjected to uniformly distributed transverse loading is presented. Mathematical formulation is based on the higher order shear deformation theory and principle of virtual work is applied to derive the equations of equilibrium subjected to small deformation. A solution methodology based on the fast converging finite double Chebyshev series is used to solve the linear partial differential equations along with the simply supported boundary condition. The effect of span to thickness ratio, radius of curvature to span ratio, stacking sequence, power index are investigated. The accuracy of the solution is checked by the convergence study of non-dimensional central deflection and moments. Present results are compared with those available in the literature.

• Geomechanics and Engineering
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• v.38 no.2
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• pp.179-189
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• 2024

This paper presents a geomechanical framework for designing and optimizing layout patterns of cutterheads for rock Tunnel Boring Machines (TBMs), aiming to enhance their engineering performance. By examining the forces and moments exerted by rock, the study addresses geometric constraints associated with cutter boxes in key regions of the cutterhead, including the center, face, and gage areas, as well as the three-dimensional effects of cutterhead curvature on the geometric constraints of the back of the cutter boxes in the gage area. Novel formulas are proposed for determining the center points of cutter boxes and calculating both the minimum angular spacing and distance spacing between consecutive cutter boxes along a spiral path. The paper outlines an optimized layout design process for four cutterhead configurations: random, random paired, radial, and double spiral designs. Examples are provided to illustrate the results of applying these designs. The findings underscore the efficacy of the proposed methods in achieving a uniform and symmetrical distribution of cutters and buckets on the cutterhead surface. This approach effectively eliminates boundary overlap and minimizes unbalanced forces and moments. From a geomechanical standpoint, this framework offers a robust strategy for enhancing the performance and reliability of TBM cutterheads in rock tunneling operations.

• Fashion & Textile Research Journal
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• v.23 no.6
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• pp.781-789
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• 2021

To enhance the design and comfort of waist-protection corsets, this study analyzed the product characteristics of five types of posture-correction corsets that are available commercially. Additionally, subjective evaluation of the corsets was conducted on women aged 20 to 60 years, in terms of design, material preference, fit, comfort, degree of correction, freedom of movement, tightness, and convenience of front fastening. Following product analysis, the five corset types were divided into: two soft, one semi-hard, and two hard types in terms of the degree of elongation. As a result of pattern analysis, the soft type was designed to improve fit by reflecting the body curvature, whereas the semi-hard and hard types were relatively flat. Through the wearing sensation assessment, the hard type manufactured by company S was the best in terms of design, material, fit, comfort, correction degree, and freedom of movement. The soft type was average in design, material, and fit while relatively poor in the correction degree and tightness. The results indicated that soft materials, flexible bones with appropriate tension, patterns designed to snugly fit the body with large curvature at the top and bottom for better inflection, and adjustable support belts that can be double-fixed are crucial elements in improving the corset design to boost the comfort of wearing. These study results are helpful in the development of waist-protection corsets with excellent wearing comfort and design appreciated by customers.

• Korean Journal of Ichthyology
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• v.33 no.2
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• pp.148-154
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• 2021

Two specimens (1770~1850 mm disc width) of Mobula thurstoni, belonging to the family Myliobatidae, order Myliobatiformes, were first collected from the central coast of the Southern Sea of Korea in September 2018. This species is characterized by an anterior margin of disc with double curvature, a white-tipped dorsal fin, and the absence of a caudal spine. This species is morphologically similar to Mobula kuhlii, but has an anterior margin of pectoral fins with a double curvature and the dorsal coloration is bluish black rather than white. In addition, M. thurstoni was well distinguished from M. kuhlii as determined by mitochondrial DNA 16S rRNA sequences with genetic distances ranging from 0.030 to 0.069. The Korean name 'Mae-kkeun-kko-li-jwi-ga-o-li' is proposed for the species M. thurstoni.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.155-162
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• 2004

An analytical method to predict the time dependent flexural behavior of composite girder is presented based on sectional analysis. The time dependent constitutive relation accounting for the early-age concrete properties including maturing of elastic modulus, creep and shrinkage is derived in an incremental format by the first order Taylor series expansion. The sectional analysis calculates the axial and curvature strains based on the force and moment equilibriums. The deflection curve of the girder approximated by the quadratic polynomial function is calculated by applying to the proper boundary conditions in the consecutive segments. Numerical applications are made for the 3-span double composite steel box girder which is a composite bridge girder filled with concrete at the bottom of the steel box in the negative moment region. The calculated results are compared with those by finite element analysis results. Close agreement is observed between the two approaches.