Search results for " scienza delle costruzioni"

MECHANICAL RESPONSE OF BERNULLI EULER BEAMS ON FRACTIONAL ORDER ELASTIC FOUNDATION

2014

Stationary and non-stationary stochastic response of linear fractional viscoelastic systems

2012

Abstract A method is presented to compute the stochastic response of single-degree-of-freedom (SDOF) structural systems with fractional derivative damping, subjected to stationary and non-stationary inputs. Based on a few manipulations involving an appropriate change of variable and a discretization of the fractional derivative operator, the equation of motion is reverted to a set of coupled linear equations involving additional degrees of freedom, the number of which depends on the discretization of the fractional derivative operator. As a result of the proposed variable transformation and discretization, the stochastic analysis becomes very straightforward and simple since, based on stand…

Markovian approximation of linear systems with fractional viscoelastic term

2017

It is well known that the response of a linear system enforced by a Gaussian white noise is Markovian. The order of Markovianity is n-1 being n the maximum order of the derivative of the equation ruling the evolution of the system. However when a fractional operator appears, the order of Markovianity of the system becomes infinite. Then the main aim developed in the proposed paper, consists of rewriting the system with fractional term of order r with an "equivalent" one, in which the fractional operator is substituted by two classical differential terms with integer order of derivative int(r) and int(r + 1) (for a real r). In this way the fractional differential equation reverts into a clas…

Strutture in muratura - Le catene nel consolidamento

2011

This text analyzes the behavior of masonry structures subject to external actions and represents a contribution to the preservation of the substantial heritage of monumental and non-monumental historical buildings, which characterizes most of the Italian cities.

Ultrasonic inspection for the detection of debonding in CFRP-reinforced concrete

2017

Fibre-reinforced plastic (FRP) composites are extensively used to retrofit civil structures. However, the quality and the characteristics of the bond between the FRP and the structure are critical to ensure the efficacy of the retrofit. For this reason, effective non-destructive evaluation (NDE) methods are often necessary to assess the bonding conditions. This article presents an ultrasonic technique for detecting defects at the FRP-substrate interface. The technique uses the Akaike Information Criterion, to detect automatically the onset of the ultrasonic signals, and the novel Equivalent Time Lenght (ETL) parameter, to quantify the energy of the propagating ultrasonic signals along the i…

Electromechanical Impedance Method to Assess the Stability of Dental Implants

2017

In this paper we illustrate the application of the electromechanical impedance (EMI) technique, popular in structural health monitoring, to assess the stability of dental implants. The technique consists of bonding a piezoelectric transducer to the element to be monitored. When subjected to an electric field, the transducer induces low to high frequency structural excitations which, in turn, affect the transducer's electrical admittance. As the structural vibrations depend on the mechanical impedance of the host structure (in this case the implant secured to the jaw), the measurement of the PZT's admittance can infer the progress of the osseointegration process. In the study presented in th…

Frictional effect in mode II delamination: Experimental test and numerical simulation

2013

Abstract The present paper proposes an experimental and a numerical analysis of the frictional effect on the mode II delamination. Frictional stresses between the crack edges can absorb and dissipate significant energy contributions in the delamination zones, especially under cyclic loading conditions. The experimental tests are performed for a set of unidirectional End-Notched Flexure (ENF) composite specimens, which are subjected to fatigue loading law with increasing mean value. The numerical analyses are performed considering a cohesive–frictional constitutive model, which is able to reproduce the transition of the interface behavior from the sound elastic condition to the fully cracked…

A physical description of fractional-order Fourier diffusion

2014

In this paper the authors introduce a physical picture of anomalous heat transfer in rigid conductor. The analysis shows that a fractional-order Fourier transport is obtained by the analysis of the heat transport in a functionally graded conductor. The order of the fractional-type operator obtained is related to the grading of the physical properties of the conductor.

On the dynamics of non-local fractional viscoelastic beams under stochastic agencies

2018

Abstract Non-local viscoelasticity is a subject of great interest in the context of non-local theories. In a recent study, the authors have proposed a non-local fractional beam model where non-local effects are represented as viscoelastic long-range volume forces and moments, exchanged by non-adjacent beam segments depending on their relative motion, while local effects are modelled by elastic classical stress resultants. Long-range interactions have been given a fractional constitutive law, involving the Caputo's fractional derivative. This paper introduces a comprehensive numerical approach to calculate the stochastic response of the non-local fractional beam model under Gaussian white no…

Cohesive delamination and frictional contact on joining surface via XFEM

2018

In the present paper, the complex mechanical behaviour of the surfaces joining two different bodies is analysed by a cohesive-frictional interface constitutive model. The kinematical behaviour is characterized by the presence of discontinuous displacement fields, that take place at the internal connecting surfaces, both in the fully cohesive phase and in the delamination one. Generally, in order to catch discontinuous displacement fields, internal connecting surfaces (adhesive layers) are modelled by means of interface elements, which connect, node by node, the meshes of the joined bodies, requiring the mesh to be conforming to the geometry of the single bodies and to the relevant connectin…