473 pubblicazioni classificate nel seguente modo:

Influence of uncertainties and noise on basins/attractors topology and integrity of Duffing oscillator
INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS
Autore/i: Benedetti, Kaio C. B.; Gonçalves, Paulo B.; Lenci, Stefano; Rega, Giuseppe
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/326712

New bearing model with flexible cage and study of dynamic behavior under variable-speed
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
Autore/i: Shuaijun, Ma; Chang, Tian; Chao, Yang; Ke, Yan; Lenci, Stefano; Jun, Hong
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/326713

Stability in Parametric Resonance of a Controlled Stay Cable with Time Delay
INTERNATIONAL JOURNAL OF STRUCTURAL STABILITY & DYNAMICS
Autore/i: Peng, Jian; Xia, Hui; Sun, Hongxin; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: The stability of the parametric resonance of a controlled stay cable with time delay is investigated. The in-plane nonlinear equations of motion are initially determined via the Hamilton principle. Then, utilizing the method of multiple scales, the modulation equations that govern the nonlinear dynamics are obtained. These equations are then utilized to investigate the effect of time delays on the amplitude and frequency-response behavior and, subsequently, on the stability of the parametric resonance of the controlled cable, that it is shown to depend on the excitation amplitude and the commensurability of the delayed-response frequency to the excitation frequency. The stability region of the parametric resonance is shifted, and the effects of control on the cable become worse by increasing time delay. The work plays a guiding role in the parametric design of the control system for stay cables.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/327937

On the static condensation of initially not rectilinear beams
ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK
Autore/i: Lenci, Stefano; Sorokin, Sergey
Classificazione: 1 Contributo su Rivista
Abstract: Two weakly nonlinear integral equations of motion commonly used in the literature to study the nonlinear dynamics of straight and initially not rectilinear Euler-Bernoulli beams, respectively, are further investigated. Attention is focused on the process known as "static condensation", which consists of neglecting the axial inertia in the exact, fully nonlinear system of equations of motion to determine the axial displacement as a function of the transversal one. The novelty of the paper relies on showing that, contrarily to expectation and somehow surprisingly, the integral equation for beams with a not rectilinear initial configuration cannot be obtained by the static condensation process starting from the exact, fully nonlinear, equations of motion, apart from a very particular and specific case. On the contrary, it is confirmed the well-known result that for rectilinear beams the integral equation can be obtained by the static condensation. This highlights a major difference between the two integral equations in terms of reliability and allows us a better understanding of the integral equation of rectilinear beams, underlying its stronger mathematical background than the classical counterpart for not straight beams (i.e., its being obtainable from the exact, fully nonlinear, equations of motion via static condensation), which provides it with a "special" behavior and makes it more trustworthy.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/326751

Imperfection-induced internal resonance in nanotube resonators
JOURNAL OF SOUND AND VIBRATION
Autore/i: Belardinelli, P; Lenci, S; Alijani, F
Classificazione: 1 Contributo su Rivista
Abstract: Through molecular dynamics simulations, we demonstrate the possibility of internal resonances in single-walled carbon nanotubes. The resonant condition is engineered with a lack of symmetry in the boundary condition and activated by increasing the energy exchange with a coupled thermal bath. The critical temperature threshold for initiating modal interaction is found to be chirality-dependent. By applying the proper orthogonal decomposition algorithm to molecular dynamics time responses, we show how the thermal fluctuations influence the vibrational behaviour of the nanotube leading to both flexural–flexural and flexural–longitudinal resonances. Understanding the interaction between nanotube resonators and the thermal bath is crucial for designing and optimizing their performance for various nanoscale sensing, actuation, and signal processing applications.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/325838

A novel view on the canonical 'stretching-due-to-bending' nonlinear effect: A slighly curved beam
EUROPEAN JOURNAL OF MECHANICS. A, SOLIDS
Autore/i: Sorokin, Sv; Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: The analysis of nonlinear coupling between flexural and longitudinal vibrations of ideally straight elastic beams is a classical topic in vibration theory. The boundary conditions usually applied in this analysis are formulated as immobile hinges, which generate the canonical 'stretching-due-to-bending' nonlinear effect. The key assumption in formulation of this model is neglecting the longitudinal inertia, which may be referred to as 'static condensation'. The aims of this work are, first, to re-consider this problem from the viewpoint of a nonlinear theory of curved beams, and, second, employ alternative type of boundary conditions, known as class-consistent ones. A paradoxical difference in nonlinear parts of Duffing equations obtained in the limit of vanishing curvature of an initially curved beam and in the case of an ideally straight beam is demonstrated and explained.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/325837

Nonlinear free vibrations of Timoshenko–Ehrenfest beams using finite element analysis and direct scheme
NONLINEAR DYNAMICS
Autore/i: Firouzi, Nasser; Lenci, Stefano; Amabili, Marco; Rabczuk, Timon
Classificazione: 1 Contributo su Rivista
Abstract: In this work, nonlinear free vibrations of fully geometrically exact Timoshenko-Ehrenfest beams are investigated. First, the exact strong form of the Timonshenko-Ehrenfest beam, considering the geometrical nonlinearity, is derived, and the required formulations are obtained. Since the strong forms of governing equations are highly nonlinear, a nonlinear finite element analysis (FEA) is employed to obtain the weak form. The FEA is utilized to compute natural frequencies and mode shapes; the direct scheme is adopted to solve the eigenvalue problem which is obtained by eliminating nonlinear terms. Then, each eigenvector is normalized, and the nonlinear stiffness matrix is derived and the nonlinear free vibration analysis is carried out. A recursive procedure is adopted to proceed until the convergence criterion is satisfied. Finally, the applicability of the proposed formulation is provided with some examples and results are compared with those available in the literature.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/328660

Time-delay feedback control of a suspended cable driven by subharmonic and superharmonic resonance
CHAOS, SOLITONS AND FRACTALS
Autore/i: Peng, Jian; Li, Yanan; Li, Luxin; Lenci, Stefano; Sun, Hongxin
Classificazione: 1 Contributo su Rivista
Abstract: The longitudinal time-delay feedback control strategy is implemented to suppress the subharmonic and superharmonic responses of the suspended cable. Formulated based on the Hamilton variational principle and the longitudinal time-delay feedback strategy, the in -plane nonlinear differential equations for a suspended cable are formulated, and Galerkin method is utilized to transform the equations into delayed differential equations. By using the method of multiple scales, approximate solutions for the 1/2-subharmonic and second-order superharmonic resonance responses of the controlled suspended cable were derived. The effects of the time delay and control gain are obtained through numerical examples. The research results demonstrate that through the adjustment of control gain and time delay, resonance regions can be avoided, effectively suppressing large-amplitude vibrations in the suspended cable, thereby achieving favorable control performance.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/328661

Post-earthquake continuous dynamic monitoring of the twin belfries of the Cathedral of Santa Maria Annunziata of Camerino, Italy
Materials Research Proceedings
Autore/i: Standoli, G.; Clementi, F.; Gentile, C.; Lenci, S.
Editore: Association of American Publishers
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In this paper the results of over two years of continuous monitoring of the twin bell towers of the Cathedral of Camerino (Italy) are presented. The monitoring activity target is the evaluation of the dynamic behavior of the twin belfries after the damages occurred during the seismic events of 2016 and the application of fast securing. The experimental data are acquired in continuous using four triaxial MEMS accelerometers, two for each structure, on two opposite corners of the bell cells. Data processing is managed with an automatic system which elaborates the signals and executes Operational Modal Analysis to track the modal characteristics of the structures and their evolution in time. Correlation with environmental factors allows to discern the effect of climatic conditions on the variations of dynamics.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/313889

Application of digital image correlation to compression tests on tuff masonry panels strengthened by textile reinforced mortar
INTERNATIONAL JOURNAL OF MASONRY RESEARCH AND INNOVATION
Autore/i: Maracchini, G; Chiappini, G; Donnini, J; Quagliarini, E; Corinaldesi, V; Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: Digital image correlation (DIC) is a contactless full-field optical technique for measuring displacements that can be potentially used in place of more common linear variable differential transformers (LVDTs) to avoid instrumentation damage during destructive tests. However, despite being already adopted in several fields, its potentialities in testing full-scale masonry walls strengthened with textile reinforcing mortar (TRM) have not been fully investigated yet. In this paper, the results obtained by applying a stereo-DIC technique to compression tests of unstrengthened and TRM-strengthened tuff masonry walls (1.0 x 1.2 x 0.25 m(3)) are reported. Results showed that the presence of helical steel bars used to connect the two TRM layers caused crack localisation to the masonry wall, leading to a reduction of compression strength. Compared with the results obtained with LVDTs, the DIC technique was able to accurately monitor tridimensional displacements and cracking pattern evolution. The potentialities and limits of this technique are finally highlighted.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/320491

Dynamic identification and numerical model updating of an old bell-tower in Marche Region (Italy)
INTERNATIONAL JOURNAL OF MASONRY RESEARCH AND INNOVATION
Autore/i: Giordano, E; Ferrante, A; Salachoris, Gp; Schiavoni, M; Clementi, F; Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: In this paper, the dynamic characterisation of the civic bell-tower of Rotella (a small village in the Marche Region, Central Italy) is presented. The tower after being monitored, using four tri-axial piezo-electric accelerometers, and obtaining its dynamic characteristics, was modelled through a finite element software. The difference between measured and real values has been smoothed out by acting on all unknown parameters such as Young's moduli, thus obtaining a model with frequency differences, compared to reality, less than 5% and the MAC values between the modal shapes close to the unit.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/320492

Attractors' Analysis and Bifurcation Diagrams for an Impacting Inverted Pendulum in the Presence of a Two-Terms Harmonic Excitation
JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS
Autore/i: Petrini, Milena; Demeio, Lucio; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: In this work, we examine the nonlinear dynamics of an inverted pendulum between lateral rebounding barriers. We continue the numerical investigation started in (Demeio et al., 2006, “Response Scenario and Non-Smooth Features in the Nonlinear Dynamics of an Impacting Inverted Pendulum,” ASME J. Comput. Nonlin. Dyn., 1(1), pp. 56–64) by adding the contribution of the second harmonic in the external forcing term. We investigate the behavior of the periodic attractors by bifurcation diagrams with respect to each amplitude and by behavior charts of single attractors in the amplitude parameters plane for fixed frequency. We study the effects of the second harmonic term on the existence domain of each attractor, on local bifurcations, and on the changes in the basins of attraction. The behavior of some robust chaotic attractor is also considered. In the evolution of the periodic attractors we have observed that the addition of the second harmonic generates a rich variety of behaviors, such as loss of stability and formation of isolas of periodic orbits. In the case of chaotic attractors, we have studied one attractor at high frequency, ω = 18, and one at low frequency, ω = 3. In the high frequency case we detect a transition from a scattered to a confined attractor, whereas at the lower frequency the chaotic attractor is present over a wide range of the second harmonic's amplitude. Finally, we extend the investigation of the chaotic attractors by bifurcation diagrams with respect to the frequency.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/323111

Global analysis of stochastic and parametric uncertainty in nonlinear dynamical systems: adaptative phase-space discretization strategy, with application to Helmholtz oscillator
NONLINEAR DYNAMICS
Autore/i: Benedetti, Kcb; Goncalves, Pb; Lenci, S; Rega, G
Classificazione: 1 Contributo su Rivista
Abstract: An adaptative phase-space discretization strategy for the global analysis of stochastic nonlinear dynamical systems with competing attractors considering parameter uncertainty and noise is proposed. The strategy is based on the classical Ulam method. The appropriate transfer operators for a given dynamical system are derived and applied to obtain and refine the basins of attraction boundaries and attractors distributions. A review of the main concepts of parameter uncertainty and stochasticity from a global dynamics perspective is given, and the necessary modifications to the Ulam method are addressed. The stochastic basin of attraction definition here used replaces the usual basin concept. It quantifies the probability of the response associated with a given set of initial conditions to converge to a particular attractor. The phase-space dimension is augmented to include the extra dimensions associated with the parameter space for the case of parameter uncertainty, being a function of the number of uncertain parameters. The expanded space is discretized, resulting in a collection of transfer operators that enable obtaining the required statistics. A Monte Carlo procedure is conducted for the stochastic case to construct the proper transfer operator. An archetypal nonlinear oscillator with noise and uncertainty is investigated in-depth through the proposed strategy, showing significative computational cost reduction.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/320472

Unveiling the complexity of twin church bells dynamics using ambient vibration tests
INTERNATIONAL JOURNAL OF MASONRY RESEARCH AND INNOVATION
Autore/i: Ferrante, A.; Giordano, E.; Standoli, G.; Bianconi, F.; Clementi, F.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: On the Italian territory, many monumental structures need to be preserved. Given their great historical and architectural value, it is essential to use minimally invasive, but effective, techniques able to evaluate their current structural capabilities and monitor their structural health. The technique that currently appears most appropriate is the ambient vibration monitoring, which, through the analysis of recorded accelerometric time-histories in operating conditions, returns the current dynamic properties of the structure. This work shows the results of the short-term monitoring carried out on the two towers of the San Francesco Church, located in the city of Ascoli Piceno. Modal identification allowed obtaining its frequencies, modal shapes, and damping. With these data, the finite element model of the complex was calibrated, acting on the elastic parameters of the masonry, making numerical modal shapes and frequencies match with the experimental results.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/320831

WAVE PROPAGATION ON A STRING RESTING ON A GENERAL NONLINEAR SUBSTRATE
SIAM JOURNAL ON APPLIED MATHEMATICS
Autore/i: Demeio, L; Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: Traveling waves propagating on a taut cable resting on an elastic substrate are in-vestigated by an equivalent mechanical model based on the classical Klein-Gordon equation. The formulation is devised for an elastic response of generally arbitrary shape, and permits one to compute the propagation wave velocity without solving the equation of motion, thus providing a unified the-oretical framework for a large class of response functions, linear or nonlinear, smooth or nonsmooth. The general solution is then applied to the cases of a general polynomial substrate, a bilinear sub-strate, a bilinear substrate with a cubic correction, and a negative linear stiffness substrate, all of them falling within the realm of nonsmooth systems when a piecewise continuous stiffness is chosen; in the second one, we recover results present in the literature and obtained by employing a method based on matching conditions, which are spared in the approach used in this paper. Finally, the application to the sine-Gordon equation is considered.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/320232

Novel Sustainable Masonry from Ancient Construction Techniques by Reusing Waste Modern Tiles
SUSTAINABILITY
Autore/i: Quagliarini, Enrico; Carosi, Marta; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: The recycling and reuse of wastes, especially Construction Waste (CW), is a fundamental way for sustainability. The act of reusing is not a modern practice; as early as in Ancient Rome and even more during the Middle Ages, materials were already being taken from existing buildings in order to reuse them in different ways. Starting from these general considerations and taking inspiration from specific construction techniques found in some Roman and Romanesque masonries made by unbroken tiles and tile fragments, two novel sustainable masonry constructive techniques are proposed here. They are composed of modern U-shaped tiles and their fragments so as to use CW. Monotonic and cyclic compression tests were performed so as to determine their main mechanical characteristics, such as compressive strength, Young's modulus, and failure mode, and a first attempt at establishing their possible use in the construction sector is sought. A comparison with the literature values from other constructive techniques with similar values was also performed. It results that both the wall typologies showed satisfactory mechanical properties (i.e., compressive strengths are in the range of 1.28 divided by 2.27 MPa), provided that their use is restricted for constructions of moderate dimensions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/327935

Parameter uncertainty and noise effects on the global dynamics of an electrically actuated microarch
JOURNAL OF MICROMECHANICS AND MICROENGINEERING
Autore/i: Benedetti, Kcb; Goncalves, Pb; Lenci, S; Rega, G
Classificazione: 1 Contributo su Rivista
Abstract: This work aims to study the effect of uncertainties and noise on the nonlinear global dynamics of a micro-electro-mechanical arch obtained from an imperfect microbeam under an axial load and electric excitation. An adaptative phase-space discretization strategy based on an operator approach is proposed. The Ulam method, a classical discretization of flows in phase-space, is extended here to nondeterministic cases. A unified description is formulated based on the Perron-Frobenius, Koopman, and Foias linear operators. Also, a procedure to obtain global structures in the mean sense of systems with parametric uncertainties is presented. The stochastic basins of attraction and attractors' distributions replace the usual basin and attractor concepts. For parameter uncertainty cases, the phase-space is augmented with the corresponding probability space. The microarch is assumed to be shallow and modeled using a nonlinear Bernoulli-Euler beam theory and is discretized by the Galerkin method using as interpolating function the linear vibration modes. Then, from the discretized multi degree of freedom model model, an accurate single degree of freedom reduced order model, based on theory of nonlinear normal modes, is derived. Several competing attractors are observed, leading to different (acceptable or unacceptable) behaviors. Extensive numerical simulations are performed to investigate the effect of noise and uncertainties on the coexisting basins of attraction, attractors' distributions, and basins boundaries. The appearance and disappearance of attractors and stochastic bifurcation are observed, and the time-dependency of stochastic responses is demonstrated, with long-transients influencing global behavior. To consider uncertainties and noise in design, a dynamic integrity measure is proposed via curves of constant probability, which give quantitative information about the changes in structural safety. For each attractor, the basin robustness as a function of a stochastic parameter is investigated. The weighted basin area can quantify the integrity of nondeterministic cases, being also the most natural generalization of the global integrity measure. While referring to particular micro-electro-mechanical system, the relevance of the dynamical integrity analysis for stochastic systems to quantify tolerances and safety margins is underlined here.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/317971

Stapes vibrations induced by piezoelectric floating mass transducer
JOURNAL OF SOUND AND VIBRATION
Autore/i: Rusinek, R; Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: The paper presents a problem of nonlinear vibrations in the human middle ear stimulated by a piezoelectric floating mass transducer. The transducer is connected to the malleus by means of a coupler that is nonlinear. This nonlinearity together with the transducer has a key meaning for the middle ear behaviour because the improved model of piezoelectric transducer is used compared to previous papers. Nonlinear coupler stiffness and the applied voltage to the transducer produce a change of middle ear natural frequency. Moreover, a bistability effect of periodic solution and irregular vibrations are observed as well. The chaotic motion can exist in the hearing range that is especially harmful for patients who use implants with piezoelectric floating mass transducer.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/311548

Piecewise integrable neural network: An interpretable chaos identification framework
CHAOS
Autore/i: Novelli, N.; Belardinelli, P.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/311975

Non-Smooth Dynamics of Tapping Mode Atomic Force Microscopy
JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS
Autore/i: Belardinelli, P; Chandrashekar, A; Alijani, F; Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: This study examines the nonlinear dynamics in tapping-mode atomic force microscopy (AFM) with tip-surface interactions that include van der Waals and Derjaguin-Muller-Toporov contact forces. We investigate the periodic solutions of the hybrid system by performing numerical pseudo-arclength continuation. Through the use of bifurcation locus maps in the set of parameters of the discontinuous model, the overall dynamical response scenario is assessed. We demonstrate the influence of various dissipation mechanisms that are related with the AFM touching or lacking contact with the sample. Local and global analyses are used to investigate the stability of the stable solution in the repulsive regime. The impacting nonsmooth dynamics framed within a higher-mode Galerkin discretization is able to capture windows of irregular and complex motion.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/320233

Optimization of the closed-loop controller of a discontinuous capsule drive using a neural network
MECCANICA
Autore/i: Zarychta, S; Balcerzak, M; Denysenko, V; Stefanski, A; Dabrowski, A; Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: In this paper the construction of a neural-network based closed-loop control of a discontinuous capsule drive is analyzed. The foundation of the designed controller is an optimized open-loop control function. A neural network is used to determine the dependence between the output of the open-loop controller and the state of the system. Robustness of the neural controller with respect to variation of parameters of the controlled system is analyzed and compared with the original optimized open-loop control. It is expected that the presented method can facilitate the construction of closed-loop controllers for which alternative methods are not effective, such as non-smooth or discontinuous ones.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/314099

An asymptotic approach for large amplitude motions of generic nonlinear systems
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
Autore/i: Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: Starting from the observation that classical asymptotic methods fail to correctly describe the resonance peak of the frequency response curve of a nonlinear oscillator under moderate and large excitation amplitudes, an alternative approach is proposed to overcome this problem. The differences between the multiple time scale method (one of the most performant classical methods) and numerical simulations are initially shown with reference to on the paradigmatic Duffing equation. They are also shown some characteristics of the near peak behavior. Then, the proposed asymptotic approach is illustrated. The basic idea is that of having the zero-order problem nonlinear, while in classical methods it is linear. Thanks to the energy conservation, the zero-order problem is solved exactly. Also, the exact solution of the higher-order problems is obtained in closed-form, thus providing a fully analytical approach. Although the proposed method is valid for any kind of motion, special attention is dedicated to periodic nonlinear oscillations, because of their interest in practical applications. A simple formula for determining the exact intersection of the frequency response and backbone curves is obtained, and it is shown that it can be computed without the need of solving explicitly not even the zero-order problem. Some illustrative examples are finally reported.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/322052

Suppression of overshoots and undershoots in nonlinear structural and mechanical systems
ACTA MECHANICA
Autore/i: Lenci, S; Udwadia, Fe
Classificazione: 1 Contributo su Rivista
Abstract: In this work, we consider the problem of having a transit in a nonlinear SDOF system from a given rest position to another one, both associated to given and constant values of the external force, without spurious undershoots or overshoots of the solution after the final state is reached. It extends to the nonlinear regime the same problem considered in Udwadia (Acta Mech 231:3157-3182, 2020) in the linear realm. Two different approaches are considered. In the first, which is the more general, the free dynamics of the nonlinear system is not considered, and a very simple solution is obtained, showing how it is robust with respect to perturbations. In the second case, on the other hand, the free dynamics of the system is exploited during the transits, thereby allowing less control parameters to be determined. However, aiming at having a closed form solution, we limit this study to the Duffing equation, although the ideas are general and can be applied to other systems even when closed form solutions are not available.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/309788

Along-wind and cross-wind coupled nonlinear oscillations of wind turbine towers close to 1:1 internal resonance
RENEWABLE & SUSTAINABLE ENERGY REVIEWS
Autore/i: Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: An approximate analytical solution is obtained to detect the along-wind and cross-wind coupled oscillations of wind turbine towers, in the neighbourhood of a 1:1 internal resonance. The obtained formulas are general, and they are applied to the NREL 5-MW reference wind turbine. It is shown that the coupled solution is branched (by a pitchfork bifurcation) from the main uncoupled along-wind oscillation. The coupled motion is initially stable, but for increasing excitation amplitudes it becomes unstable in favour of quasi-periodic solutions, a fact that is particularly dangerous from a practical point of view and so must be avoided. The critical threshold is determined for varying excitation amplitude, and the analytical solution is checked by means of numerical simulations.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/327091

An operator methodology for the global dynamic analysis of stochastic nonlinear systems
THEORETICAL & APPLIED MECHANICS LETTERS
Autore/i: Benedetti, Kcb; Goncalves, Pb; Lenci, S; Rega, G
Classificazione: 1 Contributo su Rivista
Abstract: In a global dynamic analysis, the coexisting attractors and their basins are the main tools to understand the system behavior and safety. However, both basins and attractors can be drastically influenced by uncertainties. The aim of this work is to illustrate a methodology for the global dynamic analysis of nondeterministic dynamical systems with competing attractors. Accordingly, analytical and numerical tools for calculation of nondeterministic global structures, namely attractors and basins, are proposed. First, based on the definition of the Perron-Frobenius, Koopman and Foias linear operators, a global dynamic description through phase-space operators is presented for both deterministic and nondeterministic cases. In this context, the stochastic basins of attraction and attractors' distributions replace the usual basin and attractor concepts. Then, numerical implementation of these concepts is accomplished via an adaptative phase-space discretization strategy based on the classical Ulam method. Sample results of the methodology are presented for a canonical dynamical system.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/320471

Fractional damping effects on the transient dynamics of the Duffing oscillator
COMMUNICATIONS IN NONLINEAR SCIENCE & NUMERICAL SIMULATION
Autore/i: Coccolo, M; Seoane, Jm; Lenci, S; Sanjuan, Maf
Classificazione: 1 Contributo su Rivista
Abstract: We consider the nonlinear Duffing oscillator in presence of fractional damping which is characteristic in different physical situations. The system is studied with a smaller and larger damping parameter value, that we call the underdamped and overdamped regimes. In both we have studied the relation between the fractional parameter, the amplitude of the oscillations and the times to reach the asymptotic behavior, called asymptotic times. In the overdamped regime, the study shows that, also here, there are oscillations for fractional order derivatives and their amplitudes and asymptotic times can suddenly change for small variations of the fractional parameter. In addition, in this latter regime, a resonant-like behavior can take place for suitable values of the parameters of the system. These results are corroborated by calculating the corresponding Q-factor. We expect that these results can be useful for a better understanding of fractional dynamics and its possible applications as in modeling different kind of materials that normally need complicated damping terms. (c) 2022 Elsevier B.V. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/309789

Exact solutions for coupled Duffing oscillators
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
Autore/i: Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: The exact analytical solution of a system made of two coupled Duffing oscillators is obtained. The mathematical solution is illustrated by means of some examples aimed at showing the dynamical phenomena occurring in the considered system. Frequency response curves are reported for different value of the parameters, highlighting the effects of the linear and nonlinear coupling between the two variables. The presence of various solution branches, up to four coexisting attractors, is reported.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/294621

Seismic Assessment of a Masonry Structure Damaged by Central Italy Earthquake
AIP Conference Proceedings - International Conference on Numerical Analysis and Applied Mathematics 2020, ICNAAM 2020
Autore/i: Giordano, E.; Ferrante, A.; Clementi, F.; Lenci, S.
Editore: American Institute of Physics Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The present work shows the seismic vulnerability analysis of a building located in Matelica, a village that has reported extensive damages, especially to the monumental historical structures, after the Central Italy Earthquakes. The building is studied with local and global analysis, these last are performed using accurate 3D Finite Element Models where the post-elastic behavior of masonry is considered by the Total Strain Crack Model. The study showed as the use of non-linear static analysis, in addition to be useful to evaluate the seismic capacity, can reproduce with good approximation the cracks provoke by the quakes. After the estimation of actual capacity, the improvement of a seismic retrofitting intervention is evaluated
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/300364

SHEAR AND THERMO-HYGROMETRIC PERFORMANCE OF STRUCTURAL INSULATED PANELS COMPRISING EPS CORE AND OSB SKINS
CESARE Conference Publications
Autore/i: Serpilli, M.; Stazi, F.; Lenci, S.; Di Perna, C.
Editore: Jordan University of Science and Technology
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In the last decades, the need for improved thermal-structural integrated solutions for building construction has prompt towards the development of Structural Insulated Panels (SIPs), a cost-effective wall system capable of transferring shear loads among panel layers and minimizing localized heat loss This study explored both mechanical and thermal behaviour of SIPs, composed by an Expanded Polystyrene (EPS) core within two oriented strand board (OSB) sheets. Six panels (1200x1200x170mm3) were tested under in-plane horizontal load in two configurations: (i) three single SIP wall; (ii) three double SIPs wall, joined together with a block spline and metal connections. Both specimens were anchored to a lower steel metal beam through anchor bolts and hold-downs. Moreover, the panels were characterized as regard the steady-state thermal behaviour. The study demonstrated that this wall system is a viable solution for sustainable buildings since it presents high shear strength, elevated ductility and good thermal-hygrometric performance.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/304919

Boosting the Model Discovery of Hybrid Dynamical Systems in an Informed Sparse Regression Approach
JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS
Autore/i: Novelli, Nico; Lenci, Stefano; Belardinelli, Pierpaolo
Classificazione: 1 Contributo su Rivista
Abstract: We present an efficient data-driven sparse identification of dynamical systems. The work aims at reconstructing the different sets of governing equations and identifying discontinuity surfaces in hybrid systems when the number of discontinuities is known a priori. In a two-stage approach, we first locate the switches between separate vector fields. Then, the dynamics among the manifolds are regressed, in this case by making use of the existing algorithm of Brunton et al. (2016, "Discovering Governing Equations From Data by Sparse Identification of Nonlinear Dynamical Systems," Proc. Natl. Acad. Sci., 113(15), pp. 3932-3937). The reconstruction of the discontinuity surfaces comes as the outcome of a statistical analysis implemented via symbolic regression with small clusters (microclusters) and a rigid library of models. These allow to classify all the feasible discontinuities that are clustered and to reduce them into the actual discontinuity surfaces. The performances of the sparse regression hybrid model discovery are tested on two numerical examples, namely, a canonical spring-mass hopper and a free/impact electromagnetic energy harvester (FIEH), engineering archetypes characterized by the presence of a single and double discontinuity, respectively. Results show that a supervised approach, i.e., where the number of discontinuities is pre-assigned, is computationally efficient and it determines accurately both discontinuities and set of governing equations. A large improvement in the time of computation is found with the maximum achievable reliability. Informed regression-based identification offers the prospect to outperform existing data-driven identification approaches for hybrid systems at the expense of instructing the algorithm for expected discontinuities.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/311547

Machine learning to probe modal interaction in dynamic atomic force microscopy
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
Autore/i: Belardinelli, P.; Chandrashekar, A.; Wiebe, R.; Alijani, F.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/305780

A discussion regarding reduced-order modelling of inclined elastic and immersed cables under support excitation
INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS
Autore/i: Vernizzi, G. J.; Lenci, S.; Franzini, G. R.
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/304861

Periodic traveling waves in a taut cable on a bilinear elastic substrate
APPLIED MATHEMATICAL MODELLING
Autore/i: Demeio, L; Lenci, S
Classificazione: 1 Contributo su Rivista
Abstract: The wave propagation problem in a second-order nonlinear PDE, with specific reference to a mechanical system consisting of a taut cable, or string, resting on a piecewise linear foundation is investigated, without and with a distribute transversal load. The piecewise nature of the problem offers a sufficiently simple kind of nonlinearity as to permit a closed form solution both for the wave phase velocity and the wave form. We show that the solution depends only on the ratio between the two soil stiffnesses, and that no waves propagate if one side of the substrate is rigid. Some numerical simulations, based on a finite difference method, are performed to confirm the analytical findings. The stability of the proposed waves is discussed theoretically and numerically, also by using return maps in phase space. (C) 2022 Elsevier Inc. All rights reserved.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/306040

Post-earthquake continuous dynamic monitoring of the twin belfries of the Cathedral of Santa Maria Annunziata of Camerino, Italy
Procedia Structural Integrity
Autore/i: Standoli, G.; Clementi, F.; Gentile, C.; Lenci, S.
Editore: Elsevier B.V.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In this paper the results of over two years of continuous monitoring of the twin bell towers of the Cathedral of Camerino (Italy) are presented. The monitoring activity target is the evaluation of the dynamic behavior of the twin belfries after the damages occurred during the seismic events of 2016 and the application of fast securing. The experimental data are acquired in continuous using four triaxial MEMS accelerometers, two for each structure, on two opposite corners of the bell cells. Data processing is managed with an automatic system which elaborates the signals and executes Operational Modal Analysis to track the modal characteristics of the structures and their evolution in time. Correlation with environmental factors allows to discern the effect of climatic conditions on the variations of dynamics.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/325052

On the Dynamics of a Biomimetic Model of a Sympodial Tree: From Bifurcations Diagrams and 6D Basins of Attraction to Dynamical Integrity and Robustness
JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS
Autore/i: Andonovski, N.; Kovacic, I.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: This work is concerned with a mechanical model of a sympodial tree with first-level branches, which has been shown to exhibit certain properties potentially suitable for biomimetic applications. To investigate these potential benefits further from the viewpoint of the system nonlinear behavior under external periodic excitation, modern numerical tools related to the concept of dynamical integrity are either adjusted or newly developed for this system for the first time. First, multistable regions of interest are isolated from bifurcation diagrams and the effect of damping is investigated. Then, in order to obtain the corresponding basins of attraction of this highly dimensional model, an original computational procedure is developed that includes cell mapping with 406 cells, where each cell represents an initial condition required to construct the map. Full 6D basins are computed, and they are reported for various values of the damping parameter and the excitation frequency. Those basins are then used to calculate the dynamic integrity factors so that the dominant steady-state can be determined. Finally, the integrity profiles are reported to illustrate how the robustness varies by changing the system parameters.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/294622

Flexural-flexural internal resonances 3:1 in initially straight, extensible Timoshenko beams with an axial spring
JOURNAL OF SOUND AND VIBRATION
Autore/i: Kloda, Lukasz; Lenci, Stefano; Warminski, Jerzy; Szmit, Zofia
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/304821

Natural Frequencies And Internal Resonance Of Beams With Arbitrarily Distributed Axial Loads
JOURNAL OF APPLIED AND COMPUTATIONAL MECHANICS
Autore/i: Lenci, S.; Clementi, F.
Classificazione: 1 Contributo su Rivista
Abstract: An exact analytical solution for transversal free vibrations of a beam subjected to an arbitrary distributed axial load and a tip tension is obtained by means of a power series representation, whose coefficients are determined recursively in an easy way. The dependence on the natural frequencies on the load is then investigated, and the buckling load (corresponding to vanishing frequency) is also discussed. Next, the 1:3 internal resonance between the first and the second mode is deeply studied, and an interesting (and unexpected) property is found for linearly distributed axial loads
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/291395

Mode Coupling in Dynamic Atomic Force Microscopy
PHYSICAL REVIEW APPLIED
Autore/i: Chandrashekar, A.; Belardinelli, P.; Lenci, S.; Staufer, U.; Alijani, F.
Classificazione: 1 Contributo su Rivista
Abstract: Increasing the signal-to-noise ratio in dynamic atomic force microscopy plays a key role in nanomechanical mapping of materials with atomic resolution. In this work, we develop an experimental procedure for increasing the sensitivity of higher harmonics of an atomic-force-microscope cantilever without modifying the cantilever geometry but instead by utilizing dynamical mode coupling between its flexural modes of vibration. We perform experiments on different cantilevers and samples and observe that via nonlinear resonance frequency tuning we can obtain a frequency range where strong modal interactions lead to 7-fold and 16-fold increases in the sensitivity of the 6th and 17th harmonics while reducing sample indentation. We derive a numerical model that captures the observed physics and confirms that nonlinear mode coupling is the reason for the increase of the amplitude of higher harmonics during tip-sample interactions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/288570

Propagation of periodic waves in beams on a bilinear foundation
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
Autore/i: Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: The propagation of periodic flexural waves in an Euler-Bernoulli beam resting on a bilinear elastic foundation is investigated. Although the problem is nonlinear, the closed form solution is obtained thanks to its piecewise linear nature. The dependence of the phase velocity on the two stiffnesses of the substrated is investigated in depth, and it is shown that a very complex behaviour is observed when the stiffnesses are large. Veering-like phenomena has been discovered, apparently for the first time. It is shown that some branches end with cusp points, not related to classical bifurcations. The stability of the considered waves is also addressed, in a restricted class of perturbations.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/292564

Continuous and discontinuous descriptions of blocked structures: The case study of Santissimo Crocifisso Church in Pretare (Italy)
COMPDYN Proceedings
Autore/i: Clementi, F.; Ferrante, A.; Giordano, E.; Lenci, S.
Editore: National Technical University of Athens
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Advanced numerical modelling of the masonry “Apennine Church” of Santissimo Crocifisso in Pretare, Arquata del Tronto (AP), was here utilized to have an insight into the dynamic properties and behavior of the structure under strong nonlinear dynamic excitations. The objectives were achieved by comparing nonlinear dynamic analyses through discontinuous and continuous approaches. In the discrete element approach, the Non-Smooth Contact Dynamics method, implemented in LMGC90©, was applied, adopting a full 3D detailed discretization. The Church was schematized as an arrangement of discrete rigid blocks, subjected to sliding by friction and perfect plastic collisions, governed by Signorini's impenetrability condition and dry-friction Coulomb's law, with a null restitution coefficient. In the finite element approach, the Concrete Damaged Plasticity model available in Midas FEA NX© was involved. This model allows reproducing the tensile cracking, the compressive crushing, and the degradation of the material under cyclic loads. At the end, the structure exhibited a complex dynamic behavior, because of the geometrical nonlinearity and the non-smooth nature of the contact laws. Finally, the numerical analyses provided a valuable picture of the actual behavior of the church, which is mandatory for future strengthening interventions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/293922

Time-delay dynamics of the MR damper–cable system with one-to-one internal resonances
NONLINEAR DYNAMICS
Autore/i: Peng, J.; Wang, L.; Zhao, Y.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: In this study, we investigate the nonlinear resonant response of a magnetorheological (MR) damper–stay cable system with time delay, and the one-to-one internal resonance is considered. Based on Hamilton’s principle, the motion equations of the MR damper–cable system are derived, and the Galerkin method is applied to obtain the discrete model. Then, the method of multiple scales is applied to determine the modulation equations and the second-order solution of the nonlinear response of the MR damper–cable system. Following, the equilibrium solution and dynamic solution of the modulation equations are examined via the Newton–Raphson method and shooting method. The results show that the equilibrium solution may undergo Hopf bifurcation, resulting in the periodic solution. Moreover, the effects of the time delay and the inclination angle on the resonant response of the MR damper–cable system are investigated as well as those of the damper position. The numerical results show that the time delay increases the amplitudes of in-plane and out-of-plane modes and results in the more remarkable hardening behavior and relatively poor mitigation performance of the MR damper. However, the large time delay may suppress the complex chaotic modulation motion of the MR damper–cable system.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/291396

Earthen claddings in lightweight timber framed buildings: An experimental study on the influence of fir boards sheathing and GFRP jacketing
CONSTRUCTION AND BUILDING MATERIALS
Autore/i: Serpilli, M.; Stazi, F.; Chiappini, G.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: The aim of this research was to investigate the mechanical performance of an earthen massive cladding, recently used for external/internal layers in Platform Frame technology, through an extensive experimental campaign. The masonry is built with extruded unbaked earth blocks and characterized by dovetail horizontally staggered bed joints. The wall is secured to the structural timber studs through 45 degree-angled fir boards sheathing panels, fixed with steel connectors, and finished with an external plaster with an embedded Glass Fibre Reinforced Polymer (GFRP) mesh, wrapping the whole masonry. The influence of the fir board panels and GFRP jacketing on the mechanical behavior of the earth blocks masonry is investigated and compared with the results obtained for the unreinforced configuration (bare wallettes) in (Stazi et al., 2020). The experimental program consisted of compression, diagonal compression and combined shear-compression tests on 18 wallettes. Digital Image Correlation technique was also adopted to investigate the full field strain maps. The results showed that under compression all the samples (with and without reinforcements) behave as a series of independent slender columns, without significant differences among reinforcement type. Both diagonal compression and shear with compression tests revealed the optimal behavior of GFRP plaster reinforcement that increases the strength values and thanks to an effective confinement effect, limits the out-of-plane bending and determines a monolithic response of the wall.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/288772

An experimental and numerical study on the in-plane axial and shear behavior of sprayed in-situ concrete sandwich panels
ENGINEERING STRUCTURES
Autore/i: Serpilli, Michele; Clementi, Francesco; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: The pa­per deals with the ex­per­i­men­tal and nu­mer­i­cal char­ac­ter­i­za­tion of the in-plane ax­ial and shear me­chan­i­cal be­hav­ior of sprayed in-situ re­in­forced con­crete (RC) sand­wich pan­els, used as struc­tural walls. Ax­ial com­pres­sion tests were car­ried out on spec­i­mens with dif­fer­ent slen­der­ness ra­tios to study their be­hav­ior un­der ax­ial ver­ti­cal loads. While the di­ag­o­nal com­pres­sion test and shear load with con­stant com­pres­sion test were re­spec­tively per­formed on squared pan­els, an­a­lyz­ing their re­sponse to in-plane hor­i­zon­tal lat­eral forces. Ul­ti­mate ax­ial and shear loads have been ex­per­i­men­tally de­ter­mined and the most sig­nif­i­cant load–dis­place­ment di­a­grams have been re­ported. The ob­tained re­sults have been com­pared with other ex­per­i­men­tal cam­paigns on RC sand­wich pan­els and with con­ven­tional RC walls equa­tions, avail­able in codes of prac­tice and lit­er­a­ture. The struc­tural po­ten­tial­i­ties of RC sand­wich pan­els as load-bear­ing and shear walls are high­lighted. The ex­per­i­men­tal in­ves­ti­ga­tion is cor­rob­o­rated by a 3D non­lin­ear fi­nite el­e­ment (FE) nu­mer­i­cal analy­sis, con­sid­er­ing the in­flu­ence of the in­su­la­tion layer, the ef­fi­ciency of steel con­nec­tors, and the in­volved ma­te­r­ial non­lin­ear­i­ties.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287329

Size-dependent response of electrically pre-deformed micro-plates under mechanical shock incorporating the effect of packaging, a frequency-domain analysis
JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING
Autore/i: Askari, A. R.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: Complementing the time-history solution by the frequency-domain analysis can provide a better understanding of micro-structures dynamics. Nevertheless, there exist no research studies in the literature dealing with the dynamics of plate-type MEMS undergoing mechanical shock via the frequency-domain analysis. Therefore, the main object of the present work is to introduce a frequency-domain analysis for predicting the size-dependent behavior of packaged plate-type MEMS experiencing shock environments. To this end, employing the Hamilton principle, the coupled governing equations of motion are obtained based on the modified couple stress geometric nonlinear thin plate theory and reduced to a system of initial value problems utilizing the Galerkin weighted residual method. The accuracy of the present model is validated by available results in the literature as well as those obtained through three-dimensional finite element simulations performed in COMSOL Multiphysics commercial software. The behaviors of the micro-plate and its package under mechanical shock are then investigated through the use of the linear shock spectrum together with the backbone curves of the system for the first time. Employing this approach, the critical shock durations, at which the influence of mechanical shock becomes extreme, as well as the internal resonances of the system, are obtained. The results reveal that decreasing the shock duration does not increase the influence of mechanical shock all the time. In addition, it is found that the occurrence of the one-to-one internal resonance, which can drastically increase the micro-plate deflections and provide an unexpected pull-in behavior, is not possible except for cases with very small micro-plate to package mass ratios. Furthermore, it is observed that the occurrence of the one-to-three internal resonance cannot put the micro-plate into a dangerous situation.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287330

Discontinuous approaches for nonlinear dynamic analyses of an ancient masonry tower
ENGINEERING STRUCTURES
Autore/i: Ferrante, A.; Loverdos, D.; Clementi, F.; Milani, G.; Formisano, A.; Lenci, S.; Sarhosis, V.
Classificazione: 1 Contributo su Rivista
Abstract: The aim of this paper is to present the development of discontinuous approaches to simulate the nonlinear dynamic behaviour of the civic clock tower of Rotella, in the province of Ascoli Piceno (Italy). The study involves the use of the Non-Smooth Contact Dynamics method implemented in the LMGC90© code, where sliding motions are governed by Signorini's impenetrability condition and dry-friction Coulomb's law, and the Discrete Element Method with cohesive and tensional behaviours at the joints in the 3DEC© code. The tower was represented using three different geometric models ranged from the most complex one, including the full geometry and multi-leaf masonry walls, to the simplest one, including the single-leaf walls as a simplification of the real masonry. The numerical results highlighted the modes of failure depending on the shape, size and texture of the masonry and the modalities of progressive damage under dynamic actions. Moreover, both numerical approaches have proven to be capable of simulating large displacements and complete block separations, reproducing complex mechanical behaviours and making predictions on the vulnerability assessment of the historical masonry buildings.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/286753

TRM reinforced tuff and fired clay brick masonry: Experimental and analytical investigation on their in-plane and out-of-plane behavior
CONSTRUCTION AND BUILDING MATERIALS
Autore/i: Donnini, J.; Maracchini, G.; Lenci, S.; Corinaldesi, V.; Quagliarini, E.
Classificazione: 1 Contributo su Rivista
Abstract: The paper presents the results of an experimental campaign aimed at investigating the in-plane and out-of-plane behavior of tuff and fired clay brick masonry panels reinforced by a commercial, not yet tested, Textile Reinforced Mortar (TRM) system. The TRM, consisting of hydraulic lime mortar coupled with a bidirectional glass fabric (total thickness of 30 mm), was applied on both sides of the panels and connected through stainless-steel helical bars. First, a mechanical characterization of the TRM system was carried out, according to recent guidelines (AC434 and CNR-DT215) by means of tensile tests and single-shear bond tests on the two different substrates. Then, the effectiveness of the reinforcement was investigated through uniaxial compression, diagonal compression and three-point bending tests on masonry panels. After that, experimental results were compared to the predictions of recent guidelines and analytical models available in the literature, by using the mechanical parameters obtained from the TRM mechanical characterization. TRM showed to be very effective in increasing the in-plane shear strength of tuff panels, of about 170%, whereas in the case of fired clay brick ones the increase was limited to 33%. Besides, the diagonal compression strength of reinforced specimens seemed to be strongly influenced by the mortar matrix, instead of by the fabric reinforcement, as it usually happens i.e. for Fabric Reinforced Cementitious Matrix (FRCM) systems. Thus, novel simplified analytical formulations to predict the shear strength of reinforced panels by only considering the contribution of the TRM matrix were provided, discussed and compared to current analytical approaches for FRCM systems. As regards the out-of-plane behavior, the TRM system significantly increased the out-of-plane bending strength and ductility of both tuff and fired clay brick panels. The applicability of current analytical approaches, as well as possible amendments, was also investigated. Finally, the compressive behavior of the walls was not substantially modified by the reinforcement, reasonably due to the low axial stiffness of the connectors and, to a minor extent, because they were dry inserted within the masonry and simply folded over the glass fabric.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287962

A Preliminary Validation of a New Surgical Procedure for the Treatment of Primary Bladder Neck Obstruction Using a Computational Modeling Approach
BIOENGINEERING
Autore/i: Serpilli, Michele; Zitti, Gianluca; Dellabella, Marco; Castellani, Daniele; Maranesi, Elvira; Morettini, Micaela; Lenci, Stefano; Burattini, Laura
Classificazione: 1 Contributo su Rivista
Abstract: A new surgical procedure for the treatment of primary bladder neck obstruction with maintenance of anterograde ejaculation is proposed. In place of monolateral or bilateral bladder neck incision, associated with a loss of ejaculation rate of up to 30%, the new surgical procedure consists of laser drilling the bladder neck with a number of holes and without muscle fiber disrup- tion. The effect of this novel procedure has been studied numerically, with a simplified two-dimen- sional numerical model of the internal urethral sphincter, varying the position and the number of holes in the fibrotic region of the urethral tissue. Results show an improvement of the urethral sphincter opening by increasing the number of holes, ranging from about 6% to 16% of recovery. Moreover, a non-aligned position of holes positively influences the opening recovery. The concen- trations of maximum principal strain and stress have been registered in the proximity of the inter- face between the physiologic and diseased sphincter, and in those regions where the radial thick- ness is significantly thinner. The effects on the first five patients have been included in the study, showing improvement in micturition, lower urinary tract symptoms, sustained ejaculatory func- tion, and quality of life.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/290912

Nonlinear vibrations of a composite beam in large displacements: Analytical, numerical, and experimental approaches
JOURNAL OF COMPUTATIONAL AND NONLINEAR DYNAMICS
Autore/i: Utzeri, M.; Sasso, M.; Chiappini, G.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: This paper investigates the nonlinear dynamic behavior of a cantilever beam made of composite material without and with lumped mass fixed along its length. The analysis compares the results coming from analytical and numerical modeling with experimental observations. The first part focuses on the analytical model. The model takes into account the nonlinearity derived from large amplitude vibration and inertia. The second part deals with the experimental test, where the specimen and the data acquisition are defined. Then, the nonlinearity of the acquired data is determined by the fitting time history (FTH) technique. The third part deals with the finite element model. Finally, the results obtained by the analytical method, the experimental method, and the numerical method are compared between each other.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/286637

Modelling of low-velocity impacts on composite beams in large displacement
FRATTURA E INTEGRITÀ STRUTTURALE
Autore/i: Utzeri, M.; Sasso, M.; Chiappini, G.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: The paper provides an evaluation of the nonlinear dynamic response of a cantilever beam made of composite material subjected to low-velocity impacts. The structure is assumed to respond in a quasi-static manner and modelled by a continuous beam in large displacement with a lumped mass attached. First, an analytical model was developed to study the free vibrations of a beam, taking into account the nonlinearities due to large displacements and inertia. Then, the analytical findings were compared with experimental test data. The vibration of a real composite beam has been acquired through high-speed imaging technique. The displacements of the beam were extracted by digital image analysis; then, the nonlinear parameters of the analytical model were determined by the Fitting Time History technique. The results obtained by the analytical model and the experimental test are compared with numerical analysis. The validated analytical model was adapted to study a low-velocity impact; the lumped mass was associated with a rigid projectile, whose initial speed represents the impact velocity.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/293482

Boosting the Model Discovery of Hybrid Dynamical Systems in an Informed Sparse Regression Approach
Volume 9: 17th International Conference on Multibody Systems, Nonlinear Dynamics, and Control (MSNDC)
Autore/i: Novelli, Nico; Lenci, Stefano; Belardinelli, Pierpaolo
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/299086

Miglioramento sismico della scuola “Puccini” in Senigallia. Dalla diagnosi all’intervento
MODULO
Autore/i: Quagliarini, E; Lenci, S; Clementi, F; Maracchini, G; Monni, F
Classificazione: 1 Contributo su Rivista
Abstract: Questo articolo riporta l'esperienza dell'intervento progettato ed eseguito sull'edificio scolastico "Puccini" in Seni­gallia, il quale presenta caratteristiche architettoniche e vulnerabilità sismiche tipiche di edifici scolastici costruiti in I­talia nel secondo dopoguerra. La scuola, insieme ad altre localizzate sempre nel Comune di Senigallia, ed aventi carat­teristiche simili a livello di materiali e tecnologia costruttiva, è stata oggetto di studio ed analisi approfondite nell'ambi­to della convenzione di ricerca scienti­fica stipulata tra l'Università Politecnica delle Marche e il Comune di Senigallia inerente ''La valutazione e la stesura di linee guida per la riduzione del rischio sismico dell'edilizia scolastica del dopo guerra".
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/294383

TECHNOLOGICAL ANALYSIS, TYPOLOGICAL FEATURES AND SEISMIC VULNERABILITIES OF POST-WORLD WAR II ITALIAN SCHOOL BUILDINGS
REHABEND 2020. Euro-American Congress. Construction Pathology, Rehabilitation Technology and Heritage Management
Autore/i: Monni, F; Maracchini, G; Quagliarini, E; Lenci, S
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Many Italian school buildings, built just after the post-World War II, share similar geometrical and spatial characteristics. Some of these features may negatively affect the building seismic response, generating typical seismic vulnerabilities. In order to mitigate them, and then to foster an effective transition towards a safer and more sustainable society, it is important to provide exemplary cases on how to proceed correctly. For this reason, in this paper typical vulnerabilities of Italian post-World War II RC school buildings are individuated and discussed. For one of the most representative case study an in situ experimental campaign has been carried out in order to identify the specific seismic vulnerabilities related to specific geometrical aspects or material properties. Results of structural assessment have evidenced that some typological vulnerabilities such as wide atriums, eccentric stairs and tall windows, along with irregularity in plan configuration, strongly affect the global seismic behavior of the school buildings. Finally, a structural intervention aimed to improve the performance against seismic actions has been proposed and described for the case study. The intervention concerned RC jacketing of the columns, shear strengthening of beams through Carbon Fiber Reinforced Polymers (CFRP) sheets and strengthening of the beam-columns joints. The strengthening efficiency has been evaluated by means of pushover analysis. The proposed intervention can improve the seismic resistance of the building.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/294389

Aftershock fragility assessment of Italian cast–IN–place RC industrial structures with precast vaults
JOURNAL OF BUILDING ENGINEERING
Autore/i: Poiani, Marina; Gazzani, Valentina; Clementi, Francesco; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: Through a fragility analysis carried out with different probabilistic methods, the vulnerability of an Italian cast-in-place RC industrial structure with precast reinforced hollow brick light-weight vaults is evaluated via nonlinear analyses. After a brief description of the vault construction system, a typical case study built in the 1960s is considered and the influence of FE numerical modelling through three different representations of the vault system is assessed. Fragility curves are calculated by Incremental Dynamic Analysis (IDA), with three damage limit threshold values corresponding to local limit conditions regarding bending or shear that first occur in a few elements, as determined through pushover analyses. A comparison of fragility curves in the two horizontal directions (X–Y) for the three models is reported. Concerning the model with the greatest probability of collapse, seismic sequence effects on structural damage with the same ground motions for mainshock and aftershock are taken into account. Double Incremental Dynamic Analysis (D-IDA), with the mainshock represented by several fixed percentages of Near Collapse PGAs previously evaluated in X–Y directions and scaled aftershocks, is performed and compared to the IDA results. Aftershock fragility curves created with only the damage limit threshold value of Near Collapse are likened to the case that analyses a single seismic event (undamaged structure). Furthermore, ductility damage indices are calculated for maximum displacements obtained by each nonlinear dynamic analysis of IDA and D-IDA.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273195

Modal localisation in a beam modelled as a continuous system: A discussion on the use of auxiliary oscillators
JOURNAL OF SOUND AND VIBRATION
Autore/i: Ribeiro, E. A. R.; Lenci, S.; Mazzilli, C. E. N.
Classificazione: 1 Contributo su Rivista
Abstract: In this work, we show that perfectly localised modal vibrations can be obtained in continuous linear elastic structures, provided that, in addition to the regular boundary and continuity/jump conditions, extra (admissibility) conditions are met. They are derived with the aid of: (i) new parameters and/or DOFs of auxiliary systems, and/or (ii) admissible relationships amongst the original structural parameters. In both cases, however, the solution resorts to a fine-tuning problem. To illustrate the main ideas, we discuss three examples: two simply-supported beams with cantilever extensions and attached lumped oscillators, and a “tuning-fork-like” structure. Finally, to show that there are also systems in which fine-tuning is not possible, we discuss the case of two lumped oscillators attached to the free end of a cantilever beam.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/285291

Flexural wave propagation in infinite beams on a unilateral elastic foundation
NONLINEAR DYNAMICS
Autore/i: Lenci, S.; Clementi, F.
Classificazione: 1 Contributo su Rivista
Abstract: The problem of flexural wave propagation on a beam resting on a unilateral elastic substrate is addressed. The Euler–Bernoulli beam theory, which is valid for slender beams and for large enough wave length, is used. The governing equations are recalled, and the boundary conditions corresponding to the “single wave” periodic solutions are determined. The ensuing system of three algebraic transcendental equations is solved, and the exact solution of the problem is provided, in spite of the nonlinearity due to the piecewise behavior of the soil. The wave velocity as function of the foundation stiffness is obtained and compared with the classical case of the bilateral foundation. The main wave propagation properties are discussed, and some of them are illustrated with graphs reporting wave shapes.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/265852

Tracking modal parameter evolution ofdifferent cultural heritage structures damaged by central Italy earthquake of 2016
AIP Conference Proceedings
Autore/i: Ribilotta, E.; Giordano, E.; Ferrante, A.; Clementi, F.; Lenci, S.
Editore: American Institute of Physics Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The preliminary results of an ambient-vibration based investigation conducted on a large sample of historic masonry towers in the Marche region (Central Italy) are presented, with a focus on the belfry of Collegiata of Santa Maria in Visso (Italy). The assessment procedure includes full-scale ambient vibration testing, ambient modal identification, finite element modeling and dynamic-based identification of the uncertain structural parameters of the model. As the most doubtful parameters, the modulus of elasticity of the masonry is adjusted to achieve the experimental results with numerical model by simple operations.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287430

Nonlinear vibrations of an extensional beam with tip mass in slewing motion
MECCANICA
Autore/i: Warminski, J.; Kloda, L.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: Dynamics of a rotor composed of a flexible beam attached to a slewing rigid hub is presented in the paper. Dynamics of the structure is studied for a slender beam model, based on extended Bernoulli–Euler theory, which takes into account a nonlinear curvature, coupled transversal and longitudinal oscillations and non-constant angular velocity of the hub. Moreover, to demonstrate a general case for dynamical boundary conditions, lumped mass fixed at the beam tip is added. The partial differential equations (PDEs) are derived from Hamilton principle of the least action. The analytical solutions of the PDEs are obtained by the multiple time scale method applied directly to PDEs. Forced vibrations around selected resonance zones are studied and the influence of beam rotation, preset angle, hub radius, tip mass is presented. Hardening and softening phenomena, respectively for the first and the second mode, are obtained for various angular velocity values.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/285556

Modal parameters identification on environmental testd of ancient bell towers and validation of their numerical models
Proceedings of the International Conference on Structural Dynamic , EURODYN
Autore/i: Clementi, F.; Standoli, G.; Giordano, E.; Ferrante, A.; Lenci, S.
Editore: European Association for Structural Dynamics
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Masonry towers are quite widespread in Europe and represent an important portion of the built heritage that must be preserved, especially in high-seismicity regions. Very often, such masonry towers exhibit unique peculiar morphologic and typological characteristics, which might affect their different structural behaviors under horizontal loads. For this reason, accurate knowledge of their dynamical parameters is useful for seismic assessment and the design of risk mitigation interventions. In this work, the opportunities provided by dynamic identification techniques for the non-destructive evaluation of heritage structures are discussed with a focus on different bell towers, located in the Marche region (Italy). All of them were stricken by a long seismic sequence (Center Italy earthquakes between August and October 2016), and are investigated in detail in order to have an insight into their dynamic behavior. Furthermore, the experimental investigations and the operational modal analysis results are presented, and they are useful for defining the Finite Element (FE) model of the towers with a continuum approach. The monitoring system consists of several elements adequately connected. Many operative problems have conditioned the positioning of the instrumentation due to the limited accessibility of the structure, not only to the primary access but also to reach the top. However, it has been possible to identify with certain confidence the first three frequencies of the towers and their corresponding mode shapes. The results carried out after the updating procedure may be considered very good. The material data values estimated in this way will constitute an important reference for the evaluation of the state of the building.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287434

Hardening vs. softening dichotomy of a hinged-simply supported beam with one end axial linear spring: Experimental and numerical studies
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
Autore/i: Kloda, L.; Lenci, S.; Warminski, J.
Classificazione: 1 Contributo su Rivista
Abstract: The aim of this paper is to validate experimentally a nonlinear model of a kinematically excited hinged-simply supported beam with a spring subjected to one end. An experimental setup configuration enables to test different variants of axial boundary conditions: first a typical simply supported beam (no spring), and next two different spring systems. The prototype is kinematically excited with different amplitudes of excitation and then full frequency response curves are drawn wherein hardening/softening dichotomy is recognized. A set of mechanical properties of the system is identified and then used to reproduce tests with finite element simulations. Consequently numerical vs. experiment results are compared. The analysis demonstrates amplitude dependent damping as well as that the natural frequency depends on environmental conditions, and thus may change over experiments.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/283224

1:1 internal resonance in a two d.o.f. complete system: a comprehensive analysis and its possible exploitation for design
MECCANICA
Autore/i: Clementi, F.; Lenci, S.; Rega, G.
Classificazione: 1 Contributo su Rivista
Abstract: The internal resonance of a two degree-of-freedom mechanical system with all typical (quadratic and cubic) geometric nonlinearities is studied, limiting to the case of free dynamics. The Multiple Time Scale method is used to provide an analytical, closed form, approximation of the backbone curves. The cornucopia of different possible behaviours that can been obtained by varying the nonlinear stiffnesses is discussed in depth, illustrating them with some examples and verifying with numerical simulations. Some partially unexpected or relevant behaviours are highlighted, and some hints on how to exploit the proposed results to design nonlinearly tailored systems are given.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/280902

A Genetic Algorithm Procedure for the Automatic Updating of FEM Based on Ambient Vibration Tests
SENSORS
Autore/i: Bianconi, F.; Salachoris, G. P.; Clementi, F.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: The dynamic identification of the modal parameters of a structure, in order to gain control of its functionality under operating conditions, is currently under discussion from a scientific and technical point of views. The experimental observations obtained through structural health monitoring (SHM) are a useful calibration reference of numerical models (NMs). In this paper, the procedures for the identification of modal parameters in historical bell towers using a stochastic subspace identification (SSI) algorithm are presented. Then, NMs are manually calibrated on the identification’s results. Finally, the applicability of a genetic algorithm for the automatic calibration of the elastic parameters is considered with the aim of searching for the properties of the autochthonous material, in order to reduce modelling error following the model assurance criterion (MAC). In this regard, several material values on the same model are examined to see how to approach the evolution and the distribution of these features, comparing the characterization proposed by the genetic algorithm with the results considered by the manual iterative procedure.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/282515

Chaos in one-dimensional structural mechanics
NONLINEAR DYNAMICS
Autore/i: Rega, G.; Settimi, V.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: Notwithstanding the presence of some books summarizing specific research bodies on structural systems, reviews on nonlinear dynamics and chaos in mechanical systems and structures are quite few. This paper aims at giving a first contribution in this direction, focusing on chaos in one-dimensional structural mechanics, and reviewing fundamental studies and main outcomes obtained for macromechanical systems and applications in classical areas of mechanical, aeronautical and civil engineering. Research material is presented according to a tentatively comprehensive perspective, by suitably framing the overviewed complex dynamic phenomena of a given class of structures within the underlying continuous/reduced modelling context and the regular phenomena from which they ensue. This is a demanding perspective, which also entails leaving a number of important topics aside. Chaos in cable, beam/arch, and coupled cable-beam structures is reviewed, as highlighted in both engineering-oriented studies and theoretically driven ones, paying attention also to some relevant applications.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/285292

The modelling of multiple leaf masonry walls of the arquata del tronto fortress as a non-smooth dynamical system
Proceedings of the International Conference on Structural Dynamic , EURODYN
Autore/i: Ferrante, A.; Giordano, E.; Clementi, F.; Sarhosis, V.; Milani, G.; Lenci, S.
Editore: European Association for Structural Dynamics
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In the present paper has been reported the Non-Smooth Contact Dynamics method (NSCD) used for the damage evaluation of the multiple leaf masonry walls of the medieval fortress of Arquata del Tronto, strongly affected by the last Centre Italy earthquakes of August and October 2016. Pursuing this approach, a system of rigid blocks has been used for the assembly of the masonry structure. By means of contacts between blocks, which are governed by the Signorini's impenetrability condition and by dry-friction Coulomb's law, the building exhibits discontinuous dynamics. Finally, the NSCD method has proved to be an effective instrument for investigating the dynamical behaviour of the masonry structures under the ground seismic accelerations. Indeed, several possible failure mechanisms have been confirmed through the numerical results, which have given a deep insight into the seismic vulnerability of this damaged medieval fortress.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287437

Longitudinal–transversal internal resonances in Timoshenko beams with an axial elastic boundary condition
NONLINEAR DYNAMICS
Autore/i: Lenci, S.; Clementi, F.; Kloda, L.; Warminski, J.; Rega, G.
Classificazione: 1 Contributo su Rivista
Abstract: The internal resonances between the longitudinal and transversal oscillations of a forced Timoshenko beam with an axial end spring are studied in depth. In the linear regime, the loci of occurrence of 1 : ir, ir∈ N, internal resonances in the parameters space are identified. Then, by means of the multiple time scales method, the 1 : 2 case is investigated in the nonlinear regime, and the frequency response functions and backbone curves are obtained analytically, and investigated thoroughly. They are also compared with finite element numerical simulations, to prove their reliability. Attention is paid to the system response obtained by varying the stiffness of the end spring, and it is shown that the nonlinear behaviour instantaneously jumps from hardening to softening by crossing the exact internal resonance value, in contrast to the singular (i.e. tending to infinity) behaviour of the nonlinear correction coefficient previously observed (without properly taking the internal resonance into account).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/283809

An impact model of a ball bouncing on a flexible beam
MECCANICA
Autore/i: Demeio, L.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: In this work we investigate a model for the description of the impact of a ball with a flexible beam. The coupling of the kinematic parameters of the ball (the velocity components) with the vibration modes of the beam are taken into account by using the Hertz theory of impact. We solve the model equations numerically in a few physically relevant cases and illustrate the variation of the modal coefficients of the beam and of the velocity components of the ball during the impact. The restitution coefficient, the size of the deformation region and the impact duration are also reported as functions of the impact velocity and of the impact location.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/285290

Tehcnological analysis, typological features and seismic vulnerabilities of post-World War II Italian school buildings
REHABEND 2020. Euro-American Congress. Construction Pathology, Rehabilitation Technology and Heritage Management
Autore/i: Monni, F; Maracchini, G; Quagliarini, E; Lenci, S
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Many Italian school buildings, built just after the post-World War II, share similar geometrical and spatial characteristics. Some of these features may negatively affect the building seismic response, generating typical seismic vulnerabilities. In order to mitigate them, and then to foster an effective transition towards a safer and more sustainable society, it is important to provide exemplary cases on how to proceed correctly. For this reason, in this paper typical vulnerabilities of Italian post-World War II RC school buildings are individuated and discussed. For one of the most representative case study an in situ experimental campaign has been carried out in order to identify the specific seismic vulnerabilities related to specific geometrical aspects or material properties. Results of structural assessment have evidenced that some typological vulnerabilities such as wide atriums, eccentric stairs and tall windows, along with irregularity in plan configuration, strongly affect the global seismic behavior of the school buildings. Finally, a structural intervention aimed to improve the performance against seismic actions has been proposed and described for the case study. The intervention concerned RC jacketing of the columns, shear strengthening of beams through Carbon Fiber Reinforced Polymers (CFRP) sheets and strengthening of the beam-columns joints. The strengthening efficiency has been evaluated by means of pushover analysis. The proposed intervention can improve the seismic resistance of the building.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/294387

Damage assessment of ancient masonry churches stroked by the Central Italy earthquakes of 2016 by the non-smooth contact dynamics method
BULLETIN OF EARTHQUAKE ENGINEERING
Autore/i: Clementi, F.; Ferrante, A.; Giordano, E.; Dubois, F.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: The non-smooth contact dynamics method was selected to investigate the damage occurred to typical masonry churches (namely Apennine churches) belonging to Central Italy areas affected by the seismic activity started in 2016. The investigated buildings show discontinuous dynamics since the optioned method gave the chance to properly model the temples as multi rigid body systems using the Signorini’s impenetrability condition and the dry-friction Coulomb’s law, achieving a thoughtful response to ground seismic solicitations. The results provided by the assessment grant an overview of the most common damages and failure mechanisms, giving the guidelines to restoration projects that fully respond to structural needs.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/264833

Crumbling of Amatrice clock tower during 2016 Central Italy seismic sequence: Advanced numerical insights
FRATTURA E INTEGRITÀ STRUTTURALE
Autore/i: Clementi, F.; Milani, G.; Ferrante, A.; Valente, M.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: The dynamic behaviour and the seismic vulnerability of the ancient civic tower of Amatrice, dramatically damaged by the last shocks sequence of 2016 that occurred in Central Italy, have been studied in this paper by means of advanced 3D numerical analyses with the Discrete Element Method (DEM). Thus, a discontinuous approach has been used to assess the dynamic properties and the vulnerability of the masonry structure, through large deformations regulated by the Signorini’s law, concerning the impenetrability between the rigid bodies, and by the Coulomb’s law, regarding the dry-friction model. Afterward, different values have been assigned to the friction coefficient of the models and real seismic shocks have been applied in the nonlinear analyses. The major purpose of this study is to highlight that relevant data on the real structural behaviour of historical masonry can be provided through advanced numerical analyses. The comparison between the results of the numerical simulation and the survey of the existing crack pattern of the bell tower permitted to validate the approach used. Finally, from the results and conclusions of this case study, it is possible to affirm that the used methodology can be applied to a wide variety of historical masonry structure in Europe.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272571

Advanced seismic analyses of "Apennine churches" stroked by the central Italy earthquakes of 2016 by the non-smooth contact dynamics method
AIP Conference Proceedings
Autore/i: Ferrante, A.; Ribilotta, E.; Giordano, E.; Clementi, F.; Lenci, S.
Editore: American Institute of Physics Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The dynamic behaviour and the seismic vulnerability of different masonry "Apennine Churches". dramatically damaged by the last shocks sequence of 2016 that occurred in Central Italy, have been studied in this paper by means of advanced 3D numerical analyses with the Discrete Element Method (DEM). Thus, a discontinuous approach has been used to assess the dynamic properties and the vulnerability of the masonry structure, through large deformations regulated by the Signorini's law, concerning the impenetrability between the rigid bodies, and by the Coulomb's law, regarding the dry-friction model. The major purpose of this study is to highlight that relevant data on the real structural behaviour of historical masonry can be provided through advanced numerical analyses. The comparison between the results of the numerical simulation and the survey of the existing crack pattern of the churches permitted to validate the used approach. Finally, from the results and conclusions of these cases study, it is possible to affirm that the used methodology can be applied to a wide variety of historical masonry structure in Europe.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287431

Experimental study of the mechanical behaviour of a new extruded earth block masonry
CONSTRUCTION AND BUILDING MATERIALS
Autore/i: Stazi, Francesca; Serpilli, Michele; Chiappini, Gianluca; Pergolini, Marianna; Fratalocchi, Evelina; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: The aim of this research is to investigate, through the Digital Image Correlation (DIC) technique, the mechanical performance of a new type of earth masonry, built with extruded blocks and characterized by dovetail horizontally staggered bed joints. The experimental program consists of two levels of investigations: (i) preliminary phase on components, (ii) compression, diagonal compression and combined shear-compression tests on 12 wallettes. Regarding the components, results showed that the mean compressive strength of the earth block was low (3.5 MPa) with respect to traditional bricks and similar to adobe blocks. The dovetail joints were effective in their joining role showing a rather good strength (2.4 MPa) when tested in triplet configuration. Regarding the wallettes, the DIC highlighted failure modes complying with the ones of a traditional masonry under shear, while it showed a ‘‘column behaviour” with vertical sliding under compressive tests. Fragile failures occurred during the diagonal compression test. DIC revealed to be a promising technique to recover the full-field strain and crack maps.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/276215

The Non-smooth Dynamics of Multiple Leaf Masonry Walls of the Arquata Del Tronto Fortress
Proceedings of XXIV AIMETA Conference 2019
Autore/i: Clementi, Francesco; Ferrante, Angela; Lenci, Stefano
Editore: Springer
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The progressive damage of the multiple leaf masonry walls of the Arquata del Tronto medieval fortress, inside the epicentral zone of the last Centre Italy earthquakes of August and October 2016, has been investigated by means of the Non-Smooth Contact Dynamics method (NSCD). According to this model, the masonry structure has been modelled as a system of rigid blocks, and since the contacts between blocks are governed by the Signorini’s impenetrability condition and by dry-friction Coulomb’s law, the building exhibits discontinuous dynamics. The NSCD method has proved to be a powerful tool for investigating the dynamics induced by ground seismic accelerations. Indeed, the numerical results have given a deep insight into the seismic vulnerability of this damaged medieval fortress, confirming several possible failure mechanisms.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/275745

Damage assessment of churches in the city of camerino after the 2016 central Italy seismic sequence
Proceedings of the International Conference on Structural Dynamic , EURODYN
Autore/i: Giordano, E.; Ferrante, A.; Clementi, F.; Lenci, S.
Editore: European Association for Structural Dynamics
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In the present work, the importance of considering the exact nonlinear and three-dimensional behavior of masonry structures is shown, in order to highlight all the structural deficiencies of different churches damaged by the last Centre Italy earthquake in the city of Camerino. For this purpose, the exact geometries of the structures are reconstructed, while information regarding the mechanical properties of masonry material are derived from previous investigations and literature references. Based on this information, different numerical models are used to reconstruct the damages. Different three-dimensional FE models, endowed with an elastic plastic (softening) damage constitutive law, are adopted to determine the seismic vulnerability of the building by means of nonlinear static analyses using the smeared fracture energy approach. With this method it is possible to establish, with a right degree of approximation, the areas where the most important cracks are expected and, in general, the location of the potential damage caused by horizontal forces.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287433

Damage assessment of san francesco church in amandola hit by central Italy 2016-2017 seismic event
AIP Conference Proceedings
Autore/i: Giordano, E.; Ferrante, A.; Ribilotta, E.; Clementi, F.; Lenci, S.
Editore: American Institute of Physics Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Italy is a high seismic risk country. Since 1900 more than 30 earthquakes with magnitude greater than Mw=5.8 occurred, and the last one is the Central Italy seismic sequence. The first shock aroused in the 24th August (Mw=6.2) followed by another stronger quake in the 30th October (Mw=6.5). It heavily hit the regions of Marche, Umbria, and Abruzzo causing many deaths, injuries and extensive damages on the cultural heritage. This paper analyses the church of San Francesco in Amadola, located in the Marche region that has been considered condemned for the severe damages reported after these earthquakes. The church is globally analyzed by the application of nonlinear static analysis on a Finite Element Model where the nonlinearity of masonry is taking into account with a proper constitutive law. The study wants to prove how global analysis combined by the local analysis can reproduce the behavior of this structure during a quake, showing that it can repeat the real damages produced by earthquakes.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287432

A detailed study of the parametric excitation of a vertical heavy rod using the method of multiple scales
MECCANICA
Autore/i: Vernizzi, G. J.; Lenci, S.; Rosa Franzini, G.
Classificazione: 1 Contributo su Rivista
Abstract: An analytical solution for the problem of an immersed flexible and vertical heavy rod subjected to a vertical top motion is developed using the multiple scales method directly applied to the partial differential equations of motion. The obtained results show good agreement with a numerical solution obtained using the finite element method for a study case. The analytical solution is then used to carry out some sensitivity studies. The effects of the structural nonlinearities, hydrodynamic and structural damping terms are investigated. It is shown that the nonlinearities play a role in defining the frequency of the top motion that causes the maximum amplitude of response, but not the value of the amplitude itself. In turn, the major role played by the hydrodynamic damping in defining the response amplitude is addressed. It is also shown that the structural damping have an important effect on the response amplitude even in the case of small damping ratio. This occurs due to the combined effect of the structural with the hydrodynamic damping. Finally, it is pointed out that small differences in the structural damping ratio can lead to significant differences in the response amplitude.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/285658

Global Nonlinear Dynamics for Engineering Design and System Safety
CISM INTERNATIONAL CENTRE FOR MECHANICAL SCIENCES
Autore/i: Lenci, Stefano; Rega, Giuseppe
Classificazione: 7 Curatele
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/261164

IUTAM Symposium on Exploiting Nonlinear Dynamics for Engineering Systems
IUTAM Symposium on Exploiting Nonlinear Dynamics for Engineering Systems
Autore/i: Kovacic, I.; Lenci, S.
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/269318

Interpreting and Predicting Experimental Responses of Micro- and Nano-Devices via Dynamical Integrity
Global Nonlinear Dynamics for Engineering Design and System Safety
Autore/i: Ruzziconi, L.; Lenci, S.; Younis, M.
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/261166

Dynamical Integrity: A Novel Paradigm for Evaluating Load Carrying Capacity
Global Nonlinear Dynamics for Engineering Design and System Safety
Autore/i: Rega, G.; Lenci, S.; Ruzziconi, L.
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/261165

Nonlinear Dynamics, Safety, and Control of Structures Liable to Interactive Unstable Buckling
Global Nonlinear Dynamics for Engineering Design and System Safety
Autore/i: Goncalves, P. B.; Orlando, D.; Silva, F. M. A.; Lenci, S.; Rega, G.
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/261167

Flood impact on masonry buildings: The effect of flow characteristics and incidence angle
JOURNAL OF FLUIDS AND STRUCTURES
Autore/i: Postacchini, Matteo; Zitti, Gianluca; Giordano, Ersilia; Clementi, Francesco; Darvini, Giovanna; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: Climate change and the raising number of extreme events, such as severe floods, has increased the attention on their effects on urban systems. Urban floods generate important hydrodynamic loads on building and this work proposes a first systematic study on the actions generated by floods with different characteristics (depth, velocity and incidence angle) on masonry buildings. The study is carried out with experimental tests reproducing a masonry bay with scale 1:10, while the effect of the flow hitting the building has been obtained by moving the building in the water at rest. The pressure generated by the fluid at the four walls of the building was recorded using pressure transducers. It has been found that the overpressure acting on the building depends on the flow characteristics in different manner for the frontal, lateral and rear walls. Further, the incidence angle plays a major role in the generation of a pressure gradient along the impacted wall, and significantly affects both peak frequency and spectral energy. Use of theoretical models suggests that (i) the drag coefficient of the building decreases with the Froude number, and only slightly depends on the incidence angle, and (ii) the blocking effect largely affects the hydrodynamics around the structure.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/266247

Tracking modal parameters evolution of a school building during retrofitting works
BULLETIN OF EARTHQUAKE ENGINEERING
Autore/i: Pierdicca, Alessio; Clementi, Francesco; Fortunati, Andrea; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: During a seismic improvement intervention that lasted more than one year, a reinforced concrete (RC) school building had been surveyed through dynamic monitoring, granting continuous updates on its global response. Operational Modal Analysis (OMA) was carried out to have a proper understanding of the structure’s dynamic evolution, using a Finite Element Model (FEM) to perform a non-invasive and quantitative structural assessment taking into account the interactions with the surroundings. During the whole restoration works, the long-term (periodic) monitoring campaign showed the increment of the building performance remarked by the variation of natural frequencies. Also, the experimental assessment of the influence of infill masonry panels on the dynamics of RC frame is shown at each upgraded configuration. Additional restoration works, that may eventually occur, could benefit from the data collected during the present Ambient Vibration Survey (AVS), providing useful parameters to enhance the retrofitting and the dynamic behavior of the structure.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/260611

Damage Assessment by Numerical Modeling of Sant'Agostino's Sanctuary in Offida During the Central Italy 2016–2017 Seismic Sequence
FRONTIERS IN BUILT ENVIRONMENT
Autore/i: Giordano, Ersilia; Clementi, Francesco; Nespeca, Andrea; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: The subject of this work is the Sant'Agostino Sanctuary in Offida (Italy); we investigated both the dynamic behavior and the seismic vulnerability of the complex, used nowadays in its parts as school building, oratory, and church. Offida is in central Italy; the village has been severely damaged by the last seismic events of 2016. The sanctuary was heavily damaged by the earthquake of 24 August 2016. We recurred to finite elements to estimate the vulnerability of the sanctuary and its dynamic response, considering masonry's non-linear behavior by means of proper constitutive assumptions. To estimate how the monastery bears the lateral loads related to the expected demands resulting from seismic actions (N2 method) using non-linear static analysis (Pushover), we recurred to a homogenized material and smeared cracking and crushing constitutive law. As may be remarked by observing buildings that share the same features of the sanctuary and, moreover, by comparing seismic demand vs. capacity, the structure is prone to massive damage leading to collapse. The paper underlines how advanced numerical analysis grants fundamental data on how historical masonry buildings behave under seismic action, providing a method that may easily be implemented at historic monasteries in Europe.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/262744

Comparative fragility methods for seismic assessment of masonry buildings located in Muccia (Italy)
JOURNAL OF BUILDING ENGINEERING
Autore/i: Chieffo, N.; Clementi, F.; Formisano, A.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: The current paper focuses on a sector of the historic centre of Muccia, in the district of Macerata (Italy), affected by the seismic sequence that involved Central Italy in 2016. The main goal is comparison, in terms of fragility curves, among two vulnerability assessment methodologies (empirical and mechanical). The study area has been structurally and typologically identified according to the Building Typology Matrix (BTM). Physical vulnerability analysis of the urban-sector was performed through application of an index-based method, specifically for masonry building aggregates. An isolated masonry building, damaged after the seismic sequences, has been selected as a case study. For the assessed building, empirical fragility curves are presented according to Guagenti & Petrini’s correlation law. Furthermore, a numerical model has been set up by using the macro-element approach, which has allowed to perform non-linear static analyses. Mechanical properties of masonry were defined according to the New Technical Codes for Constructions (NTC18), assuming a limited knowledge level (LC1). Refined mechanical fragility functions have been derived and compared to the empirical ones. Analysis results have shown that the empirical method tends to overestimate by 5% and 10% the expected damage for slight and moderate thresholds. For PGA values greater than 0,3 g the damage levels decreased by 30% and 20%, with reference to the near collapse and collapse conditions, respectively.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/267525

Sustainable Engineering for Resilient Built and Natural Environments
The First Outstanding 50 Years of “Università Politecnica delle Marche”
Autore/i: Alici, Antonello; Bocci, Maurizio; Bonvini, Paolo; Brocchini, Maurizio; Calamai, Alessandro; Canestrari, Francesco; Capozucca, Roberto; Carbonari, Alessandro; Carbonari, Sandro; Cardone, Fabrizio; Clementi, Francesco; Clini, Paolo; Cocchi, Giammichele; Corvaro, Sara; Darvini, Giovanna; Davì, Fabrizio; Dezi, Luigino; Di Giuseppe, Elisa; D’Orazio, Marco; Ferretti, Maddalena; Ferrotti, Gilda; Gara, Fabrizio; Giretti, Alberto; Graziani, Andrea; Lancioni, Giovanni; Lemma, Massimo; Lenci, Stefano; Lorenzoni, Carlo; Malinverni, Eva Savina; Mancinelli, Alessandro; Mariano, Fabio; Mentrasti, Lando; Mondaini, Gianluigi; Montecchiari, Piero; Munafò, Placido; Naticchia, Berardo; Postacchini, Matteo; Quagliarini, Enrico; Quattrini, Ramona; Ragni, Laura; Serpilli, Michele; Soldini, Luciano; Virgili, Amedeo; Zampini, Giovanni
Editore: Springer
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272866

An Overview of the Structural Safety-Oriented Research in the Region Marche Seismic Area
The First Outstanding 50 Years of “Università Politecnica delle Marche”
Autore/i: Capozucca, R.; Carbonari, S.; Clementi, F.; Cocchi, G.; Davi, F.; Dezi, L.; Gara, F.; Lancioni, G.; Lenci, S.; Mentrasti, L.; Ragni, L.; Serpilli, M.
Editore: Springer, Cham
Classificazione: 2 Contributo in Volume
Abstract: In recent years, Italy has been hit by earthquakes, causing significant damage to masonry and reinforced concrete (RC) structures. Especially, common buildings and ordinary structures in many small historical towns of Italian central regions, such as Marche, have suffered dramatic consequences and destruction. Dynamic analysis and seismic structural safety are important topics in civil engineering, which have been studied and deepened for many years by the researchers of the Structural Division of the Department of Civil and Building Engineering, and Architecture of UnivPM. The researches have been oriented towards the investigation of structures under seismic loads in order to improve the knowledge of the structural response under high actions, due to the soil dynamic movements and, thus, define adequate techniques to strengthen the damaged structures. In this paper we present a wide spectrum of main results of our research group, comprising experimental studies, vulnerability analysis and assessment of existing structures, new methods of modelling and theoretical approaches to define the dynamic behavior of structures, also in presence of damage. Finally, we show and discuss new prospects of research for safety, employing advanced techniques and materials to prevent collapse and/or relevant damages in structures.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/281739

On a Geometrically Exact Beam Model and Its Finite Element Approximation
IUTAM Symposium on Exploiting Nonlinear Dynamics for Engineering Systems
Autore/i: Babilio, Enrico; Lenci, Stefano
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/269317

Introduction to Scientific Computing Technologies for Global Analysis of Multidimensional Nonlinear Dynamical Systems
Nonlinear Structural Dynamics and Damping
Autore/i: Andonovski, Nemanja; Moglie, Franco; Lenci, Stefano
Editore: Springer International Publishing
Classificazione: 2 Contributo in Volume
Abstract: To determine global behaviour of a dynamical system, one must find invariant sets (attractors) and their respective basins of attraction. Since this cannot be made extensively with analytical methods, the numerical global analysis is currently the subject of intensive research, especially for strongly nonlinear, multidimensional dynamical systems. Numerical analysis in dimensions higher than four present a challenge, since it requires significant computing resources. Numerical methods used in global analysis that can benefit from high-power computing are those that can parallelize either data or task elaboration on a large scale. Mass parallelization comes with large number of difficulties, restrictions and programming hazards. When not implemented in compliance with hardware organization, data and instruction management can lead to severe loss of parallel algorithm performance. Systematic and methodical approach to design parallel programs is, therefore, critical to get the most from expensive high-power computing systems and to avoid unrealistic speed-up expectation. Considering these difficulties, the goal of this chapter is to introduce readers to the world of high-power computing systems for science and global analysis of strongly nonlinear, multidimensional dynamical systems. Topic covered are classification and performance of hardware and software, classes of computing problems and methodical design of programs. Two major hardware platforms used for scientific computing, clusters and systems with computational GPU are considered. Functionality of widely utilized software solutions (OpenMP, MPI, CUDA and OpenCL) for high-power computing systems is described. Performance of individual computer components are addressed so that the reader can understand advantages, disadvantages, efficiency and limits of each hardware platform. With this knowledge users can judge if their computation problem is suitable for mass parallelization. If this is the case, which hardware and software platforms to use. To avoid many traps of parallel programming, one of the methodical design approaches is covered. Topic is closed with example applications in science and global analysis.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/264456

Basins of Attraction for Higher-Dimensional Nonlinear Dynamical Systems: Preliminary Results on the Case Study of a Sympodial Tree
IUTAM Symposium on Exploiting Nonlinear Dynamics for Engineering Systems
Autore/i: Andonovski, Nemanja; Lenci, Stefano; Kovacic, Ivana
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/269315

Nonlinear Dynamics of a Planar Hinged-Simply Supported Beam with One End Spring: Higher Order Resonances
IUTAM Symposium on Exploiting Nonlinear Dynamics for Engineering Systems
Autore/i: Kloda, Lukasz; Lenci, Stefano; Warminski, Jerzy
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/269316

Global dynamics and integrity of a micro-plate pressure sensor
COMMUNICATIONS IN NONLINEAR SCIENCE & NUMERICAL SIMULATION
Autore/i: Belardinelli, P.; Sajadi, B.; Lenci, S.; Alijani, F.
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/262764

Influence of geometric nonlinearities on the asynchronous modes of an articulated prestressed slender structure
JOURNAL OF VIBRATION AND ACOUSTICS
Autore/i: Ribeiro, Eduardo A. R.; Mazzilli, Carlos E. N.; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/264671

Diagnostic survey on frescoes paintings in Pompei by active Ir-thermography
IMEKO International Conference on Metrology for Archaeology and Cultural Heritage, MetroArchaeo 2017
Autore/i: Castellini, P.; Martarelli, M.; Lenci, S.; Quagliarini, E.; Silani, M.; Martellone, A.
Editore: International Measurement Confederation (IMEKO)
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272664

Damage assessment by the non-smooth contact dynamics method of the iconic crumbling of the clock tower in Amatrice after the 2016 Central Italy seismic sequence
Proceedings of the International Conference on Numerical Analysis and Applied Mathematics 2018, ICNAAM 2018
Autore/i: Clementi, F.; Milani, G.; Gazzani, V.; Poiani, M.; Lenci, S.
Editore: American Institute of Physics Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The dynamics of the medieval civic clock tower of Amatrice (Rieti-Italy) has been studied using the Non-Smooth Contact Dynamics (NSCD) method, implementing a discrete element numerical model in the LMGC90© code. Schematised as a system of rigid blocks, undergoing frictional sliding and plastic impacts, the tower has exhibited complex dynamics, because of the geometrical non-linearity and the non-smooth nature of the contact laws. Numerical simulations are performed with the aim of comparing the numerical result and the observed damages after the seismic sequence of the Central Italy earthquakes.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/269306

Evaluation of different approaches for the seismic vulnerability assessment of RC structures
Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2019, ICCMSE 2019
Autore/i: Gazzani, Valentina; Poiani, Marina; Clementi, Francesco; Pace, Giuseppe; Lenci, Stefano
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The seismic vulnerability of school buildings located in the municipality of Trecastelli (Marche, Central Italy) is evaluated with three different numerical models: the lumped plasticity, the distributed plasticity (fibre) and the 3D Continuum FE approaches. Nonlinear static (pushover) analyses are performed to assess the global seismic behaviour of the structures, and the limitations in the representativeness respect to the reality of different approaches are analysed
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272691

The Lossetti Tower in Beura-Cardezza (Italy): Structural Assessment and Rehabilitation of a Historical Dry Stone Masonry Building
RILEM Bookseries
Autore/i: Monni, F.; Quagliarini, E.; Lenci, S.
Editore: Springer Netherlands
Classificazione: 2 Contributo in Volume
Abstract: Dry stone masonry (DSM) is an ancient construction method widely used for vernacular and military buildings in rural and mountain regions. The use of this particular method is due to the large availability of natural stone that characterized these areas. The consolidation of DSM buildings is a challenging issue: in fact, this kind of masonry proved to be scarcely reliable under eccentric and horizontal loads and in absence of elements that are long enough to cross the masonry in its thickness. However, there are very few techniques that can preserve the peculiarities of a masonry texture. This paper presents the design approach that was used for the structural rehabilitation of the Lossetti Tower, a medieval DSM watchtower located in Beura-Cardezza (Italy, Piemonte Region). First, a preliminary research on the building was conducted. Secondly, to better understand the masonry quality, both a 3D laser scanning geometric survey and a technological study of the masonry typology and texture of the tower were executed. Thirdly, to evaluate the mechanical behaviour, a diagonal compression test on the DSM specimens was performed. Finally, after a structural assessment, was developed a tailored design of the strengthening intervention by using the technique of continuous basalt fibers stitching. The proposed system consists in creating a mesh of basalt fiber ropes, that passes through the masonry thickness and ties the blocks together. This system also allows to connect the wall in the transverse direction and to improve the monolithic behaviour of masonry panels in perfect compatibility with the original materials and it was preferred to the more invasive ones also for its reversibility
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/268475

Six-dimensional basins of attraction computation on small clusters with semi-parallelized SCM method
INTERNATIONAL JOURNAL OF DYNAMICS AND CONTROL
Autore/i: Andonovski, N.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273244

Damage survey and advanced seismic analyses of different masonry churches after the central Italy earthquake of 2016
COMPDYN 2019 Proceedings
Autore/i: Clementi, F.; Giordano, E.; Ferrante, A.; Lenci, S.
Editore: National Technical University of Athens
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This study presents a detailed failure analysis of different masonry churches, which were severely damaged during the 2016 Centre of Italy seismic sequence, using nonlinear (i.e., kinematic limit and pushover) analyses. The main aims of the numerical investigations are: (i) to carry out a sufficiently wide sensitivity study on different specific case studies to have an insight into the role played by the geometry - which is always unique for churches - and by the irregularities; (ii) to validate or address the limits of applicability of the most widespread conventional static approaches recommended by Italian Code.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/274950

Influence of FE Modelling Approaches on Vulnerabilities of RC School Buildings and Proposal of a CFRP Retrofitting Intervention
THE OPEN CONSTRUCTION & BUILDING TECHNOLOGY JOURNAL
Autore/i: Gazzani, V.; Poiani, M.; Clementi, F.; Pace, G.; Lenci, S.
Classificazione: 1 Contributo su Rivista
Abstract: Background: The vulnerability assessment of existing school buildings against earthquakes represents a priority concern for society. In recent years, several countries promote seismic rehabilitation projects of school buildings, including the allocation of funds to regions with high seismic hazard. Objectives: This research aims to highlight some key role aspects related to difficulties encountered in the numerical modelling of RC structures hosting school activities. This work evaluates the seismic vulnerability of school buildings located in the municipality of Trecastelli (Marche, Central Italy) to quantify the effective influence of typical and specific seismic vulnerabilities detected on the global seismic behaviour of each building. The effectiveness of a possible Carbon Fibre Reinforced Polymer (CFRP) local strengthening intervention, for the case study, aimed to confine unconfined beam-column joints is also considered. Methods: Three different numerical models of a Reinforced Concrete (RC) school building are implemented with the lumped plasticity, the distributed plasticity (fibre) and the 3D Continuum Finite Element (FE) approaches. Nonlinear static (pushover) analyses are performed to assess the global seismic behaviour of the structure, and the limitations to represent the reality with different approaches. After the seismic vulnerability assessment of the case study, a CFRP retrofitting intervention is proposed to confine external beam-column joints. Results: The comparison of the numerical results of three models shows that the fibre model is the least suitable means to represent shear problems, while the lumped plasticity model is closer to reality than the previous one even if it does not take into account the concomitance of bending, shear and axial force and the interaction between them in the inelastic response. Of course, the 3D Continuum model is the most accurate representation to describe the complex and combined mechanisms developed in the joint panels. Nonlinear static (pushover) analyses carried out on unreinforced and reinforced structures of Continuum model demonstrate that the Fibre Reinforced Polymer (FRP) strengthening improves the displacement capacity of the structure. Conclusion: This study has highlighted the strengths and weaknesses of different modelling types. The meaningful information about mechanisms developed in joints given by the 3D Continuum FE model is useful to identify shortcomings of the design project and to conceive a retrofitting strengthening intervention. CFRP sheets externally bonded on beam-column joints may improve the seismic frame performances without a significant change of the structural stiffness, promoting a ductile failure mode with a higher displacement capacity than the unreinforced case.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272403

Can textile reinforced mortar (TRM) systems be really effective to increase compressive strength of masonry panels?
Key Engineering Materials
Autore/i: Donnini, J.; Maracchini, G.; Chiappini, G.; Corinaldesi, V.; Quagliarini, E.; Lenci, S.
Editore: Trans Tech Publications Ltd
Classificazione: 2 Contributo in Volume
Abstract: The use of Textile Reinforced Mortar (TRM) systems represent a valid alternative to traditional strengthening techniques, to improve mechanical strength and seismic performance of masonry buildings. Their effectiveness has been validated by several studies [1-4]. However, the TRM contribution in the mechanical behavior of masonry walls, subjected to simple compression, has not yet been fully investigated. In this study, an experimental campaign with the objective of studying the efficiency of TRM systems, applied to clay brick masonry panels, is presented. Compression tests were conducted on clay brick masonry panels with dimensions of 250x1000x1200 mm3 . Glass fiber bidirectional fabrics were applied on both sides of the panels, coupled with lime-based mortar, and connected with stainless steel helical connectors. The total thickness of the reinforcement system is 30 mm. The effect of the TRM reinforcement on the mechanical behavior of the panel is analyzed and experimental results are compared with those of unreinforced panels in terms of ultimate strength and failure modes.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/270983

Influence of transient escape and added load noise on the dynamic integrity of multistable systems
INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS
Autore/i: Orlando, Diego; Gonçalves, Paulo B.; Rega, Giuseppe; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/265401