• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 춘계학술대회논문집
• /
• pp.864-869
• /
• 2003

The purpose of this paper is to investigate the free vibration characteristics of tapered beams with translational and rotational springs and point masses at the ends. The beam model is based on the classical Bernoulli-Euler beam theory which neglects the effects of rotatory inertia and shear deformation. The governing differential equation for the free vibrations of linearly tapered beams is solved numerically using the corresponding boundary conditions. Numerical results are compared with existing solutions by other methods for cases in which they are available. The lowest four natural frequencies are calculated over a range of non-dimensional system parameters.

• Structural Engineering and Mechanics
• /
• 제52권5호
• /
• pp.971-995
• /
• 2014

The parts of semi-rigid connected and partially embedded piles in elastic soil, above the soil and embedded in the soil are called the first region and second region, respectively. The upper end of the pile in the first region is supported by linear-elastic rotational spring. The forth order differential equations of both region for critical buckling load of partially embedded and semi-rigid connected pile with shear deformation are established using small-displacement theory and Winkler hypothesis. These differential equations are solved by differential transform method (DTM) and analytical method and critical buckling loads of semirigid connected and partially embedded pile are obtained, results are given in tables and graphs are presented for investigating the effects of relative stiffness of the pile and flexibility of rotational spring.

• Steel and Composite Structures
• /
• 제33권2호
• /
• pp.163-180
• /
• 2019

A semi analytical method is employed to analyze free vibration characteristics of uniform and stepped functionally graded circular cylindrical shells under complex boundary conditions. The analytical model is established based on multi-segment partitioning strategy and first-order shear deformation theory. The displacement functions are handled by unified Jacobi polynomials and Fourier series. In order to obtain continuous conditions and satisfy complex boundary conditions, the penalty method about spring technique is adopted. The solutions about free vibration behavior of functionally graded circular cylindrical shells were obtained by approach of Rayleigh-Ritz. To confirm the dependability and validity of present approach, numerical verifications and convergence studies are conducted on functionally graded cylindrical shells under various influencing factors such as boundaries, spring parameters et al. The present method apparently has rapid convergence ability and excellent stability, and the results of the paper are closely agreed with those obtained by FEM and published literatures.

• Steel and Composite Structures
• /
• 제41권6호
• /
• pp.821-829
• /
• 2021

Nonlinear dynamic response of a sandwich beam considering porous core and nano-composite face sheet on nonlinear viscoelastic foundation with temperature-variable material properties is investigated in this research. The Hamilton's principle and beam theory are used to drive the equations of motion. The nonlinear differential equations of sandwich beam respect to time are obtained to solve nonlinear differential equations by Homotopy perturbation method (HPM). The effects of various parameters such as linear and nonlinear damping coefficient, linear and nonlinear spring constant, shear constant of Pasternak type for elastic foundation, temperature variation, volume fraction of carbon nanotube, porosity distribution and porosity coefficient on nonlinear dynamic response of sandwich beam are presented. The results of this paper could be used to analysis of dynamic modeling for a flexible structure in many industries such as automobiles, Shipbuilding, aircrafts and spacecraft with solar easured at current time step and the velocity and displacement were estimated through linear integration.

• 콘크리트학회논문집
• /
• 제15권6호
• /
• pp.848-855
• /
• 2003

콘크리트 타설중, 콘크리트 타설경로로 인한 부분재하는 동바리의 연결부에 횡력을 발생시킨다. 이러한 횡력을 구속하기 위해 동바리의 상$.$하부 접합부가 못으로 긴결되어야 한다. 그러나 시공성과 동바리 철거의 편의성을 위해 작업자들은 못을 거의 사용하지 않는다. 이러한 경우 동바리의 접합부는 전단력과 회전에 저항할 수 없다. 그리고 이러한 상황은 거푸집-동바리 시스템의 붕괴를 유발시킬 것이다. 그러므로 시공현장의 상황을 고려한다면 거푸집-동바리 시스템의 접합부 해석을 위해 접촉모델 및 스프링모델이 요구된다. 이에 따라 동바리에서의 접합부의 몇가지 유형에 따른 전단강성과 회전강성의 효과를 이해할 필요가 있다. 본 논문은 못의 길이, 개수, 위치의 변수에 따라 동바리의 연결부의 회전강성값과 전단강성값을 실험을 통해 평가하고자 하며 동바리의 지지단에 따른 결과를 보여준다. 그리고 이러한 결과는 실제 상황과 유사한 스프링모델 설정 및 좌굴하중 평가에 사용될 수 있다.

• 대한기계학회논문집
• /
• 제16권7호
• /
• pp.1244-1254
• /
• 1992

본 연구에서는 탄성, 점탄성 및 탄성박판으로 이루어진 복합적층구조물의 진 동특성을 해석함에 있어서 모재 및 구속재의 길이방향변위, 회전관성 그리고 전단변형 의 영향과 접착제의 법선 및 전단변형의 영향을 고려한 계의 운동방정식을 연립 1계 미분방정식의 형태로 유도하고 수치계산 결과를 실험과 비교하였다. 그리고 구속재 와 접착제의 두께변화에 따라서 접착제의 법선 및 전단변형이 계의 감쇠특성에 미치는 영향을 고찰하였다.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1994년도 가을 학술발표회 논문집
• /
• pp.113-120
• /
• 1994

Large Concrete Panel Structures behave quite differently from frame or monolithic shear wall structures because of the weakness of Joint in stiffness and strength. The joint experiences large deformation such as shear-slip in vertical and horizontal joint and rocking and crushing in horizontal joint because of localized stress concentration, but the wall panels behave elastically under cyclic loads. In order to describe the nonlinear behavior of the joint in the analysis of PC structures, different analysis technique from that of RC structures is needed. In this paper, for analysis of large concrete panel subassemblage subjected to cyclic loads, the wall panels are idealized by elastic finite elements, and the joints by nonlinear spring elements with various load-deflection relationship. The analytical results are compared with the experimental results on the strength, stiffness, energy dissipation and lateral drift, and the effectiveness of this computer analysis modelling technique is checked.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 추계학술대회논문집
• /
• pp.340-343
• /
• 2007

The differential equations governing free, in-plane vibrations of non-circular arches with the translational (radial and tangential directions) and rotational springs at the ends, including the effects of rotatory inertia, shear deformation and axial deformation, are solved numerically using the corresponding boundary conditions. The lowest four natural frequencies for the parabolic geometry are calculated over a range of non-dimensional system parameters: the arch rise to span length ratio, the slenderness ratio, and the translational and rotational spring parameters.

• 항공우주기술
• /
• 제7권1호
• /
• pp.170-176
• /
• 2008

고체모터 추력제어를 위한 플렉시블 셀 개념 설계를 수행하였다. 개념 설계를 통해 플렉시블 씰의 구동 점 위치, 플렉시블 씰의 형상, 고무 및 보강재 소재를 결정하였으며, 연소가스로부터 플렉시블 씰을 보호하기 위한 적절한 열 차폐 시스템을 선정하였다. 플렉시블 씰의 회전 중심은 노즐 후방에 위치하며, 단면 형상은 원뿔형 으로 설계하였다. 노즐의 구동 토크를 만족하기 위해 고무의 전단 계수는 약 0.6MPa 이하가 되도록 개발 하였으며, 전단 응력은 2.5MPa 이상이다.

• Advances in concrete construction
• /
• 제6권6호
• /
• pp.585-610
• /
• 2018

In this study, vibration analysis of a concrete foundation-reinforced by $SiO_2$ nanoparticles resting on soil bed is investigated. The soil medium is simulated with spring constants. Furthermore, the Mori-Tanaka low is used for obtaining the material properties of nano-composite structure and considering agglomeration effects. Using third order shear deformation theory or Reddy theory, the total potential energy of system is calculated and by means of the Hamilton's principle, the coupled motion equations are obtained. Also, based an analytical method, the frequency of system is calculated. The effects of volume percent and agglomeration of $SiO_2$ nanoparticles, soil medium and geometrical parameters of structure are shown on the frequency of system. Results show that with increasing the volume percent of $SiO_2$ nanoparticles, the frequency of structure is increased.