Search

In the literature, we can find many studies that investigate the so-called truncated version of the Timoshenko beam system. In general, the truncated version eliminates the second spectrum of velocity and therefore does not require equal wave velocities to achieve exponential decay. However, the truncated system does not satisfy a Cauchy problem, which makes studying its qualitative properties more challenging. In this article, we present the truncated version of the laminated beam system. Our main results are the well-posedness of the problem using the classical Faedo-Galerkin method combined with a priori estimates and the exponential decay of the energy functional without requiring equal wave velocities. [ABSTRACT FROM AUTHOR]

In the present work, we analyze the stability properties of a one dimensional thermoelastic laminated beam with structural damping, where the heat conduction is given by Gurtin–Pipkin's law. We show that the associated solution semigroup is exponentially stable if and only if the new introduced stability number χ is null. Furthermore, if χ ≠ 0 we prove the lack of exponential stability. The proofs are based on the energy method and Gearhart–Herbst–Prüss–Huang theorem. [ABSTRACT FROM AUTHOR]

• For existence of weak solution in Signorini's contact problem in the previous works was used the Div-Curl lemma. • We follow a different and new approach applying the semigroup theory. • We prove the existence of at least one solution to the Signorini problem by using the hybrid-penalized method. • We prove uniform stabilization assuming equal wave speeds in the first and second equations of the system. • The uniqueness of the solution to Signorini's problem remains an open question. In this paper, we study Signorini's problem for a laminated Timoshenko beam with interfacial slip. We assume that the transverse displacements at the end of the beam are in the presence of two rigid obstacles (Signorini conditions). We prove the existence of solution and analyze the asymptotic behavior of the system. We use the hybrid-penalized method to show the global existence of at least one solution to Signorini's problem and finally, numerical experiments verify the theoretical results. [ABSTRACT FROM AUTHOR]

In this work, we study the effect of heat conduction theories pioneered by Green and Naghdi, popularly called thermoelasticity of type Ⅲ, on the stability of laminated Timoshenko beams. Without the structural (interfacial slip) damping or any other forms of damping mechanisms, we establish an exponential stability result depending on the equality of wave velocities of the system. Our work shows that the thermal effect is strong enough to stabilize the system exponentially without any additional internal or boundary dampings. The result extends some of the developments in literature where structural damping (in addition to some internal or boundary dampings) is necessary to bring about exponential stability.

In this paper we consider a model of laminated beams combining viscoelastic damping and strong time-delayed damping. The global well-posedness is proved by using the theory of semigroups of linear operators. We prove the lack of exponential stability when the speed wave propagations are not equal. In fact, we show in this situation, that the system goes to zero polynomially with rate t − 1 / 2 . On the other hand, by constructing some suitable multipliers, we establish that the energy decays exponentially provided the equal-speed wave propagations hold. [ABSTRACT FROM AUTHOR]

In this paper, we study the stabilization of a laminated beam system under the action of a new thermal coupling. Motivated by the work of Almeida Júnior et al. in the context of the Timoshenko system, we consider a thermoelastic coupling acting on the shear force. The present work constitutes a generalization of Almeida Júnior's paper because our study model considers an interfacial slip. More precisely, if we make the parameter γ$$ \gamma $$ of our system go to infinity, we obtain the Timoshenko beam system studied by the authors. We show that the weakly dissipative system of our manuscript is exponentially stable if, and only if, the wave propagation speeds are equal. Otherwise, we show that the system is polynomially stable and that the associated semigroup decays with rate t−1/2$$ {t}^{-1/2} $$. Furthermore, we show that this decay rate is optimal. [ABSTRACT FROM AUTHOR]

In this work, we study the effect of heat conduction theories pioneered by Green and Naghdi, popularly called thermoelasticity of type III, on the stability of laminated Timoshenko beams. Without the structural (interfacial slip) damping or any other forms of damping mechanisms, we establish an exponential stability result depending on the equality of wave velocities of the system. Our work shows that the thermal effect is strong enough to stabilize the system exponentially without any additional internal or boundary dampings. The result extends some of the developments in literature where structural damping (in addition to some internal or boundary dampings) is necessary to bring about exponential stability. [ABSTRACT FROM AUTHOR]

In this paper, we consider laminated beams model with structural damping. With one internal frictional damping in the first equation and one boundary damping both modulated by time-dependent coefficients, we establish a uniform stability result without imposing any conditions on the physical parameters of the system. The same stability result will be obtained in the absence of the structural damping provided that the wave speeds are equal. [ABSTRACT FROM AUTHOR]

In this manuscript, we study the asymptotic behavior of two laminated beams systems formed by two identical layers of uniform thickness, whose surfaces are held together by an adhesive layer that allows interfacial sliding. We prove that when single Kelvin–Voigt damping acts on the transverse displacement equation, the system is not exponentially stable. When the system has two frictional dampings, one working on the transverse displacement and the other on the interface, the system is exponentially stable as long as the wave propagation speeds are equal. Then, one could think that if we replace the frictional damping (weak damping), acting on the transverse displacement, with Kelvin–Voigt damping (strong damping), the system should also be exponentially stable, at least when the wave speeds are equal. However, as we show in this work, Kelvin–Voigt damping causes the loss of exponential stability of the system, even when the system's waves' propagation speeds coincide. Therefore, we are in a situation where the weak damping (frictional) is stronger than the strong damping (Kelvin–Voigt). Due to these results of lack of exponential decay, we study the polynomial stability of each of these two systems by obtaining an optimal decay rate in each case. [ABSTRACT FROM AUTHOR]

Of concern is a laminated beam system with a neutral delay in the transverse displacement. We prove that despite of the destructive nature of delays in general, the solution goes back to the equilibrium state in an exponential behavior with a reasonable condition on the wave propagation speed. In other words, we prove that the dissipation through structural damping is strong enough to stabilize the system exponentially even in the presence of neutral delay. [ABSTRACT FROM AUTHOR]

In this study, the time-dependent mechanics of multilayered thick hyperelastic beams are investigated for the first time using five different types of shear deformation models for modelling the beam (i.e. the Euler–Bernoulli, Timoshenko, third-order, trigonometric and exponential shear deformable models), together with the von Kármán geometrical nonlinearity and Mooney–Rivlin hyperelastic strain energy density. The laminated hyperelastic beam is assumed to be resting on a nonlinear foundation and undergoing a time-dependent external force. The coupled highly nonlinear hyperelastic equations of motion are obtained by considering the longitudinal, transverse and rotation motions and are solved using a dynamic equilibrium technique. Both the linear and nonlinear time-dependent mechanics of the structure are analysed for clamped–clamped and pinned–pinned boundaries, and the impact of considering the shear effect using different shear deformation theories is discussed in detail. The influence of layering, each layer's thickness, hyperelastic material positioning and many other parameters on the nonlinear frequency response is analysed, and it is shown that the resonance position, maximum amplitude, coupled motion and natural frequencies vary significantly for various hyperelastic and layer properties. The results of this study should be useful when studying layered soft structures, such as multilayer plastic packaging and laminated tubes, as well as modelling layered soft tissues. [ABSTRACT FROM AUTHOR]

A shear-deformable beam theory is proposed to model the torsional behavior of laminated beams composed of variable stiffness layers. The displacement field is derived by expanding mid-surface displacements in Taylor series in width coordinate and by retaining first-order terms. Stiffness of the beam is made variable by using curvilinear fibers in layers. Variable stiffness layers are categorized into three types as symmetric, asymmetric and anti-symmetric based on their fiber paths. A displacement-based finite element method is used to solve the analytical model and to predict rotations of the beam under torsional load. Beams constructed with symmetric, antisymmetric and asymmetric variable stiffness layers are investigated for several lay-ups by both including and neglecting axial displacement terms. Acquired results are compared with the results of a finite element analysis software. It is observed that the developed model is working properly for beams with variable stiffness layers and including axial displacement terms in calculations improved the model's performance. [ABSTRACT FROM AUTHOR]

In this paper, we consider a laminated Timoshenko beam system with frictional damping and an internal distributed delay feedback on the effective rotational angle. Under appropriate assumptions on the weight of the delay term and wave speeds of the first two equations of the system, we prove that the dissipation through the frictional damping is enough to stabilize the system exponentially. [ABSTRACT FROM AUTHOR]

In this article, 1 D refined beam theories based on Carrera Unified Formulation (CUF) and the Isogeometric approach (IGA) are synthesized for the free vibration analysis of laminated beam structures. The B-spline basis functions utilized in IGA are employed to approximate the displacement field due to their interesting features in analysis. Taylor expansions are utilized in the framework of CUF which presents finite element matrices in the form of fundamental nuclei that is independent of type and order of expansion. Higher-order B-spline basis functions attenuate the effect of shear locking properly and higher-order theories presented by CUF are free from Poisson locking phenomenon and utilizations of shear correction factor. Also, equivalent single layer (ESL) models have been utilized as a solution field description approach. Several numerical results including composite beams are carried out and it is shown that coupling IGA and CUF ends in a suitable methodology to analyze laminated beam structures. [ABSTRACT FROM AUTHOR]

Composites comprising a high-volume fraction of stiffre inforcements within a compliant matrix are commonly found in natural materials. The disparate properties of the constituent materials endow resilience to the composite, and here we report an investigation into some of the mechanisms at play. We report experiments and simulations of a prototype laminated composite system comprising silicon layers separated by polymer interlayers, where the only failure mechanism is the tensile fracture of the brittle silicon. Two failure modes are observed for such composites loaded in three-point bending: failure under the central roller in (i) the top ply (in contact with the roller) or (ii) the bottom ply (free surface). The former mode is benign with the beam retaining load carrying capacity, whereas the latter leads to catastrophic beam failure. Finite element (FE) simulations confirm this transition in failure mode and inform the development of a reduced order model. Good agreement is shown between measurements, FE simulations, and reduced order predictions, capturing the effects of material and geometric properties on the flexural rigidity, first ply failure mode, and failure load. A failure mechanism map for this system is reported that can be used to inform the design of such laminated composites. [ABSTRACT FROM AUTHOR]

We study the stability of a one-dimensional laminated beam which consists of two identical layers of uniform thickness. An adhesive of small thickness is bonding the two layers and creating a restoring force thereby producing a damping called adhesive or structural damping at the interface. It is well-known in the literature that this single frictional damping is not strong enough to stabilize the system exponentially. On the contrary, we prove in this paper that the unique dissipation due to the structural damping is strong enough to exponentially stabilize the system provided the wave speeds of the system are equal. [ABSTRACT FROM AUTHOR]

We study a laminated beam which consists of two identical layers of uniform thickness, taking into account that an adhesive of small thickness is bonding the two surfaces thereby producing an interfacial slip. We show that when the frictional damping acts on the effective rotation angle there is no need for any other kind of internal or boundary control to produce exponential stability for the system. [ABSTRACT FROM AUTHOR]

In this work, we consider a system of two identical beams of uniform thickness modeled as a Timoshenko system. The slip between the beams is taken into account, and the system is coupled with a heat equation. Moreover, the slip equation is subject to a distributed delay of neutral type. Delays are known to be of a destructive nature in general. Therefore, here, the delay will compete with a frictional damping and the dissipation produced by the heat equation. We provide sufficient conditions ensuring exponential and polynomial stability of the structure. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In approaching the Karman the initial-boundary value problem is formulated for the dynamic elastic-plastic deformation of flexible composite beams of irregular layered-fibrous structures with account of their weakened resistance to the transverse shear. Beams consist of walls and load-bearing layers (shelves). Walls can be reinforced longitudinally or crosswise in its plane, and the shelves are reinforced in the longitudinal direction. The mechanical behavior of the component materials of the composition is described by the equations of the theory of plasticity with isotropic hardening. The explicit “cross” scheme was constructed for numerical integration of the formulated initial-boundary value problem coordinated with the step-by-step scheme and used for the simulation of elasticplastic deformation of composite material of each layer of the beam. The calculations of dynamic and quasistatic bending behavior are carried out for homogeneous and reinforced beams of I-beam cross-section. It is found that the classical theory of bending may not be acceptable to carry out such calculations for some types of metal compositions for relatively long beams. For the adequate calculation of elastoplastic deformation of composite beams of laminated-fibrous irregular structures it is necessary to use the Timoshenko theory, which takes in account the weakened resistance of the walls to the transverse shears. It is shown that in the case of dynamic loading of composite beams, the final deflections are much larger by absolute value than in the case of quasi-static loading with the same load level.

• Adhesive free engineered wood products have been manufactured. • Multi-layer timber beams assembled using compressed wood dowels have been tested. • Push-out shear timber joints using compressed wood dowels have been tested under monotonic and cyclic loadings. • Strength and stiffness characteristics of multi-layer beams have been experimentally assessed. • Strength, stiffness and ductility characteristics as well as the cumulative energy dissipation capacity have been assessed. This paper presents an experimental investigation on a novel adhesive free engineered Wood Products (AFEWPs) as an alternative to the conventional glued EWPs which have a high degree of petrochemicals. The research outcomes demonstrate the feasibility of using compressed wood dowels (CWD) as a joint element, to connect timber laminates and members as well as to substitute for adhesives and metallic fasteners. The paper describes the production of thermo-mechanically compressed wood dowels as well as the manufacturing of the dowelled timber specimens. The strength and stiffness properties of CWD are characterized based on three-point bending tests and compared to the values obtained from uncompressed wood specimens. After that, the paper discusses the relative mechanical performances of three-layer dowelled oak beams subjected to four-point bending, in comparison to their conventional glued counterparts. Finally, the paper shows results obtained from double shear push-out tests under both monotonic and cyclic loadings, using two wood species, namely spruce and oak. The obtained results show clearly the potential of thermo-mechanically compressed wood dowel, as a joint fastener, for load bearing capacity. [ABSTRACT FROM AUTHOR]

• Fracture modes partitioning for generally layered beams with hygrothermal effect. • Analytical solutions for the mode I and II fracture energies for various tests. • Residual thermal stresses effect on the fracture toughness of fiber metal laminates. • Analytical modeling of the contact problem in the end-notched flexure test. An analytical framework is presented to calculate the mode I and II components of the strain energy release rate (SERR) of a delamination between two generally layered sub-laminates, considering the residual hygrothermal stresses effect. First, the sub-laminates are modeled as Timoshenko beams, the crack tip is assumed rotationally flexible and the mode partitioning is based on the global method. Next, SERR and mode mixity are obtained for an arbitrarily loaded delaminated beam and reduced for some typical delamination fracture tests. An asymmetrically delaminated fiber metal laminate (FML) is analyzed under double cantilever beam (DCB) and end-notched flexure (ENF) configurations. For the ENF configuration, the inherent contact problem was analytically approached. We demonstrate that the thermal effect on the SERR and mode mixity of the FML, rather ignored so far in the literature, can be non-negligible. Finally, the analytical results are validated against numerical predictions using the finite element method. [ABSTRACT FROM AUTHOR]

Wood recycling is common practice in most countries. Currently, recovered wood is used for relatively low value uses including energy generation, particleboard manufacture, animal beddings and landscape uses. This paper gives an overview of two research projects that aim to generate high-value products from recovered wood and thereby encourage even higher rates of wood recycling. One project is concerned with the extraction of nano-crystalline cellulose from waste MDF and the other produces laminated beams from recovered wood. [ABSTRACT FROM AUTHOR]

The unsteady creep of homogeneous and metal-composite beams with irregular layered structure is considered. Beams consist of thin walls and shelves attached to them at top and bottom (bearing layers). The walls and bearing layers made of homogeneous isotropic materials. The mechanical behavior of these materials is described by a nonlinear hereditary theory of creep (Yu. Rabotnov). On the basis of the hypotheses of the Timoshenko theory with involvement of the ideas of method of steps in time the problem is formulated for the inelastic flexural deformation of such beams with account of their weakened resistance of their walls to the transverse shear. It is shown that in discrete moments of time the mechanical behavior of these materials layers obeys formally the defining relations of nonlinearelastic isotropic body with an initial stress state that is known. The secant modulus method is used for linearization of the task at each discrete time moment. Characteristics of the flexural behavior of three- and five-layer homogeneous and metal-composite beams under short-and long-term loading are studied. Statically determinate double-seat and cantilever beams are considered under the action of uniformly distributed transverse load of Heaviside type. It is found that the use of the classical theory of calculation of such beams leads to the prediction of unreasonably understated their flexibility, especially under creep conditions. In beams with reinforced bearing layers it is shown that the creep mainly develops due to the shear strain which actively accumulates in the walls of such structures.

Steady-state creep of a hybrid metal-composite laminated bending beams of irregular patterns is considered. Beams consist of walls and load-bearing layers, attached at the top and bottom (shelves). The shelves are reinforced with fibers in the longitudinal direction, and the walls are reinforced either longitudinally or cross in the plane. Under the hypotheses of the Timoshenko theory the boundary value problem is formulated for the calculation of the considered beams, which allows taking into account the weakened resistance of the walls of the transverse shifts. The simple iteration method based on the idea of the se-cant modulus method is applied for linearization of the problem. The mechani-cal behavior of reinforced and unreinforced doubleseat beams and cantilevers in conditions of steady creep under the action of uniformly distributed trans-verse load is investigated. Cross sections of beams are I-shaped. It is shown that for homogeneous I-beams, the classical Bernoulli theory does not guaran-tee the calculated results in compliance within 20% accuracy, which is consid-ered to be acceptable if the width of the shelf is comparable with the height of cross sections of beams. In the cases of metal-composite beams, the classical theory becomes generally unacceptable, because it lowers by several orders of magnitude the compliance of such structures in conditions of steady creep. It is demonstrated that the rate of shear strain, actively developing in their walls, must be considered. The consideration of these strain rates within the frame-work of the Timoshenko theory led to the discovery of new mechanisms of de-formation of laminated beams which the classical theory does not find. It is shown that the change in mechanism of deformation can occur by increasing the density of reinforcement of shelves or walls.

In the present work, we study a one-dimensional laminated Timoshenko beam with a single nonlinear structural damping due to interfacial slip. We use the multiplier method and some properties of convex functions to establish an explicit and general decay result. Interestingly, the result is established without any additional internal or boundary damping term and without imposing any restrictive growth assumption on the nonlinear term, provided the wave speeds of the first equations of the system are equal.

The research at hand deals with the mechanical behavior of beam-like nanostructures. Nanobeams are assembled of multiple layers of different materials and geometry giving a layered nanobeam. To properly address experimentally noticed size effects in structures of this type, an adequate nonlocal elasticity formulation must be applied. The present model relies on the stress-driven integral methodology that effectively circumvents known deficiencies of other approaches. As a main contribution, a set of differential equations and boundary conditions governing the underlaying mechanics is proposed and applied to two benchmark examples. The obtained results show the expected stiffening nonlocal behavior exhibiting most of smaller and smaller structures and modern devices.

Conventional beam elements based on the mid-plane formulation are often used to predict vibration frequencies of beams. Recently published work on the vibration of functionally graded materials (FGM) beams shows that if the positions of immovable end supports are at a different plane to the middle-plane, beam elements based on mid-plane formulation will yield inaccurate results. This paper extends this work further by critically examining the effect of end support positions along the height of the beam in the context of vibration analysis. A formulation for vibration analysis of beams based on reference-plane formulation is proposed. In order to verify the proposed formulation, we considered FE modelling of beams based on generalized beam elements, composite shell elements and 3D solid elements that are able to accurately capture the effect of end support height position on vibration frequencies. Two vibrating beam examples are considered. The first problem deals with a single layer beams and the second problem deals with a double layer beam. Both problems are analyzed using the proposed method and FE models based on generalized beam elements, composite shell elements and 3D solid elements for different end support conditions and heights. Single layer beam was also modelled in FE using conventional beam elements. The results clearly showed that if one uses conventional beam elements for vibration analysis of beams, the results will not be accurate if immovable end supports are applied at an eccentricity to the mid-plane. Vibration frequencies predicted from the proposed reference-plane formulation were shown to agree well with the results from FE models based on generalized beam elements, composite shell elements, and 3D solid elements. [ABSTRACT FROM AUTHOR]

The present research proposes analytical solutions of simply-supported laminated beams bonded by viscoelastic interlayers under both non-uniform temperature field and mechanical loads, in order to study its time-varying thermo-mechanical coupled behavior. The temperature has two effect mechanisms to the laminated beams, including the thermal expansion difference and the temperature-dependent property of viscoelastic interlayer. In the analytical model, the non-uniform temperature field is solved first by the transfer matrix method, based on the heat transport theory. The standard linear solid model is utilized to simulate the time-varying characteristic of the interlayer, which renders the mechanical property of the laminated beam changes over time. Then, the temperature effects on the interlayer modulus degradation are determined according to the Time-Temperature-Superposition-Principle (TTSP). By virtue of the state space method and Fourier series expansion, the general solutions of stress and displacement components are solved with undetermined coefficients. The analytical solutions are solved by means of Laplace transform and Cramer rule. The analysis results indicate that the present solutions are in accordance with the finite element solution and have superior computational efficiency. The influences of temperature, geometric and material parameters on the long-term thermo-mechanical coupled behavior of the laminated beam are studied in detail. • The thermal expansion and the temperature-dependent viscoelastic property are both considered. • The present solutions are developed based on the exact thermo-elasticity theory. • The influences on the long-term thermo-mechanical coupled behavior of the laminated beam are studied in detail. [ABSTRACT FROM AUTHOR]

The article carried a generalization of the technical theory of pure bending uniform prismatic beam of constant thickness and height in case of viscoelastic laminated composite beam. Used hereditary theory of viscoelastic creep uniformly aging bodies. Calculated averaged by Voigt and Reuss values of deformation parameters of the composite beam in pure bending.The effective instantaneous elastic modulus and instantaneous radius of curvature of the neutral layer of a flexible beam. Discovered that the Hill’s effective values of instantaneous elastic modulus for bending of a beam and for uniaxial tension / compression viscoelastic composite rods are the same.

This paper investigates the possibility of energy harvesting using Fiber Reinforced Plastic beams under cyclic loading. The behaviour of E-glass fiber/epoxy and Hemp fiber/epoxy laminated beams reinforced with piezoelectric fibers is examined by evaluating their bending strain and deflection. An optimum stacking sequence for all types of reinforcement: E-glass fibers, hemp fibers, and piezoelectric fibers, is suggested such that energy harvesting potential is maximized while failure and damage accumulation remain at low levels. [ABSTRACT FROM AUTHOR]

In this paper, we revisit the FEM solution of laminated plates and shells that nowadays are mostly done by low order solid or shell finite elements enriched by stress or strain fields, or by specific kinematics dedicated to the analysis of such structures. We introduce a triangular based prismatic finite element of any approximation order capable of solving from very thin to very thick laminated plates and shells, with the following properties: (i) locking-free behavior; (ii) good stress distribution even for complex materials; (iii) geometrically exact description of large displacements; and (iv) geometry dedicated to evaluate plates and shells (laminated or not) free of problems due to distorted meshes or ill-conditioned systems as thickness decreases. This triangular based prismatic finite element can also be employed in laminated beams, holding the same properties. The proposed element uses total Lagrangian description based on positions, and its performance regarding the claimed properties is demonstrated in several examples. [ABSTRACT FROM AUTHOR]

In this work, we consider a system of laminated beams with structural damping which describes the slip occurring at the interface of two-layered objects. The system is coupled to a heat equation modeling an expectedly dissipative effect through heat conduction governed by Cattaneo's law. The well-posedness as well as the uniform stability results of the system is established. [ABSTRACT FROM AUTHOR]

Free vibration characteristics and buckling behaviors of generally laminated composite beams subjected to the concentrated axial force and various classical end conditions are investigated in this paper. The analysis is based on a unified higher-order shear deformation beam theory. The Poisson effect, axial force, extensional deformation, bending deformation, shear deformation, and rotary inertia are all incorporated in the formulation. The dynamic stiffness method is employed to perform the exact vibration and buckling analyses of laminated composite beams. The dynamic stiffness matrix is developed from the complete analytical solutions of the homogeneous governing differential equations. Numerical results for the natural frequencies and buckling loads of particular laminated beams are presented and compared with previously published results. The effects of shear deformation, axial force and end condition on the natural frequencies, buckling loads and/or mode shapes of the laminated beams are thoroughly analyzed. [ABSTRACT FROM AUTHOR]

A través del Laboratorio Nacional de Productos Forestales de la Universidad de Los Andes (Mérida, Venezuela) se realizaron los ensayos de flexión estática, según la Norma ASTM D-198-84, para la determinación de los esfuerzos de diseño de 18 vigas de madera laminada de pino caribe encoladas con adhesivo de isocianato (MDI). Las mismas fueron fabricadas íntegramente en la única industria de madera laminada existente, hasta el presente, en Venezuela. Estas vigas laminadas se dividieron en dos tipos, 9 estaban constituidas por láminas completas de madera y las otras 9 estaban constituidas por láminas de madera seccionadas y unidas por medio de la técnica del finger joint; dentro de cada uno de estos tipos se prepararon tres vigas laminadas con anchos distintos (65 mm , 95 mm y 125 mm), siendo sus alturas y sus largos iguales (270 mm y 3500 mm respectivamente). Al comparar los resultados obtenidos con valores de vigas laminadas de pino radiata de Chile, y pino resinoso de Argentina se logró determinar, que los valores de Esfuerzo Límite Proporcional, Módulo de Ruptura y Módulo de Elasticidad para todas las vigas estudiadas, estaban por debajo. El análisis morfológico de todas las vigas, definió que éstas presentaron grandes deficiencias en la calidad física de la madera y las líneas de cola, y por igual, en el proceso de fabricación. Estos factores, son la principal causa de los bajos valores obtenidos. Se recomienda, en esta primera etapa de la industria, mejorar los aspectos técnicos señalados, para aumentar la resistencia y calidad estructural de las vigas laminadas encoladasStatic flexion tests of eighteen glued-laminated timber of caribean pine glued with isocyanate-based adhesives (MDI) were carried out following ASTM- D198-84 standards at the National Laboratory of Forest Products of "La Universidad de los Andes" (Mérida, Venezuela). These beams were fabricated, in their entirety, by the only company that develops glued-laminated (GLULAM) timber in Venezuela. The glued-laminated timber was divided into two groups of nine. The first group consisted of GLULAM timber made from whole beams of wood, while the second was composed of sectioned wood that had been finger-joined and later made into GLULAM beams. Each group was divided into three subgroups with glued-laminated timber of widths 65mm, 95mm and 125mm, but with a common height of 270mm and a length of 3500mm. The values obtained for stress at proportional limit, modulus of rupture and the modulus of elasticity for all the beams studied were less than those reported for glued-laminated timber from Chilean radiata pine and Argentinean resinous pine. Morphology studies performed on all the studied beams revealed that they presented great deficiencies in the physical quality of the wood, glue lines, and fabrication process. These factors are responsible for the low-performance of the test samples. It is recommended, in this first stage of the industry, that the mentioned technical aspects be improved so that resistance and structural quality of glued-laminated timber is in turn enhanced

This paper is devoted to the static analysis of laminated beams with both compact and thin-walled cross-sections. The kinematic models are obtained by means of the Carrera Unified Formulation (CUF), which is a hierarchical formulation leading to very accurate and computationally efficient finite element (FE) models. According to the latest developments in the framework of CUF, it is possible to easily adopt both equivalent-single-layer and layer-wise approaches, by expanding the unknown kinematic variables on the beam cross-section with either Taylor-like or Lagrange-like polynomials, respectively. A number of laminated beam structures are analysed and particular attention is given to laminated single- and multi-cell cross-section beams with open and closed contours. Moreover, in order to demonstrate the effectiveness of the proposed refined elements, the results in terms of displacements and stresses are compared with solid FE solutions and, when possible, with the results available from the research literature. [ABSTRACT FROM AUTHOR]

A través del Laboratorio Nacional de Productos Forestales de la Universidad de Los Andes (Mérida, Venezuela) se realizaron los ensayos de flexión estática, según la Norma ASTM D-198-84, para la determinación de los esfuerzos de diseño de 18 vigas de madera laminada de pino caribe encoladas con adhesivo de isocianato (MDI). Las mismas fueron fabricadas íntegramente en la única industria de madera laminada existente, hasta el presente, en Venezuela. Estas vigas laminadas se dividieron en dos tipos, 9 estaban constituidas por láminas completas de madera y las otras 9 estaban constituidas por láminas de madera seccionadas y unidas por medio de la técnica del finger joint; dentro de cada uno de estos tipos se prepararon tres vigas laminadas con anchos distintos (65 mm , 95 mm y 125 mm), siendo sus alturas y sus largos iguales (270 mm y 3500 mm respectivamente). Al comparar los resultados obtenidos con valores de vigas laminadas de pino radiata de Chile, y pino resinoso de Argentina se logró determinar, que los valores de Esfuerzo Límite Proporcional, Módulo de Ruptura y Módulo de Elasticidad para todas las vigas estudiadas, estaban por debajo. El análisis morfológico de todas las vigas, definió que éstas presentaron grandes deficiencias en la calidad física de la madera y las líneas de cola, y por igual, en el proceso de fabricación. Estos factores, son la principal causa de los bajos valores obtenidos. Se recomienda, en esta primera etapa de la industria, mejorar los aspectos técnicos señalados, para aumentar la resistencia y calidad estructural de las vigas laminadas encoladas. Abstract Static flexion tests of eighteen glued-laminated timber of caribean pine glued with isocyanatebased adhesives (MDI) were carried out following ASTM- D198-84 standards at the National Laboratory of Forest Products of “La Universidad de los Andes” (Mérida, Venezuela). These beams were fabricated, in their entirety, by the only company that develops glued-laminated (GLULAM) timber in Venezuela. The glued-laminated timber was divided into two groups of nine. The first group consisted of GLULAM timber made from whole beams of wood, while the second was composed of sectioned wood that had been finger-joined and later made into GLULAM beams. Each group was divided into three subgroups with glued-laminated timber of widths 65mm, 95mm and 125mm, but with a common height of 270mm and a length of 3500mm. The values obtained for stress at proportional limit, modulus of rupture and the modulus of elasticity for all the beams studied were less than those reported for glued-laminated timber from Chilean radiata pine and Argentinean resinous pine. Morphology studies performed on all the studied beams revealed that they presented great deficiencies in the physical quality of the wood, glue lines, and fabrication process. These factors are responsible for the low-performance of the test samples. It is recommended, in this first stage of the industry, that the mentioned technical aspects be improved so that resistance and structural quality of glued-laminated timber is in turn enhanced.

This paper presents a new class of refined beam theories for static and dynamic analysis of composite structures. These beam models are obtained by implementing higher-order expansions of Chebyshev polynomials for the three components of the displacement field over the beam cross-section. The Carrera Unified Formulation (CUF) is adopted to obtain higher-order beam models. The governing equations are written in terms of fundamental nuclei, which are independent of the choice of the expansion order and the interpolating polynomials. Static and free vibration analysis of laminated beams and thin-walled boxes has been carried out. Results obtained with the novel Chebyshev Expansion (CE) model have been compared with those available in the literature. For comparison, Taylor-like Expansion (TE) and Lagrange Expansion (LE) CUF models, commercial codes, analytical and experimental data are exploited. The performances of refined beam models in terms of computational cost and accuracy in comparison to the reference solutions have been assessed. The analysis performed has pointed out the high level of accuracy reached by the refined beam models with lower computational costs than 2D and 3D Finite Elements. [ABSTRACT FROM AUTHOR]

In this paper, refined one-dimensional beam theories are implemented for the free vibration analysis of laminated beams with compact and thin-walled cross-sections. The proposed models are based on the Carrera Unified Formulation, which was formerly introduced for the analysis of plates and shells and recently extended to beam structures by the first author and his co-workers. Carrera Unified Formulation is a hierarchical modelling technique leading to very accurate and computationally efficient finite element theories. According to the latest developments in the framework of Carrera Unified Formulation, refined beam models are implemented using either Taylor-like or Lagrange-like polynomials in order to expand the unknown kinematic variables on the cross-section of the beam. Equivalent single layer models result from the former approach. On the other hand, if Lagrange polynomials are used, layer-wise models are produced. In this work, a classical one-dimensional finite element formulation along the beam length is used to develop numerical applications. A number of laminated beam structures are analyzed and particular attention is given to laminated box beams with open and closed cross-sections. The frequencies and the mode shapes obtained with the present refined beam elements are compared with solid/shell finite element solutions from the commercial code MSC/Nastran and, when possible, with those found in the literature. The modal assurance criterion is used for model-to-model comparisons so as to demonstrate the enhanced capabilities of the proposed formulation in investigating the free vibration characteristics of both compact and thin-walled box laminated beams. [ABSTRACT FROM AUTHOR]