... Luca Facchini DIC/CRIACIV, Università degli Studi di Firenze, Italia E-mail: luca@dicea.unifi... more ... Luca Facchini DIC/CRIACIV, Università degli Studi di Firenze, Italia E-mail: luca@dicea.unifi. it Michele Betti DIC/CRIACIV, Università degli Studi di Firenze, Italia E-mail: luca@dicea.unifi. it ... (15) 4. ANALISI DELL'ALEATORIETÀ DERIVANTE DAI PARAMETRI INCERTI. ...
... ³ Univ. of Florence Via S. Marta 3 50139 Firenze Italy paolo.biagini@dicea.unifi.it Key Wor... more ... ³ Univ. of Florence Via S. Marta 3 50139 Firenze Italy paolo.biagini@dicea.unifi.it Key Words: Neural networks, inverse problems, Bayesian approach, Radial basis functions. ... 543−561, (1993). [2] OC Zienkiewicz and RC Taylor, The finite element method, 4th Edition, Vol. ...
Historical masonry towers constitute a great part of Italian built heritage: wonderful towers and... more Historical masonry towers constitute a great part of Italian built heritage: wonderful towers and bell-towers can be observed all over the territory. Such structures exhibit many aspects which are difficult to describe from a numerical point of view. Among the most common: i) the restraint condition at their base is not exactly clear as they are often embedded in other buildings (such as church bell-towers); ii) the material behavior is not very clear as the masonry is often made of three layers, each one with different mechanical characteristics. Simplified models can be set up for these structures in order to assess their relative seismic risk, i.e. such models may be applied to a set of nearby towers in order to identify the most prone towers to earthquakes. A deeper insight into their behavior, nevertheless, requires reliable nonlinear numerical models. In the paper, in this respect, some constitutive models already implemented in a finite element software (Code Aster) are employed to perform static nonlinear analyses on a prototype of masonry tower (a cantilever beam), and the obtained results are then compared. The parameters required by each constitutive model have been tuned to obtain comparable values of compressive and tensile strengths, and subsequent comparison is presented. Eventually, a fiber continuous simplified numerical model is also presented; it takes into account several degrees of freedom, chosen as the displacements of the vertical axis of the tower. Nonlinear behavior and damage of the material, along with the efficiency of cross sections, are taken into consideration. The model compares satisfactorily with more complex analyses performed with Code_Aster. The comparison shows both the main advantage and the main limitations of the simplified fiber model.
This paper summarizes the results of a two-day dynamic monitoring of Michelangelo's David subject... more This paper summarizes the results of a two-day dynamic monitoring of Michelangelo's David subject to environmental loads (city traffic and pedestrian loading induced by tourists visiting the Accademia Gallery). The monitoring was carried out by a no-contact technique using an interferometric radar, whose effectiveness in measuring the resonant frequencies of structures and historic monuments has proved over the last years through numerous monitoring activities. Owing to the dynamic behavior of the measurement system (radar and tripod), an accelerometer has been installed on the radar head to filter out the movement component of the measuring instrument from the measurement of the David's displacement. Measurements were carried out in the presence and absence of visitors, to assess their influence on the dynamic behavior of the statue. A numerical model of the statue was employed to evaluate the experimental results.
The paper shows a simplified procedure to compute a seismic analysis of a masonry tower. Masonry ... more The paper shows a simplified procedure to compute a seismic analysis of a masonry tower. Masonry is modelled as a no-tensile resistant material (NTR) which might be affected by randomness in its mechanical parameters. It is assumed that the first modal shape governs the structural motion, and its behaviour is modelled by means of a Bouc & Wen approach, which is eventually linearized. Sommario. La memoria illustra una procedura semplificata per effettuare l'analisi sismica di una torre in muratura. La muratura è considerata non resistente a trazione e può essere influenzata da aleatorietà nei suoi parametri meccanici. Si ipotizza che il moto strutturale sia governato dalla prima forma modale, ed il suo comportamento viene modellato da un approccio alla Bouc & Wen, che viene infine linearizzato.
Journal of Wind Engineering and Industrial Aerodynamics, Oct 1, 2007
The paper presents the experimental tests carried out in the boundary layer wind tunnel (BLWT) fo... more The paper presents the experimental tests carried out in the boundary layer wind tunnel (BLWT) for the design of large roofs of the new Olympic stadium (Karaiskaki) in Pyraeus (Greece), Manfredonia (Italy) and “Delle Alpi” of Turin (Italy). In addition, a report about some results of the T.D. dynamic response analyses performed on the Karaiskaki structure and on the Olympic
ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering, 2015
The structural assessment of existing masonry towers under exceptional loads, such as earthquake ... more The structural assessment of existing masonry towers under exceptional loads, such as earthquake loads, requires reliable and expedite methods of analysis. These approaches should take into account both the specific nonlinear behavior of the material (for instance, the small tensile strength) and the randomness that affect the masonry material's properties (in some cases the distribution of the elastic parameters too). Considering the need of simplified but effective methods to assess the seismic response of such a class of structures, the paper proposes an expeditious approach based on an equivalent Bouc and Wen model. As a prototype of masonry towers, a cantilever masonry beam is analyzed assuming that the first mode shape governs the dynamic behavior. With this hypothesis, the nonlinear Bouc and Wen model is employed to reproduce the system hysteretic response. Subsequently, assuming the material properties as random variables, stochastic linearization and the perturbative approach are employed to evaluate the bounds of the seismic response. The results of the simplified approach are compared with the results of finite-element models to show the effectiveness of the method.
The paper, through the discussion of an experimental investigation, considers a combined approach... more The paper, through the discussion of an experimental investigation, considers a combined approach based on artificial neural networks and genetic algorithms for structural damage identification. A reduced scale three-storey steel spatial frame was instrumented by a series of 12 accelerometers and progressively damaged by cutting one of its columns just above the first storey. Accelerations induced by ambient vibrations were recorded as the frame was progressively damaged, and the deepness of the cut was taken as the entity of the damage. At every damage level the modal properties (natural frequencies and modal shapes) of the steel frame were evaluated through a neural network based approach. Subsequently, two error functions that measure the differences between the experimental results and those calculated from a finite element model of the steel frame were defined and a genetic algorithm was employed for damage detection. Results of the experimentation (where damage was known as both location and extent) were compared with the results of the optimization algorithm in order to verify its ability to match the actual damage.
This paper presents a hybrid Galerkin/perturbation approach based on Radial Basis Functions for t... more This paper presents a hybrid Galerkin/perturbation approach based on Radial Basis Functions for the dynamic analysis of mechanical systems affected by randomness both in their parameters and loads. In specialized literature various procedures are nowadays available to evaluate the response statistics of such systems, but sometimes a choice has to be made between simpler methods that could provide unreliable solutions and more complex methods where accurate solutions are provided by means of a heavy computational effort. The proposed method combines a Radial Basis Functions RBF based Galerkin method with a perturbation approach for the approximation of the system response. In order to keep the number of differential equations to be solved as low as possible, a Karhunen-Lò eve KL expansion for the excitation is used. As case study a non-linear single degree of freedom SDOF system with random parameters subjected to a stochastic windtype load is analyzed and discussed in detail ; obtained numerical solutions are compared with the results given by Monte Carlo Simulation MCS to provide a validation of the proposed approach. The proposed method could be a valid alternative to the classical procedures as it is able to provide satisfactory approximations of the system response .
... tutti i possibili meccanismi di danno dei giunti, si è imposta una condizione di emisimmetria... more ... tutti i possibili meccanismi di danno dei giunti, si è imposta una condizione di emisimmetria sulle deformazioni dei giunti principali di malta. ... Un metodo numerico per l'analisi strutturale di cupole in muratura: la chiesa di S. Maria Maddalena a Morano Calabro Katia Bernardeschi ...
Base isolation is considered one of the most effective techniques to minimize seismic risk for st... more Base isolation is considered one of the most effective techniques to minimize seismic risk for structures, and many additional applications -such as artifacts and statues -have been recently proposed. Statues, for instance, are starting to be isolated with several devices (laminated rubber bearings, sliding bearings, marble devices, etc). This paper investigates a base isolation system that employs sliders at between its basement and the floor. As an applicative case study, the seismic risk reduction of Michelangelo's David, is analyzed. Actually, the statue is located in the Accademia Gallery (Florence, Italy). The site is characterized by a medium seismicity and thus many studies have been undertaken in order to protect this masterpiece. The device herein considered consists of two sliding plates arranged, as to decouple seismic motions, in an array of movable top plates and fixed bottom plates. This paper aims to reproduce the interaction "statue -sliders -base support" taking into consideration EQX global (http://www.eqxglobal.net) seismic protection devices. Isolation system behavior has been reproduced by employing a Bouc and Wen hysteretic model whose parameters have been calibrated by shaking table tests performed by EQX global at the Pacific Earthquake Engineering Research (PEER) Center laboratories. This study represents a preliminary attempt in order to numerically reproduce the complexity of the problem with all the necessary details.
The present paper analyzes the possibility of the application of neural networks to find the solu... more The present paper analyzes the possibility of the application of neural networks to find the solution to elastic problems in two different ways: the first one is the application of radial basis functions networks trained by means of energy based criteria, such as Hu-Washizu principle, while the second analyzes the utilization of RBF functions for the enrichment of shape functions in the PUFEM approach. Training enables the optimization of nonlinear parameters of the networks, and a brief discussion of this aspect is included.
This paper describes a methodology, which is presently under examination at the CRIACIV – Univers... more This paper describes a methodology, which is presently under examination at the CRIACIV – University of Florence, to reproduce non-gaussian wind pressure fields from wind tunnel data. The data consist of records of pressure acting at discrete locations on the surface of a reduced scale model of the structure, and subsequently extended to other locations by means of a radial basis neural network interpolation. The coefficients of the neural network are determined directly from the wind tunnel recorded pressures, and can exhibit non-gaussian distribution, according to the pressure taps locations. The coefficients can be reduced to linear functions of uncorrelated noises by means of a spectral diagonalization. The key contribution of the paper is then the generation of a scalar non-gaussian process with the same statistical properties of the recorded data.
SOMMARIO Nel presente lavoro viene presentata una procedura per la modellazione di un sistema di ... more SOMMARIO Nel presente lavoro viene presentata una procedura per la modellazione di un sistema di smorzamento a massa liquida per mitigare le vibrazioni indotte dal vento sugli edifici alti. La definizione dei parametri di progetto è basata sul modello di Housner, elaborato nell'ambito dell'ingegneria sismica per serbatoi di stoccaggio acqua. Data la differenza volumetrica fra tali serbatoi ed i contenitori di cui solitamente l'intero sistema di smorzamento è composto, è stata verificata l'accettabilità dell'approssimazione con un confronto sui parametri di sloshing forniti dalla trattazione analitica. La procedura è stata quindi utilizzata per valutare la risposta di un edificio alto sottoposto a prove su un modello in scala in galleria del vento. Un modello autoregressivo è stato utilizzato per l'estensione in frequenza dei segnali registrati in galleria. Sono stati analizzati quattro modelli del caso di studio, variabili nel fattore di massa dello smorzator...
La memoria riporta i risultati ottenuti su alcuni casi studio sviluppati nell’ambito delle attivi... more La memoria riporta i risultati ottenuti su alcuni casi studio sviluppati nell’ambito delle attività preliminari del progetto di ricerca “RiSEM - Rischio Sismico negli Edifici Monumentali”. Il progetto nasce con lo scopo di mettere a punto tecniche di indagine, di analisi e di diagnosi che consentano, in maniera speditiva e con costi relativamente contenuti, di stabilire il rischio sismico di beni monumentali. In ambito specificatamente strutturale, la prima parte della ricerca è stata finalizzata al confronto tra diverse tecniche di modellazione numerica per la definizione del comportamento in campo non lineare di una serie di elementi in muratura sottoposti ad azioni orizzontali. I casi sono stati individuati seguendo il duplice obiettivo di: 1) definire in maniera corretta i parametri di crisi degli elementi strutturali, in modo da poter procedere alla messa a punto di modelli numerici semplificati; 2) fornire una stima delle incertezze di tipo epistemico, ossia collegate alle div...
This paper aims to evaluate the effectiveness of the non-linear time-history analysis to assess t... more This paper aims to evaluate the effectiveness of the non-linear time-history analysis to assess the seismic behaviour of traditional masonry building (as proposed by the new Italian Recommendation). An illustrative case study is herein discussed. The analysed masonry building is a poor masonry construction experimentally investigated at the research centre CNR-ENEA (Casaccia, Roma) by a shaking table. In these tests an increasing earthquake loading accelerations have been applied at the basement. The experimental tests have been numerically simulated by means of the finite element technique. The comparison between experimental and numerical results suggests that the non-linear time-history analysis is an effective tool for the assessment of masonry building behaviour under seismic loads. Nevertheless, a proper material characterization of the masonry material is needed to identify the numerical model.
This paper reports on an experiment carried out in the laboratory of Civil and En-vironmental Eng... more This paper reports on an experiment carried out in the laboratory of Civil and En-vironmental Engineering of the University of Florence, where a reduced scale (approximately 2.5 m width × 2.5 m depth × 4.8 m height), three storey steel spatial frame was instrumented and progressively damaged by cutting one of its pillars just above the foundation; the deep-ness of the cut could be measured and was taken as the entity of the damage. A series of 12 accelerometers was installed on the frame and 3 more accelerometers were installed on the ground; acceleration measurements induced by ambient vibrations were recorded as the frame was progressively damaged. Acceleration signals were subsequently analyzed in both time and frequency domain (SSI, EFDD, neural networks): a frequency shift and a change in the corresponding modal shapes were observed as the damage increased. The damaged truss was also modelled by means of a FEM code and the frequency shift and the change in the modal shapes were...
The structural assessment of existing masonry towers under exceptional loads, such as earthquake ... more The structural assessment of existing masonry towers under exceptional loads, such as earthquake loads, requires reliable and expedite methods of analysis. These approaches should take into account both the randomness that affect the masonry material properties (in some cases the distribution of elastic parameters too) and the specific non-linear behavior (f.i. the small tensile strength) of the material. Considering the need of simplified but effective methods to assess the seismic response of slender masonry tower, the paper aims to propose an expeditious approach for seismic assessment of masonry towers assuming the material properties as a stochastic field. As a prototype of masonry towers a cantilever beam is analyzed assuming that the first modal shape governs the structural motion. With this hypothesis a non-linear hysteretic Bouc & Wen model is employed to reproduce the system response which is eventually linearized to evaluate its bounds. The results of the simplified appro...
... Luca Facchini DIC/CRIACIV, Università degli Studi di Firenze, Italia E-mail: luca@dicea.unifi... more ... Luca Facchini DIC/CRIACIV, Università degli Studi di Firenze, Italia E-mail: luca@dicea.unifi. it Michele Betti DIC/CRIACIV, Università degli Studi di Firenze, Italia E-mail: luca@dicea.unifi. it ... (15) 4. ANALISI DELL'ALEATORIETÀ DERIVANTE DAI PARAMETRI INCERTI. ...
... ³ Univ. of Florence Via S. Marta 3 50139 Firenze Italy paolo.biagini@dicea.unifi.it Key Wor... more ... ³ Univ. of Florence Via S. Marta 3 50139 Firenze Italy paolo.biagini@dicea.unifi.it Key Words: Neural networks, inverse problems, Bayesian approach, Radial basis functions. ... 543−561, (1993). [2] OC Zienkiewicz and RC Taylor, The finite element method, 4th Edition, Vol. ...
Historical masonry towers constitute a great part of Italian built heritage: wonderful towers and... more Historical masonry towers constitute a great part of Italian built heritage: wonderful towers and bell-towers can be observed all over the territory. Such structures exhibit many aspects which are difficult to describe from a numerical point of view. Among the most common: i) the restraint condition at their base is not exactly clear as they are often embedded in other buildings (such as church bell-towers); ii) the material behavior is not very clear as the masonry is often made of three layers, each one with different mechanical characteristics. Simplified models can be set up for these structures in order to assess their relative seismic risk, i.e. such models may be applied to a set of nearby towers in order to identify the most prone towers to earthquakes. A deeper insight into their behavior, nevertheless, requires reliable nonlinear numerical models. In the paper, in this respect, some constitutive models already implemented in a finite element software (Code Aster) are employed to perform static nonlinear analyses on a prototype of masonry tower (a cantilever beam), and the obtained results are then compared. The parameters required by each constitutive model have been tuned to obtain comparable values of compressive and tensile strengths, and subsequent comparison is presented. Eventually, a fiber continuous simplified numerical model is also presented; it takes into account several degrees of freedom, chosen as the displacements of the vertical axis of the tower. Nonlinear behavior and damage of the material, along with the efficiency of cross sections, are taken into consideration. The model compares satisfactorily with more complex analyses performed with Code_Aster. The comparison shows both the main advantage and the main limitations of the simplified fiber model.
This paper summarizes the results of a two-day dynamic monitoring of Michelangelo's David subject... more This paper summarizes the results of a two-day dynamic monitoring of Michelangelo's David subject to environmental loads (city traffic and pedestrian loading induced by tourists visiting the Accademia Gallery). The monitoring was carried out by a no-contact technique using an interferometric radar, whose effectiveness in measuring the resonant frequencies of structures and historic monuments has proved over the last years through numerous monitoring activities. Owing to the dynamic behavior of the measurement system (radar and tripod), an accelerometer has been installed on the radar head to filter out the movement component of the measuring instrument from the measurement of the David's displacement. Measurements were carried out in the presence and absence of visitors, to assess their influence on the dynamic behavior of the statue. A numerical model of the statue was employed to evaluate the experimental results.
The paper shows a simplified procedure to compute a seismic analysis of a masonry tower. Masonry ... more The paper shows a simplified procedure to compute a seismic analysis of a masonry tower. Masonry is modelled as a no-tensile resistant material (NTR) which might be affected by randomness in its mechanical parameters. It is assumed that the first modal shape governs the structural motion, and its behaviour is modelled by means of a Bouc & Wen approach, which is eventually linearized. Sommario. La memoria illustra una procedura semplificata per effettuare l'analisi sismica di una torre in muratura. La muratura è considerata non resistente a trazione e può essere influenzata da aleatorietà nei suoi parametri meccanici. Si ipotizza che il moto strutturale sia governato dalla prima forma modale, ed il suo comportamento viene modellato da un approccio alla Bouc & Wen, che viene infine linearizzato.
Journal of Wind Engineering and Industrial Aerodynamics, Oct 1, 2007
The paper presents the experimental tests carried out in the boundary layer wind tunnel (BLWT) fo... more The paper presents the experimental tests carried out in the boundary layer wind tunnel (BLWT) for the design of large roofs of the new Olympic stadium (Karaiskaki) in Pyraeus (Greece), Manfredonia (Italy) and “Delle Alpi” of Turin (Italy). In addition, a report about some results of the T.D. dynamic response analyses performed on the Karaiskaki structure and on the Olympic
ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering, 2015
The structural assessment of existing masonry towers under exceptional loads, such as earthquake ... more The structural assessment of existing masonry towers under exceptional loads, such as earthquake loads, requires reliable and expedite methods of analysis. These approaches should take into account both the specific nonlinear behavior of the material (for instance, the small tensile strength) and the randomness that affect the masonry material's properties (in some cases the distribution of the elastic parameters too). Considering the need of simplified but effective methods to assess the seismic response of such a class of structures, the paper proposes an expeditious approach based on an equivalent Bouc and Wen model. As a prototype of masonry towers, a cantilever masonry beam is analyzed assuming that the first mode shape governs the dynamic behavior. With this hypothesis, the nonlinear Bouc and Wen model is employed to reproduce the system hysteretic response. Subsequently, assuming the material properties as random variables, stochastic linearization and the perturbative approach are employed to evaluate the bounds of the seismic response. The results of the simplified approach are compared with the results of finite-element models to show the effectiveness of the method.
The paper, through the discussion of an experimental investigation, considers a combined approach... more The paper, through the discussion of an experimental investigation, considers a combined approach based on artificial neural networks and genetic algorithms for structural damage identification. A reduced scale three-storey steel spatial frame was instrumented by a series of 12 accelerometers and progressively damaged by cutting one of its columns just above the first storey. Accelerations induced by ambient vibrations were recorded as the frame was progressively damaged, and the deepness of the cut was taken as the entity of the damage. At every damage level the modal properties (natural frequencies and modal shapes) of the steel frame were evaluated through a neural network based approach. Subsequently, two error functions that measure the differences between the experimental results and those calculated from a finite element model of the steel frame were defined and a genetic algorithm was employed for damage detection. Results of the experimentation (where damage was known as both location and extent) were compared with the results of the optimization algorithm in order to verify its ability to match the actual damage.
This paper presents a hybrid Galerkin/perturbation approach based on Radial Basis Functions for t... more This paper presents a hybrid Galerkin/perturbation approach based on Radial Basis Functions for the dynamic analysis of mechanical systems affected by randomness both in their parameters and loads. In specialized literature various procedures are nowadays available to evaluate the response statistics of such systems, but sometimes a choice has to be made between simpler methods that could provide unreliable solutions and more complex methods where accurate solutions are provided by means of a heavy computational effort. The proposed method combines a Radial Basis Functions RBF based Galerkin method with a perturbation approach for the approximation of the system response. In order to keep the number of differential equations to be solved as low as possible, a Karhunen-Lò eve KL expansion for the excitation is used. As case study a non-linear single degree of freedom SDOF system with random parameters subjected to a stochastic windtype load is analyzed and discussed in detail ; obtained numerical solutions are compared with the results given by Monte Carlo Simulation MCS to provide a validation of the proposed approach. The proposed method could be a valid alternative to the classical procedures as it is able to provide satisfactory approximations of the system response .
... tutti i possibili meccanismi di danno dei giunti, si è imposta una condizione di emisimmetria... more ... tutti i possibili meccanismi di danno dei giunti, si è imposta una condizione di emisimmetria sulle deformazioni dei giunti principali di malta. ... Un metodo numerico per l'analisi strutturale di cupole in muratura: la chiesa di S. Maria Maddalena a Morano Calabro Katia Bernardeschi ...
Base isolation is considered one of the most effective techniques to minimize seismic risk for st... more Base isolation is considered one of the most effective techniques to minimize seismic risk for structures, and many additional applications -such as artifacts and statues -have been recently proposed. Statues, for instance, are starting to be isolated with several devices (laminated rubber bearings, sliding bearings, marble devices, etc). This paper investigates a base isolation system that employs sliders at between its basement and the floor. As an applicative case study, the seismic risk reduction of Michelangelo's David, is analyzed. Actually, the statue is located in the Accademia Gallery (Florence, Italy). The site is characterized by a medium seismicity and thus many studies have been undertaken in order to protect this masterpiece. The device herein considered consists of two sliding plates arranged, as to decouple seismic motions, in an array of movable top plates and fixed bottom plates. This paper aims to reproduce the interaction "statue -sliders -base support" taking into consideration EQX global (http://www.eqxglobal.net) seismic protection devices. Isolation system behavior has been reproduced by employing a Bouc and Wen hysteretic model whose parameters have been calibrated by shaking table tests performed by EQX global at the Pacific Earthquake Engineering Research (PEER) Center laboratories. This study represents a preliminary attempt in order to numerically reproduce the complexity of the problem with all the necessary details.
The present paper analyzes the possibility of the application of neural networks to find the solu... more The present paper analyzes the possibility of the application of neural networks to find the solution to elastic problems in two different ways: the first one is the application of radial basis functions networks trained by means of energy based criteria, such as Hu-Washizu principle, while the second analyzes the utilization of RBF functions for the enrichment of shape functions in the PUFEM approach. Training enables the optimization of nonlinear parameters of the networks, and a brief discussion of this aspect is included.
This paper describes a methodology, which is presently under examination at the CRIACIV – Univers... more This paper describes a methodology, which is presently under examination at the CRIACIV – University of Florence, to reproduce non-gaussian wind pressure fields from wind tunnel data. The data consist of records of pressure acting at discrete locations on the surface of a reduced scale model of the structure, and subsequently extended to other locations by means of a radial basis neural network interpolation. The coefficients of the neural network are determined directly from the wind tunnel recorded pressures, and can exhibit non-gaussian distribution, according to the pressure taps locations. The coefficients can be reduced to linear functions of uncorrelated noises by means of a spectral diagonalization. The key contribution of the paper is then the generation of a scalar non-gaussian process with the same statistical properties of the recorded data.
SOMMARIO Nel presente lavoro viene presentata una procedura per la modellazione di un sistema di ... more SOMMARIO Nel presente lavoro viene presentata una procedura per la modellazione di un sistema di smorzamento a massa liquida per mitigare le vibrazioni indotte dal vento sugli edifici alti. La definizione dei parametri di progetto è basata sul modello di Housner, elaborato nell'ambito dell'ingegneria sismica per serbatoi di stoccaggio acqua. Data la differenza volumetrica fra tali serbatoi ed i contenitori di cui solitamente l'intero sistema di smorzamento è composto, è stata verificata l'accettabilità dell'approssimazione con un confronto sui parametri di sloshing forniti dalla trattazione analitica. La procedura è stata quindi utilizzata per valutare la risposta di un edificio alto sottoposto a prove su un modello in scala in galleria del vento. Un modello autoregressivo è stato utilizzato per l'estensione in frequenza dei segnali registrati in galleria. Sono stati analizzati quattro modelli del caso di studio, variabili nel fattore di massa dello smorzator...
La memoria riporta i risultati ottenuti su alcuni casi studio sviluppati nell’ambito delle attivi... more La memoria riporta i risultati ottenuti su alcuni casi studio sviluppati nell’ambito delle attività preliminari del progetto di ricerca “RiSEM - Rischio Sismico negli Edifici Monumentali”. Il progetto nasce con lo scopo di mettere a punto tecniche di indagine, di analisi e di diagnosi che consentano, in maniera speditiva e con costi relativamente contenuti, di stabilire il rischio sismico di beni monumentali. In ambito specificatamente strutturale, la prima parte della ricerca è stata finalizzata al confronto tra diverse tecniche di modellazione numerica per la definizione del comportamento in campo non lineare di una serie di elementi in muratura sottoposti ad azioni orizzontali. I casi sono stati individuati seguendo il duplice obiettivo di: 1) definire in maniera corretta i parametri di crisi degli elementi strutturali, in modo da poter procedere alla messa a punto di modelli numerici semplificati; 2) fornire una stima delle incertezze di tipo epistemico, ossia collegate alle div...
This paper aims to evaluate the effectiveness of the non-linear time-history analysis to assess t... more This paper aims to evaluate the effectiveness of the non-linear time-history analysis to assess the seismic behaviour of traditional masonry building (as proposed by the new Italian Recommendation). An illustrative case study is herein discussed. The analysed masonry building is a poor masonry construction experimentally investigated at the research centre CNR-ENEA (Casaccia, Roma) by a shaking table. In these tests an increasing earthquake loading accelerations have been applied at the basement. The experimental tests have been numerically simulated by means of the finite element technique. The comparison between experimental and numerical results suggests that the non-linear time-history analysis is an effective tool for the assessment of masonry building behaviour under seismic loads. Nevertheless, a proper material characterization of the masonry material is needed to identify the numerical model.
This paper reports on an experiment carried out in the laboratory of Civil and En-vironmental Eng... more This paper reports on an experiment carried out in the laboratory of Civil and En-vironmental Engineering of the University of Florence, where a reduced scale (approximately 2.5 m width × 2.5 m depth × 4.8 m height), three storey steel spatial frame was instrumented and progressively damaged by cutting one of its pillars just above the foundation; the deep-ness of the cut could be measured and was taken as the entity of the damage. A series of 12 accelerometers was installed on the frame and 3 more accelerometers were installed on the ground; acceleration measurements induced by ambient vibrations were recorded as the frame was progressively damaged. Acceleration signals were subsequently analyzed in both time and frequency domain (SSI, EFDD, neural networks): a frequency shift and a change in the corresponding modal shapes were observed as the damage increased. The damaged truss was also modelled by means of a FEM code and the frequency shift and the change in the modal shapes were...
The structural assessment of existing masonry towers under exceptional loads, such as earthquake ... more The structural assessment of existing masonry towers under exceptional loads, such as earthquake loads, requires reliable and expedite methods of analysis. These approaches should take into account both the randomness that affect the masonry material properties (in some cases the distribution of elastic parameters too) and the specific non-linear behavior (f.i. the small tensile strength) of the material. Considering the need of simplified but effective methods to assess the seismic response of slender masonry tower, the paper aims to propose an expeditious approach for seismic assessment of masonry towers assuming the material properties as a stochastic field. As a prototype of masonry towers a cantilever beam is analyzed assuming that the first modal shape governs the structural motion. With this hypothesis a non-linear hysteretic Bouc & Wen model is employed to reproduce the system response which is eventually linearized to evaluate its bounds. The results of the simplified appro...
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