• 한국소음진동공학회논문집
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• 제20권5호
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• pp.492-501
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• 2010

Equations of motion of thin-walled composite H-type cross-section beams incorporating a number of nonclassical effects of transverse shear and primary and secondary warping, and anisotropy of constituent materials are derived. The vibrational characteristics of a composite thin-walled beam exhibiting the circumferentially asymmetric stiffness system(CAS) and the circumferentially uniform stiffness system(CUS) are exploited in connection with the bending-transverse shear coupling and the bending-twist coupling resulting from directional properties of fiber reinforced composite materials.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.130-135
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• 2011

A study of the bending-extension-transverse shear coupled random response of the composite beams with thin-walled open sections subjected to various types of concentrated and distributed random excitations is dealt with in this paper. First of all, equations of motion of thin-walled composite H-type cross-section beams incorporating a number of nonclassical effects of transverse shear and primary and secondary warping, and anisotropy of constituent materials are derived. On the basis of derived equations of motion, analytical expressions for the displacement response of the composite beams are derived by using normal mode method combined with frequency response function method.

• 한국항행학회논문지
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• 제16권2호
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• pp.367-374
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• 2012

박판 폐단면을 갖는 프레임과 같은 보가 warping 조건하에서 동적 거동 특성이 어떠한가를 시뮬레이션과 시험을 통하여 제시하였다. 비틀림 모멘트를 받는 보는 단면은 비틀림 뿐만 아니라 warping에 의해서 변형을 일으키게 된다. 어떤 박판 단면을 갖는 보에서는 warping이 매우 커서 축방향과 전단방향 응력을 발생하고 보의 비틀림에 저항이 크게 된다. 이 논문에서는 유한요소에서 warping restraint factor가 보의 변형 거동과 동적 모드에 미치는 영향을 살펴본다. 유한 보 요소와 박판 요소 모델을 사용하여 정적변형과 고유주파수 및 모드해석을 시뮬레이션하며 이 결과를 시험 결과와 비교한다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.215-218
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• 1999

A general structural model, which is an extension of the Vlassov theory, is developed for the analysis of composite rotor blades with elastic couplings. A comprehensive analysis applicable to both thick-and thin-walled composite beams, which can have either open- or closed profile is formulated. The theory accounts for the effects of elastic couplings, shell wall thickness, and transverse shear deformations. A semi-complementary energy functional is used to account for the shear stress distribution in the shell wall. The bending and torsion related warpings and the shear correction factors are obtained in closed form as part of the analysis. The resulting first order shear deformation theory describes the beam kinematics in terms of the axial, flap and lag bending, flap and lag shear, torsion and torsion-warping deformations. The theory is validated against experimental results for various cross-section beams with elastic couplings.

• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.159-164
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• 2020

The response analysis of frame structure with open section beams considering warping conditions and short duration load have been performed. When a beam of frame structure is subjected under torsional moment, the cross section will deform a warping as well as twist. For some thin-walled sections warping will be large, and accompanying warping restraint will induce axial and shear stresses and reduce the twist of beam which stiffens the beam in torsion. Because of impact or blast loads, the wave propagation effects become increasingly important as load duration decreases. This paper presents that a warping restraint in finite element model effects the behavior of beam deformation, dynamic mode shape and response analysis. The computer modelling of frame is discussed in linear beam element model and linear thin shell element model, also presents a correlation between computer predicted and actual experimental results for static deflection, natural frequencies and mode shapes of frame. A method to estimate the number of normal modes that are important is discussed.

• International Journal of Aeronautical and Space Sciences
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• 제4권1호
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• pp.9-18
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• 2003

In this work, a closed-form analysis is performed for the structural response of coupled composite blades with multi-cell sections. The analytical model includes the effects of shell wall thickness, transverse shear, torsion warping and constrained warping. The mixed beam approach based on Reissner's semi-complementary energy functional is used to derive the beam force-displacement relations. The theory is validated against experimental test data and other analytical results for coupled composite beams and blades with single-cell box-sections and two-cell airfoils. Correlation of the present method with experimental results and detailed finite element results is found to be very good.

• Structural Engineering and Mechanics
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• 제60권6호
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• pp.1039-1061
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• 2016

Based on Vlasov's torsional theory of open thin-walled members and the nonlinear constitutive relations of materials, a nonlinear analysis model to predict response of open thin-walled RC members subjected to pure torsion is proposed in the current study. The variation of the circulatory torsional stiffness and warping torsional stiffness over the entire loading process and the impact of warping shear deformation on the torsion-induced rotation of the member are considered in the formulation. The torque equilibrium differential equation is then solved by Runge-Kutta method. The proposed nonlinear model is then applied to predict the behavior of five U-shaped thin-walled RC members under pure torsion. Four of them were tested in an earlier experimental study by the authors and the testing data of the fifth one were reported in an existing literature. Results show that the analytical predictions based on the proposed model agree well with the experimental data of all five specimens. This clearly shows the validity of the proposed nonlinear model analyzing behavior of U-shaped thin-walled RC members under pure torsion.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.467-473
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• 2017

This paper focuses on the investigation of three-dimensional (3D) warping effect on the stiffness constants of composite beams with closed section profiles. A finite element (FE) cross-sectional analysis is developed based on the Reissner's multifield variational principle. The 3D in-plane and out-of-plane warping displacements, and sectional stresses are approximated as linear functions of generalized sectional stress resultants at the global level and as FE shape functions at the local sectional level. The classical elastic couplings are taken into account which include transverse shear and Poisson deformation effects. A generalized Timoshenko level $6{\times}6$ stiffness matrix is computed for closed section composite beams with and without warping. The effect of neglecting the 3D warping on stiffness constants is shown to be significant indicating large errors as high as 93.3%.

• 한국지진공학회논문집
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• 제7권4호
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• pp.1-13
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• 2003

본 연구에서는 전단변형을 고려한 비대칭 박벽 곡선보의 자유진동해석을 수행할 수 있는 일반이론을 제시하기 위하여, 3차원 연속체에 대한 가상일의 원리로부터 전단변형 효과를 고려하고 비대칭 박벽단면과 ？(Warping)을 포함하는 변위장을 도심 축에 대해 정의한 후 곡선보의 변형도-변위관계로부터 공간 박벽 곡선보의 일반화된 탄성변형에너지와 운동에너지를 새롭게 유도한다. 또한, 전단변형이 고려된 곡선보의 총포텐셜에너지에 대해 변분을 취함으로써 평형방정식과 힘-변위관계를 제시한다. 한편, 제시된 이론에 대해 등매개 보요소를 도입하여 유한요소 정식화를 수행하였으며 곡선보의 동적 거동특성을 조사하기 위하여 전단변형, 곡률효과 그리고 진동모드에 대한 매개변수 연구를 수행한다. 마지막으로, 본 연구의 타당성을 입증하기 위하여, 다양한 해석예제에 대한 3차원 고유진동수를 산정하고 타 연구자들의 결과 및 ABAQUS의 쉘요소를 이용한 해석결과와 비교ㆍ검증한다.

• Structural Engineering and Mechanics
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• 제35권2호
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• pp.141-173
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• 2010

In this paper a boundary element method is developed for the general flexural-torsional buckling analysis of Timoshenko beams of arbitrarily shaped cross section. The beam is subjected to a compressive centrally applied concentrated axial load together with arbitrarily axial, transverse and torsional distributed loading, while its edges are restrained by the most general linear boundary conditions. The resulting boundary value problem, described by three coupled ordinary differential equations, is solved employing a boundary integral equation approach. All basic equations are formulated with respect to the principal shear axes coordinate system, which does not coincide with the principal bending one in a nonsymmetric cross section. To account for shear deformations, the concept of shear deformation coefficients is used. Six coupled boundary value problems are formulated with respect to the transverse displacements, to the angle of twist, to the primary warping function and to two stress functions and solved using the Analog Equation Method, a BEM based method. Several beams are analysed to illustrate the method and demonstrate its efficiency and wherever possible its accuracy. The range of applicability of the thin-walled theory and the significant influence of the boundary conditions and the shear deformation effect on the buckling load are investigated through examples with great practical interest.