Stefano Lenci | Università Politecnica delle Marche, Italy (original) (raw)
Papers by Stefano Lenci
INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS (ICNAAM 2016), 2017
This paper studies the influence of some aleatory and epistemic uncertainties on the seismic beha... more This paper studies the influence of some aleatory and epistemic uncertainties on the seismic behaviour of an existing RC school building through a codified sensitivity analysis that uses pushover analyses and a logic tree approach. The considered epistemic uncertainties, i.e. diaphragm stiffness and modelling of stairs, seem not influencing the final assessment in term of index of seismic risk. Vice versa, aleatory ones, i.e. concrete and steel mechanical properties, strongly affect the Index. For this reason, investigations and tests should focus on the study of the mechanical properties, and, in particular, on the study of columns’ concrete mechanical properties, which have the largest impact on the building seismic response.
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International journal of masonry research and innovation, 2016
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The Open Civil Engineering Journal, Dec 29, 2017
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One of the most important issues in civil and in mechanical engineering is the detection of struc... more One of the most important issues in civil and in mechanical engineering is the detection of structural damages, which are defined as changes of material properties, of boundary conditions and of system connectivity, which adversely affect the system’s performances. The damage identification process generally requires establishing existence, localization, type and intensity of the damage.During its service life, a structure, besides his natural aging, can be subjected to earthquakes. These events may have a deep impact on building safety and a continuous monitoring of the structure health conditions, through Structural Health Monitoring (SHM) techniques, is necessary in many cases.Within this a background, the purpose of this work is to propose an integrated novel approach for the diagnosis of structures after a seismic event. The proposed monitoring system is based on recording the accelerations of the real structure during a seismic input, and the reintroduction of them into a numerical model, suitably tuned, in order to outline a possible post-earthquake scenario.This approach provides an estimation of the health of the building and of its residual life, and to detect and quantify the damage, some of the crucial aspects of SHM. Actually, we also get both online and self-diagnosis of the structural health.The technique is applied to a real structure, an industrial building liable of some seismic vulnerabilities. It it did not undergo an earthquake, so we have not recordered accelerations, and get them from a different numerical models subjected to the ground acceleration of a realistic earthquake.Copyright © 2015 by ASME
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Structural control & health monitoring, Nov 2, 2015
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Key Engineering Materials, Sep 1, 2014
One of the most important characteristics that historical masonry should have is that of a monoli... more One of the most important characteristics that historical masonry should have is that of a monolithic behavior. Without these basic feature, no structural analysis could be considered reliable. If this characteristic is absent, strengthening bearing masonry giving it a transversal monolithic behavior is one of the first retrofitting actions to do so as to improve its seismic performance. Hence come out the idea to develop a new consolidation technique specially formulated for historical masonry. Stitching masonry through continuous flexible elements is an innovative technique, able to connect the several masonry components and to attribute to it a monolithic behavior according to the principles that govern the intervention on existing buildings: minimal intervention, compatibility, reversibility, respect of authenticity, matter conservation, control of the visual impact and possibility of recognizing the intervention. Basalt fibers ropes of 4 mm of nominal diameter (declared by manufacturer), have been used in this experimental program as continuous flexible element. The technique has been already tested and proved to be effective for improving the behavior against “in-plane” actions. Good results has been obtained also excluding synthetic adhesives (resins), with an enhancement about reversibility. In this paper, the results of an experimental campaign aimed to evaluate the technique effectiveness against “out-of-plane” loads are presented. Reinforced and unreinforced brick masonry specimens have been tested simulating vertical bending mechanism activation to evaluate the stitches contribute.
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Engineering Structures, Nov 1, 2016
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This paper explores the influence of uncertainties and noise on the global dynamics of nonlinear ... more This paper explores the influence of uncertainties and noise on the global dynamics of nonlinear systems, with emphasis on the basins and attractors’ topology and on the dynamic integrity of coexisting solutions. For this, the adaptive phase-space discretization strategy proposed in Part I [1] is employed. Two well-known archetypal oscillators found in engineering applications, the Helmholtz and Duffing oscillators under harmonic or parametric excitation with uncertain parameters or added load noise, are studied. The results demonstrate the adaptive capability of the proposed method, increasing the resolution without increasing the computational cost. Mean basins of attraction and attractors’ distributions are obtained. The time-dependency of stochastic responses is demonstrated, with long-transients influencing the short-term behavior. Finally, the effect of uncertainties and noise on the basins areas, attractors distributions and basin boundaries is discussed, which can be used to...
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An adaptative phase-space discretization strategy for the global analysis of stochastic nonlinear... more An adaptative phase-space discretization strategy for the global analysis of stochastic nonlinear dynamical systems with competing attractors considering parameter uncertainty or 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 and densities. 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 converging 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, bein...
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Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2019
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The First Outstanding 50 Years of “Università Politecnica delle Marche”, 2019
We discuss the research that is being carried out at the Department of Civil and Building Enginee... more We discuss the research that is being carried out at the Department of Civil and Building Engineering and Architecture (Dipartimento di Ingegneria Civile, Edile e Architettura, DICEA) of the Universita Politecnica delle Marche (UNIVPM). Over the years the DICEA has steadily focused its attention on resilient environments and buildings, making a growing know-how and skill available to the local and broad communities. Pivotal to this have been dedicated projects and funds, like the UNIVPM strategic projects and the MIUR Dipartimenti di Eccellenza award. In conjunction with the four companion papers, produced by researchers of the four divisions of DICEA, we illustrate the DICEA’s trajectory in the analysis of sustainable engineering for resilient built and natural environments.
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Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2021
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Engineering Structures, 2021
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Meccanica, 2020
The internal resonance of a two degree-of-freedom mechanical system with all typical (quadratic a... more 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.
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The Open Construction and Building Technology Journal, 2019
Background: The vulnerability assessment of existing school buildings against earthquakes represe... more 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. Objective: 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...
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Bulletin of Earthquake Engineering, 2019
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Archive of Applied Mechanics, 2016
Two approximate solutions for the nonlinear free oscillations of a planar Timoshenko beam are com... more Two approximate solutions for the nonlinear free oscillations of a planar Timoshenko beam are compared to each other. The beam has an axial spring that permits to consider different boundary conditions, from axially free (which has a softening nonlinear behaviour) to perfectly axially restrained (which has a hardening nonlinear behaviour). The first approximation is analytical and is obtained by the asymptotic development method, while the second is numerical and is obtained by the finite element method. The comparison is made in terms of backbone curves describing the dependence of the (nonlinear) frequency on the oscillation amplitude. Very good agreement is found, for both slender and thick beams, and for varying stiffness of the end spring. This is a cross-check verification of the reliability of both approximate solutions.
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Meccanica, 2016
The free nonlinear oscillations of a planar elastic beam are investigated based on a comprehensiv... more The free nonlinear oscillations of a planar elastic beam are investigated based on a comprehensive asymptotic treatment of the exact equations of motion. With the aim of investigating the behaviour also for low slenderness, shear deformations and rotational inertia are taken into account. Attention is payed to the influence of the geometrical and mechanical parameters, and of the boundary conditions in changing the nonlinear behaviour from softening to hardening. An axial linear spring is added to one end of the beam, and it is shown how the behaviour changes qualitatively on passing from the hinged-hinged (commonly hardening) to the hinged-supported (commonly softening) case. Some interesting, and partially unexpected, results are obtained also for values of the slenderness moderately low but still in the realm of practical applications.
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Communications in Nonlinear Science and Numerical Simulation, 2018
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Meccanica, 2017
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INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS (ICNAAM 2016), 2017
This paper studies the influence of some aleatory and epistemic uncertainties on the seismic beha... more This paper studies the influence of some aleatory and epistemic uncertainties on the seismic behaviour of an existing RC school building through a codified sensitivity analysis that uses pushover analyses and a logic tree approach. The considered epistemic uncertainties, i.e. diaphragm stiffness and modelling of stairs, seem not influencing the final assessment in term of index of seismic risk. Vice versa, aleatory ones, i.e. concrete and steel mechanical properties, strongly affect the Index. For this reason, investigations and tests should focus on the study of the mechanical properties, and, in particular, on the study of columns’ concrete mechanical properties, which have the largest impact on the building seismic response.
Bookmarks Related papers MentionsView impact
International journal of masonry research and innovation, 2016
Bookmarks Related papers MentionsView impact
The Open Civil Engineering Journal, Dec 29, 2017
Bookmarks Related papers MentionsView impact
One of the most important issues in civil and in mechanical engineering is the detection of struc... more One of the most important issues in civil and in mechanical engineering is the detection of structural damages, which are defined as changes of material properties, of boundary conditions and of system connectivity, which adversely affect the system’s performances. The damage identification process generally requires establishing existence, localization, type and intensity of the damage.During its service life, a structure, besides his natural aging, can be subjected to earthquakes. These events may have a deep impact on building safety and a continuous monitoring of the structure health conditions, through Structural Health Monitoring (SHM) techniques, is necessary in many cases.Within this a background, the purpose of this work is to propose an integrated novel approach for the diagnosis of structures after a seismic event. The proposed monitoring system is based on recording the accelerations of the real structure during a seismic input, and the reintroduction of them into a numerical model, suitably tuned, in order to outline a possible post-earthquake scenario.This approach provides an estimation of the health of the building and of its residual life, and to detect and quantify the damage, some of the crucial aspects of SHM. Actually, we also get both online and self-diagnosis of the structural health.The technique is applied to a real structure, an industrial building liable of some seismic vulnerabilities. It it did not undergo an earthquake, so we have not recordered accelerations, and get them from a different numerical models subjected to the ground acceleration of a realistic earthquake.Copyright © 2015 by ASME
Bookmarks Related papers MentionsView impact
Structural control & health monitoring, Nov 2, 2015
Bookmarks Related papers MentionsView impact
Key Engineering Materials, Sep 1, 2014
One of the most important characteristics that historical masonry should have is that of a monoli... more One of the most important characteristics that historical masonry should have is that of a monolithic behavior. Without these basic feature, no structural analysis could be considered reliable. If this characteristic is absent, strengthening bearing masonry giving it a transversal monolithic behavior is one of the first retrofitting actions to do so as to improve its seismic performance. Hence come out the idea to develop a new consolidation technique specially formulated for historical masonry. Stitching masonry through continuous flexible elements is an innovative technique, able to connect the several masonry components and to attribute to it a monolithic behavior according to the principles that govern the intervention on existing buildings: minimal intervention, compatibility, reversibility, respect of authenticity, matter conservation, control of the visual impact and possibility of recognizing the intervention. Basalt fibers ropes of 4 mm of nominal diameter (declared by manufacturer), have been used in this experimental program as continuous flexible element. The technique has been already tested and proved to be effective for improving the behavior against “in-plane” actions. Good results has been obtained also excluding synthetic adhesives (resins), with an enhancement about reversibility. In this paper, the results of an experimental campaign aimed to evaluate the technique effectiveness against “out-of-plane” loads are presented. Reinforced and unreinforced brick masonry specimens have been tested simulating vertical bending mechanism activation to evaluate the stitches contribute.
Bookmarks Related papers MentionsView impact
Engineering Structures, Nov 1, 2016
Bookmarks Related papers MentionsView impact
This paper explores the influence of uncertainties and noise on the global dynamics of nonlinear ... more This paper explores the influence of uncertainties and noise on the global dynamics of nonlinear systems, with emphasis on the basins and attractors’ topology and on the dynamic integrity of coexisting solutions. For this, the adaptive phase-space discretization strategy proposed in Part I [1] is employed. Two well-known archetypal oscillators found in engineering applications, the Helmholtz and Duffing oscillators under harmonic or parametric excitation with uncertain parameters or added load noise, are studied. The results demonstrate the adaptive capability of the proposed method, increasing the resolution without increasing the computational cost. Mean basins of attraction and attractors’ distributions are obtained. The time-dependency of stochastic responses is demonstrated, with long-transients influencing the short-term behavior. Finally, the effect of uncertainties and noise on the basins areas, attractors distributions and basin boundaries is discussed, which can be used to...
Bookmarks Related papers MentionsView impact
An adaptative phase-space discretization strategy for the global analysis of stochastic nonlinear... more An adaptative phase-space discretization strategy for the global analysis of stochastic nonlinear dynamical systems with competing attractors considering parameter uncertainty or 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 and densities. 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 converging 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, bein...
Bookmarks Related papers MentionsView impact
Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2019
Bookmarks Related papers MentionsView impact
The First Outstanding 50 Years of “Università Politecnica delle Marche”, 2019
We discuss the research that is being carried out at the Department of Civil and Building Enginee... more We discuss the research that is being carried out at the Department of Civil and Building Engineering and Architecture (Dipartimento di Ingegneria Civile, Edile e Architettura, DICEA) of the Universita Politecnica delle Marche (UNIVPM). Over the years the DICEA has steadily focused its attention on resilient environments and buildings, making a growing know-how and skill available to the local and broad communities. Pivotal to this have been dedicated projects and funds, like the UNIVPM strategic projects and the MIUR Dipartimenti di Eccellenza award. In conjunction with the four companion papers, produced by researchers of the four divisions of DICEA, we illustrate the DICEA’s trajectory in the analysis of sustainable engineering for resilient built and natural environments.
Bookmarks Related papers MentionsView impact
Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2021
Bookmarks Related papers MentionsView impact
Engineering Structures, 2021
Bookmarks Related papers MentionsView impact
Meccanica, 2020
The internal resonance of a two degree-of-freedom mechanical system with all typical (quadratic a... more 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.
Bookmarks Related papers MentionsView impact
The Open Construction and Building Technology Journal, 2019
Background: The vulnerability assessment of existing school buildings against earthquakes represe... more 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. Objective: 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...
Bookmarks Related papers MentionsView impact
Bulletin of Earthquake Engineering, 2019
Bookmarks Related papers MentionsView impact
Archive of Applied Mechanics, 2016
Two approximate solutions for the nonlinear free oscillations of a planar Timoshenko beam are com... more Two approximate solutions for the nonlinear free oscillations of a planar Timoshenko beam are compared to each other. The beam has an axial spring that permits to consider different boundary conditions, from axially free (which has a softening nonlinear behaviour) to perfectly axially restrained (which has a hardening nonlinear behaviour). The first approximation is analytical and is obtained by the asymptotic development method, while the second is numerical and is obtained by the finite element method. The comparison is made in terms of backbone curves describing the dependence of the (nonlinear) frequency on the oscillation amplitude. Very good agreement is found, for both slender and thick beams, and for varying stiffness of the end spring. This is a cross-check verification of the reliability of both approximate solutions.
Bookmarks Related papers MentionsView impact
Meccanica, 2016
The free nonlinear oscillations of a planar elastic beam are investigated based on a comprehensiv... more The free nonlinear oscillations of a planar elastic beam are investigated based on a comprehensive asymptotic treatment of the exact equations of motion. With the aim of investigating the behaviour also for low slenderness, shear deformations and rotational inertia are taken into account. Attention is payed to the influence of the geometrical and mechanical parameters, and of the boundary conditions in changing the nonlinear behaviour from softening to hardening. An axial linear spring is added to one end of the beam, and it is shown how the behaviour changes qualitatively on passing from the hinged-hinged (commonly hardening) to the hinged-supported (commonly softening) case. Some interesting, and partially unexpected, results are obtained also for values of the slenderness moderately low but still in the realm of practical applications.
Bookmarks Related papers MentionsView impact
Communications in Nonlinear Science and Numerical Simulation, 2018
Bookmarks Related papers MentionsView impact
Meccanica, 2017
Bookmarks Related papers MentionsView impact