• Interaction and multiscale mechanics
• /
• 제3권1호
• /
• pp.95-110
• /
• 2010

In recent years, study of the static response of pavements to moving vehicle and aircraft loads has received significant attention because of its relevance to the design of pavements and airport runways. The static response of beams resting on an elastic foundation and subjected to moving loads was studied by several researchers in the past. However, most of these studies were limited to steady-state analytical solutions for infinitely long beams resting on Winkler-type elastic foundations. Although the modelling of subgrade as a continuum is more accurate, such an approach can hardly be incorporated in analysis due to its complexity. In contrast, the two-parameter foundation model provides a better way for simulating the underlying soil medium and is conceptually more appealing than the one-parameter (Winkler) foundation model. The finite element method is one of the most suitable mathematical tools for analysing rigid pavements under moving loads. This paper presents an improved solution algorithm based on the finite element method for the static analysis of rigid pavements under moving vehicular or aircraft loads. The concrete pavement is discretized by finite and infinite beam elements, with the latter for modelling the infinity boundary conditions. The underlying soil medium is modelled by the Pasternak model allowing the shear interaction to exist between the spring elements. This can be accomplished by connecting the spring elements to a layer of incompressible vertical elements that can deform in transverse shear only. The deformations and forces maintaining equilibrium in the shear layer are considered by assuming the shear layer to be isotropic. A parametric study is conducted to investigate the effect of the position of moving loads on the response of pavement.

• Advances in aircraft and spacecraft science
• /
• 제2권3호
• /
• pp.345-365
• /
• 2015

This paper focuses on the design, fabrication, testing and analysis of a novel load-bearing element with energy dissipation capability. A single element comprises two von-Mises trusses (VMTs), which are sandwiched between two plates and connected to dashpots that stroke as the VMTs cycle between stable equilibrium states. The elements can be assembled in-plane to form a large plate-like structure or stacked with different properties in each layer for improved load-adaptability. Also introduced in the elements are pre-loaded springs (PLSs) that provide high initial stiffness and allow the element to carry a static load even when the VMTs cannot under harmonic disturbance input. Simulations of the system behavior using the Simscape environment show good overall correlation with test data. Good energy dissipation capability is observed over a frequency range from 0.1 Hz to 2 Hz. The test and simulation results show that a two layer prototype, having one soft VMT layer and one stiff VMT layer, can provide good energy dissipation over a decade of variation in harmonic load amplitude, while retaining the ability to carry static load due to the PLSs. The paper discusses how system design parameter changes affect the static load capability and the hysteresis behavior.

• 한국지반공학회논문집
• /
• 제34권3호
• /
• pp.13-27
• /
• 2018

사석경사식 방파제의 안정성에 있어 파랑에 의한 사석마운드내의 침투흐름의 영향이 연구되었다. 침투흐름은 일반적으로 태풍시 방파제 주변 수위차에 의해 발생된다. 기존 사석마운드의 안정해석법은 정적해석으로 활동면 상의자중(콘크리트블록, 사석, 필터, 보호층)에 의한 수직력과 콘크리트 블록에 작용하는 파압에 의한 수평력(Goda 식으로 산정)의 힘의 평형조건으로 결정된다. 그러나 이 정적방법은 사석마운드 내의 파랑에 의한 침투흐름을 고려할 수 없다. 이런 침투흐름은 사석마운드의 안정성을 감소시킬 수 있다. 본 연구에서는 침투 작용시 사석경사식 방파제의 안정성에 대해 CFD 프로그램(OpenFOAM)과 한계평형해석법(GeoStudio)을 이용하여 검토하였다. 수치해석결과 침투로 인해 사석경사식 방파제의 안정성이 감소하는 것으로 나타났다. 또한 수치해석 결과는 사석마운드의 안정성이 시간에 따라 변하는 것을 보여주었다. 특히 파가 방파제를 월류하고 침투류에 의해 상치콘크리트 측면과 하부에 강한 양압력과 사석마운드 내부에 간극수압이 크게 발생하는 시점에 가장 불안정 상태를 보이는 것으로 나타났다. 따라서 동적 파랑에 의한 침투류의 영향을 고려한 동적해석도 정적해석과 함께 검토할 필요가 있다.

• Steel and Composite Structures
• /
• 제34권2호
• /
• pp.241-260
• /
• 2020

This article presented a comprehensive model to study static buckling stability and associated mode-shapes of higher shear deformation theories of sandwich laminated composite beam under the compression of varying axial load function. Four higher order shear deformation beam theories are considered in formulation and analysis. So, the model can consider the influence of both thick and thin beams without needing to shear correction factor. The compression force can be described through axial direction by uniform constant, linear and parabolic distribution functions. The Hamilton's principle is exploited to derive equilibrium governing equations of unified sandwich laminated beams. The governing equilibrium differential equations are transformed to algebraic system of equations by using numerical differential quadrature method (DQM). The system of equations is solved as an eigenvalue problem to get critical buckling loads and their corresponding mode-shapes. The stability of DQM in determining of buckling loads of sandwich structure is performed. The validation studies are achieved and the obtained results are matched with those. Parametric studies are presented to figure out effects of in-plane load type, sandwich thickness, fiber orientation and boundary conditions on buckling loads and mode-shapes. The present model is important in designing process of aircraft, naval structural components, and naval structural when non-uniform in-plane compressive loading is dominated.

• Steel and Composite Structures
• /
• 제6권5호
• /
• pp.417-433
• /
• 2006

In this paper, a non-linear structural analysis software with pro-processing and post-recessing function is proposed by the author. The software incorporating the functions of the structural analysis and geometrical design of Tensegrity structures. Using this software, Cable Dome is analyzed as a prototype, a comprehensive study on the structural behavior of Tensegrity domes is presented in detail. Design methods of Tensegrity domes were proposed. Based on the analysis, optimizing design was performed. Several new Tensegrity domes with different geometrical design scheme are proposed, the structural analysis of the new schemes is also conducted. The analysis result shows that the proposed new forms of the Tensegrity domes are reasonable for practical applications.

• Structural Engineering and Mechanics
• /
• 제43권5호
• /
• pp.583-605
• /
• 2012

This paper presents a spatial catenary cable element for the nonlinear analysis of cable-supported structures. An incremental-iterative solution based on the Newton-Raphson method is adopted for solving the equilibrium equation. As a result, the element stiffness matrix and nodal forces are determined, wherein the effect of self-weight and pretension are taken into account. In the case of the initial cable tension is given, an algorithm for form-finding of cable-supported structures is proposed to determine precisely the unstressed length of the cables. Several classical numerical examples are solved and compared with the other available numerical methods or experiment tests showing the accuracy and efficiency of the present elements.

• Steel and Composite Structures
• /
• 제48권2호
• /
• pp.113-130
• /
• 2023

The present manuscript aims to investigate the deviation between the middle surface (MS) and neutral surface (NS) formulations on the static response of bi-directionally functionally graded (BDFG) porous plate. The higher order shear deformation plate theory with a four variable is exploited to define the displacement field of BDFG plate. The displacement field variables based on both NS and on MS are presented in detail. These relations tend to get and derive a new set of boundary conditions (BCs). The porosity distribution is portrayed by cosine function including three different configurations, center, bottom, and top distributions. The elastic foundation including shear and normal stiffnesses by Winkler-Pasternak model is included. The equilibrium equations based on MS and NS are derived by using Hamilton's principles and expressed by variable coefficient partial differential equations. The numerical differential quadrature method (DQM) is adopted to solve the derived partial differential equations with variable coefficient. Rigidities coefficients and stress resultants for both MS and NS formulations are derived. The mathematical formulation is proved with previous published work. Additional numerical and parametric results are developed to present the influences of modified boundary conditions, NS and MS formulations, gradation parameters, elastic foundations coefficients, porosity type and porosity coefficient on the static response of BDFG porous plate. The following model can be used in design and analysis of BDFG structure used in aerospace, vehicle, dental, bio-structure, civil and nuclear structures.

• Structural Engineering and Mechanics
• /
• 제35권6호
• /
• pp.677-697
• /
• 2010

This paper focuses on geometrically non-linear static analysis of a simply supported beam made of hyperelastic material subjected to a non-follower transversal uniformly distributed load. As it is known, the line of action of follower forces is affected by the deformation of the elastic system on which they act and therefore such forces are non-conservative. The material of the beam is assumed as isotropic and hyperelastic. Two types of simply supported beams are considered which have the following boundary conditions: 1) There is a pin at left end and a roller at right end of the beam (pinned-rolled beam). 2) Both ends of the beam are supported by pins (pinned-pinned beam). In this study, finite element model of the beam is constructed by using total Lagrangian finite element model of two dimensional continuum for a twelve-node quadratic element. The considered highly non-linear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. In order to use the solution procedures of Newton-Raphson type, there is need to linearized equilibrium equations, which can be achieved through the linearization of the principle of virtual work in its continuum form. In the study, the effect of the large deflections and rotations on the displacements and the normal stress and the shear stress distributions through the thickness of the beam is investigated in detail. It is known that in the failure analysis, the most important quantities are the principal normal stresses and the maximum shear stress. Therefore these stresses are investigated in detail. The convergence studies are performed for various numbers of finite elements. The effects of the geometric non-linearity and pinned-pinned and pinned-rolled support conditions on the displacements and on the stresses are investigated. By using a twelve-node quadratic element, the free boundary conditions are satisfied and very good stress diagrams are obtained. Also, some of the results of the total Lagrangian finite element model of two dimensional continuum for a twelve-node quadratic element are compared with the results of SAP2000 packet program. Numerical results show that geometrical nonlinearity plays very important role in the static responses of the beam.

• Advances in Computational Design
• /
• 제2권1호
• /
• pp.71-87
• /
• 2017

This study focuses on the efficiency and applicability of dynamic relaxation methods in form-finding of membrane structures. Membrane structures have large deformations that require complex nonlinear analysis. The first step of analysis of these structures is the form-finding process including a geometrically nonlinear analysis. Several numerical methods for form-finding have been introduced such as the dynamic relaxation, force density method, particle spring systems and the updated reference strategy. In the present study, dynamic relaxation method (DRM) is investigated. The dynamic relaxation method is an iterative process that is used for the static equilibrium analysis of geometrically nonlinear problems. Five different examples are used in this paper. To achieve the grading of the different dynamic relaxation methods in form-finding of membrane structures, a performance index is introduced. The results indicate that viscous damping methods show better performance than kinetic damping in finding the shapes of membrane structures.

• 대한기계학회논문집A
• /
• 제28권1호
• /
• pp.100-108
• /
• 2004

In this paper, the new casing oscillator, which is a construction machine and which structure is similar to that of a parallel manipulator with redundancy, is proposed. The singularity analysis of this machine is performed by two different methods. First, the singularities are found by the numerical method at configurations where the rank of the Jacobian matrix becomes deficient. The singularities are outside the workspace. To investigate the physical information on these configurations, the singularities are examined by the geometric method at configurations where the casing oscillator cannot resist the external forces and moments applied to the upper platform due to losing static equilibrium. The results of the geometric method are the same as those of the numerical method. It proves that the new casing oscillator is free from the singularity, which causes serious problems to a parallel manipulator.