Efstratios Nikolaidis

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This paper compares probabilistic and possibility-based methods for design under uncertainty. It studies the effect of the amount of data about uncertainty on the effectiveness of each method. Only systems whose failure is catastrophic are considered, where catastrophic means that the boundary between success and failure is sharp. First, the paper examines(More)
This paper compares Evidence Theory (ET) and Bayesian Theory (BT) for uncertainty modeling and decision under uncertainty, when the evidence about uncertainty is imprecise. The basic concepts of ET and BT are introduced and the ways these theories model uncertainties, propagate them through systems and assess the safety of these systems are presented. ET(More)
In reliability design, often, there is scarce data for constructing probabilistic models. It is particularly challenging to model uncertainty in variables when the type of their probability distributions is unknown. Moreover, it is expensive to estimate the upper and lower bounds of the reliability of a system involving such variables. A method for modeling(More)
Thin walled stiffened composite panels, which are among the most utilized structural elements in engineering, possess the unfortunate property of being highly sensitive to geometrical imperfections. Existing analysis codes can predict the buckling load of a structure with specified initial imperfections. However, it is impossible to determine the amplitude(More)
Methods for designing targeted tests for reliability validation of structures obtained from reliability-based design are presented. These methods optimize the test parameters to minimize the variance in the estimated reliability (or equivalently the failure probability) estimated from the tests. The tests are designed using information from analytical(More)
To address the need for efficient and unbiased experimental testing of methods for decision under uncertainty, we devise an approach for probing weaknesses of these methods by running numerical experiments on readily available or easily obtainable databases of real life data. Since the approach uses real life data, it allows us to study the effect of(More)
A bilinear formulation is used for developing the time finite element method (TFM) to obtain transient responses of both linear, nonlinear, damped and undamped systems. Also the formulation, used in the h-, p-and hp-versions, is extended and found to be readily amenable to multi-degree-of-freedom systems. The resulting linear and nonlinear algebraic(More)