• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.589-596
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• 2015

The occurrence of an inclined edge crack in transversely piezoelectric material is analyzed. Concentrated antiplane mechanical and inplane electrical loads are applied at the boundary and crack surface, respectively. The crack surfaces are assumed to be impermeable to the electric field. Using the Mellin transform with the introduction of a generalized displacement vector, the problem is formulated, and the Wiener-Hopf equation is derived. By solving the equation, the solution is obtained in a closed form. The intensity factors of the stress, the electric displacement, and the energy release rate are obtained for any crack length and inclination angle. These solutions can be used as fundamental solutions and can be superimposed to represent any arbitrary electromechanical loading.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.327-334
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• 1998

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and toll.or structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the special orthotropic plates with free edges supported on elastic foundation and with a pair of opposite edges under axial forces is presented. Such plates represent the concrete highway slab and hybrid composite pavement of bridges. The reinforced concrete slab can be assumed as a special orthotropic plate, as a close approximation. The highway slab is supported on elastic foundation, with free boundaries. Sometimes, the pair of edges perpendicular to the traffic direction may be subject to the axial forces. The plate is subject to the concentrated load/loads, in the form of traffic loads, or the test equipments. Any method nay be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation, the aspect ratio of the plate, and the magnitudes of the axial forces and the concentrated attached mass on the plate, on the natural frequency is thoroughly studied.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.419-428
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• 2000

Multiconductor transmission line(MTL) equations are solved by FDTD(Finite-Difference Time-Domain) method to predict crosstalk and fields to transmission line coupling on lossy multiconductor transmission lines terminated in arbitrary linear loads. Skin effect losses as well as dc losses are included in the analysis. In order to increase computational efficiency, the convolution integral of internal impedance of conductors and the line currents is computed by using Prony method. For boundary conditions of MTLs terminated in linear loads, state-variable formulation is adopted. The simulated results by FDTD method are compared with the measured ones obtained by using TEM cell. The predictions are in good agreement with the measurements. In addition, it has been found that skin effect losses as well as dc losses of the conductors should be included for accurate predictions on relatively high loss transmission lines such as PCB. It has also been found that dc losses and skin-effect losses affect late-time responses and early-time responses, respectively.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.2
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• pp.50-60
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• 1999

In order to design a safe and economic catamaran, it is of clime importance to rigorously estimate the dynamic loads on the catamaran in waves. In this paper, the 2-D strip method by Lee et al.[3] is. extended to a 3-D method which can estimate the dynamic loads(horizontal and vertical shear forses, and bending and torsional moments) acting on the center of the cross deck of the catamaran travelling in an arbitrary wave heading angle. The computational results are compared with Wahab et al's experimental data[2], and also 2-D and 3-D numerical results published. It is found that in general, the 3-D method give much improved correlations with the experimental data compared with 2-D methods, but there are some discrcrepancy between the same 3-D results used by the same theory. In order to improve the accuracy, the effect of the viscous flow and the rigid consideration of the forward speed effect seem to be necessary.

• Structural Engineering and Mechanics
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• v.34 no.2
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• pp.143-157
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• 2010

This paper presents theoretical solutions for the three-dimensional (3D) stress field in an infinite isotropic elastic plate containing a through-the-thickness circular hole subjected to far-field in-plane loads by using Kane and Mindlin's assumption. The dangerous position, where the premature fracture or failure of the plate will take place, the expressions of the tangential stress at the surface of the hole and the out-of-plane stress constraint factor are found in a concise, explicit form. Based on the present theoretical solutions, a comprehensive analysis is performed on the deviated degree of the in-plane stresses from the related plane stress solutions, stress concentration and out-of-plane constraint, and the emphasis has been placed on the effects of the plate thickness, Poisson's ratio and the far-field in-plane loads on the stress field. The analytical solution shows that the effects of the plate thickness and Poisson's ratio on the deviation of the 3D in-plane stress components is obvious and could not be ignored, although their effects on distributions of the in-plane stress components are slight, and that the effect of the far-field in-plane loads is just on the contrary of that of the above two. When only the shear stress is loaded at far field, the stress concentration factor reach its peak value about 8.9% higher than that of the plane stress solutions, and the out-of-plane stress constraint factor can reach 1 at the surface of the hole and is the biggest among all cases considered.

• Bulletin of the Society of Naval Architects of Korea
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• v.13 no.4
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• pp.19-24
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• 1976

Some method of analysis of rectangular plates under distributed load of various intensity with all edges built in are presented in. Analysis of many structures such as bottom, side shell, and deck plate of ship hull, and flat slab, deck systems of bridges is a problem of plate with continuous supports or clamped edges. When the four edges of rectangular plate is simply supported, the double fourier series solution developed by Navier can represent an exact result of this problem. If two opposite edges are simply supported, Levy's method is available to give an "exact" solution. When the loading condition and boundary condition of a plate does not fall into these cases, no simple analytic method seems to be feasible. Analysis of a plate under distributed loads of various intensity with all edges built in is carried out by applying Navier solution and Levy's method as well as "Principle of Superposition" In discussing this problem we start with the solution of the problem for a simply supported rectangular plate and superpose on the deflection of such a plate the deflections of the plate by slopes distributed along the all edges. These slopes we adjust in such a manner as to satisfy the condition of no rotation at the boundary of the clamped plate. This method can be applied for the cases of plates under irregularly distributed loads of various intensity with two opposite edges simply supported and the other two edges clamped and all edges simply supported and this method can also be used to solve the influence values of deflection, moment and etc. at arbitrary position of plates under the live load.

• Structural Engineering and Mechanics
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• v.77 no.4
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• pp.441-461
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• 2021

Reinforced concrete (RC) columns are crucial in building structures and they are of higher vulnerability to terrorist threat than any other structural elements. Thus it is of great interest and necessity to achieve a comprehensive understanding of the possible responses of RC columns when exposed to high intensive blast loads. The primary objective of this study is to derive analytical formulas to assess vulnerability of RC columns using an advanced numerical modelling approach. This investigation is necessary as the effect of blast loads would be minimal to the RC structure if the explosive charge is located at the safe standoff distance from the main columns in the building and therefore minimizes the chance of disastrous collapse of the RC columns. In the current research, finite element model is developed for RC columns using LS-DYNA program that includes a comprehensive discussion of the material models, element formulation, boundary condition and loading methods. Numerical model is validated to aid in the study of RC column testing against the explosion field test results. Residual capacity of RC column is selected as damage criteria. Intensive investigations using Arbitrary Lagrangian Eulerian (ALE) methodology are then implemented to evaluate the influence of scaled distance, column dimension, concrete and steel reinforcement properties and axial load index on the vulnerability of RC columns. The generated empirical formulae can be used by the designers to predict a damage degree of new column design when consider explosive loads. With an extensive knowledge on the vulnerability assessment of RC structures under blast explosion, advancement to the convention design of structural elements can be achieved to improve the column survivability, while reducing the lethality of explosive attack and in turn providing a safer environment for the public.

• The Journal of the Acoustical Society of Korea
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• v.17 no.2E
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• pp.53-58
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• 1998

In this paper, we study the response of several anisotropic systems to buried transient line loads. The problem is mathematically formulated based on the equations of motion in the constitutive relations. The load is in form of a normal stress acting with arbitrary axis on the plane of monoclinic symmetry. Plane wave equation is coupled with vertical shear wave, longitudinal wave and horizontal shear wave. We first considered the equation of motion in reference coordinate system, where the line load is coincident with symmetry axis of the orthotrioic material. Then the equation of motion is transformed with respect to general coordiante system with azimuthal angle by using transformation tensor. The load is first described as a body force in the equations of the motion for the infinite media and then it is mathematically characterized. Subsequently the results for semi-infinite spaces is also obtained by using superposition of the infinite medium solution together with a scattered solution from the free surface. Consequently explicit solutions for the displacements are obtained by using Cargniard-DeHoop contour. Numerical results which are drawn from concrete examples of orthotropic material belonging to monoclinic symmetry are demonstrated.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.191-194
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• 2001

A partially coupled thermo-piezoelectric-mechanical triangular finite element model of composite laminates with surface bonded piezoelectric actuators, subjected to externally applied mechanical load, temperature change load, electric field load is developed. The governing differential equations are obtained by applying the principle of free energy and variational techniques. A higher order zigzag theory displacement field is employed to accurately capture the transverse shear and normal effects in laminated composite plates of arbitrary thickness. Nonconforming shape functions by Specht are employed in the transverse displacement variables. Numerical examples demonstrate the accuracy and efficiency of the proposed triangular plate element.

• Steel and Composite Structures
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• v.15 no.1
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• pp.57-79
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• 2013

This paper studies the dynamic instability of laminated composite plates under thermal and arbitrary in-plane periodic loads using first-order shear deformation plate theory. The governing partial differential equations of motion are established by a perturbation technique. Then, the Galerkin method is applied to reduce the partial differential equations to ordinary differential equations. Based on Bolotin's method, the system equations of Mathieu-type are formulated and used to determine dynamic instability regions of laminated plates in the thermal environment. The effects of temperature, layer number, modulus ratio and load parameters on the dynamic instability of laminated plates are investigated. The results reveal that static and dynamic load, layer number, modulus ratio and uniform temperature rise have a significant influence on the thermal dynamic behavior of laminated plates.