Search results for " scienza delle costruzioni"

Mode-superposition correction method for deterministic and stochastic analysis of structural systems

2001

The role played by the modal analysis in the framework of structural dynamics is fundamental from both deterministic and stochastic point of view. However the accuracy obtained by means of the classical modal analysis is not always satisfactory. Therefore it is clear the importance of methods able to correct the modal response in such a way to obtain the required accuracy. Many methods have been proposed in the last years but they are meaningful only when the forcing function is expressed by an analytical function. Moreover in stochastic analysis they fail for white noise excitation. In the paper a method able to give a very accurate response for both deterministic and stochastic input is p…

A state-space approach to dynamic stability of fractional-order systems: The extended Routh-Hurwitz theorem

2017

This paper considers the case of Beck’s column, a linear elastic cantilever column subjected to a constant follower load at its free end. The column foundation is modeled as bed of hereditary elements that react with a vertical force distributed along the beam axis. The reacting supports are modeled with spring-pot element that is a two parameters mechanical elements (C; ) with an intermediate behavior between spring and dashpot. The constitutive equation of the spring-pot involves the so called fractional order derivatives and dynamic stability problem in presence of fractional-order operator must be faced for the Beck’s column. In this study , the authors generalize Routh-Hurwitz theorem …

Fractional Derivatives in Interval Analysis

2017

In this paper, interval fractional derivatives are presented. We consider uncertainty in both the order and the argument of the fractional operator. The approach proposed takes advantage of the property of Fourier and Laplace transforms with respect to the translation operator, in order to first define integral transform of interval functions. Subsequently, the main interval fractional integrals and derivatives, such as the Riemann–Liouville, Caputo, and Riesz, are defined based on their properties with respect to integral transforms. Moreover, uncertain-but-bounded linear fractional dynamical systems, relevant in modeling fractional viscoelasticity, excited by zero-mean stationary Gaussian…

An extended shakedown theory for elastic-plastic-damage material models

1996

Internal variable elastic-plastic-damage, or elastic-damage, material models endowed with free energy are considered. Referring to a structure of such a material subjected to loads varying inside a given domain, the classical notion of (elastic) shakedown is widened to signify that the structure eventually responds to the loads in an elastic manner after certain (finite) amounts of plastic strain and/or damage have been produced. For structures fulfilling an ad-hoc D-stability requisite, an extended shakedown theorem is presented as a generalization of the classical Melan theorem to nonlinear elasticity and damage - besides nonlinear hardening. For common materials exhibiting linear elastic…

MULTICRITERIA OPTIMAL DESIGN OF CONTINUOUS CIRCULAR PLATES

2010

The paper is devoted to a quite general version of the multicriteria optimal (minimum volume) design of axisymmetric circular plates. The constitutive material is considered as elastic perfectly plastic without any ductility limit and the actions are assumed as quasi-statically variable within a given load domain. In the design problem formulation different resistance criteria are considered, in order to investigate all the possible structural limit responses, and for each one a suitably chosen safety factor is chosen. The optimal design problem is formulated as the search for the minimum structure volume according with a statical approach. The features of the optimal structures will be stu…

Reliable measures of plastic deformations for elastic plastic structures in shakedown conditions

2020

A new formulation for evaluating reliable measures of the plastic deformations occurring in the transient phase of a structure in shakedown conditions is proposed. The structure is thought as constituted by elastic perfectly plastic material and subjected to a combination of fixed and cyclic loads. The proposed formulation consists in the search for the optimal plastic strain field that minimize a suitable objective function defining a strain energy measure related to the plastic strains at the shakedown limit. The typical self-stress field can be obtained as the elastic structural response to an assigned plastic strain field respecting appropriate ductility limits for the material. Without…

Influence of protecting devices on the optimal design of elastic plastic structures

2008

The paper concerns the minimum volume design of structures constituted by elastic perfectly plastic material. The relevant optimal design problem is formulated on the grounds of a statical approach and two different resistance limits are considered: in particular, it is required that the optimal structure satisfies the elastic shakedown limit and the instantaneous collapse limit, imposing for each different condition a suitably chosen safety factor. For sake of generality, the structure is thought as discretized into compatible finite elements and subjected to loads quasi-statically acting as well as to dynamic (seismic) loads. The effects of the dynamic actions are studied on the grounds o…

Discussion: “Chaotic Motion of an Elastic-Plastic Beam” (Poddar, B., Moon, F. C., and Mukherjee, S., 1988, ASME J. Appl. Mech., 55, pp. 185–189)

1988

Discussion on caotic motion of a pinned beam subjected to pulse loading

Elastoplastic analysis by the multidomain Symmetric Boundary Element Method

2009

On the FE·Meshless computational homogenization for the analysis of two-dimensional heterogeneous periodic materials

2017

Over the last few years, substantial progresses have been made in the two-scales com- putational homogenization. This method is essentially based on the assessment of the macroscopic constitutive behavior of heterogeneous materials through the boundary value problem (BVP) of a statistically representative volume element, named as unit cell (UC). In this framework, the first-order method has now matured to a standard tool and several extensions have been addressed in the literature [1, 2]. In the present study, a first-order homogenization scheme based on a discontinuous- continuous approach is presented. At the mesoscopic level the formation and propagation of fracture is modeled employing …