Browsing by Author "Matta, Emiliano"
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Item Open Access Model updating of strategic building structures under real earthquake loading(CRC Press, 2013-12-31) Ceravolo, Rosario; Matta, Emiliano; Quattrone, Antonino; Zanotti Fragonara, Luca; De Stefano, AlessandroPublic buildings such as hospitals, schools, churches and city halls constitute an asset of strategic importance into the life of a community. The assessment of the safety conditions and the vulnerability to natural catastrophic events must be checked, also resorting to experimental techniques. The adoption of vibration monitoring procedures represents a particularly appealing perspective for existing structures. The growing use of permanent monitoring systems allows collecting data of the structural response during earthquakes. An invaluable tool for structural health monitoring and damage detection, parametric system identification through model-updating is an inverse problem, affected by several kinds of modelling assumptions and measurement errors. By minimizing the discrepancy between the measured data and the simulated response, traditional model-updating techniques identify one single optimal model that behaves similarly to the real structure.Item Open Access An optimal sensor placement strategy for reliable expansion of mode shapes under measurement noise and modelling error(Elsevier, 2020-11-24) Jaya, Mahesh Murugan; Ceravolo, Rosario; Zanotti Fragonara, Luca; Matta, EmilianoModal expansion techniques are typically used to expand the experimental modal displacements at sensor positions to all unmeasured degrees of freedom. Since in most cases, sensors can be attached only at limited locations in a structure, an expansion is essential to determine mode shapes, strains, stresses, etc. throughout the structure which can be used for structural health monitoring. Conventional sensor placement algorithms are mostly aimed to make the modal displacements at sensor positions of different modes as linearly independent as possible. However, under the presence of modelling errors and measurement noise, an optimal location based on this criterion is not guaranteed to provide an expanded mode shape which is close to the real mode shape. In this work, the expected value of normal distance between the real mode shape and the expanded mode shape is used as a measure of closeness between the two entities. Optimal sensor locations can be determined by minimizing this distance. This new criterion is applied on a simple cantilever beam and an industrial milling tower. In both cases, by using an exhaustive search of all possible sensor configurations it was possible to find sensor locations which resulted in a significant reduction in the distance when compared to a conventional optimal sensor placement strategy. Sufficiently accurate sub-optimal sequential sensor placement algorithm is also suggested as an alternative to the exhaustive search which is then compared with a genetic algorithm-based search. The efficiency of this new sensor placement criterion is further verified using Monte Carlo simulations for some realistic modelling error conditions.Item Open Access Structural system identification in the presence of resonant non-structural appendages(Civil-Comp Press, 2012-12-31) Matta, Emiliano; Ceravolo, Rosario; De Stefano, Alessandro; Quattrone, Antonino; Zanotti Fragonara, LucaAccurate finite element (FE) models are required in many applications of civil engineering. Non-structural elements (NSEs) often interfere with the main structure, altering its stiffness and modal signature. Neglecting such interaction in modelling, although a common design practice, may lead to unreliable predictions of future events and biased interpretations of in-field dynamic tests. In the current literature, the role of NSEs in vibration-based structural system identification (SSI) is well documented for NSEs working in parallel (P-NSEs) with the main structure (e.g.masonry infills in buildings, pavements or railings in bridges and footbridges) but is totally unexplored for NSEs working in series (S-NSEs) with the main structure (e.g. non-structural appendages such as chimneys, parapets, tanks, but also partitions and claddings in their out-of-plane modes). Presenting various numerical and experimental case studies, the present paper shows how in-series NSEs, through augmenting the modal model and by chance resonating with some structural mode, might significantly alter the dynamic behaviour of the main structure, and severely invalidate SSI if not properly accounted for while performing modelling and dynamic identification.Item Open Access Tuned mass dampers for the mitigation of impulsive ground motions(Civil-Comp Press, 2012-12-01) Matta, Emiliano; Ceravolo, Rosario; De Stefano, Alessandro; Quattrone, Antonino; Zanotti Fragonara, LucaThe performance of tuned mass dampers (TMDs) diminishes as the input duration shortens. As a result, they are not recommended for use against short-duration, pulse-like ground motions, such as those occurring in near-field (NF) zones in the presence of forward-directivity or fling-step effects. Yet a systematic assessment of this control loss is still missing. In this paper, a recent analytical model of ground motion pulses is applied to the design and evaluation of TMDs against impulsive earthquakes. Based on this model, first a new optimization method is introduced as an alternative to the classical H∞ approach. Then the two strategies are tested on single- and multi- degrees-of-freedom linear structures subject both to analytical pulses and to a large set of NF records possessing pulse-like features. The resulting statistical evaluation, expressed by percentile response spectra, shows the advantages and disadvantages of a pulse-oriented TMD design, and improves the general understanding of TMDs effectiveness under impulsive ground motions.Item Open Access Unscented kalman filter for the identification of passive control devices(Taylor & Francis, 2013-12-31) Ceravolo, Rosario; De Stefano, Alessandro; Matta, Emiliano; Quattrone, Antonino; Zanotti Fragonara, LucaThe Unscented Kalman Filter (UKF) is a technique which allows dealing with nonlinear systems and it is able to handle any type of non-linearity. In detail, differently from Extended Kalman Filter (EKF), UKF does not require the computation of the Jacobian of the non-linear function. Estimation of parameters through the UKF approach is an indirect procedure, consisting of transforming the parameter estimation problem into a state estimation problem. This is done by augmenting the system state vector by artificially defining the unknown parameters as additional state variables. In the present study the UKF is proposed to the purpose of the nonlinear identification of rolling-pendulum tuned vibration absorbers.