1,721,283 research outputs found
Natural frequencies of angle-ply laminated plates
No full textDynamic analysis of laminated rectangular simply-supported plates with antisimmetric lamination is performed. The accuracy of existing theories for the estimate of natural frequency is investigated. The 3D elasticity solution is obtained and used as a benchmark solution for four different plate theories: CLT, FSDT , HSDT [1] and the 2D-theory recently proposed by the second Author
Assessment of plate theories for multilayered angle-ply plates
No full textThe accuracy of laminated plate theories for the analysis of angle-ply multilayered plates is investigated. Classical Lamination Theory, First Order and Reddy’s High Order Shear Deformation Theories are considered, together with a new two-dimensional theory recently proposed by the second Author (2D-theory). Deflections and through-the-thickness stress distributions are compared with the exact 3D elasticity solution. Energy errors of stress fields obtained from the various theories through both constitutive and equilibrium equations are also evaluated. It is shown that equilibrium equations are required to obtain sufficiently accurate stress distributions from CLT, FSDT and HSDT, whereas stresses can be obtained directly from constitutive equations for the 2D-theory
Logarithmic stress singularities at clamped-free corners of cantilever orthotropic beam under flexure
No full textThe rectangular orthotropic beam under flexure is studied by decomposing the problem into an interior problem and a boundary problem. The interior problem is required to satisfy field equations and boundary conditions at the lateral faces, whereas the boundary conditions at the beam ends are imposed in the average sense. The boundary problem, which reestablishes the pointwise boundary conditions at the beam ends, is solved via eigenfunction expansion under the assumption of transverse inextensibility. It is shown that logarithmic stress singularities are present at the corners of the clamped end section and the corresponding stress-intensity factor is computed
Shear strain effects in flexure and torsion of thin-walled beams with open or closed cross-section
No full textIn this study a unified approach is presented for the analysis of the shear strain effects in thin-walled beams subjected to both non-uniform bending and torsion. Middle surface shear strains are taken into account for open as well as closed cross-sections. A suitable axial displacement field is introduced by making the basic choice that the solution to the St. Venant problems is to be reproduced for v = 0. By making use of a variational formulation, a system of differential equations is derived which rules the behaviour of a thin-walled beam with any cross-section. Hence the influence of the shear strains on the stress state as well as on the global deformation of the beam is shown through some significant examples
Nonlinear creep, Poisson's ratio, and creep-damage interaction of concrete in compression
No full textThe results of a set of short-term uniaxial creep tests at low, medium, high, and very high stress levels are presented. Creep Poisson's ratio evolution with time, nonlinear creep strain amplification, damage growth, and creep-damage interaction of concrete in compression are investigated. The electronic speckle pattern interferometry (ESP1) technique has been used to measure transverse strain also when, at high stress levels, cracks grow and propagate in concrete specimens. Under high stresses, creep Poisson 's ratio shows variation in lime, associated with damage evolution. Moreover, tests showed that for medium to high stress levels, nonlinear creep strain amplification occurs, even if not accompanied by significant concrete damage
Torsional response of inhomogeneous and multilayered composite beams
No full textThe elastic response of inhomogeneous orthotropic beams with general cross-section and subject to uniform torsion is investigated. The problem is formulated both in terms of the warping and of the Prandtl stress function. Moreover, the exact solution for rectangular orthotropic beams constituted by any number of layers is derived, making use of a series form which is unaffected by unstable behaviours. Several examples are presented, showing that approximate solutions based on simplified kinematical models can yield very poor estimates of the torsional rigidity. Finally, it is shown that the plating of homogeneous beams by means of thin carbon or glass fibre-reinforced laminae can be used to make the torsional rigidity 8-10 times as much
Decay rate of Saint-Venant end effects for multilayered orthotropic strips
No full textSaint-Venant decay rate of end effects is investigated for generally laminated orthotropic strips under self-equilibrated end loads. The problem is governed by a fourth-order partial differential equation for the Airy stress function with discontinuous coefficients at the layer interfaces, where displacements and traction continuities are imposed. The solution is found in the form of product of an exponentially decaying function along the strip and an unknown function defined over its total height. External face and interface conditions are used to obtain the characteristic; equation for the eigenvalues governing the decay rate of end effects along the strip. For orthotropic and strongly orthotropic sandwich strips the transcendental eigenvalue equation is explicitly given. The case of laminated strips with periodic layout is finally considered. Making use of the homogenization method, both effective elastic constants and expressions for the local stress variation at the layer level are obtained. Numerical calculations confirm that the eigenvalues of the homogenized material are the asymptotic values of those of periodically laminated strips when the number of layers increases. Moreover, homogenization method is shown to be very powerful also in the calculation of local stress distributions
Torsione non uniforme in travi ortotrope
No full textSi studia il comportamento torsionale di travi omogenee in materiale elastico monoclino. Introducendo la sola ipotesi di indeformabilità trasversale della sezione, il corrispondente problema elastico viene risolto mediante decomposizione in un interior problem e in un boundary problem. Si dimostra la completezza dell’insieme di funzioni coordinate definite sulla sezione ed introdotte per descrivere lo spostamento in direzione assiale. Infine, i risultati ottenuti sono confrontati con quelli forniti dalla teoria di Reissner
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