• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.4A
• /
• pp.475-485
• /
• 2008

This paper intends to enhance the reliability and performance of domestic elastomeric bearings through the proposal of directions for the improvement of their stiffness regard to the Korean industrial standard KS F 4420 relative to the evaluation of design/fabrication/quality. Therefore, comparative analysis of the compressive elastic modulus, stiffness measurement method and performance evaluation method of KS F 4420 with those of Eurocode, Japanese bearing manual, and ISO code was performed, and measurement tests on the compressive stiffness and shear stiffness of common elastomeric bearings produced in Korea were conducted. The experimental results reveal that differences of about 20% and 13% occurred respectively for the compressive stiffness and shear stiffness according to the definition adopted for the stiffness. The measured values for the stiffness of the domestic elastomeric bearings were also verified to exhibit large deviation from the formula proposed by KS F 4420. Elastomeric bearings that does not have appropriate compressive stiffness required at the design can result in uneven deflection at supports of bridges and excessive stress in girders. Accordingly, the establishment of compressive elastic modulus formula and performance evaluation criteria fitted to the domestic circumstances through the execution of performance evaluation of bearings presenting diversified shapes and shape factors appears to be necessary for the domestic bearings to meet the performance required in design.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.25 no.4
• /
• pp.69-80
• /
• 1988

This paper proposes simple formulae for buckling and ultimate strength estimation of plates subjected to water pressure and uniaxial compression. For the construction of a formula for elastic buckling strength estimation, parametric study for actual ship plates with varying aspect ratios and the magnitude of water pressure is carried out by means of principle of minimum potential energy. Based on the results by parametric study, a new formula is approximately expressed as a continuous function of loads and aspect ratio. On the other hand, in order to get a formula for ultimate strength estimation, in-plane stress distribution of plates is investigated through large deflection analysis and total in-plane stresses are expressed as an explicit form. By applying Mises's plasticity condition, ultimate strength criterion is then derives. In the case of plates under relatively small water pressure, the results by the proposed formulae are in good agreement compared with those by other methods and experiment. But present formula overestimates the ultimate strength in the range of large water pressure. However, actual ship plates are subjected to relatively small water pressure except for the impact load due to slamming etc.. Therefore, it is considered that present formulae can be applied for the practical use.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.16 no.2
• /
• pp.133-140
• /
• 2003

The sandwich plate has been widely used as an efficient structural member because it has high strength-to-weight and high stiffness-to-weight ratios. To properly design the aluminum extrusion plate , it is necessary to analyze structural behaviors of the extrusions, however, the aluminum extrusions have been rarely studied until now. In the optimization process through numerous iterative calculations, finite element analysis of the sandwich plate with hollow core section requires a considerable amount of computation time and cost. In this paper, the aluminum extrusion plate with truss-core is transformed into an equivalent homogeneous orthotropic plate with appropriate elastic constants. The procedure to evaluate accurate equivalent elastic constants is also established. Using these elastic constants, simple theoretical formulas of the stresses and deflection are proposed in case of the simply-supported orthotropic thick plate under uniform pressure. Through the comparison with the results by commercial FEM code(ANSYS), it is verified that the proposed simpified formula has a good efficiency and accuracy.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.29 no.1
• /
• pp.55-60
• /
• 2005

Plate that have cutout inner bottom and girder and floor etc. in hull construction absence is used much, and this is strength in case must be situated, but establish in region that high stress interacts sometimes fatally in region that there is no big problem usually by purpose of weight reduction, a person and change of freight, piping etc.. Because cutout's existence gnaws in this place, and, elastic buckling strength by load causes large effect in ultimate strength. Therefore, perforated plate elastic buckling strength and ultimate strength is one of important design criteria which must examine when decide structural elements size at early structure design step of ship. Therefore, and, reasonable elastic buckling strength about perforated plate need design ultimate strength. Calculated ultimated strength change several aspect ratioes and cutout's dimension, and thickness in this investigation. Used program applied ANSYS F.E.A code based on finite element method.

• Journal of the Korean Society for Precision Engineering
• /
• v.7 no.4
• /
• pp.23-28
• /
• 1990

This study is to investigate the magnitude, direction and distribution of residual stresses in surface ground plate according to working conditions. The specimens were made of structural carbon steel and were machined in various grinding conditions. These were divided in two groups; heat-treated materials and non-heat-treated materials. In each working condition, let the ground specimen generate displacements using deflection-etching techniques. At the same time, these displacements were precisely measured with electronic micrometer. Through the relation formula between the plane stress and strain, which was derived using these measured data, the values of residual stress are calculated, and the results are analyzed. These results are as follows : 1. According to the working conditions in this experiment, it can be seen that the distribution of residual stress generally had same trend and the maximum residual stress remained in 20~30 ((${\mu}m$) beneath the surface. 2. It is observed that compressive residual stress changes into tensile stress in 5~20 (${\mu}m$) beneath the surface. It is suggested that such phenomenon is originated from the friction effect in grinding process. 3. As the hardness increases by the heat treatment, residual stress increases. 4. As the fatigue strength increases by the compressive residual stress, it is desirable that the dowm feed and table feed reduce. 5. It can be seen that the more great the down feed and table feed increase, the more close the changing point, where the stress changed from compressive to tensile, is colse to the surface. This is due to the resultant effects of the grinding temperature and resistence are larger than the effect of the friction.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.9 no.2
• /
• pp.1301-1305
• /
• 1967

Ground water flow can be studied with model test. Model test of ground water works are necessary for economic and safe design of the works. Also influence of the ground water flow to the durability and safety of hydraulic structures can be studied with this model. a. Sand model ; Water flow through porous media is the principle of sand model. Darcy's formula is the basic equation, $q=k{\frac{dh}{ds}}^{\circ}. The effect of the ground water flow on the grain system itself is represented with this model only. b. Hele-Shaw model ; In this model use is made of the viscous flow analogy. Viscous fluid such as glycerine flowing through two parallel plates depends on Poiseuille law, $q=-c{\frac{dh}{ds}}$. The analogue can be used vertically and horizontally. c. Heat model ; This is based on the analogy of the Fourier's law for heat conduction and Darcy's law for ground water flow. Especially unsteady problem can be studied with this model. A difficulty of the construction of this model is the isolation, which has to prevent losses of the heat. d. Electirc model ; Ohm's law for electric current is analogous to Darcy's law. Resistance material such as metal foil, graphite block, water with salt added, gelatine with salt added, ete. is connected to electric sources and resistor, and equi-voltage line is detected with galvanometer, $N_aCl$, $CuSo_4$, etc. are used as salt in the model. e. Membrane model ; This model is based on the facts that the deflection of a thin membrane obeys Laplace's equation if there is no load in the direction perpendicular to the membrane, and if the dellection is small.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.3
• /
• pp.53-60
• /
• 1997

Generally, a safety estimation based on the buckling strength is carried out to evaluate the strength of plate members in the design process of ship hull structures and more accurate and efficient tool for the buckling strength estimation of enormous plate members of ship structure is naturally demended for saving design process. While, in the reason that the design codes of classification societies do not consider the various effects or include some effects roughly, considerate safe side results are suggested occasionally. In this study, advanced buckling strength estimation system prepared various classification buckling evaluation codes and new evaluation code considering the effects of in-plane tension, plate boundary condition, lateral load & residual stress is developed using the window management system of engineering workstation. Additionally maximum deflection estimation formula is equipped for the increase of fabrication reliability of thin plate ship structure. From this evaluation system, more reliable buckling safety of plate panel will be guaranteed in the ship hull design stage. In order to expand the use of this system pc version system will be developed sooner or later.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.10 no.1 s.20
• /
• pp.29-33
• /
• 2004

Design of general steel structure had applied to achieve elastic designing concept so far. Because elastic design supposes that whole structure complies with elasticity formula so that achieve via allowable stress of material. It is concept that calculate stress distribution of construction about action external load and estimate load when the maximum stress reaches equally with allowable stress that is established by maximum safety load of the structure. But, absence that compose actuality structure by deal with external load increase small success surrender and structure hardness falls and structure in limited state finally on the whole as showing complicated process by interference between collapse and buckling under compression. Applied ANSYS (elasto-plasticity large deformation finite element method) to be mediocrity finite element program for analysis method and analysis control used in Newton-Raphson method & Arc-length method.

• Journal of the Society of Naval Architects of Korea
• /
• v.33 no.4
• /
• pp.97-105
• /
• 1996

For the minimum weight design of ship structures it is desirable that tank arrangement is predetermined to obtain the minimum weight and then structural arrangement and scanting of each murder is determined to obtain the minimum weight within the given tank arrangement. To carry out the tank arrangement to give minimum weight a minimum weight design program which covers whole ship structures is developed by the combination of minimum weight design program of longitudinal members by classification rules and minimum weight design program of transverse members by generalized slope deflection method which were developed by the authors. The hullweight is estimated by summation of the weight of cargo hold part and the weight except cargo hold part which can be estimated by the empirical formula. In this study, the variation of hullweight is shown with the number of tank, the number of web and the location of longitudinal bulkhead. For the application of actual design alternative designs of tank arrangement which satisfy MARPOL regulation are determined. And several minimum weight designs of whole ship structures are carried out to obtain the tank arrangement which gives minimum weight and then the hullweight is compared with that of existing ship.

• Structural Engineering and Mechanics
• /
• v.60 no.6
• /
• pp.1001-1019
• /
• 2016

The connector is the most important part of a composite beam and promotes a composite action between a steel beam and concrete slab. This paper presents the experiment results for three large-scale beams with a newly puzzle shape of crestbond. The behavior of this connector in a composite beam was investigated, and the results were correlated with those obtained from push-out-test specimens. Four-point-bending load testing was carried out on steel-concrete composite beam models to consider the effects of the concrete strength, number of transverse rebars in the crestbond, and width of the concrete slab. Then, the deflection, ultimate load, and strains of the concrete, steel beam, and crestbond; the relative slip between the steel beam and the concrete slab at the end of the beams; and the failure mechanism were observed. The results showed that the general behavior of a steel-concrete composite beam using the newly puzzle shape of crestbond shear connectors was similar to that of a steel-concrete composite beam using conventional shear connectors. These newly puzzle shape of crestbond shear connectors can be used as shear connectors, and should be considered for application in composite bridges, which have a large number of steel beams.