• Journal of the Society of Naval Architects of Korea
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• v.47 no.6
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• pp.843-849
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• 2010

This paper presents definition of symmetry of a ship section where three symmetries are proposed: material, geometric, and load symmetries. Precise terminologies of centroid, moment plane, and neutral axis plane are also defined. It is suggested that force vector equilibrium as well as force equilibrium are necessary condition to determine new position of neutral axis due to translational and rotational mobility. It is also stated that new reference datum of ENMP(elastic neutral moment plane), PNMP(fully plastic moment plane), ENAP(elastic neutral axis plane), and INAP(inelastic neutral moment plane) are required to define asymmetric section properties such as second moment of area, elastic section modulus, yield moment, fully plastic moment, and ultimate moment. Since collision-induced damage and flooding-induced biaxial bending moment produce typical asymmetry of section, the section properties are calculated for a typical VLCC. Geometry asymmetry is determined from ABS and DNV rules and two moment planes of 0/30 degs are assumed for load asymmetry. It is proved that the property reduction ratios directly calculated from second moment of area are usually larger than area reduction ratio. Reduction ratio of ultimate moment capacity shows almost linearly proportional to area reduction ratio. Mobility of elastic and inelastic neutral axis planes is visually provided.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.268-273
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• 2004

This study is conducted to clarify the effect of internal pressure on the deformation and collapse behaviors of wall thinned elbow under in-plane bending moment. Thus the nonlinear three-dmensional finite element analyses were performed to obtain the moment-rotation curve of elbow contatining various wall thinning defects located at intrados and extrados under in-plane bending (closing and opening modes) with internal pressure of $0{\sim}15MPa.$ From the results of analysis, the effect of internal of collapse moment of elbow on the global deformation behavior of wall thinned elbow was discussed, and the dependence of collapse moment of elbow on the magnitude of internal pressure was investigated under different loading mode, defect location, and defect shape.

• Structural Engineering and Mechanics
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• v.9 no.5
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• pp.469-482
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• 2000

A numerical study using nonlinear finite element analysis is performed to investigate the behavior of isolated reinforced concrete walls subjected to combined axial force and in-plane and out-of-plane bending moments. For a nonlinear finite element analysis, a computer program addressing material and geometric nonlinearities was developed. Through numerical studies, the internal force distribution in the cross-section is idealized, and then a new design method, different from the existing methods based on the plane section hypothesis was developed. According to the proposed method, variations in the interaction curve of the in-plane bending moment and axial force depends on the range of the permissible axial force per unit length, that is determined by a given amount of out-of-plane bending moment. As the out-of-plane bending moment increases, the interaction curve shrinks, indicating a decrease in the ultimate strength. The proposed method is then compared with an existing method, using the plane section hypothesis. Compared with the proposed method, the existing method overestimates the ultimate strength for the walls subjected to low out-of-plane bending moments, while it underestimates the ultimate strength for walls subject to high out-of-plane bending moments. The proposed method can address the out-of-plane local behavior of the individual wall segments that may govern the ultimate strength of the entire wall.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.249-258
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• 2006

In this paper, deformation capacity of steel moment connections with RHS column was investigated. Initially, non-linear finite element analysis of five bate steel beam models was conducted. The models were designed to have different detail at their beam-to-column connection, so that the flexural moment capacity was different respectively. Analysis results showed 4hat the moment transfer efficiency of the analytical model with RHS-column was poor when comparing to model with WF(Wide flnage)-column due to out-of-plane deformation of the RHS-column flange. The presence of scallop and thin plate of RHS column was also a reason of the decrease of moment transfer efficiency, which would result in a potential fracture of tile steel beam-to-column connections. Further test on beam-to-column connections with RHS column revealed that the moment transfer efficiency of a beam web decreased due to the out-of-plane deformation of column flange, which led to premature failure of the connection.

• Journal of Ship and Ocean Technology
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• v.8 no.4
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• pp.17-25
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• 2004

Hull girder stress monitoring system for container ship uses four long-base-strain-gages at mid-ship to monitor the resultant stresses and the applied moment components of horizontal, vertical and torsional moments. The bending moments are estimated by using the conventional strain-moment relations, however, the torsional moment related to the warping strain requires the assumption of the shape of torsional moments over the hull girder. Though this shape could be a sine function with an adequate period, it largely depends upon certain empirical formulas. This paper introduces additional four long-base-strain-gages at mid-ship to derive the longitudinal slope of the warping strain because this slope is directly related to the torsional moment by Bi-moment concept. An open-channel-type cantilever beam has been selected as a simplified model for container ship and the result has proved that the suggested concepts can estimate the torsional component accurately. Finally this method can become reliable technique to derive all external moments in hull girder stress monitoring system for container ships.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.290-293
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• 2003

In this paper, infinite frequency selective surface comprised with rectangular plates which are arranged periodically is analyzed using Method of Moment based on Galerkin's method. In analysis, it is assumed that the plates are infinite thin perfect conductors. Based on this assumption, the reflection characteristics of the FSS is compared according to the polarization of plane-wave and the direction of incidence. In the results, the variation of reflection characteristics of the FSS highly depends on the direction of incidence when the polarization of the plane-wave is parallel to the plane of incidence, but the variation is nearly independent upon direction of incidence when the polarization of the plane-wave is perpendicular to the plane of incidence.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.3
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• pp.281-287
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• 2011

This paper explains the basic theory and a new development of for the residual strength prediction program of the asymmetrically damaged ships, being capable of searching moment-curvature relations considering neutral axis mobility. It is noted that moment plane and neutral axis plane should be separately defined for asymmetric sections. The validity of the new program is verified by comparing moment-curvature curves of 1/3 scaled frigate model where the results from new algorithm well coincide with experimental and nonlinear FEA results for intact condition and with nonlinear FEA results for damaged condition. Applicability of new algorithm is also verified by applying VLCC model to the newly developed program. It is proved that reduction of residual strengths is visually presented using the new algorithm when damage specifications of ABS, DNV and IMO are applied. It is concluded that the new algorithm shows very good performance to produce moment-curvature relations with neutral axis mobility on the asymmetrically damaged ships. It is expected that the new program based on the developed algorithm can largely reduce design period of FE modeling and increase user conveniences.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.211-219
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• 2009

The purpose of the study described in this paper was to experimentally investigate branch squared T joints with cold formed hollow structural sections under the in plane moment in a Vierendeel Truss. The branch in the T joints was welded to the upper flange of the chord. The main experimental parameters were the ratio of the width to the thickness of the chord ($2{\gamma}$), with ${16.7{\leq}2{\gamma}{\leq}33.3}$, and the width ratio of the branch to the chord ($\beta$), with ${0.40{\leq}{\beta}{\leq}0.71}$. Nine specimens were tested and manufactured in joints under the in plane bending moment. Based on the results of the test, the in plane moment strength of the branch squared T joints was determined according to the bending deformation of the chord flange yielding, regardless of the ratio of the width to the thickness of the chord and the ratio of the width of the branch to the width of the chord. Also, the in plane moment strength of the branch squared T joints in the hollow structural sections can be defined as 1.5 times the moment load at M1%B the strength of the joints that governed the serviceability in the control group. Finally, the experimental results with the branch squared T joints show that the in lane moment strength of the joint increased as $2{\gamma}$ decreased and $\beta$ increased.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1260-1263
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• 2013

Plane wave scattering from a spherical resonator is calculated by solving the combined field integral equation (CFIE) with Rao-Wilton-Glisson (RWG) basis functions and the moment method. The calculations show that magnetic and electric dipoles are found at resonant modes. These characteristics are confirmed by radiation patterns in the far field region. In addition, an analysis of a magnetodielectric sphere is discussed.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.5
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• pp.288-295
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• 2022

In this study, the force and moment acting on a Joubert BB2 submarine model at depths near the free surface were measured through a captive model test with the scale ratio of 1/15. Based on the experiment, the pitch moment and heave force due to the "Tail suction effect", including the change in surge force with depth near the free surface, were quantitatively analyzed. The change of force and moment according to the relative position of the sail and the free surface was reviewed with the free surface waves generated for each depths. As a result, the angle of attack of the hull to counteract the pitch moment induced by the tail suction effect was derived. The effect of the hydrostatic moment component according to the angle of attack on the equilibrium of pitch moment was also taken into account. The control plane performance tests for the X-type rudder and sail plane were conducted in snorkel and surface depth conditions to figure out the control plane angles for the neutral level flight of the submarine at near free surface. The results of this study are expected to be used as a reference data for the neutral level flight of the submarine at near free surface operation in the free running model test as well as numerical studies.