Numerical simulations versus theoretical predictions for a non-Gaussian noise induced escape problem in application to full counting statistics

A theoretical approach for characterizing the influence of asymmetry of noise distribution on the escape rate of a multistable system is presented. This was carried out via the estimation of an action, which is defined as an exponential factor in the escape rate, and discussed in the context of full counting statistics paradigm. The approach takes into account all cumulants of the noise distribution and demonstrates an excellent agreement with the results of numerical simulations. An approximation of the third-order cumulant was shown to have limitations on the range of dynamic stochastic system parameters. The applicability of the theoretical approaches developed so far is discussed for an adequate characterization of the escape rate measured in experiments

L'Aquila, Central Italy, April 6, 2009: a Further Lesson to Civil Engineers

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Structural Health Monitoring by Lyapunov Exponents of Non-linear Time Series

In this study, structural health monitoring is pursued by collecting multi-channel measurements and by computing, directly from them, the Lyapunov exponents. The latter quantities are invariants of the dynamic system, so that their different values, associated with different time histories obtained from the same structure, denote damage. First, the problem is framed in the general theory. The structural health monitoring strategy is then formulated, with special care being devoted to its capability of localizing damage. The procedure is finally validated by using the time histories which were collected during the experimental tests on the model of a monumental arch. Copyright © 2005 John Wiley & Sons, Ltd

HIL Excitation in the Damage Assessment of a Timber Footbridge

Casciati, Sara; Faravelli, Lucia; Casciati, Fabio Edited by: Chang, FK; Kopsaftopoulos, F Conference: Date: Sponsor(s): Natl Sci Fdn; Air Force Off Sci Res; Boeing; Airbus; Embraer; Verizo

A contribution to the modelling of human induced excitation on pedestrian bridges

Human induced vibration is a common problem in the design of planking levels as both flooring or decking. The source of the vibration is the so-called "human induced loading (HIL)". Models are available for a single exciting person and for a dense aggregation of persons. Small groups of persons should also be considered in view of serviceability limit state design. This paper introduces a model for the time variant stochastic fields of forces induced by the walking of a small group of persons. A numerical example is presented dealing with the evaluation of vertical and transversal accelerations at nodes of a finite element model of an existing wood footbridge. The example considers different idealizations of the human induced excitation and the results of these models are compared to actual records