• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.93-100
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• 1998

The basic systems of spatial structures such as shells, membrane, cable-nets and tensegrity structure have been developed to create the large spaces without column. These structures may have large freedom in scale and form, and especially tensegrity structures are received much attention from the view points of their light weight and aesthetics. But There re some difficulties concerning structural stability, surface formation and construction method. One of the way to solve these problems reasonably is a combination of tensile members and rigid members. A structural system based on this concept is referred to as the "HTS ( Hybrid Tension Structure )". This is a type of flexible structural system which is unstable initially, because the cable material has little initial rigidity. As cable - dome hybrid structures is a type of HTS, the initial stress for the self- equilibrated system having stable state have to be introduced. To determine initial stress having stable state, the shape finding analysis is required before the stress - deformation analysis. In this paper, the primary objective is to derive the nonlinear finite element formula of cable and truss members considering geometric nonlinearity for shape finding of cable-dome, and to propose the method to decide the initial stress by the shape analysis of cable-dome hybrid structure with the self-equilibrated state.

• Journal of the Korean Geosynthetics Society
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• v.4 no.3
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• pp.3-10
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• 2005

This paper aims at investigating the characteristics of discharge capacity according to lateral pressure, hydraulic gradient and deformation of drain materials. A series of experiments were conducted to achieve this objective. In experiments, fiver drain boards as well as harmonica and castle types of drain boards were installed in a rubber membrane, and clay in sully was filled around them. The test results showed that the harmonica type of drain boards have the greatest discharge capacity comparing to castle and fiber drain boards. The results also indicated that the hydraulic gradient has more effect on reduction of discharge capacity than the lateral pressure.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.379-384
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• 2018

This study showed the development process of structural design method of BHB(Blast Hardened Bulkhead) which are applicable in preliminary design stage. In the previous 1st report, the simplified structural scantling equations of BHB were formulated theoretically using the modified plastic hinge method supplemented by considering the membrane effects due to large plastic deformation. And the scantling methodology of plate thickness and section area of stiffeners of the curtain plate type BHB was dealt with. In the present 2nd report, derivation process of the correction factors which can adjust the developed scantling equations considering the uncertainties contained in the design parameters was introduced. Considering the actual BHB structures of 3 warship, the correction factors for the developed scantling equations for curtain plate type BHB were derived. Finally the applicability, validity of them and the strategy of future improvement were considered.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.109-116
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• 2019

The mechanical deformation of a battery separator causes internal short-circuiting of the cathode - anode, which directly affects the explosion/ignition of batteries. To increase the mechanical properties of the separator fabricated by electro-spinning, use of a thermal pressing method is inevitable. Therefore, this research aims to maximize the mechanical strength of a porous separator by finding the proper thermal press temperatures given to Electro-spun Polyacrylonitrile (PAN) nanofibers. The different thermal press temperatures $25^{\circ}C$, $50^{\circ}C$, $75^{\circ}C$, and $100^{\circ}C$ were applied to the electro-spun fiber at 30 MPa pressure for one hour. The higher the temperature, the higher the resultant tensile strength; however, a higher temperature also lowered the strain and porosity. Thus, the membrane thermal pressed at $50^{\circ}C$ showed the best mechanical properties and the second highest porosity. Using the data, $50^{\circ}C$ was judged as the best thermal pressing temperature in terms of performance.

• Steel and Composite Structures
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• v.31 no.2
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• pp.187-199
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• 2019

This paper presents the semi-analytical development of the dynamic instability behavior and the dynamic response of functionally graded (FG) cylindrical shallow shell panel subjected to different type of periodic axial compression. First, in prebuckling analysis, the stresses distribution within the panels are determined for respective loading type and these stresses are used to study the dynamic instability behavior and the dynamic response. The prebuckling stresses within the shell panel are the same as applied in-plane edge loading for the case of uniform and linearly varying loadings. However, this is not true for the case of parabolic loadings. The parabolic edge loading produces all the stresses (${\sigma}_{xx}$, ${\sigma}_{yy}$ and ${\tau}_{xy}$) within the FG cylindrical panel. These stresses are evaluated by minimizing the membrane energy via Ritz method. Using these stresses the partial differential equations of FG cylindrical panel are formulated by applying Hamilton's principal assuming higher order shear deformation theory (HSDT) and von-$K{\acute{a}}rm{\acute{a}}n$ non-linearity. The non-linear governing partial differential equations are converted into a set of Mathieu-Hill equations via Galerkin's method. Bolotin method is adopted to trace the boundaries of instability regions. The linear and non-linear dynamic responses in stable and unstable region are plotted to know the characteristics of instability regions of FG cylindrical panel. Moreover, the non-linear frequency-amplitude responses are obtained using Incremental Harmonic Balance (IHB) method.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.4
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• pp.81-93
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• 1989

The present study attempts to develop the theoretical model for the damage estimation of offshore tubular members which are subjected to the accidental impact loads due to collision, falling objects and so on. For the reasons of the simplicity of the problem being considered, however, this paper postulates that the accidental load can be approximated to be the quasi-static one, in which dynamic effects are negelcted. Based upon the theoretical and experimental results which are obtained from the present study as well as the existing literature, the load-displacement relations taking the interaction effect between the local denting and the global bending deformation into account are presented in the explicit form when the concentrated lateral load acts on the tubular member whose end condition is supposed to be rotation ally free and axially restrained, in which membrane forces develop. Thus, the practical estimation of damage deformation for the local denting and the global bending damage of tubular members against the accidental loads is possible and also the collision absorption capability of the member can be calculated by performing the integration of the area below the given load-displacement curves, provided that all the energy is dissipated to the deforming the member itself.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.6
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• pp.994-1001
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• 2007

Changes in shear force value, transverse sections, myofibrils and intramuscular connective tissue of bovine skeletal muscle exposed to the combination of high-pressure up to 400 MPa and heat (30 and $60^{\circ}C$) were studied. The shear force value decreased by pressure-heat treatment up to 200 MPa at 30 and $60^{\circ}C$, and then slightly increased over 200 MPa at $30^{\circ}C$. Shear force values of treated muscles were lower than those of untreated ones. Gaps between muscle fibers in the untreated muscle were a little clear, and then they became very clear in the treated muscles up to 200 MPa at 30 and $60^{\circ}C$. However, the gaps reduced significantly over 200 MPa at $30^{\circ}C$. The remarkable rupture of I-band and loss of M-line materials progressed in the myofibrils with increasing pressure applied. However, degradation and loss of the Z-line in myofibrils observed in the muscle treated at $60^{\circ}C$ was not apparent in the muscle treated at $30^{\circ}C$. The length of the sarcomere initially contracted by pressure-heat treatment of 100 MPa at $30^{\circ}C$ seemed to have recovered with increase of the pressure up to 400 MPa. In the muscle treated at $60^{\circ}C$, the length of sarcomere gradually decreased with increase of the pressure up to 400 MPa. In the treated muscles, changes in the honeycomb-like structure of endomysium were observed and accelerated with increase of the pressure. A wavy appearance clearly observed at the inside surface of endomysium in the untreated muscles gradually decreased in the treated muscles with increase of the pressure. Tearing of the membrane was observed in the muscles treated over 150 MPa at $30^{\circ}C$, as observed in the sample pressurized at 100 MPa at $60^{\circ}C$. The roughening, disruption and fraying of the membrane were observed over 200 MPa at $60^{\circ}C$. From the results obtained, the combination of high-pressure and heat treatments seems to be effective to tenderize tough meat. The shear force value may have some relationship with deformation of intramuscular connective tissue and myofibrils.

• Membrane Journal
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• v.19 no.3
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• pp.252-260
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• 2009

The effects of the treatment of an acidic solution at pH 2 on polyacrylonitrile ultrafiltration (UF) membranes were investigated using a circular cross-flow filtration bench with a membrane module. A substantial reduction in the membrane permeability was observed after 80 hours' treatment of the acidic solution. In addition, the analyses of the sample solutions by ultraviolet/visible absorption spectroscopy and gas chromatography/mass spectrometry (GC/MS), which were taken from the feed tank as a function of the treatment time, showed that a new organic compound was produced in the course of the treatment. From a thorough search of the mass spectral library we presumed the new compound to be 1,6-dioxacyclododecane-7,12-dione (DCD), one of the well-known additives for polyurethane. Based on further experimental results, including the scanning electron microscope (SEM) images and the solid-state NMR spectra of the membranes used for the treatment of the acidic solution, we suggested that the decrease of the permeate flux resulted not from the deformation of the membranes, but from the fouling by DCD eluted from the polyurethane tubes in the filtration bench during the treatment. Those results imply that the reactivity to an acidic solution of the parts comprising the filtration bench is as important as that of the membranes themselves for effective treatments of acidic solutions, for efficient chemical cleaning by strong acids, and also in determining the pH limit of the solutions that can be treated by the membranes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.247-258
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• 2004

The composite shell element is developed for the solution of undamped forced vibration problem of composite curved panels. The finite element used in the current study is an 4-node enhanced assumed shell element with six degrees of freedom per node. The composite shell element is free of both shear and membrane locking phenomenon by using the enhanced assumed strain(EAS) method. A modification to the first-order shear deformation shell theory is proposed, which results in parabolic thorough-thickness distribution of the transverse shear strains and stresses. It eliminates the need for shear correction factors in the first order theory. Newmark's direct integration technique is used for carrying out the integration of the equation motion, to obtain the repones history. Parametric studies of curved composite panels are carried out for forced vibration analysis by geometrical shapes and by laminated composite; such as fiber orientation, stacking sequence.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.47-60
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• 2007

In this paper, we investigate the natural frequencies and buckling loads of functionally graded material (FGM) plates and shells, using a quasi-conforming shell element that accounts for the transverse shear strains and rotary inertia. The eigenvalue of the FGM plates and shells are calculated by varying the volume fraction of the ceramic and metallic constituents using a sigmoid function, but their Poisson's ratios of the FGM plates and shells are assumed to be constant. The expressions of the membrane, bending and shear stiffness of FGM shell element are more complicated combination of material properties than a homogeneous element. In order to validate the finite element numerical solutions, the Navier's solutions of rectangular plates based on the first-order shear deformation theory are presented. The present numerical solutions of composite and sigmoid FGM (S-FGM) plates are proved by the Navier's solutionsand various examples of composite and FGM structures are presented. The present results are in good agreement with the Navier's theoretical solutions.