Alba Sofi - Academia.edu (original) (raw)

Papers by Alba Sofi

Probabilistic Engineering Mechanics, Jul 1, 2022

Theoretical and Applied Mechanics - AIMETA 2022

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licens... more Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under license by Materials Research Forum LLC.

Materials research proceedings, Mar 17, 2023

The analysis of structures with uncertain properties modeled as random variables with imprecise P... more The analysis of structures with uncertain properties modeled as random variables with imprecise Probability Density Function (PDF) characterized by interval basic parameters (mean-value, variance, etc.) is addressed. A novel procedure able to provide approximate explicit expressions of the bounds of the interval mean-value and variance of the random stresses is proposed. The procedure stems from the joint application of the Improved Interval Analysis via Extra Unitary Interval and the Rational Series Expansion, introduced in the literature by the last two authors. The influence of imprecision of the PDF of the input parameters on structural performance is also investigated. For validation purposes, a 3D truss structure with uncertain Young's moduli is analyzed.

The present study is devoted to the reliability analysis of linear discretized structures, with u... more The present study is devoted to the reliability analysis of linear discretized structures, with uncertain-but-bounded mass and stiffness parameters, subjected to stationary Gaussian multi-correlated random excitation. The reliability function for the extreme value stress process is evaluated in the framework of the first-passage theory. Due to the interval uncertainties affecting structural parameters, the reliability function is an interval function. The aim of the paper is to propose an efficient procedure for the evaluation of the bounds of the interval reliability function which provides a range of structural performance. To this aim, a sensitivity-based approach is applied. So operating, the dangerous overestimation of the solution, caused by the dependency phenomenon, is overcome. The main advantage of this approach is to provide appropriate combinations of the values of the uncertain-but-bounded parameters which yield accurate predictions of the bounds of the interval reliability function for the extreme value stress process. A case study is analyzed to demonstrate the accuracy and efficiency of the presented method.

$Research paper thumbnail of Improved pseudo-force approach for Monte Carlo Simulation of non-linear fractional oscillators under stochastic excitation$

Probabilistic Engineering Mechanics, 2023

Computers & Structures, May 1, 2017

This paper addresses the analysis of structures with random axial stiffness described by imprecis... more This paper addresses the analysis of structures with random axial stiffness described by imprecise probability density function (PDF). Uncertainties are modelled as random variables whose PDF is assumed to depend on interval basic parameters (mean-value, variance, etc.). The main purpose of the analysis is to propagate the imprecise PDF of the random axial stiffness by establishing approximate bounds on the mean-value and variance of the response. To this aim, an efficient method is proposed which relies on the combination of standard probabilistic analysis with the so-called improved interval analysis via extra unitary interval and the Rational Series Expansion, recently introduced by the authors. The accuracy of the proposed bounds of response statistics is demonstrated by appropriate comparisons with the results obtained performing standard Monte Carlo Simulation in conjunction with a combinatorial procedure.

Probabilistic Engineering Mechanics, Apr 1, 2023

CRC Press eBooks, Jan 9, 2014

Wind and Structures, Apr 25, 2004

ABSTRACT

Computers & Structures, Aug 1, 2015

A non-probabilistic approach for analyzing the effects of Young's modulus uncertainty on the resp... more A non-probabilistic approach for analyzing the effects of Young's modulus uncertainty on the response of Euler-Bernoulli beams under deterministic static loads is presented. The uncertain material property is described by applying an interval field model based on the so-called improved interval analysis. The bounds of the interval response are determined in approximate closed-form by performing a finite difference discretization of the governing interval ordinary differential equation and applying the so-called Interval Rational Series Expansion. The proposed procedure is applied to investigate the effects of Young's modulus uncertainty on the bending response of beams with different boundary conditions.

The stochastic analysis of linear structures, with slight variations of the structural parameters... more The stochastic analysis of linear structures, with slight variations of the structural parameters, subjected to zero-mean Gaussian random excitations is addressed. To this aim, the fluctuating properties, represented as uncertain-but-bounded parameters, are modeled via interval analysis. In the paper, a novel procedure for estimating the lower and upper bounds of the second-order statistics of the response is proposed. The key idea of the method is to adopt a first-order approximation of the random response derived by properly improving the ordinary interval analysis, based on the philosophy of the so-called affine arithmetic. Specifically, the random response is split as sum of two aliquots: the midpoint or nominal solution and a deviation. The latter is approximated by superimposing the responses obtained considering one uncertain-but-bounded parameter at a time. After some algebra, the sets of first-order ordinary differential equations ruling the midpoint covariance vector and the deviations due to the uncertain parameters separately taken are obtained. Once such equations are solved, the region of the response covariance vector is determined by handy formulas. To validate the procedure, two structures with uncertain stiffness properties under uniformly modulated white noise excitation are analyzed.

Probabilistic Engineering Mechanics, Apr 1, 2016

Probabilistic Engineering Mechanics, Oct 1, 2002

$Research paper thumbnail of Reliability analysis of structures controlled by external fractional viscoelastic dampers with interval parameters$

Proceedings of the Ninth International Conference on Civil and Structural Engineering Computing

Probabilistic Engineering Mechanics, 2017

In this paper, finite element analysis of structures with uncertain properties is addressed withi... more In this paper, finite element analysis of structures with uncertain properties is addressed within both a probabilistic and non-probabilistic framework. Specifically, uncertainties affecting structural parameters are modelled either as interval or random variables. In both cases, uncertainty propagation analysis is performed by applying a ratio of polynomial response surface which enables to derive approximate closed-form expressions of the main descriptors of interval and random response variability by requiring just a few deterministic analyses at selected sampling points. A unified response surface framework for interval and stochastic finite element analysis is thus developed which allows comparisons of structural response variability under different uncertainty models. Numerical results focusing on the comparison between the interval and stochastic response of structures with uncertain Young's modulus are presented.