• Journal of the Society of Naval Architects of Korea
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• v.58 no.6
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• pp.400-406
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• 2021

The primary effect of the far-field underwater explosion (UNDEX) is the whipping of the ship hull girder. This paper aims to verify why inelastic effects should be considered in the whipping response estimations from the UNDEX simulations. A navy ship was modeled using Timoshenko beam elements over the ship length uniformly keeping the constant midship section modulus. The transient UNDEX pressure was produced using two types of the Geers-Hunter doubly-asymptotic models: compressible and incompressible fluids. Because the UNDEX model based on incompressible fluid assumption provided more increased fluid volume acceleration in the bubble phase, the incompressible fluid-based UNDEX model was adopted for the inelastic whipping response analyses. The non-linear hull girder bending moment-curvature curve was used to embed inelastic effects in the UNDEX analyses where the Smith method was applied to derive the non-linear stiffness. We assumed two stand-off distances to see more apparent inelastic effects: 40.5 m and 35.5 m. In the case of the 35.5 m stand-off distance, there was a statistically significant inelastic effect in terms of the average of peak moments and the average exceeding proportional limit moments. For the conservative design of a naval ship under UNDEX, it is recommended to use incompressible fluid. In the viewpoint of cost-effective naval ship design, the inelastic effects should be taken into account.

• Steel and Composite Structures
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• v.47 no.6
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• pp.693-707
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• 2023

This article investigates the static thermo-mechanical response of anisotropic thick laminated composite plates on Visco-Pasternak foundations under various thermal load conditions (linear, non-linear, and uniform) along the transverse direction (thickness) of the plate, while keeping the mechanical load constant. The governing equations, which represent the thermo-mechanical behavior of the composite plate, are derived from the principle of virtual displacements. Using Navier's type solution, these equations are solved for the composite plate with simply supported condition. The Visco-Pasternak foundation type is included by considering the impact of the damping on the classical foundation model, which is modeled by Winkler's linear modulus and Pasternak's shear modulus. The excellent accuracy of the present solution is confirmed by comparing the results with those available in the literature. The study investigates the impact of geometric ratios, thermal expansion coefficient ratio, damping coefficient and foundation parameters on the thermo-mechanical flexural response of the composite plate. Overall, this article provides insights into the behavior of composite plates on visco-Pasternak foundations and may be useful for designing and analyzing composite structures in practical applications.

• Journal of Korean Society of Steel Construction
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• v.16 no.2 s.69
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• pp.215-224
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• 2004

The inelastic lateral-torsional buckling behavior of the beam-columns and the columns was investigated in this paper. The energy method was deployed to study the inelastic buckling behavior of the beam-columns and columns. which requires the iterative solution of a fourth-order eigenproblem. Hitherto, the patterns of residual stress that satisfies the I-section manufacturing in Korea is not available, therefore the pattern of residual stress used in this study is a 'well-known' simplified pattern. The simplified pattern of the residual stresses is incorporated with the flow theory of plasticity to model the inelastic response. Firstly, this study investigates the inelastic lateral-torsional buckling behavior of the I-section beam-columns under a concentric axial compressive force and uniform bending, and the effect of residual stress on the inelastic buckling behavior of beam-columns is studied. The study is then extended to the inelastic buckling of the columns by eliminating a bending moment. These results are compared it with the design method in the Korean Steel Designers Manual (KSDM 1995). This study has found that design method in KSDM (1995) is excessively conservative.

• Structural Engineering and Mechanics
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• v.68 no.1
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• pp.53-66
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• 2018

This paper presents an analysis of the bending, buckling and free vibration of functionally graded sandwich beams resting on elastic foundation by using a refined quasi-3D theory in which both shear deformation and thickness stretching effects are included. The displacement field contains only three unknowns, which is less than the number of parameters of many other shear deformation theories. In order to homogenize the micromechanical properties of the FGM sandwich beam, the material properties are derived on the basis of several micromechanical models such as Tamura, Voigt, Reuss and many others. The principle of virtual works is used to obtain the equilibrium equations. The elastic foundation is modeled using the Pasternak mathematical model. The governing equations are obtained through the Hamilton's principle and then are solved via Navier solution for the simply supported beam. The accuracy of the proposed theory can be noticed by comparing it with other 3D solution available in the literature. A detailed parametric study is presented to show the influence of the micromechanical models on the general behavior of FG sandwich beams on elastic foundation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.95-100
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• 2002

The wing in ground effect (WIG) ship is an energy saying vessel that uses the lift from its air-wing along with the lift increase from the ground effect by flying low above the sea surface. The WIG Ship should consist of thin plate in order to float on the sea and to fly in the air. Therefore, the structure of WIG, Ship has very thin and light shell plate and stiffener like stringer and frame has comparatively large cross section area. This structure makes shell plate nearly pure shear field when shell plate is pressed by in-plane load. This complex thin plate structure of WIG Ship can he considered as a closed section beam which makes it possible to analyze structure response of WIG Ship affected by shear load and bending load. In this respect, the present study will show basic theory for analysing shear stress and focus on the analysis of structure strength of model WIC Ship's wing.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.5
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• pp.326-332
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• 2010

Critical response of seawater pump impeller shaft structure to various exciting loads is a fundamental factor in re-designing of the structure after its functional failure. In this paper, a typical case of the shaft structure's failure is investigated for re-designing purposes. Failure causes of interest are excessive bending moment, fatigue loads and dynamic resonance due to relevant motor rotation and unbalancing of the rotation loads. Static analyses of shaft structure under the conditions of concerned loads are carried out, followed by a dynamic investigation of the effects of resonance between the shaft and the motor on the structure. The relevant structural analyses are carried out using the Finite Element Methods combined with ANSYS code. Based on these, the primary cause for the shaft's structural failure is obtained. It is found that the change of the bending stiffness of the shaft is the primary concern in the re-designing process. A guideline for the re-design process of the seawater pump shaft structure is established, and a re-design scheme of the structure is proposed.

• Archives of Plastic Surgery
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• v.36 no.1
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• pp.38-45
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• 2009

Purpose: The congenital muscular torticollis is a neck deformity involving shortening of the sternocleidomastoid muscle, which is detected at birth or shortly after birth. This childhood disease is the third most common congenital musculoskeletal anomaly. The indication for surgery is a persistent head tilt with dificit of passive rotation and lateral bending of the neck and a tight band or tumor in the sternocleidomastoid muscle even after physical therapy. The purpose of this article is to report surgical outcomes with patients who had no or little response to physical therapy. Methods: Surgery was performed on 29 patients and their average age was 4.1 years (from 6 months to 20.1 years). The unipolar open release and partial myectomy were done in 28 cases and the muscle lengthening was done in 1 case. Physical therapy was started from postoperative seventh day. Follow - up period was ranged from 2 months to 5.4 years(mean follow - up, 20.4 months). Result: There were neither rotation nor lateral bending deficit after surgical treatment. Mild head tilt was noticed in 3 cases and residual bend was observed in 4 cases. The subjective assessments of surgical results by parents were excellent. Conclusion: Our surgical outcome encourages the surgical treatment of congenital muscular torticollis for patients who failed to respond to physical therapy.

• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.317-325
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• 2008

As a result of recent research, it is reported that the periodic replacements criterion of rails is able to extend as grinding rail surface and using the continuous welded rail (CWR). This study evaluated correlation between conditions of track and load capacity of rail by analysing the dynamic response of track while the metro train is running. Also, it was converted the measured stress waveform into stress frequency histogram by the rain-flow counting methods, and then accumulated fatigue damage ratio and remaining service life of laid rail were calculated so as the apply the equivalence of stress to S-N curve of a new welded rail. Finally, this study suggests a revision of the periodic replacements criterion of CWR, which was based on accumulated passing tonnage, classified by the types and conditions of track system.

• Steel and Composite Structures
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• v.9 no.2
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• pp.131-158
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• 2009

This paper presents a modelling technique for the nonlinear analysis of composite steel-concrete beams with partial shear interaction. It extends the applicability of two stiffness elements previously derived by the authors using the direct stiffness method, i.e. the 6DOF and the 8DOF elements, to account for material nonlinearities. The freedoms are the vertical displacement, the rotation and the slip at both ends for the 6DOF stiffness element, as well as the axial displacement at the level of the reference axis for the 8DOF stiffness element. The solution iterative scheme is based on the secant method, with the convergence criteria relying on the ratios of the Euclidean norms of both forces and displacements. The advantage of the approach is that the displacement and force fields of the stiffness elements are extremely rich as they correspond to those required by the analytical solution of the elastic partial interaction problem, thereby producing a robust numerical technique. Experimental results available in the literature are used to validate the finite element proposed in the paper. For this purpose, those reported by Chapman and Balakrishnan (1964), Fabbrocino et al. (1998, 1999) and Ansourian (1981) are utilised; these consist of six simply supported beams with a point load applied at mid-span inducing positive bending moment in the beams, three simply supported beams with a point load applied at mid-span inducing negative bending moment in the beams, and six two-span continuous composite beams respectively. Based on these comparisons, a preferred degree of discretisation suitable for the proposed modelling technique expressed as a function of the ratio between the element length and depth is proposed, as is the number of Gauss stations needed. This allows for accurate prediction of the nonlinear response of composite beams.

• Korean Journal of Food Science and Technology
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• v.35 no.4
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• pp.617-622
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• 2003

Experimental designs were applied to optimize the mixture ratio for the extrudate made by soymilk residue and corn grits. Nine candidate points were examined for their significance on extrudate using the modified distance design. Bending force, expansion ratio, bulk density, water solubility index (WSI), water absorption index (WAI) and color $(L^*,\;a^*,\;b^*)$ were the significant factors improving the extruded cereal production, and these values were applied to the mathematical models. Results showed that bending force, expansion ratio WSI, WAI and color $(L^*,\;b^*)$ increased with increasing the corn grits, whereas bulk density tended to decrease. The statistical study showed that the fitted models were adequate to describe the contour plot and all responses. Optimum mixture ratio allowing to maximize the two responses (expansion ratio and $b^*$) and minimize the response (WAI) were examined with a numerical optimization methods. The numerical optimization method was obtained as 53.18% : 46.19% (corn grits : soymilk residue).