Browsing by Author "Ceravolo, Rosario"
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Item Open Access Comparison of semi-active control strategies for rocking objects under pulse and harmonic excitations(Elsevier, 2016-12-28) Ceravolo, Rosario; Pecorelli, Marica Leonarda; Zanotti Fragonara, LucaRecently, a considerable literature has grown up around the theme of seismic protection of rigid blocks, with a special focus on strategies to reduce the overturning vulnerability due to rocking motion. The present paper investigates a semi-active control method for rocking blocks and compares different strategies for its implementation. In more detail, a feedback control algorithm was developed to adjust the stiffness of the restraints placed at the two lower corners of the block. The utility of the proposed control was quantified through “ad hoc” indices derived from overturning spectra. The performance of a feedback strategy was numerically investigated and specific simulations were performed to quantify the control method degradation when implemented for a real-world application. Finally, the stability of the block controlled with the proposed strategy is compared with the stability of the block whose anchorage is set according to different control strategies.Item Open Access A computational methodology for assessing the time-dependent structural performance of electric road infrastructures(Wiley, 2016-04-05) Ceravolo, Rosario; Miraglia, Gaetano; Surace, Cecilia; Zanotti Fragonara, LucaAn infrastructure adapted to dynamic wireless recharging of electric vehicles is often referred to generically as Electric Road (“e-road”). E-roads are deemed to become essential components of future grid environments and smart city strategies. Several technologies already exist that propose different ways to integrate dynamic inductive charging systems within the infrastructure. One e-road solution uses a very thin rail with box-section made of fibre-reinforced polymer, inside which an electric current flows producing a magnetic field. In spite of the great interest and research generated by recharging technologies, the structural problems of e-roads, including vibrations and structural integrity in the short and/or long period, have received relatively little attention to date. This article presents a novel computational methodology for assessing the time-dependent structural performance of e-roads, including a recursive strategy for the estimation of the lifetime of surface layers. The article also reports some numerical findings about e-roads that will drive further numerical analyses and experimental studies on this novel type of infrastructure. Finally, numerical simulations have been conducted to compare an e-road with a traditional road (“t-road”), in terms of static, dynamic and fatigue behavior.Item Open Access Dynamic investigation on the Mirandola bell tower in post-earthquake scenarios(Springer Verlag (Germany), 2016-07-19) Zanotti Fragonara, Luca; Boscato, Giosue; Ceravolo, Rosario; Lentile, Silvia; Russo, Salvatore; Pecorelli, Marica Leonarda; Quattrone, AntoninoAfter the seismic events of the 20th and 29th of May 2012 in Emilia (Italy), most of the monumental and historic buildings of the area were severely damaged. In a few structures, partial collapse mechanisms were observed (e.g. façade tilting, out-of-plane overturning of panels…). This paper presents the case-study of the bell tower of the Santa Maria Maggiore cathedral, located in Mirandola (Italy). The dynamic response of the structure was evaluated through operational modal analysis using ambient vibrations, a consolidated non-destructive procedure that estimates the dynamic parameters of the bell-tower. The dynamic tests were carried out in pre-intervention and post-intervention conditions in order to understand the sensitivity of dynamic measurements to safety interventions. Furthermore, a comparative study is made with similar cases of undamaged masonry towers up to the 6th mode. Finally, an investigation on the state of connections and of the building itself is carried out via FE model updating.Item Open Access Experimental testing of a masonry arch bridge model subject to increasing level of damage(European Commission, 2011-01-31) Degiovanni, L.; Quattrone, Antonino; Zanotti Fragonara, Luca; Ceravolo, Rosario; De Stefano, AlessandroMasonry arch bridges are particularly sensitive to the bearings loss produced by scour of the streambed soil at the piers foundations. A 1:2 scaled experimental model of a masonry arch bridge was built to study the evolution of the damage mechanism related to the application of foundation movements. The model was built with handmade clay bricks and a mortar with poor mechanical properties in order to reproduce typical materials of historical constructions, and an extensive characterization of the materials has been carried out. The mid-span pier is placed on a settlement application system, expressly designed to simulate the scour effect, quantified through hydraulic flume tests performed on a further scaled down model. Damage levels of increasing intensity have been simulated through the application of pier settlements and rotations. Experimental vibration tests were performed on the undamaged structure and after each settlement step. Both the environmental noise and the impacts of a sledge hammer were used as excitation sources. A complete dynamic identification was carried out and the variation of modal parameters at different levels of damage monitored. Moreover, the use of a testing shaker allowed investigating the non - linear behaviour of the damaged model.Item Open Access Measurement of weak non-linear response of Kevlar® fibre damaged by UV exposure(Elsevier, 2017-10-21) Ceravolo, Rosario; De Marchi, Andrea; Pinotti, Elena; Surace, Cecilia; Zanotti Fragonara, LucaThis paper deals with a high-sensitivity method for the assessment of damage in high-strength fibres exposed to UV radiation. A recently developed experimental testing machine, based on an optical measurement system and electro-magnetic driving force, was used to characterize fibre materials. Stiffness, damping, and non-linearity were measured on several Kevlar® fibre samples previously exposed to UV light for different lengths of time. The results show that UV radiation increases the material non-linearity by amounts which can be clearly observed even at low vibration amplitudes. On the contrary, uncertainties affecting the determination of stiffness and damping with the adopted approach don’t seem to allow a similarly unambiguous UV damage assessment. Result confirm our initial hypothesis that non-linearity may be a valuable index of damage, at least in case of UV exposure, for applications in the Structural Health Monitoring (SHM) field.Item Open Access Monitoring of masonry historical constructions: 10 years of static monitoring of the world's largest oval dome(Monitoring of masonry historical constructions: 10 years of static monitoring of the world's largest oval dome, 2017-02-03) Ceravolo, Rosario; De Marinis, A.; Pecorelli, M. L.; Zanotti Fragonara, LucaThis paper presents the analyses conducted on the data acquired by the monitoring system of the “Regina Montis Regalis” Basilica of Vicoforte (Italy) in the decade 2004–2014. The Basilica is a building of great historical, architectural, and structural significance, owing its fame to its impressive masonry oval dome, the world's largest of this shape (internal axes of 37.23 by 24.89 m). The dome-drum system of the Basilica has suffered over the years of significant structural problems, partly due to the settlements of the building induced progressively by newly built masses and also to the sliding of the underground. In 1983, concerns over the severe settlements and cracking phenomena affecting the structure prompted the decision to undertake strengthening interventions. A special hooping system, consisting of 56 tie bars, placed around the oval perimeter of the dome, was thus conceived to limit the crack opening. The monitoring system of the Basilica installed in the early 1980s underwent several renovations, and in 2004, its acquisition procedure was automatized. One hundred twelve instruments, consisting of temperature sensors, crackmeters, load cells, pressure cells, wire gauges, hygrometer, piezometers, and hydrometer, are currently installed on the Basilica. This study is primarily focused on data acquired by the crackmeters, the extensometers along the main axes of dome, and the load cells placed at the ends of the tie bars. The main aim of the reported analysis is to evaluate the possible progression of the cracks on the Basilica, and the structural performance of the strengthening interventions put in place in 1985–1987.Item Open Access A multi‐objective genetic algorithm strategy for robust optimal sensor placement(Wiley, 2021-02-17) Civera, Marco; Pecorelli, Marica Leonarda; Ceravolo, Rosario; Surace, Cecilia; Fragonara, Luca ZanottiThe performance of a monitoring system for civil buildings and infrastructures or mechanical systems depends mainly on the position of the deployed sensors. At the current state, this arrangement is chosen through optimal sensor placement (OSP) techniques that consider only the initial conditions of the structure. The effects of the potential damage are usually completely neglected during its design. Consequently, this sensor pattern is not guaranteed to remain optimal during the whole lifetime of the structure, especially for complex masonry buildings in high seismic hazard zones. In this paper, a novel approach based on multi‐objective optimization (MO) and genetic algorithms (GAs) is proposed for a damage scenario driven OSP strategy. The aim is to improve the robustness of the sensor configuration for damage detection after a potentially catastrophic event. The performance of this strategy is tested on the case study of the bell tower of the Santa Maria and San Giovenale Cathedral in Fossano (Italy) and compared to other classic OSP strategies and a standard GA approach with a single objective function.Item Open Access A new testing machine for the dynamic characterization of high strength low damping fiber materials(Springer, 2016-09-14) Ceravolo, Rosario; De Marchi, Andrea; Pinotti, Elena; Surace, Cecilia; Zanotti Fragonara, LucaThis work describes a novel method for measuring the damping, the elastic modulus and the non-linear behavior of high strength low damping fiber materials such as para-aramids, silicon carbide (SiC) and carbon. The method is based on resonant response characterization of a spring-mass system excited by a sine-wave forcing term which is applied as a vertical force to the suspended mass. The damping is obtained from the measured resonance quality factor Q, the elasticity modulus is calculated from the resonance frequency, and the non-linear coefficient is obtained with the backbone approach from resonance profile variations as a function of the forcing term amplitude. It is argued that the method is very sensitive, to the point that a maximum excitation amplitude of the order of a few percent of resistance is sufficient to obtain an estimate of the non-linear coefficient. This claim is supported by experimental results. A testing machine is also discussed, which provides the necessary sensitivity at such small excitation amplitudes and the capability of evaluating very small damping values, as expected in high strength low damping fiber materials. The sensitivity is guaranteed by an optical position sensor with sub-micron resolution. To evaluate small damping values, particular care has been taken to ensure that energy dispersions in the generator are much smaller than energy dispersions in the fibers themselves. Examples of dynamic characterization are shown for para-aramid, silicon carbide, and carbon fibers.Item Open Access Non-destructive testing on aramid fibres for the long-term assessment of interventions on heritage structures(IOP Publishing: Conference Series / Institute of Physics (IoP), 2015-07-09) Ceravolo, Rosario; De Marchi, Andrea; Pinotti, Elena; Surace, Cecilia; Zanotti Fragonara, LucaHigh strength fibre reinforced polymers (FRPs) are composite materials made of fibres such as carbon, aramid and/or glass, and a resin matrix. FRPs are commonly used for structural repair and strengthening interventions and exhibit high potential for applications to existing constructions, including heritage buildings. In regard to aramid fibres, uncertainties about the long-term behaviour of these materials have often made the designers reluctant to use them in structural engineering. The present study describes simple and non-destructive nonlinearity tests for assessing damage or degradation of structural properties in Kevlar fibres. This was obtained by using high precision measurements to detect small deviations in the dynamic response measured on fibres and ropes. The change in dynamic properties was then related to a damage produced by exposure of the sample to UV rays for a defined time period, which simulated long-term sun exposure. In order to investigate the sensitivity of such an approach to damage detection, non-linearity characterisation tests were conducted on aramid fibres in both damaged and undamaged states. With the purpose of carrying out dynamic tests on small fibre specimens, a dedicated instrumentation was designed and built in cooperation with the Metrology Laboratory of the Department of Electronics at the Politecnico di Torino.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 Parametric identification of damaged dynamic systems with hysteresis and slip(IOP Publishing, 2011-12-31) Ceravolo, Rosario; Zanotti Fragonara, Luca; Erlicher, S.; Bursi, O. S.The improvement of performance-based seismic design techniques requires the understanding of the overall behaviour of a structure up to collapse. Therefore, both experimental data and analytical models are needed. In a greater detail, material and geometrical nonlinearities, strength degradation and stiffness deterioration should be identified. Also in view of probabilistic-based simulations, hysteretic models, i.e. models able to describe with accuracy the hysteretic and degrading nature of the dynamic response of structures, have to be striven for. At higher level of excitation or under seismic loading, civil structures can exhibit slip effects. This paper presents a technique for the identification of non-linear in framed systems. A new a model for simulating slip effects is also introduced, which demonstrated to be suitable for identification purposes.Item Open Access Semi-active control of the rocking motion of monolithic art objects(Elsevier, 2016-04-12) Ceravolo, Rosario; Leonarda Pecorelli, Marica; Zanotti Fragonara, LucaThe seismic behaviour of many art objects and obelisks can be analysed in the context of the seismic response of rigid blocks. Starting from the pioneering works by Housner, a large number of analytical studies of the rigid block dynamics were proposed. In fact, despite its apparent simplicity, the motion of a rigid block involves a number of complex dynamic phenomena such as impacts, sliding, uplift and geometric nonlinearities. While most of the current strategies to avoid toppling consist in preventing rocking motion, in this paper a novel semi-active on–off control strategy for protecting monolithic art objects was investigated. The control procedure under study follows a feedback–feedforward scheme that is realised by switching the stiffness of the anchorages located at the two lower corner of the block between two values. Overturning spectra have been calculated in order to clarify the benefits of applying a semi-active control instead of a passive control strategy. In accordance with similar studies, the numerical investigation took into account the dynamic response of blocks with different slenderness and size subject to one-sine pulse excitation.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.Item Open Access Vibration-based monitoring and diagnosis of cultural heritage: A methodological discussion in three examples(Taylor & Francis, 2014-09-09) Ceravolo, Rosario; Pistone, Giuseppe; Zanotti Fragonara, Luca; Massetto, Stefano; Abbiati, GiuseppeModern monitoring techniques contribute to accurately describing the structural health conditions of historical buildings and to optimizing the plan of maintenance as well as the restoring intervention. Particularly, dynamic testing gives knowledge about global structural behavior and can be used to calibrate numerical models and to predict the response to dynamic and earthquake loading. In some circumstances, vibration-based monitoring can also help in evaluating safety conditions. The present article proposes a discussion about the methodological multidisciplinary approach to modal testing when applied to architectural heritage buildings and structures, along with the description of selected case studies. These examples were chosen to cover the various issues connected to test design and interpretation.