0000000000964278
AUTHOR
A. Pirrotta
Structural response to stochastic agencies: damage detection
Experimental Investigation of Random Vibration Control Through Dry Friction
The purpose of this experimental investigation is to measure the response statistics in the presence of base friction and other friction sources. The experimental model emulates a one-floor building supported on four leaf springs, subjected to band limited random excitation. Two different types of model base are considered, a friction base and a frictionless base. In both cases friction can also be applied at two sides of the model’s main mass against the direction of its motion. Excitation and response transducer signals are processed to estimate excitation and response statistics in the presence and in the absence of top mass friction. Measured statistics include mean squares, autocorrela…
Numerical validation of an approximate formulation for the design of TLCD
Experimental validation of a damage identification procedure based on the analytical signal
Two-dimensional model of cross-flow electrodialysis units for the assessment of membrane deformation effects on the process performance
Non Gaussian closure techniques for the analysis of R-FBI isolation system
The Resilient-Friction Base Isolator (R-FBI) stochastic response under severe ground motion modelled as a stationary and non-stationary zero mean stochastic white noise processes is performed. The moment equation approach is applied and the non-normal response is obtained by means of a non-Gaussian closure technique, based on the Gram-Charlier asymptotic expansion of the response probability density function. Results are compared with the equivalent non linearization technique and with results obtained by means of Monte Carlo simulation.
Stochastic response of beams equipped with tuned mass dampers subjected to Poissonian loads
This contribution deals with the vibrational response of Euler-Bernoulli beams equipped with tuned mass dampers, subjected to random moving loads. The theory of generalised functions is used to capture the discontinuities of the response variables at the positions of the tuned mass dampers, which involves deriving exact complex eigenvalues and eigenfunctions from a characteristic equation built as the determinant of a 4 x 4 matrix, regardless of the number of tuned mass dampers. Building pertinent orthogonality conditions for the deflection eigenfunctions, the stochastic responses, under Poissonian white noise, are evaluated. In a numerical application, a beam with multiple tuned mass dampe…
Moving multi-loads problem in layered cracked beams with interlayer slip
This contribution concerns the vibration response of layered cracked uniform beams with interlayer slip under moving multiple loads. Considering a linear constitutive relation between the horizontal slip and the interlaminar shear force, the Euler-Bernoulli hypothesis is assumed to hold for each layer separately. Modeling cracks as internal elastic rotational joints, related discontinuities of the response variables are treated by the theory of generalized functions. In this manner, exact eigenfunctions are derived from a characteristic equation built as determinant of 6x6 matrix, for any number of cracks. Building pertinent orthogonality conditions for the deflection eigenfunctions, the re…
Stochastic dynamic analysis of fractional viscoelastic systems
A method is presented to compute the non-stationary response of single-degree-of-freedom structural systems with fractional damping. Based on 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 half oscillators, the number of which depends on the discretization of the fractional derivative operator. In this context, it is shown that such a set of oscillators can be given a proper fractal representation, with a Mandelbrot dimension depending on the fractional derivative order a. It is then seen that the response second-order statistics of the derived set of c…
La Cupola del Teatro Massimo: Il contemporaneo nel 1876
The Control Performance of TLCD and TMD: Experimental Investigation
Markovian approximation of linear systems with fractional viscoelastic term
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…
A process model of electrodialysis including membrane deformation effects
Electrodialysis (ED) is an electro-driven process that makes use of ion exchange membranes (IEMs) under an applied electric field. The main application of ED is the desalination for drinking water production. A transmembrane pressure (TMP) distribution may arise in ED stacks due to an uneven pressure distribution in the two fluid channels, thus causing membrane/channel deformation and flow redistribution. This can occur in large-scale non-parallel configurations, e.g. crossflow arrangements. Detrimental effects of membrane deformation have widely been studied with reference to several membrane processes. However, this aspect has been neglected in ED applications. In this work, a novel proce…
Ion Exchange Membrane deformation and its relevance in Reverse ElectroDialysis
Reverse electrodialysis (RED) is an innovative electro-membrane technology for electric energy generation from two salt solutions with different concentration. This different concentration is the driving force to a selective movement of ions from the concentrate channel to the dilute one oriented by Ion Exchange Membranes (IEMs). Typically, RED stack are made by piling alternatively cation exchange membranes and anion exchange membranes with the aid of spacers or profiles built on the membrane surface. Two electrodic compartments are placed at the two ends of the stack, where the ion flux generated is converted into an electric current able to circulate through an external load connected to…