• Bulletin of the Society of Naval Architects of Korea
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• v.19 no.4
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• pp.11-18
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• 1982

When the perforated plate is under in-plane load of compression, buckling analysis becomes to be necessary because of the presence of stress concentration around holes. To constraint it, we need reinforcement. The methods of reinforcement are attaching doubler around hole and attaching stiffener in the direction of initial stress. In this paper, two methods are investigated mentioned above, which of the two better effective reinforcement. In the consequence of the above investigation, following conclusion was obtained. The method of doubler reinforcement was less buckling stress than that of stiffener because the former had large compressive stress. So, effective method of reinforcement is stiffener reinforcement.

• Bulletin of the Society of Naval Architects of Korea
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• v.24 no.3
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• pp.35-42
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• 1987

For the analysis of natural vibrations of a rectangular stiffened plate with inner cutouts, an application of the Rayleigh-Ritz method is investigated. In construction of the trial function for the Rayleigh quotient, only the outer boundary conditions are satisfied with combination of Euler beam functions. As to the modeling of stiffened plates for the energy calculations, a lumping stiffener-effects method and the orthotropic plate analogy are considered for the purpose of comparison. Some numerical results obtained by the Rayleigh-Ritz method are compared with results by experiments and the finite element method. The following are major conclusions; (1) With the lumping stiffener-effects modeling the Rayleigh-Ritz method gives good results of both natural frequencies and mode shapes. The orthotropic plate analogy in cases of regularly stiffened plates is of restrictive use i.e. acceptable for a small cutout. (2) The natural frequency of a stiffened plate with inner cutouts between stiffeners is higher than that of without cutouts and increase as the hole area ratio increases as long as there are no discontinuous stiffeners due to the cutout.

• Structural Engineering and Mechanics
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• v.31 no.3
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• pp.277-296
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• 2009

The paper investigates the dynamic behaviour of stiffened panels. The coupled differential equations for eccentric stiffening configuration are first derived. Then a semi-analytical procedure for dynamic analysis of stiffened panels is presented. Unlike finite element or finite strip methods, where the plate is discretized into a set of elements or strips, the plate in this procedure is treated as a single element. The potential energy of the structure is first expressed in terms generalized functions that describe the longitudinal and transverse displacement profiles. The resulting non-linear strain energy functions are then transformed into unconstrained optimization problem in which mathematical programming techniques are employed to determine the magnitude of the lowest natural frequency and the associated mode shape for pre-selected plate/stiffener geometric parameters. The described procedure is verified with other numerical methods for several stiffened panels. Results are then presented showing the variation of the natural frequency with plate/stiffener geometric parameters for various stiffening configurations.

• Composites Research
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• v.13 no.5
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• pp.37-43
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• 2000

In this paper an analytical investigation pertaining to the elastic shear buckling behavior of transversely stiffened orthotropic plate under in-plane shear forces is presented. All edges of plate are assumed to be simply supported and the evenly placed stiffener is considered as a beam element neglecting its torsional rigidity. For the solution of the problem Rayleigh-Ritz method is employed. Using the derived equation, the limit of buckling stress of transversely stiffened plate is suggested as a graphical form. Based on the limit of buckling stress of stiffened plate, graphical form of results for finding the required stiffener rigidity is presented when one and two stiffeners are located, respectively.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.42-49
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• 2005

The vibration analysis of a rectangular plate with stiffeners is formulated by using the transfer stiffness coefficient method (TSCM). This method is based on the concept of the successive transmission of stiffness coefficients which are defined as the relationship between the force vector and the displacement vector at an arbitrary nodal line. In order to confirm the validity of the present method, bending vibration analysis for a rectangular plate with stiffener is carried out on a personal computer by using the present method and the finite element method (FEM). Through comparing computational results of the TSCM and the FEM, the effectivness of the TSCM from the viewpoint of computational cost, that is, computational time and storage is demonstrated.

• Selected Papers of The Society of Naval Architects of Korea
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• v.1 no.1
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• pp.91-100
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• 1993

A displacement-based finite element method Is presented for the geometrically nonlinear analysis of eccentrically stiffened plates. A nonlinear degenerated shell element and a nonlinear degenerated eccentric isoparametric beam (isobeam) element are formulated on the basis of Total Agrangian and Updated Lagrangian descriptions. In the formulation of the isobeam element, some additional local decrees of freedom are implementd to describe the stiffener's local plate buckling modes. Therefore this element can be effectively employed to model the eccentric stiffener with fewer D.O.F's than the case of a degenerated shell element. Some detailed buckling and nonlinear analyses of an eccentrically stiffened plate are performed to estimate the critical buckling loads and the post buckling behaviors including the local plate buckling of the stiffeners discretized with the degenerated shell elements and the isobeam elements. The critical buckling loads are found to be higher than the analytical plate buckling load but lower than Euler buckling load of the corresponding column, i.e, buckling strength requirements of the Classification Societies for the stiffened plates.

• Bulletin of the Society of Naval Architects of Korea
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• v.3 no.1
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• pp.19-24
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• 1966

The maximum shear stress distribution in a stiffening flat attached to a plat undergoing a single tensile force has been investigated by photoelastic method. In the experiments a photoelastic model, as shown in Fig. 1, has been studied in the fields of a polariscope, as shown in Fig. 2. Fig. 3 shows the isoclinics and Fig. 4 and 5 are stress trajectories of the principal stresses and maximum shear stresses, respectively. Fig. 6 is the isochromatics in light field. The maximum shear stress at each point in the stiffener were determined from the isochromatics in both of light field of light field and dark field. Then the maximum shear stresses were divided by the average shear stress in the model, to obtain the ratio ${\tau}max/{\tau}av$ at each point. Finaly the variations of the ratio ${\tau}max/{\tau}av$ along the horizontal and vertical lines in the stiffener have been plotted, as shown in Fig. 7 and 8. The conclusions reached in this investigation are as follows: (1) The shear stresses transmitted to the stiffener through the juncture are concentrated on the end portions. (2) The maximum shear stress at the ends of the stiffener reaches to about 4 times of average shear stress. (3) The irregularities in the stress distribution are restricted in the end portions of the stiffener.

• Structural Engineering and Mechanics
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• v.65 no.2
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• pp.141-154
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• 2018

In this study, the bend-buckling strength of the web in longitudinally stiffened plate girder was numerically investigated. The buckling strength of the reinforced web was evaluated through an eigenvalue analysis of the hypothetical model, in which the top and bottom junctions of the web to the flanges were assumed as simple support conditions. Major parameters in the analysis include asymmetrical cross-sectional property, aspect ratio of the web, stiffener locations, and bending rigidity of the stiffeners. The numerical results showed that current AASHTO LRFD specifications (2014) provides the buckling strength from considerably safe side to slightly unsafe side depending on the location of the stiffeners. A modified equation for buckling coefficients was proposed to solve the shortcomings. The bending rigidity requirements of longitudinal stiffeners stipulated in AASHTO were also investigated. It is desirable to increase the rigidity of the stiffeners when the aspect ratio is less than 1.0.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.130-138
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• 1994

Bottom plates of empty hold are subjected to not only water pressure but also bi-axial inplane loads, specially in the alternate full loading full loading condition of bulk carrier. This kind of plate behaviours is very difficult to be explained and to be estimated using common buckling design guide in the initial design stage of hull structure, therefore, some more concrete studies for this plate structure was performed based on the currently developed buckling estimation formula. In this buckling formula, torsional stiffness effects of edge stiffener are included additionally and effects of elastic buckling strength of plate panel are treated as characteristic value problem. Also considering boundary stiffener effects and inplane and lateral loading, evaluation of bottom plate scantling using this formula, calculated results using various classification regulation of buckling strength and results of first report approach are compared each other and useful guides using developed formula for bottom plate scantling design are discussed.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.37-49
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• 1997

The buckling behavior of the web of steel girders are largely dependent on the size and the location of stiffeners and the restraining effect of top and bottom flanges. Elastic and inelastic buckling analyses based or the Spline Finite Strip Method were executed to study the stiffening effect of the longitudinal stiffener on the web of box girders and to find how the top and bottom flanges had effects on the web, where geometric boundary conditions were limited by both hinged, both fixed and the flange sections. The basic assumption for the longitudinal end boundary conditions was that the vertical stiffeners had the rigidity enough to force nil deflection line on the web panel so that the junction line between web and vertical stiffener was assumed to be hinged boundary conditions. The provisions on the longitudinal stiffener of the plate and box girders of the Korean Standard Highway Bridge Specifications(1995) and AASHTO Specifications(1994 LRFD) were compared with the results obtained numerically for the various longitudinal stiffener size of box girders. Simple equations and design curves for the longitudinal stiffener of the web were proposed for the practical use.