Search results for " scienza delle costruzioni"
showing 10 items of 496 documents
A generalized model of elastic foundation based on long-range interactions: Integral and fractional model
2009
The common models of elastic foundations are provided by supposing that they are composed by elastic columns with some interactions between them, such as contact forces that yield a differential equation involving gradients of the displacement field. In this paper, a new model of elastic foundation is proposed introducing into the constitutive equation of the foundation body forces depending on the relative vertical displacements and on a distance-decaying function ruling the amount of interactions. Different choices of the distance-decaying function correspond to different kind of interactions and foundation behavior. The use of an exponential distance-decaying function yields an integro-d…
Long-range interactions in 1D heterogeneous solids with uncertainty
2013
Abstract In this paper, the authors aim to analyze the response of a one-dimensional non-local elastic solid with uncertain Young's modulus. The non-local effects are represented as long-range central body forces between non-adjacent volume elements. Following a non-probabilistic approach, the fluctuating elastic modulus of the material is modeled as an interval field. The analysis is conducted resorting to a novel formulation that confines the overestimation effect involved in interval models. Approximate closed-form expressions are derived for the bounds of the interval displacement field.
The mechanically-based approach to 3D non-local linear elasticity theory: Long-range central interactions
2010
Abstract This paper presents the generalization to a three-dimensional (3D) case of a mechanically-based approach to non-local elasticity theory, recently proposed by the authors in a one-dimensional (1D) case. The proposed model assumes that the equilibrium of a volume element is attained by contact forces between adjacent elements and by long-range forces exerted by non-adjacent elements. Specifically, the long-range forces are modelled as central body forces depending on the relative displacement between the centroids of the volume elements, measured along the line connecting the centroids. Further, the long-range forces are assumed to be proportional to a proper, material-dependent, dis…
Mechanically-based approach to non-local elasticity: Variational principles
2010
Abstract The mechanically-based approach to non-local elastic continuum, will be captured through variational calculus, based on the assumptions that non-adjacent elements of the solid may exchange central body forces, monotonically decreasing with their interdistance, depending on the relative displacement, and on the volume products. Such a mechanical model is investigated introducing primarily the dual state variables by means of the virtual work principle. The constitutive relations between dual variables are introduced defining a proper, convex, potential energy. It is proved that the solution of the elastic problem corresponds to a global minimum of the potential energy functional. Mo…
One-dimensional heterogeneous solids with uncertain elastic modulus in presence of long-range interactions: Interval versus stochastic analysis
2013
The analysis of one-dimensional non-local elastic solids with uncertain Young's modulus is addressed. Non-local effects are represented as long-range central body forces between non-adjacent volume elements. For comparison purpose, the fluctuating elastic modulus of the material is modeled following both a probabilistic and a non-probabilistic approach. To this aim, a novel definition of the interval field concept, able to limit the overestimation affecting ordinary interval analysis, is introduced. Approximate closed-form expressions are derived for the bounds of the interval displacement field as well as for the mean-value and variance of the stochastic response.
TRADITION AND MODERNITY OF CATALAN VAULTS: HISTORICAL AND STRUCTURAL ANALYSIS
2012
Il lavoro analizza da diversi punti di vista un particolare tipo di strutture voltate noto come volte catalane (bóveda tabicada) e la tecnica costruttiva correlata. Le volte catalane sono volte realizzate da strati alterni di mattoni e malta, caratterizzate da un esiguo spessore in relazione alle altre dimensioni. Il primo passo presentato nel lavoro è quello di investigare tutti gli aspetti storici al fine di inquadrare sia la tipologia che la tecnica costruttiva correlata all'interno della storia dell'architettura e di individuare le ragioni di un così grande successo lungo i secoli. Successivamente, è stata effettuata una campagna di indagini sperimentali, che completa una precedente, su…
Dynamic analysis of prestressed cables with uncertain pretension
2002
This paper deals with finite element dynamic analysis of prestressed cables with uncertain pretension subjected to deterministic excitations. The theoretical model addressed for cable modeling is a two-dimensional finite-strain beam theory, which allows us to eliminate any restriction on the magnitude of displacements and rotations. The dynamic problem is formulated by referring the motion to the inertial frame, which leads to a simple uncoupled quadratic form for the kinetic energy. The effect of the externally applied stochastic pretension is approximately described by means of an uncertain 'axial' component of stress resultant, which is assumed constant along the cable in its dead load c…
Strutture continue a parametri incerti
2005
Obiettivo del presente lavoro è la valutazione della risposta di strutture continue in campo elastico lineare che presentano incertezze nei parametri geometrici e/o meccanici
Il principio di gerarchia delle resistenze capacity design
2012
The devastating effects generated by earthquakes occurred in different parts of the world have attract at a major interest in Earthquake Engineering. This branch of Structural Engineering studies the response and capacity of structural systems subjected to seismic actions, and develops design and prediction methods aimed at achieving adequate safety standards in presence of seismic events. A strategy used for the seismic prediction of RC structures, based on the capacity design of structural elements is the "hierarchy of strengths" (HS) principle. The paper shows how a proper use of the HS capacity design method can be included within the seismic design of RC structures achieving high level…
On the use of fractional calculus for the probabilistic characterization of random variables
2009
In this paper, the classical problem of the probabilistic characterization of a random variable is re-examined. A random variable is usually described by the probability density function (PDF) or by its Fourier transform, namely the characteristic function (CF). The CF can be further expressed by a Taylor series involving the moments of the random variable. However, in some circumstances, the moments do not exist and the Taylor expansion of the CF is useless. This happens for example in the case of $\alpha$--stable random variables. Here, the problem of representing the CF or the PDF of random variables (r.vs) is examined by introducing fractional calculus. Two very remarkable results are o…