• Structural Engineering and Mechanics
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• 제60권2호
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• pp.271-299
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• 2016

In this article, based on the higher-order shear deformation plate theory, buckling analysis of a rectangular plate made of functionally graded piezoelectric materials and its effective parameters are investigated. Assuming the transverse distribution of electric potential to be a combination of a parabolic and a linear function of thickness coordinate, the equilibrium equations for the buckling analysis of an FGP rectangular plate are established. In addition to the Maxwell equation, all boundary conditions including the conditions on the top and bottom surfaces of the plate for closed and open circuited are satisfied. Considering double sine solution (Navier solution) for displacement field and electric potential, an analytical solution is obtained for full simply supported boundary conditions. The accurate buckling load of FGP plate is presented for both open and closed circuit conditions. It is found that the critical buckling load for open circuit is more than that of closed circuit in all loading conditions. Furthermore, it is observed that the influence of dielectric constants on the critical buckling load is more than those of others.

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.247-268
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• 2006

The parts of pile, above the soil and embedded in the soil are called the first region and second region, respectively. The forth order differential equations of both region for critical buckling load of partially embedded pile with shear deformation are obtained using the small-displacement theory and Winkler hypothesis. It is assumed that the behavior of material of the pile is linear-elastic and that axial force along the pile length and modulus of subgrade reaction for the second region to be constant. Shear effect is included in the differential equations by considering shear deformation in the second derivative of the elastic curve function. Critical buckling loads of the pile are calculated for by differential transform method (DTM) and analytical method, results are given in tables and variation of critical buckling loads corresponding to relative stiffness of the pile are presented in graphs.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.489-496
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• 2002

The lateral buckling of a laminated composite beam is studied. A general analytical model applicable to the lateral buckling of a composite beam subjected to various types of loadings is derived. This model is based on the classical lamination theory, and accounts for the material coupling for arbitrary laminate stacking sequence configuration and various boundary conditions. The effects of the location of applied loading on the buckling capacity are also included in the analysis. A displace-based one-dimensional finite element model is developed to predict critical loads and corresponding buckling modes for a thin-walled composite beam with arbitrary boundary conditions. Numerical results are obtained for thin-walled composites under central point load, uniformly distributed load, and pure bending with angle-ply and laminates. The effects of fiber orientation location of applied load, and types of loads on the critical buckling loads are parametrically studied.

• Steel and Composite Structures
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• 재36권6호
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• pp.671-687
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• 2020

The aim of this research is to analyze buckling and bending behavior of a sandwich Reddy beam with porous core and composite face sheets reinforced by boron nitride nanotubes (BNNTs) and shape memory alloy (SMA) wires resting on Vlasov's foundation. To this end, first, displacement field's equations are written based on the higher-order shear deformation theory (HSDT). And also, to model the SMA wire properties, constitutive equation of Brinson is used. Then, by utilizing the principle of minimum potential energy, the governing equations are derived and also, Navier's analytical solution is applied to solve the governing equations of the sandwich beam. The effect of some important parameters such as SMA temperature, the volume fraction of SMA, the coefficient of porosity, different patterns of BNNTs and porous distributions on the behavior of buckling and bending of the sandwich beam are investigated. The obtained results show that when SMA wires are in martensite phase, the maximum deflection of the sandwich beam decreases and the critical buckling load increases significantly. Furthermore, the porosity coefficient plays an important role in the maximum deflection and the critical buckling load. It is concluded that increasing porosity coefficient, regardless of porous distribution, leads to an increase in the critical buckling load and a decrease in the maximum deflection of the sandwich beam.

• 항공우주시스템공학회지
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• 제1권4호
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• pp.28-36
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• 2007

This paper presents critical buckling loads of laminated composites under cylindrical bending. In-plane displacements are assumed to vary exponentially through plate thickness. The accuracy of this theory is examined for symmetric/antisymmetric cross-ply, angle-ply and unsymmetric laminates under cylindrical bending. Analytical solutions are provided to investigate the effect of transverse shear deformation on critical buckling loads of the laminated plates, and the results are compared with those obtained from the first-order shear deformation plate theory and the classical laminated plate theory.

• Structural Engineering and Mechanics
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• 제57권5호
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• pp.861-876
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• 2016

The determination of the critical buckling load of multistory structures is important since this load is used in second order analysis. It is more realistic to determine the critical buckling load of multistory structures using the whole system instead of independent elements. In this study, a method is proposed for designating the system critical buckling load of torsion-free structures of which the load-bearing system consists of frames and shear walls. In the method presented, the multistory structure is modeled in accordance with the continuous system calculation model and the differential equation governing the stability case is solved using the differential transform method (DTM). At the end of the study, an example problem is solved to show the conformity of the presented method with the finite elements method (FEM).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.812-818
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• 2001

The drop type impact test and finite element analysis are established for examining the buckling behavior of a square tube under the lateral impact load. Based on these results, the effects by the boundary conditions for supporting the structure are reviewed, which are as follows. One is pinned condition by screw; the other is fixed by welding. The critical impact force and acceleration by test are nearly same between two cases. However, the critical impact velocity of the pinned condition is higher than that of the fixed case. Therefore, the dynamic buckling behavior of a pinned structure is better than the fixed condition in view of critical impact velocity. These test and analysis results will be adaptable for predicting the dynamic structural integrity of a tube structure not only the axial impact event but the lateral impact event.

• Structural Engineering and Mechanics
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• 제65권4호
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• pp.491-504
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• 2018

Because of sandwich structures with low weight and high stiffness have much usage in various industries such as civil and aerospace engineering, in this article, buckling and free vibration analyses of coupled micro composite sandwich plates are investigated based on sinusoidal shear deformation (SSDT) and most general strain gradient theories (MGSGT). It is assumed that the sandwich structure rested on an orthotropic elastic foundation and make of four composite face sheets with temperature-dependent material properties that they reinforced by carbon and boron nitride nanotubes and two flexible transversely orthotropic cores. Mathematical formulation is presented using Hamilton's principle and governing equations of motions are derived based on energy approach and applying variation method for simply supported edges under electro-magneto-thermo-mechanical, axial buckling and pre-stresses loadings. In order to predict the effects of various parameters such as material length scale parameter, length to width ratio, length to thickness ratio, thickness of face sheets to core thickness ratio, nanotubes volume fraction, pre-stress load and orthotropic elastic medium on the natural frequencies and critical buckling load of double-bonded micro composite sandwich plates. It is found that orthotropic elastic medium has a special role on the system stability and increasing Winkler and Pasternak constants lead to enhance the natural frequency and critical buckling load of micro plates, while decrease natural frequency and critical buckling load with increasing temperature changes. Also, it is showed that pre-stresses due to help the axial buckling load causes that delay the buckling phenomenon. Moreover, it is concluded that the sandwich structures with orthotropic cores have high stiffness, but because they are not economical, thus it is necessary the sandwich plates reinforce by carbon or boron nitride nanotubes specially, because these nanotubes have important thermal and mechanical properties in comparison of the other reinforcement.

• Selected Papers of The Society of Naval Architects of Korea
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• 제1권1호
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• pp.91-100
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• 1993

A displacement-based finite element method Is presented for the geometrically nonlinear analysis of eccentrically stiffened plates. A nonlinear degenerated shell element and a nonlinear degenerated eccentric isoparametric beam (isobeam) element are formulated on the basis of Total Agrangian and Updated Lagrangian descriptions. In the formulation of the isobeam element, some additional local decrees of freedom are implementd to describe the stiffener's local plate buckling modes. Therefore this element can be effectively employed to model the eccentric stiffener with fewer D.O.F's than the case of a degenerated shell element. Some detailed buckling and nonlinear analyses of an eccentrically stiffened plate are performed to estimate the critical buckling loads and the post buckling behaviors including the local plate buckling of the stiffeners discretized with the degenerated shell elements and the isobeam elements. The critical buckling loads are found to be higher than the analytical plate buckling load but lower than Euler buckling load of the corresponding column, i.e, buckling strength requirements of the Classification Societies for the stiffened plates.

• 대한토목학회논문집
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• 제33권3호
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• pp.865-873
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• 2013

본 연구에서는 부식이나 보강재가 고려된 비균일한 두께를 가지는 파이프라인에 대하여 일정한 외압을 받을 때의 탄성 좌굴하중을 이론적으로 산정하였다. 길이가 매우 긴 원통형 쉘 구조물인 파이프라인을 단순한 링 구조물로 가정하였고, 고유함수를 유도하여 좌굴 임계하중을 산정하였다. 또한, 두께 변화와 두께가 감소된 구간의 범위에 따른 변수해석을 수행하였다. 이론식에 의해 산정된 좌굴 임계하중 결과를 유한요소해석 결과와 비교하여 검증하였고, 두 결과는 잘 일치함을 알 수 있었다.