• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.443-455
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• 2001

An energy method has been used for an elastic formulation of bending vibration and buckling analysis of laminated composite plates on two-parameter elastic foundations. A quasi-elastic method is used for the solution of viscoelastic analysis of the laminated composite plates. The third-order shear deformation theory is applied by using the double-fourier series. To validate the derived equations the obtained displacements for simply supported orthotropic plates on elastic foundations are compared with those of LUSAS program Numerical results of the viscoelastic bending vibration and buckling analysis are presented to show the effects of layup sequence number of layers material anisotropy and shear modulus of foundations.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.65-79
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• 1997

Composite materials are consist of two or more different materials to produce desirable properties for structural strength. Because of their superiority in strength, corrosion resistance, and weight reduction, they are used extensively as structural members. The objective of this study is to present the effectivness of the laminated composite elements by analyzing in-plane displacement and stress of the anisotropic laminated annular elements. Anisotropic laminated structures are very difficult to analyze and apply, compared with isotropic and orthotropic cases for arbitrary boundaries and fiber angle -ply. Boundary conditions for the examples used in this study consist of two opposite edges clamped and the other two edges free, and finite difference method is used in this study for numerical analysis. From the numerical result, it is found that the program used in this study can be used to obtain the displacement of the straight beams considering it's transverse shear deformation as well as anisotropic laminated elements. Several numerical examples show the advantages of the stiffness increase when the angle-ply composite materials are used. Therefore it gives a guide in deciding how to make use of fiber's angle for the subtended angle, load cases, and boundary conditions.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.2
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• pp.85-95
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• 1996

An iterative Kantorovich method is presented for the vibration analysis of rectangular isotopic and orthotropic thick plates. Mindlin plate characteristic functions are derived in general forms by the Kantorovich method initially starting with Timoshenko beam functions consistent with the boundary conditions of the plate. Through numerical calculations of natural pairs, i.e. natural frequencies and corresponding modes, and dynamic responses of appropriate models, it has been confirmed that the presented method is superior to the Rayleigh-Ritz analysis or the FEM analysis in accuracy and computational efficiency.

• Structural Engineering and Mechanics
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• v.13 no.3
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• pp.313-328
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• 2002

Based on the orthotropic hypoelasticity formulation, a triaxial constitutive model of concrete is proposed. To account for increasing ductility in high confinement of concrete, the ductility enhancement is considered using so called the strain enhancement factor. It is also developed a three-dimensional finite element model for reinforced concrete structural members based on the proposed constitutive law of concrete with the smeared crack approach. The concrete confinement effects due to the beam-column joint are investigated through numerical examples for simple beam and structural beam member. Concrete at compression fibers in the vicinity of beam-column joint behaves dominant not only by the uniaxial compressive state but also by the biaxial and triaxial compressive states. For the reason of the severe confinement of concrete in the beam-column joint, the flexural critical cross-section is observed at a small distance away from the beam-column joint. These observations should be utilized for the economic design when the concrete structural members are subjected to high confinement due to the influence of beam-column joint.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.440-449
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• 2003

Residual strength of fiber metal laminates after impact was studied. 3/4 lay up FML was fabricated using 4 ply prepreg, 2 ply aluminum sheets, and 1 ply steel sheet. Quasi isotropic ([0/45/90/-45]s) and orthotropic ([0/90/0/90]s) FRP were also fabricated to compare with FML. Impact test were conducted by using instrumented drop weight impact machine (Dynatup, Model 8250). Penetration load and absorbed energy of FML were superior to those of FRPs. Tensile tests were conducted to evaluate the residual strength after impact. Strength degradation of FML was less than that of FRP. This means that the damage tolerance of FML is excellent than that of FRP. Residual strength of each specimen was predicted by using Whitney and Nuismer(WN) Model. Impact damage area is assumed as a circular notch in WN model. Damage width is defined as the average of back face and top face damage width of each specimen. Average stress and point stress criterions were used to calculate the characteristic length. It is supposing that a characteristic length is a constant. The distribution of characteristic length shows that the assumption is reasonable. Prediction was well matched with experiment under both stress criterions.

• Composites Research
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• v.29 no.6
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• pp.388-394
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• 2016

Fiber reinforced plastic (FRP) composites have drawn increasing attentions worldwide for decades due to its outstanding properties. Stress concentration factor (SCF) as an essential parameter in materials science are critically considered in structure design and application, strength assessment and failure prediction. However, investigation of stress concentration in FRP composites has been rarely reported so far. In this study, three resource-conserving analyses (Isotropic analysis, Orthotropic analysis and Finite element analysis) were introduced to plot the $K_T^A-d/W$ curve for E-glass/epoxy composite plate with the geometrical defect of circular hole placed centrally. The plates were loaded to uniaxial direction for simplification. Finite element analysis (FEA) was carried out via ACP (ANSYS composite prepost module). Based on the least squares method, a simple expression of fitting equation could be given based on the simulated results of a set of discrete points. Finally, all three achievable solutions were presented graphically for explicit comparison. In addition, the investigation into customized efficient SCFs has also been carried out for further reference.

• Steel and Composite Structures
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• v.9 no.6
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• pp.569-584
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• 2009

Corrosion of steel rebars in bridge decks which are faced to harsh conditions, is a common problem in construction industries due to the porosity of concrete. In this research, the behavior of one-way concrete slabs reinforced with Glass fiber reinforced polymer (GFRP) molded grating is investigated both theoretically and experimentally. In the analytical method, a closed-form solution for load-deflection behavior of a slab under four-point bending condition is developed by considering a concrete slab as an orthotropic plate and defining stiffness coefficients in principal directions. The available formulation for concrete reinforced with steel is expanded for concrete reinforced with GFRP molded grating to predict ultimate failure load. In finite element modeling, an exact nonlinear behavior of concrete along with a 3-D failure criterion for cracking and crushing are considered in order to estimate the ultimate failure load and the initial cracking load. Eight concrete slabs reinforced with steel and GFRP grating in various thicknesses are also tested to verify the results. The obtained results from the models and experiments are relatively satisfactory.

• Computers and Concrete
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• v.25 no.3
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• pp.245-253
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• 2020

Vibrational analysis in microtubules is examined based on the nonlocal theory of elasticity. The complete analytical formulas for wave velocity are obtained and the results reveal that the small scale effects can reduce the frequency, especially for large longitudinal wave-vector and large circumferential wave number. It is seen that the small scale effects are more significant for smaller wave length. The methods and results may also support the design and application of nano devices such as micro sound generator etc. The effects of small scale parameters can increase vibrational frequencies of the protein microtubules and cannot be overlooked in the analysis of vibrating phenomena. The results for different modes with nonlocal effect are checked.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.468-475
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• 2007

The Steel deck a structural analysis in head plate form change the objective bridge which it sells it accomplished a detailed structural analysis from the research which it sees and Bulk-head plate it accomplished. The length rib where the fatigue crack which is considerable generally occurs, width rib connection department and the length rib side, the width rib side it compares principal stress in the object and it does to sleep. It applied the grudge element model which it describes consequently after words and a load and a boundary condition and it executed it compared a static test and principal stress. It grasped the stress conduct of the The Steel deck petal which it follows in hand weaving rib affix location and the affix location to sleep in order to analyze a same location Bulk-head the head and comparison considered. From the detailed section which is reinforced with the stress investigation result hand weaving rib of the location which is weak in structural analysis result fatigue crack of form star reinforcement details basic form and Bulk-head the form which is reinforced with the head plate compared to principal stress investigation hour it is judged at the section which separates most.

• Structural Engineering and Mechanics
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• v.60 no.5
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• pp.795-807
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• 2016

This study tries to examine the effect of different parameters on stress analysis of infinite plates with central quasi-triangular cutout using particle swarm optimization (PSO) algorithm and also an attempt has been made to introduce general optimum parameters in order to achieve the minimum amount of stress concentration around this type of cutout on isotropic and orthotropic plates. Basis of the presented method is expansion of analytical method conducted by Lekhnitskii for circular and elliptical cutouts. Design variables in this study include fiber angle, load angle, curvature radius of the corner of the cutout, rotation angle of the cutout and at last material of the plate. Also, diagrams of convergence and duration time of the desired problem are compared with Simulated Annealing algorithm. Conducted comparison is indicative of appropriateness of this method in optimization of the plates. Finite element numerical solution is employed to examine the results of present analytical solution. Overlap of the results of the two methods confirms the validity of the presented solution. Results show that by selecting the aforementioned parameters properly, less amounts of stress can be achieved around the cutout leading to an increase in load-bearing capacity of the structure.