Search results for "scienza"
showing 10 items of 1408 documents
Numerical Simulations of the Hydrodynamics of the Abdominal Aorta Aneurysm (AAA) Using a Smoothed Particle Hydrodynamics Code with Deformable Wall Pr…
2018
We present some preliminary results of the numerical simulations of the hydrodynamic characteristics of an abdominal aorta aneurysm (AAA) patient specific test case. Images of the AAA lumen have been acquired in 10 discrete time-steps through a stabilized cardiac cycle by electrocardiogram-gated computer tomography angiography, and are used to approximate the in vivo, time dependent kinematic fields of the (internal) arterial wall. The flow field is simulated by a Smoothed Particle SPH numerical model, where the kinematics of the boundary of the computational domain (the internal aortic vessel) is the one computed by the above procedure. The outputs of the SPH model, i.e., pressure and flow…
Deterministic and Random Vibration of Linear Systems with Singular Parameter Matrices and Fractional Derivative Terms
2021
Both time- and frequency-domain solution techniques are developed for determining the response of linear multi-degree-of-freedom systems exhibiting singular parameter matrices and endowed with derivative terms of noninteger orders modeled as rational numbers. This is done based on the Moore-Penrose matrix inverse theory, in conjunction with a state variable formulation and with a complex modal analysis treatment. It is worth noting that, for the class of systems considered herein, this treatment also yields decoupled governing equations, thus facilitating further their numerical solution. Next, a generalization of the standard frequency-domain input-output (excitation-response) relationship…
Testing mechanical characteristics of chestnut stakes used in bed sills for stream restoration
2017
Using of wood elements for constructing bed sills in Mediterranean streams, where the banks are not protected by tree vegetation, needs an evaluation of biological and mechanical characteristics for evaluating both the wood durability and the effectiveness of the stream restoration project. Very few studies have dealt both with the decay of mechanical characteristics of wood elements employed for stream restoration works and with the changes over time of physical and chemical wood characters. In this paper, for a wood and stone bed sill located in a stream having no shaded banks, the changes of physical and chemical characters detected after 12, 18, 24, 30, 36, 42 and 48 months on chestnut …
Dynamic shakedown of structures under repeated seismic loads
1995
Elastic, perfectly plastic structures are considered under the action of repeated short-duration exitations of seismic type acting in an unknown time sequence, but belonging to a given polyhedral excitation domain. The basic excitations (vertices of the polyhedron) are chosen as discrete-spectrum waves each with frequencies coincident with the first natural frequencies of the structure, and amplitudes related to the ground features and earthquake intensity (according to the Kanai and Tajimi filter model) in such a way that every admissible excitation-obtained as a linear convex combination of the basic ones-has a maximum power not exceeding a given value. In the framework of unrestricted dy…
The Transverse Crack Tension test revisited
2016
Several problems arise when measuring the mode II interlaminar fracture toughness using a Transverse Crack Tension specimen; in particular, the fracture toughness depends on the geometry of the specimen and cannot be considered a material parameter. A preliminary experimental campaign was conducted on TCTs of different sizes but no fracture toughness was measured because the TCTs failed in an unacceptable way, invalidating the tests. A comprehensive numerical and experimental investigation is conducted to identify the main causes of this behaviour and a modification of the geometry of the specimen is proposed. It is believed that the obtained results represent a significant contribution in …
Erratum to: Letter to the Editor [Engineering Fracture Mechanics 2003 (70) 1219-21]
2004
Erratum and Corrections
A microplane model for plane-stress masonry structures
2003
Publisher Summary For a refined nonlinear finite element analysis of masonry structures, an accurate constitutive model that is able to reproduce the desired phenomenological material features is required. Constitutive models for quasi-brittle materials, as plain concrete, have been proposed in the chapter, which allow to reproduce the very complex response in the two- or three-dimensional state of stress. Usually, the constitutive relations proposed are based on some appropriate extensions of elastic-plastic continuum models and more recently on continuum damage models. It has been observed that for these tensorial-based constitutive relations to be effective often require a large number o…
Combining TMD and TLCD: analytical and experimental studies
2017
Abstract In these years several research efforts have been focused on developing efficient and reliable control devices for mitigating the structural response of tall and lightly damped buildings in case of strong dynamic excitations, such as wind and earthquake ones. In this context, Tuned Mass Dampers (TMDs) represent probably the most common control device due to their high control performances. On the other hand, Tuned Liquid Column Dampers (TLCDs) are increasingly becoming more popular because of some of their attractive features, cost-effectiveness among the others, even though they yield slightly less control performance compared to the classical TMDs. Aiming at combining the benefic…
Bending test for capturing the fractional visco-elastic parameters: theoretical and experimental investigation on giant reeds
2014
In this paper attention is devoted on searching a proper model for characterizing the behavior of giant reeds. To aim at this, firstly, meticulous experimental tests have been performed in the Laboratory of structural materials of University of Palermo. Further, the novel aspect of this paper is that of using an advanced Euler-Bernoulli model to fit experimental data of bending tests. Such a model of continuum beam takes into account different constitutive laws of visco-elasticity, being real materials visco-elastic.
Low stiffness variation in structural systems: identification and localization
2008
When a very low damage occurs, the undamaged structural response totally overlaps the damaged one either in time domain or in frequency domain; on the other hand, by considering some characteristics of the analytical signal, such as the phase, it has been possible to develop a damage identification procedure that allows the identification and localization of damage even if the structure experiences multiple damages at the same time. This procedure is also robust with respect to the presence of measuring noise. In order to assess the validity of the proposed damage identification procedure, numerical applications on single degree of freedom and 2 DOF and 4 DOF are presented using data record…