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In this research, the thermally induced vibration of the plates on the elastic foundation has been investigated. The plate is made of functionally graded materials (FGMs) that is graded along the thickness. All mechanical and thermal properties dependent on temperature are taken into account. To apply the temperature dependence of thermomechanical properties, the well-known Touloukian equation is used. The two-parameter elastic foundation, Winkler–Pasternak, is considered to be linear, isotropic, and homogeneous. The general formulation and equations governing the phenomenon of thermally induced vibration have been written under the assumptions of linear uncouple thermoelasticity. The one-dimensional transient heat conduction equation has been discretized with the help of the finite element method in the direction of thickness, and it has been solved over time by applying the Crank–Nicolson method. Also, the thermally induced force and moment resultants in each time step have been calculated based on the temperature profile. To obtain the equations of motion, Hamilton's principle based on the first-order shear deformation theory has been used, and the obtained equations and boundary conditions have been discretized by applying the generalized differential quadrature (GDQ) method and solved by using Newmark time marching scheme. [ABSTRACT FROM AUTHOR]

The mechanical and thermal stability equations of asymmetric functionally graded discs subjected to the Pasternak foundation are developed by employing Hamilton’s energy principle based on the first-order shear theory. The material properties are temperature-dependent and vary according to power-law and exponentially in thickness and radial direction, respectively. Accordingly, the temperatu re is also varying in both directions. Using the well-developed differential quadrature method, stability equations are discretized along with the boundary conditions, leading to a complete algebraic linear equations system. The validation of results is performed to certify the results. Numerical and illustrative results are presented to study the effect of elastic foundation parameters, graded indexes, nodal lines, and boundary conditions on thermal and mechanical buckling. Also, the impact of compressive in-plane force on thermal buckling and thermal environment on mechanical buckling is presented. [ABSTRACT FROM AUTHOR]

This paper analyzes the free vibration of micro-sized plates placed on the Winkler-Pasternak elastic foundation. The microplate is made from functionally graded material (FGM) and reinforced with graphene nanoplatelets (GPLs). The properties of the new material (GPL-reinforced FGM) are determined using the Halpin-Tsai model and the rule of mixtures. The governing equation for the free vibration of the micro-sized plate on the elastic foundation is developed based on a four-variable plate theory, the modified couple stress theory, and the Rayleigh-Ritz approach. The solution is compared and validated against existing studies, followed by an investigation of the effects of various parameters (material parameters, size-dependent effect, boundary conditions, and foundation coefficients) on the natural frequency of the microplate. [ABSTRACT FROM AUTHOR]

Article deals with the calculation issues of deflection and stress in the rail and pins, which are a part of the anchoring design for rack-railway tracks. The rack-railway track, is intended for the transport of excessively heavy loads and people inside mines. A longitudinal track dip can be up to ± 35deg. Practical application is focused on the calculations of pins and rails, for which a novel combination of analytical approaches and FEM is used, with dynamic loading and the theory of beams on an elastic foundation. The methodology is explained in details and the first results are listed. Everything stated in this article can be used to design transport systems not only in mining/underground constructions.

Featured Application: Receding contacts appear in systems with conformal or almost conformal contacts e.g., bolted joints, guides, or cylindrical or spherical joints (including human hip joints). Receding contacts appear in many composite technical and biological systems at the points where tensile stresses would appear otherwise. Here, we consider the contact of a beam placed on an elastic foundation (or thin elastic layer) in the presence of adhesion. In contrast to non-adhesive receding contact, the contact area in adhesive receding contact does depend on the applied load. Decreasing the load from the state of initial contact opening leads to an increase in the contact area. At a certain critical load, the beam jumps into contact at once along its entire length. For long beams, the point of opening of the contact does not depend on the intensity of forces of adhesion, and the opening occurs in an unstable way. This can lead to acoustic effects like joint cracking. [ABSTRACT FROM AUTHOR]

The key aim of this research is to develop an analytical model for the forced vibration of graphene-reinforced composite (GRC) cylindrical shell with viscous damping and thermal environment effects under several boundary conditions. The prescribed mechanical and thermal characteristics of the GRC layer are evaluated utilizing a micromechanical extended Halpin–Tsai technique. Further, the governing equations are determined to be grounded on the shear deformation theory (SDT) with the von Kármán-form in terms of the geometric nonlinearity. The basic nonlinear partial differential governing equation is transformed into a nonlinear ordinary differential equation with the Galerkin-based method. The resulting ordinary governing differential equations are systematically solved based on the multiple scales scheme in order to obtain the nonlinear forced vibration frequency response of the laminated GRC cylindrical shell in the presence of damping impact and subjected to multiple boundary conditions. The validation of the obtained expressions is achieved by comparing them with the available literature data where the comparison revealed a clear consistency between them. Moreover, a parametric investigation is provided to illustrate the impacts of the distribution of graphene layers, elastic foundation coefficients, damping ratios, temperature effects and dimensionless radial excitation amplitude on the forced nonlinear amplitude-frequency ratio responses for a functionally-graded graphene-reinforced composite (FG-GRC)-layered cylindrical shells. The analytical outcomes indicate that the different distribution types of graphene, elastic foundation coefficients, damping ratios, temperature, and radial excitation parameters have a noteworthy impact on the frequency–amplitude behaviors of an FG-GRC-layered cylindrical shell. In addition, the new insights gained from this research might contribute to a deeper understanding of the nonlinear forced vibration responses in subsequent analysis and design techniques for giving appropriate benchmark findings. [ABSTRACT FROM AUTHOR]

In this research, natural frequency response of functionally-graded multilayer graphene-reinforced composite plate with circular cutout reinforced by orthogonal stiffeners is investigated for the first time. The structure is surrounded by Winkler-type elastic support. The plate is composed of polymethyl methacrylate (PMMA) as matrix material and reinforced by graphene platelets (GPLs). The material of the orthogonal stiffeners is the same as that for the matrix. Rule of mixtures and Halpin–Tsai approach are applied to estimate the effective material properties of the composite plate. Third-order shear deformation plate theory and finite element procedure is employed to obtain the element matrices of the structure. Natural frequencies and mode shapes of the stiffened plate are reported for different variables such as nanofillers dispersion patterns, width and height of the stiffeners, aspect ratio of plate, plate thickness ratio, weight fraction of nanofillers, number of stiffeners, boundary conditions, elastic foundation stiffness parameter and size of circular cutout. The obtained results denote that with the addition of a set of stiffeners, fundamental frequency enhanced up to 32.3% with just about 10% increase of mass. [ABSTRACT FROM AUTHOR]

WE PRESENT A NONLINEAR FINITE ELEMENT ANALYSIS to investigate the buckling and post-buckling behaviour of functionally graded material (FGM) plates resting on the elastic foundation. The material properties are assumed to vary gradually across the thickness according to a power law distribution. The starting point of the investigation is the generalized third-order plate theory and the Vlasov model of elastic foundation having properties varying throughout the depth. The plates are subjected to bending to verify the formulation and compression loads including buckling and post-buckling analysis to investigate the influence of various parameters on the structural response. [ABSTRACT FROM AUTHOR]

This paper presents a novel shear deformation theory for analyzing porous microbeams' bending, buckling, and free vibration resting on a foundation. The proposed shear function incorporating three kinetic variables satisfies zero-traction boundary conditions on the top and bottom surfaces of the beams and does not require a shear correction factor. The modified couple stress theory accounts for the size-dependent effects, and the governing equations are derived from Lagrange's equation using the proposed shear function. Legendre–Ritz functions are developed to analyze the porous microbeams' buckling, free vibration, and bending behaviors. The effects of material length scale parameter, porosity, span-to-height ratio, boundary condition, and foundation parameter on the mechanical responses of beams are investigated. Numerical results demonstrate the accuracy and efficiency of the proposed theory and can serve as benchmarks for future analysis of porous microbeams on elastic foundations. [ABSTRACT FROM AUTHOR]

The main goal of this study is to use higher-order isogeometric analysis (IGA) to study the dynamic response of sandwich shells with an auxetic honeycomb core and two different functionally graded materials (FGM) skin layers (namely honeycomb-FGS shells) subjected to dynamic loading. Touratier's non-polynomial higher-order shear deformation theory (HSDT) is used due to its simplicity and performance. The governing equation is derived from Hamilton's principle. After verifying the present approach, the effect of input parameters on the dynamic response of honeycomb-FGS shells is carried out in detail. [ABSTRACT FROM AUTHOR]

Hyperelastic functionally graded materials have a wide range of application prospects in soft robotics and biomedical fields. This paper investigates the nonlinear free and forced vibrations of a hyperelastic functionally graded beam (HFGB) based on higher-order shear deformation beam theory. The geometrical nonlinearity is considered by using the von-Kármán’s nonlinear theory. The three-material-parameter free energy function named as Ishihara model is employed to characterize the hyperelastic material. The power-law gradient form along the thickness direction is adopted. The HFGB is resting on the elastic foundation. The Winkler, Pasternak and nonlinear stiffness coefficients are considered. The time-harmonic external force is applied to the HFGB. The nonlinear governing equations for the vibration of the HFGB are derived by using Hamilton’s principle, and are subsequently transformed into ordinary differential equations via Galerkin’s method. The nonlinear free vibration and primary resonance of the HFGB are investigated analytically by employing the extended Hamiltonian method and multiple scales method, respectively. The results indicate that the power-law index, slenderness ratio, material properties, and elastic foundation parameters have significant influences on the nonlinear frequency of free vibration as well as the frequency–response and force–response curves of forced vibration. The phase plane method is employed to analyze the system’s stability states under various excitation amplitudes. The relative error between the results of the current computational model and the published literature is less than 0.1 percent. [ABSTRACT FROM AUTHOR]

In this paper, an analytical solution for exploring the buckling characteristics of functionally graded (FG) plate is presented based on a quasi-3D shear deformation theory. It is considered that the plate is subjected to different types of in-plane compressive load. The FG plate is placed on three-parameter foundation WinklerPasternak-Kerr. The overall material properties of FG plate are assumed to be varied across the thickness and are estimated through the Voigt micromechanical model. The governing equations are obtained on the base of the quasi-3D deformation theory that contain undetermined integral forms and involves only four unknowns to derive. Equations of motion are derived from the principal of virtual work and the analytical solution is used to determine the critical buckling loads. By the discussion of numerical examples and the comparison with those of the reports in the literature, the convergence and the reliability of the present approach are validated. Finally, the parametric investigations of the in-plane buckling are carried out, including the influence of boundary conditions, elastic foundation, plate geometric parameters and power law index. The results reveal that the critical buckling loads are strongly influenced by several parameters such as boundary conditions, elastic foundation parameters and geometric shape of the plate. [ABSTRACT FROM AUTHOR]

Environmental responses to deep excavations are combined results of numerous factors. The effects of some factors are relatively straightforward and can be considered carefully during the design. On the other hand, more features impact excavation-induced performances indirectly, making their influences difficult to be clearly understood. Unfortunately, the complexity and non-repeatability of practical projects make it impossible to thoroughly understand these issues through realistic deep excavation projects. Therefore, parametric studies based on repeatable laboratory and numerical tests are desired to investigate these issues further. This work examines the influence of several key features on excavation-induced displacements through a series of 3D numerical tests. The study includes the choice of soil constitutive models, the modeling method of the soil–wall interface, and the influences of various key soil parameters. The comparison shows that the MCC model can yield a displacement field similar to the HSS model, while its soil movement is greatly improved compared to the MC model. Both the soil–wall interface properties and soil parameters impact the excavation-induced displacement to a large extent. In addition, the influence mechanisms of these parameters are analyzed, and practical suggestions are given. The findings of this paper are expected to provide practical references to the design and construction of future deep excavation projects. [ABSTRACT FROM AUTHOR]

Based on the three-dimensional elasticity theory, the free vibration of functionally graded porous (FGP) sandwich rectangular plates is studied, and a unified solution for free vibration of the plates is proposed in this study. The arbitrary boundary conditions of FGP sandwich rectangular plates are simulated by using the Rayleigh–Ritz method combined with artificial spring theory. The calculation performances of the unified solution for FGP sandwich rectangular plates such as convergence speed and computational efficiency are compared extensively under different displacement functions. In addition, three kinds of elastic foundation (Winkler/Pasternak/Kerr foundations) and three porosity distributions are considered. Some benchmark results and accurate values for the free vibration of FGP sandwich rectangular plates resting on elastic foundations are given. Finally, the effects of diverse structural parameters, elastic foundations with different parameters, and boundary conditions on the free vibration of the FGP sandwich rectangular plates are analyzed. [ABSTRACT FROM AUTHOR]

The nonlinear vibration response of rectangular plates made of functionally graded porous materials (FGPs) induced by hygrothermal loading is investigated in this article using a numerical approach. The effect of elastic foundation on the vibrations is taken into account according to the Winkler–Pasternak model. Hygroscopic stresses produced due to nonlinear rise in moisture concentration are also considered. The temperature-dependent material properties of plate are computed based on the modified Voigt's rule of mixture and Touloukian experiments for even and uneven distribution patterns of porosity. Within the framework of the first-order shear deformation plate theory and von-Kármán nonlinearity, Hamilton's principle is utilized in order to derive the equations of motions. To achieve the temporal evolution of maximum lateral deflection of hygrothermally-induced plates, the generalized differential quadrature (GDQ) and Newmark integration methods are employed. Selected numerical results are presented to study the influences of temperature distribution, porosity volume fraction, moisture concentration, geometrical parameters, elastic foundation parameters and FG index on the geometrically nonlinear vibrations of FG porous plates with various boundary conditions. [ABSTRACT FROM AUTHOR]

To ensure the stability of broken surrounding rock under the influence of advance abutment pressure and the reliability of support system, the 21104 working face of Hulusu Coal Mine is taken as the research background. By means of theoretical calculation, numerical simulation and field measurement, a mechanical model of the elastic foundation beam for the deformation of the super front roof is established, the influencing factors of the bending deformation of the roof, the leading bearing pressure and the main controlling factors of the concentration coefficient are determined, and the advance grouting anchor cable reinforcement technology for broken surrounding rock is proposed. The results show that the roof elastic modulus only affects the roof deflection above the roadway, and the side elastic modulus controls the overall bending deformation of the roof. The advanced support pressure and concentration coefficient show a rapid increase followed by a slow increase trend with the advancement of the working face, and finally tend to stabilize. There is a 35 m high stress area in the grouting anchor cable reinforcement test face, the anchor cable has a high abundance coefficient, the surrounding rock deformation is low (

Vibration behaviors of elastically supported functionally graded (FG) sandwich beams resting on elastic foundations under moving loads are investigated. The transformed-section method is first applied to establish the bending vibration equations of FG sandwich beams, then the Chebyshev collocation method is used to study free and forced vibrations. Two types of sandwich beams with FG faces-isotropic core and isotropic faces-FG core are considered. The material properties of FG materials are assumed to vary across the beam thickness according to a simple power function. Regarding the free vibration analysis, bending vibration frequencies are calculated numerically by forming a matrix eigenvalue equation. As for the forced vibration analysis, the backward differentiation formula method is employed to solve the time-dependent ordinary differential equations to obtain the dynamic deformations of the beam. To ensure the accuracy of the proposed model, some calculated results are compared with those in the published literature. Parametric studies are then performed to demonstrate the effects of material gradient indexes, stack types, layer thickness ratios, slenderness ratios, excitation frequency and speed of moving loads, and foundation and support stiffness parameters on the dynamic characteristics of FG sandwich beams. [ABSTRACT FROM AUTHOR]

The nonlinear buckling response of laminated composite cylindrical shells reinforced with graphene nanoplatelets (GNPs) is studied in this paper. The functionally graded (FG) shell reinforced by GNPs is analytically studied under external pressure and uniform temperature rise loadings. It is also assumed that the GNP-reinforced laminated composite shell is in contact with an elastic foundation. Various types of profiles are employed for the GNP distribution patterns in the shell thickness including 10 nanocomposite layers. The nonlinear strain-displacement relations of the shallow cylindrical panel are established utilizing the third-order shear deformation shell theory. Governing equilibrium equations of the laminated GNP-reinforced composite shell are formulated employing the principle of virtual displacement. The coupled system of nonlinear differential equations is solved analytically for the hinged–hinged and fixed–fixed boundaries of the shell using a perturbation-based technique. Correctness of presented formulations and obtained solutions is proved by comparisons with results from previous studies for an isotropic cylindrical shell. Novel numerical results reveal that the material properties, geometrical characteristics and load parameters significantly affect on the buckling behavior of laminated composite cylindrical shells. [ABSTRACT FROM AUTHOR]

Deep excavations clearly impact adjacent existing properties and threaten their operational safety. Predicting the deformation of existing infrastructure induced by nearby underground construction is the main concern of urban underground development. This paper presents an analytical calculation method for predicting underground pipe gallery deformations induced by adjacent deep excavations. First, the authors assume the existing pipe gallery to be nonexistent in the soil and propose a solution to calculate the excavation-induced vertical movements of the soil at the position of the existing pipe gallery. Thereafter, the authors simplify the existing pipe gallery as an elastic beam on a Winkler foundation to calculate its deformation. Finally, the method is verified by the good agreement found between the calculated result and the field measurement of the construction of the Shanghai Hongqiao CBD project. The proposed analytical method of this work can provide accurate evaluation results for similar engineering projects. [ABSTRACT FROM AUTHOR]

The nonlinear vibration analysis of functionally graded reinforced with graphene platelet (FG-GRC) porous truncated conical shells surrounded by the Winkler-Pasternak elastic foundation is presented in this paper. An improved model for evaluating the material properties of porous composites is proposed. Three types of porous distribution and three patterns of graphene nanoplatelets (GPLs) dispersion are estimated. Coupled with the effect of the Winkler-Pasternak elastic foundation, the nonlinear governing equations are developed by using the Hamilton principle. The Galerkin integrated technique is employed to obtain the linear and nonlinear frequencies of the shells. After the present method is validated, the effects of the pores, GPLs, the Winkler-Pasternak foundation, and the semi-vertex are investigated in detail. The results show that the linear frequency can be raised by increasing the values of the mass volume of the GPL and foundation parameters. In contrast, the ratio of nonlinear to linear frequency declines as the mass volume of the GPLs and foundation parameters rises. Furthermore, it is found that the minimum ratio of nonlinear to linear frequency can be obtained as the semi-vertex angle is about 55º, and the effect of porosity distribution on the linear and linear frequencies might be neglected. [ABSTRACT FROM AUTHOR]

Natural fibers have been extensively researched as reinforcement materials in polymers on account of their environmental and economic advantages in comparison with synthetic fibers in the recent years. Bamboo fibers are renowned for their good mechanical properties, abundance, and short cycle growth. As beams are one of the fundamental structural components and are susceptible to mechanical loads in engineering applications, this paper performs a study on the free vibration and buckling responses of bamboo fiber reinforced composite (BFRC) beams on the elastic foundation. Three different functionally graded (FG) layouts and a uniform one are the considered distributions for unidirectional long bamboo fibers across the thickness. The elastic properties of the composite are determined with the law of mixture. Employing Hamilton's principle, the governing equations of motion are obtained. The generalized differential quadrature method (GDQM) is then applied to the equations to obtain the results. The achieved outcomes exhibit that the natural frequency and buckling load values vary as the fiber volume fractions and distributions, elastic foundation stiffness values, and boundary conditions (BCs) and slenderness ratio of the beam change. Furthermore, a comparative study is conducted between the derived analysis outcomes for BFRC and homogenous polymer beams to examine the effectiveness of bamboo fibers as reinforcement materials, demonstrating the significant enhancements in both vibration and buckling responses, with the exception of natural frequencies for cantilever beams on the Pasternak foundation with the FG-⟡) fiber distribution. Eventually, the obtained analysis results of BFRC beams are also compared with those for carbon nanotube reinforced composite (CNTRC) beams found in the literature, indicating that the buckling loads and natural frequencies of BFRC beams are lower than those of CNTRC beams. [ABSTRACT FROM AUTHOR]

In this paper, the effect of coefficient of viscous damping on the dynamic analysis of Euler-Bernoulli beam resting on elastic foundation was investigated using Integral-Numerical method which reduces to an ordinary differential equation with series representation of Heaviside function. The dynamic responses of the beam in terms of normalized deflection and bending moment has been investigated for different velocity ratios under moving load and moving mass conditions. Generally, closed-form solution to the generalized mathematical model for prismatic beam was computed by means of symbolic programming approach through MAPLE 18. Results obtain revealed that the presence of an elastic foundation and the provision of sufficient reinforcement in beams and beam-like structure reduces vibration intensity and ensure safe passage of load and prolong the beam life. [ABSTRACT FROM AUTHOR]

In engineering design methods, it is assumed that the structure is located on a fixed base, and the effects of the soil environment on the structural response are generally ignored. However, research showed that the environment of the soil and the structure can interact with each other. This phenomenon is called soilstructure interaction effect. Therefore, the soil environment should be modeled in structural analysis. There are different methods for soil modeling. One of the practical methods is to use separate springs to model the soil environment. In this article, the effect of the number of floors and the period of the structure on the soil springs' stiffness has been investigated. In this regard, three-dimensional structures with the number of floors 1, 3, 5, 10 and 15 were modeled in Opensees software with continuous soil environment. Then, from the results of the structural analysis, the reaction of the soil under the foundation was calculated and relations were presented to determine the stiffness of the soil. These relationships are dependent on the structure's period. [ABSTRACT FROM AUTHOR]

Large deflection nonlinear bending of functionally graded (FG) porous cylindrical panels reinforced with graphene platelets (GPLs) on a Pasternak-type elastic foundation is examined by developing a reliable and effective 2D meshfree-based nonlinear numerical method. The large displacement field is express by the first-order shear deformation theory (FSDT) and the von Kármán nonlinearity, and approximated by 2D natural element method (NEM) in conjunction with the stabilized MITC3+ shell concept and the shell surface–rectangular grid geometry transformation. The nonlinear simultaneous equations are solved by a load incremental Newton–Raphson scheme. The developed nonlinear numerical method is justified from by comparing with the reference solutions, and the load–deflection and bending moment of FG-GPLRC porous cylindrical panels on elastic foundation are scrutinizingly examined. Four different symmetric GPL distribution patters (except for FG-Λ) and three different symmetric porosity distributions are considered and their combined effects on the nonlinear bending behavior are investigated, as well as the effects of foundation stiffness and GPL amount. Also, the results are compared with those of FG CNT-reinforced porous cylindrical panels. [ABSTRACT FROM AUTHOR]

Free vibrations of porous functionally graded material (FGM) plates with complex shapes are analyzed by using the R-functions method. The thickness of the plate is variable in the direction of one of the axes. Two types of porosity distributions through the thickness are considered: uniform (even) and non-uniform (uneven). The elastic foundation is defined by two parameters (Winkler and Pasternak). To obtain the mathematical model of the problem, the first-order shear deformation theory of the plate (FSDT) is used. The effective material properties in the thickness direction are modeled by means of a power law. Variational Ritz's method joined with the R-functions theory is used for obtaining a semi-analytical solution of the problem. The approach is applied to a number of case studies and validated by means of comparative analyses carried out on rectangular plates with a traditional finite element approach. The proof of the efficiency of the approach and its capability to handle actual engineering problems is fulfilled for FGM plates having complex shapes and various boundary conditions. The effect of different parameters, such as porosity distribution, volume fraction index, elastic foundation, FGM types, and boundary conditions, on the vibrations is studied. [ABSTRACT FROM AUTHOR]

A finite element method using a 9-node isoparametric plate bending element, incorporating the effects of transverse shear based on the first-order shear deformation theory, is proposed for the free vibration analysis of rectangular cut-out plates resting on an elastic foundation. The elastic foundation is modeled on the Winkler and the Pasternak type, and equations of motion are obtained using the principle of virtual work. To account for the parabolic strain variation through the thickness, a shear correction factor of 5/6 is used, and the effect of rotary inertia has been included in the formulation. The present formulation is compared with established results obtained using analytical methods, with and without rotary inertia, and the max variation observed is 2.24% without rotary inertia and 0.02% with rotary inertia. Cut-out plates are validated with results obtained using the finite element method, and the max variation observed between established results and present formulation is 1.3%. Establishing the accuracy of the current formulation, new results are obtained for rectangular cut-out plates resting on an elastic foundation of various stiffness parameters. The effect of incrementing cut-out dimensions and different layouts of cut-outs in the plate on the free vibration response of plates resting on an elastic foundation is investigated, along with the effects of varying aspect ratios and thickness-to-side ratios. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to use the higher-order isogeometric analysis (IGA) to study the vibration behaviour of sandwich plates with an auxetic honeycomb core and two different functionally graded materials (FGM) skin layers (namely h-FGS plates) resting on an elastic foundation (EF) under double blast loading. Reddy's HSDT is used due to its simplicity and efficiency. The foundation model incorporates two parameters as springer stiffness (k1) and the shear layer stiffness (k2). The governing equation is derived from Hamilton's principle. After verifying the present approach, the effect of input parameters on the vibration characteristics of h-FGS plates is carried out in detail. The obtained results are expected to be useful for calculating and designing h-FGS plates in practice.

Receding contacts appear in many composite technical and biological systems at the points where tensile stresses would appear otherwise. Here, we consider the contact of a beam placed on an elastic foundation (or thin elastic layer) in the presence of adhesion. In contrast to non-adhesive receding contact, the contact area in adhesive receding contact does depend on the applied load. Decreasing the load from the state of initial contact opening leads to an increase in the contact area. At a certain critical load, the beam jumps into contact at once along its entire length. For long beams, the point of opening of the contact does not depend on the intensity of forces of adhesion, and the opening occurs in an unstable way. This can lead to acoustic effects like joint cracking.

Abstract An analytical solution was used to investigate the elastic response of a sandwich beam with a graphene‐reinforced aluminum‐based composite (GRAC) on an elastic foundation using copper as the face layer of the functionally graded composite beam and a simply supported boundary condition. Mantari's higher‐order shear deformation theory was utilized to derive the equations, which were solved in Laplace space and then converted into space–time using Laplace inversion. The exact response of the GRAC sandwich beam was obtained by considering the displacement at the mid‐span of the sandwich beam. Two moving loads with different speed ratios were applied at a single point, and the effect of various parameters, including the spring constant, the speed ratio, the percentage of graphene, the moving load speed, and the distribution pattern, was investigated. This study aimed to eliminate any overlap and improve the accuracy of the results. The exact solving method presented has not been reported in other articles so far. Additionally, due to the difficulty of solving mathematical equations, this method is only applicable to simple boundary conditions.

In this paper, the effect of coefficient of viscous damping on the dynamic analysis of Euler-Bernoulli beam resting on elastic foundation was investigated using Integral-Numerical method which reduces to an ordinary differential equation with series representation of Heaviside function. The dynamic responses of the beam in terms of normalized deflection and bending moment has been investigated for different velocity ratios under moving load and moving mass conditions. Generally, closed-form solution to the generalized mathematical model for prismatic beam was computed by means of symbolic programming approach through MAPLE 18. Results obtain revealed that the presence of an elastic foundation and the provision of sufficient reinforcement in beams and beam-like structure reduces vibration intensity and ensure safe passage of load and prolong the beam life.

Excessive vibration has always been a serious problem for conical shell structures, while the application of the graphene-based free-constrained layer (GFCL) based on carbon fiber-reinforced composite (CFRC) structure is a novel way to improve structural performance. An analytical model for vibration and dynamic characteristics of the GFCL-CFRC conical shell resting on the Winkler–Pasternak elastic foundation with arbitrary boundary conditions is constructed, and four types of GFCL porosity distribution and GFCL dispersion pattern are considered in this model. The multi-segment technique and virtual spring technique are utilized to simulate arbitrary boundary conditions. Then, the first-order shear deformation theory (FSDT) and Hamilton's principle are employed to obtain the motion equation of the GFCL-CFRC conical shell, and the motion equation of the GFCL-CFRC conical shell is solved by the Ritz method. In conclusion, the dispersion mode of GFCL, thickness ratio of GFCL, and fiber angle have influence on the dynamic performance. With a reasonable design, the dynamic performance of the GFCL-CFRC conical shell can be further improved. [ABSTRACT FROM AUTHOR]

In this article, an elastic foundation is used to study the characteristics of flexural edge waves propagating on a piezoelectric structure. The nonlocal elasticity theory is introduced to investigate the microscale effect on edge wave propagation. The traditional Kirchhoff plate hypothesis is used to determine the kinematics of the piezoelectric plate. By considering the sinusoidal waveform, a closed-form dispersion relation can be obtained. In the context of a flexural edge wave on a piezoelectric plate, an analytical and graphical comparison between the two boundary conditions (i.e. short circuit and open circuit) is discussed. In the presence of nonlocal elasticity, the dispersion relation is implied as an implicit function of frequency and wave number. A significant difference occurred between the dispersion curves for piezoelectric plates with different foundations and nonlocal parameters. Due to the Pasternak elastic foundation, an increasing rate of the fundamental mode of frequency is observed at the traction-free edge of a thin, semi-infinite piezoelectric plate. In contrast, the nonlocal elasticity tends to decrease this fundamental frequency mode for a particular wave number value. The corresponding phase velocity decreases rapidly within a short range of wave numbers. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to use the higher-order isogeometric analysis (IGA) to study the vibration behaviour of sandwich plates with an auxetic honeycomb core and two different functionally graded materials (FGM) skin layers (namely h-FGS plates) resting on an elastic foundation (EF) under double blast loading. Reddy's HSDT is used due to its simplicity and efficiency. The foundation model incorporates two parameters as springer stiffness (k 1) and the shear layer stiffness (k 2). The governing equation is derived from Hamilton's principle. After verifying the present approach, the effect of input parameters on the vibration characteristics of h-FGS plates is carried out in detail. The obtained results are expected to be useful for calculating and designing h-FGS plates in practice. [ABSTRACT FROM AUTHOR]

Today, due to the many applications of sandwich beams in industry, studying the forced vibrations of these structures is important. In these structures, amplifiers are used to improve mechanical properties. In this paper, metal-based graphene (copper) is used to improve the mechanical properties. This research uses a functionally graded (FG) graphene-reinforced copper-based composite (GRCC) sandwich beam and FG soft porous core, subjected to two moving loads and located on an elastic foundation. The equations are derived using Soldatos' higher-order shear deformation theory in axial and transverse directions. The exact problem under the magnetic field is solved using the Laplace method, which has not been done. The advantages of this method are the simplicity of solving and reducing to zero the error percentage that exists in numerical solutions. The results are compared with previous works. Finally, the effect of various parameters such as magnetic, porosity coefficient, elastic constant, thickness ratio, and velocity of moving load on the dynamic response of the sandwich beam is investigated. It should be noted that the results can be used to construct this type of structure. [ABSTRACT FROM AUTHOR]

A laminated composite plate designed is supposed to be used under different end supports. The elastic foundation is one of such conditions. The strength of the laminated composite plates can be enhanced by altering constituents or by the addition of filler materials. For localized strengthening of laminated composite plates, such as at particular layers, it is not cost-effective to strengthen the whole structure. So, the laminated composite plates are strengthened at a particular layer by adding the fillering materials, for example, graphene or flyash. The addition of these filler materials in a particular region sometimes causes agglomeration. Agglomeration of filler materials causes adverse effects such as stress concentration or strain aging. In theoretical formulation, Eringen's nonlocal principle is applied to account for the impact of agglomeration. In the current study, neat epoxy glass laminated composite plates as well as rectangle laminated composite plate variants with outer layer graphene, core layer graphene, functionally graded laminated composite plate, laminated composite plates exclusively rich in graphene, and laminated composite plates only rich in flyash are taken into consideration. Using a layer-wise model, the fifth-order shear deformation theory is applied. The laminated composite plates are assumed to rest on an elastic foundation. The consequence of elastic coefficient of foundation on procured parameters such as fundamental frequencies, stress parameters, center deflections, and buckling performance is determined. For this purpose, computerized programs are developed using MATLAB and validated first for isotropic material. Further, the work is extended to study these effects on the laminated composite plate variants. [ABSTRACT FROM AUTHOR]

The present paper deals with the modal analysis of sigmoid functionally graded (S-FGM) rectangular plate resting on elastic foundation by using the dynamic stiffness method (DSM). The DSM is formulated based on the exact solutions of the governing differential equations, and thereby it results in the very accurate computation of the natural frequencies. To obtain the DSM results for thicker plates, the study incorporates first-order shear deformation theory (FSDT) which includes the important effects of transverse shear deformation and rotatory inertia. The governing equations and the associated natural boundary conditions are derived using Hamilton's principle, and the solution is sought in the Levy form where two opposite edges of the plate are simply supported. The present study also contributes by highlighting mistakes in the classical plate theory (CPT)-based DSM formulation published in a recent work and presents a correct CPT-based mathematical formulation. For both these cases, the frequency-dependent dynamic stiffness matrix of the S-FGM plate gives rise to the transcendental eigenvalue problem, which is solved by using the Wittrick and Williams algorithm. Comparison with the available literature establishes the accuracy of the method. In addition, a parametric study is presented for various geometric and stiffness parameters of the elastically supported S-FGM plates using both CPT- and FSDT-based formulations, and accurate frequency results are reported. [ABSTRACT FROM AUTHOR]

This paper deals with a nonlinear static plate model based on Berger theory, which is a specific case of a generalization of the Woinowsky-Krieger mathematical model of beam bending. It is considered a plate bending with forces acting in the middle plane of the plate and a contact problem with an elastic foundation, where the normal compliance condition is employed. A variational equation of the problem and a functional of the total potential energy corresponding to the variational equation are derived. Under additional assumptions on the data (e.g., clamped plate), the existence and uniqueness of the solution are proved. A numerical solution is based on the Galerkin method and Courant approximation. The theory is illustrated by a numerical example. [ABSTRACT FROM AUTHOR]

Free flexural vibration of a simply supported sandwich beam on an elastic foundation is the main purpose of the presented investigation. An analytical model of multi-layered beam on elastic foundation has been prepared. The authors submitted an original beam-foundation interaction model which based on variable parameters of the foundation and their influence on the beam response. This explanation leads to the possibility of continuous characterization of the beam-foundation interplay. A nonlinear mathematical function for symmetrical properties of the foundation has been adopted. The frequency equation as a function of geometric and mechanical properties of the beam and the parameters of the elastic foundation was derived using the Galerkin method. The analytical investigation has been divided into two parts: the analysis of elastic foundation with constant and variable properties. The unconventional shape function and the function of deflection have been introduced and employed. Moreover, the finite element analysis has been performed. Sample analytical and numerical calculations have been performed, demonstrating a good concurrence between both models. The difference between analytical and numerical values of the fundamental natural frequency did not exceed 0:5%. [ABSTRACT FROM AUTHOR]

We consider the boundary value problem of finite beam deflection on elastic foundation with two point boundary conditions of the form $ u^{(p)}(-l) = u^{(q)}(-l) = u^{(r)}(l) = u^{(s)}(l) = 0 $, $ p < q $, $ r < s $, which we call elementary. We explicitly compute the fundamental boundary matrices corresponding to 7 special elementary boundary conditions called the dwarfs, and show that the fundamental boundary matrices for the whole 36 elementary boundary conditions can be derived from those for the seven dwarfs.

Environmental responses to deep excavations are combined results of numerous factors. The effects of some factors are relatively straightforward and can be considered carefully during the design. On the other hand, more features impact excavation-induced performances indirectly, making their influences difficult to be clearly understood. Unfortunately, the complexity and non-repeatability of practical projects make it impossible to thoroughly understand these issues through realistic deep excavation projects. Therefore, parametric studies based on repeatable laboratory and numerical tests are desired to investigate these issues further. This work examines the influence of several key features on excavation-induced displacements through a series of 3D numerical tests. The study includes the choice of soil constitutive models, the modeling method of the soil–wall interface, and the influences of various key soil parameters. The comparison shows that the MCC model can yield a displacement field similar to the HSS model, while its soil movement is greatly improved compared to the MC model. Both the soil–wall interface properties and soil parameters impact the excavation-induced displacement to a large extent. In addition, the influence mechanisms of these parameters are analyzed, and practical suggestions are given. The findings of this paper are expected to provide practical references to the design and construction of future deep excavation projects.

Buckling analyses of orthogonally stiffened functionally graded graphene platelet reinforced composite plate with circular cutout supporting on Winkler elastic foundation is conducted according to the third order shear deformation plate theory and the finite element method to achieve the desired solutions. Material properties of the composite plate are evaluated using Rule of mixture and Halpin-Tsai approach. Graphene platelet reinforcements and Poly methyl methacrylate matrix are considered as the two components of the composite media. The material of the stiffeners is selected the same as that of the polymer matrix. In one efficient case, adding a set of stiffeners increased the critical buckling load by 41.8 % with only a 10.3 % increase in weight of the structure. Influence of broad range of factors such as GPLs nanofillers distribution pattern and weight fraction, Winkler-type elastic foundation, uniaxial and biaxial normal and shear loads, plate thickness and aspect ratio, width, height and number of longitudinal and transverse stiffeners are reported in several tabular and graphical data in detail.

In this study, a new algorithm for the nonlinear buckling behavior of the stiffened functionally graded graphene-reinforced composite laminated (FG-GRCL) toroidal shell segments in the thermal environment surrounded by the elastic foundation and subjected to torsional load is introduced. The FG-GRCL shell segment is stiffened by the FG-GRCL ring and/or stringer stiffener system. Based on the Donnell shell theory with the Stein and McElman approximation, considering the von Karman geometrical nonlinearity and the anisotropic smeared stiffener technique for FG-GRCL stiffeners, the formulations to investigate the critical buckling load and postbuckling torsional load-deflection curves are determined. A new algorithm is fully developed by adding the effect of circumferential stress into the stress function. The significant effects of temperature, stiffener system, geometrical parameters, and elastic foundation are considered and studied in detail. [ABSTRACT FROM AUTHOR]

This work is based on Winkler's theory to analyze laterally loaded single piles using the finite element method. Soil nonlinearity is considered via nonlinear springs "p-y" curves. Exact element displacement shape functions and stiffness matrix are used for the element in the case of linear Winkler's modulus of subgrade reaction. In the nonlinear stage, an averaging technique for the element secant Winkler modulus is used to calculate the shape functions and stiffness matrix. An iterative technique is used to consider the nonlinearity of the soil. Few elements are required to simulate the pile efficiently. Unlike other analytical methods, the current method can be used to analyze piles with any load-transfer curves with arbitrary variation with depth. [ABSTRACT FROM AUTHOR]

Coal bump seriously threatens the safe and efficient mining of coal, and the research on the occurrence mechanism of coal bump is of great significance. The roadway coal bump accounts for 86.8% of the total. The occurrence of coal bump in gateroad is summarized. It is considered that hard roof and hard coal are the geological characteristics of coal bump, and the sliding instability of rib coal mass is the failure characteristics of coal bump. Based on the elastic foundation theory, the upward deflection characteristics of the front and lateral roof of the working face under the condition of hard roof are analyzed, and compared with the engineering practice of roof rebounding. Taking the roadway coal mass as the research object, the unloading sliding mechanical model of roof-coal-floor composite structure is established. By analyzing the relationship between horizontal ground stress of coal mass, frictional force of coal-roof and coal-floor and tensile resistance of coal mass, the critical equation of coal bump is established. It is proposed that the vertical pressure of coal seam is reduced due to the upward deflection of the roof, and the coal mass loses its clamping and moves into the roadway after overcoming the friction between roof and floor and the tensile strength of coal mass under the action of horizontal ground stress, that is, the unloading and slippage mechanism of coal bump in hard roof mining roadway. The model reasonably explains the causality of coal bump in hard roof mining roadway. Based on the unloading-slippage model, the principle of influencing factors of coal bump, includes the buried depth, roof strength, roof elastic modulus and roof thickness, coal mass strength and elastic modulus. Finally, two coal bump events, "8.2" coal bump in Tangshan coal mine and "11.11" coal bump in Hongyang mine are analyzed and the unloading-slippage mechanism are the reasoning of two events. [ABSTRACT FROM AUTHOR]

In the present work, geometric nonlinearity is taken into consideration to study the free vibration response of nonlinearly deflected Timoshenko beam with bi-directional gradation, resting on an elastic foundation of Winkler type. Exponential variation of material properties is considered along the thickness and length direction. In order to carry out the present numerical study, the entire physical domain of analysis is converted into a normalized domain and suitable number of computational points are created on it to conduct a whole domain analysis. The adopted mathematical formulation is displacement based and semi-analytical. A unique methodology is used for the formulation, in which the static analysis is taken first under large amplitude static force, then a subsequent eigenvalue analysis is performed on the known statically deformed beam profile. Appropriate energy principles are utilized for both analyses to derive the equation of motion in matrix form, which are solved with the help of the algorithm of direct substitution method. Generated results are validated with the results of previously published paper. New sets of result are also presented as benchmark results to represent the impact of bi-directional gradation and elastic foundation on nonlinear vibration response. [ABSTRACT FROM AUTHOR]

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This paper aims to carry out comprehensively the static bending, free vibration, and buckling analyses of two-layer FGM plates with shear connectors resting on elastic foundations, where two-layer FGM plates resting on Winker's-Pasternak elastic foundations taking into account relative sliding movements are analyzed by using the combination of Navier's solution and finite element method based on nth-order shear deformation plate theory. The plate is made up of two layers of FG materials joined by metal shear connectors. Lagrange and Hermitian shape functions are used to establish stiffness matrices, mass matrices, geometric stiffness matrices, and element force vectors. The suggested method and mechanical model are accurate when compared to the computed data from this research and reputable literature. The computed data accurately describes the mechanical response of the structure. Then a series of parameter investigations are conducted to capture the effects of the structure's geometrical and material features on the mechanical behavior of two-layer FG plates. The numerical results of this study may be utilized as a basis for future research, applications, and design of similar structures in mechanical and civil engineering practice. This is also a critical foundation for studying the dynamic behavior of structures with shear connectors.

The authors deal with the vibration of the pipeline that occurs during the transportation of a gas-containing liquid due to the uneven distribution of gas accumulation along the length of the pipeline, which produces pulsating movements of the center of gravity of the moving liquid, when the conditions for supporting the middle part change. The solution is constructed using the calculation scheme of a beam lying on an elastic foundation described by the Winkler model. To assess the impact on the stress-strain state of the beam of the sudden exclusion of the elastic foundation under the middle part of the beam, the circular frequencies and forms of natural transverse vibrations of the beam that occur in the absence of disturbing forces are determined. The given solution of the problem of vibrations of a pipe, through which a gas-containing liquid is transported, with a change in the conditions of support of the middle part of the beam, can be used to predict the durability of the pipe.

A finite element modeling combined with the strain gradient theory (SGT) and the refined higher-order shear deformation beam theory is developed to study the dynamic instability of magnetically embedded functionally graded porous (FGP) nanobeams. Nanobeams with elastic foundation (EF) subjected to an axially oscillating load are analyzed. Nanobeams are made of functionally graded material (FGM) with an uneven porosity distribution. A three-node beam element with 8 degrees of freedom (DOFs) for two outer nodes and 2 DOFs for the middle node, which has the C1 and C2 continuous Hermite shape functions, is used to simulate nanobeams. Besides, Bolotin’s method is employed to determine the instability region of FGP nanobeams. The accuracy of the proposed method is tested by comparing it with other published works. In addition, the influences of various parameters such as magnetic potential, small-scale parameter, porosity coefficient, stiffness foundation, boundary conditions (BCs) on the dynamic instability of nanobeams are studied in detail.