Bridges are essential to infrastructure and transportation networks, but face challenges from hea... more Bridges are essential to infrastructure and transportation networks, but face challenges from heavier traffic, higher speeds, and modifications like busway integration, leading to potential overloading and costly maintenance. Structural Health Monitoring (SHM) plays a crucial role in assessing bridge conditions and predicting failures to maintain structural integrity. Vibration-based condition monitoring employs non-destructive, in situ sensing and analysis of system dynamics across time, frequency, or modal domains. This method detects changes indicative of damage or deterioration, offering a proactive approach to maintenance in civil engineering. Such monitoring systems hold promise for optimizing the management and upkeep of modern infrastructure, potentially reducing operational costs. This paper aims to assist newcomers, practitioners, and researchers in navigating various methodologies for damage identification using sensor data from real structures. It offers a comprehensive review of prevalent anomaly detection approaches, spanning from traditional techniques to cutting-edge methods. Additionally, it addresses challenges inherent in Vibration-Based Damage (VBD) SHM applications, including establishing damage thresholds, corrosion detection, and sensor drift.
Still nowadays masonry structures represent most of the global built environment in seismic regio... more Still nowadays masonry structures represent most of the global built environment in seismic regions. Despite their diffusion and long age, their dynamic behavior under earthquake loads is still extremely hard to predict, since it depends on several site-dependent factors, such as local empirical expertise, that are difficult to generalize. Furthermore, considerable and often economically disproportionate efforts are usually required to achieve a sufficient knowledge level for characterizing the basic variables affecting their response. The problem is challenging and the recent earthquakes have highlighted the extreme urgency to provide structural engineers with reliable yet simple procedures to seismically assess such buildings. This work intends to propose a new approach for dealing with ex-isting masonry structures, by expressing their seismic vulnerability in terms of failure probability, using only two (or three, if needed) sim-plified non-linear deterministic analyses, where the standard devia-tions of a selected number of variables are appropriately combined. The method has been applied to five Structural Units, where two types of wall connections and four masonry types were considered. Numeri-cal models are purposely developed in spreadsheets, to calculate the base shear/displacement response of each floor and then build the global response of the equivalent SDOF system. For the purpose of comparison, the proposed approach was validated against a fully probabilistic analysis by including all uncertainties affecting the struc-tural response. The probabilistic response of each considered structural unit is rep-resented through Capacity/Demand (C/D) ratios and exceedance prob-abilities. Sensitivity analyses are used to quantify and rank the effects of each variable on the global response. The viability of the overall procedure is commented upon, with due attention to the ensuing er-rors, which are deemed to be more than acceptable, given that only a few analyses have to be carried out
The challenge against the waste of resources in the world of construction industry, starts from t... more The challenge against the waste of resources in the world of construction industry, starts from the seismic and thermal retrofitting of existing buildings with low environmental impact innovative technologies. When the buildings are especially vulnerable, for instance in the case of double-layer infills -often without thermal insulation -it's really hard to achieve satisfactory performance levels without resorting to radical interventions. In these cases the interaction with the building internal activities is unavoidable and forms a further design constraints. This work shows an innovative technology based on recycled plastic parts, optimized for the double-layer infills of existing buildings in which the maintaining of the internal activity is fundamental for the successful of the intervention. The system with recycled plastic joints is aiming at improving thermal and seismic performances, avoiding the residents relocation, consistently reducing the demolitions of existing infills and using plastic from recycled waste. Such system was preliminarily tested on a real-scale double-layer infill equipped with two joint lines under horizontal force at the testing laboratory of materials and structures (LPMS) of the University of L'Aquila. On the basis of this previous experimental tests, the present study proposes the calibration of a macroelement and a later numerical modelling of a multi-storey frame representative of r.c. buildings of the 80's. The results of the retrofitted configuration with plastic joints were compared with bare frame and infilled frame with different macroelement available for traditional infills.
In this study, a direct displacement-based method is proposed for the design of hysteretic dissip... more In this study, a direct displacement-based method is proposed for the design of hysteretic dissipative bracings to be applied to gravity-load-designed (GLD) reinforced concrete (RC) frames. The direct, i.e., non-iterative, design procedure aims at limiting the interstorey drifts of the GLD frame to prevent damage in the existing columns, thanks to the added stiffness and damping of the bracings. The method is based on a simplified yet accurate representation of the braced frame, through a so-called stick model, whose elements stiffness and damping are obtained by equivalent linearization of each braced storey. The method allows obtaining an optimal design of the bracing system at each storey, both in terms of stiffness and damping. The design method efficiency has been validated by comparing the performance of three GLD RC frames retrofitted with bracing systems designed with two other methods available in the literature.
I centri storici sono comunemente il risultato di una serie di eventi succedutisi nel tempo che d... more I centri storici sono comunemente il risultato di una serie di eventi succedutisi nel tempo che danno luogo a una stratificazione temporale e spaziale di sistemi aggregativi di costruzioni che presentano, agli occhi dell’analista strutturale, una profonda complessità che rende ardua la valutazione della loro vulnerabilità sismica.. Per la prima volta, nel 2003, l’OPCM 3274 introduce il concetto di aggregato edilizio, proponendo un metodo di riconoscimento delle sue Unità Strutturali, nonché di modellazione ed analisi di queste, fondato sulla consapevolezza che “in questi casi lo studio assume una natura convenzionale”. Nonostante ciò, si fornisce al professionista uno strumento agevole per gestire tale complessità, attraverso una serie di ipotesi semplificative, al tempo stesso imponendo, però, il ricorso all’analisi non lineare di ogni singola Unità Strutturale. Essendo la normativa di natura prestazionale, essa non fornisce indicazioni su come eseguire tale analisi. Il lavoro di q...
Modern approaches in buildings design strive to fulfill multiple performance requirements simulta... more Modern approaches in buildings design strive to fulfill multiple performance requirements simultaneously. Accordingly, as far as buildings in earthquake-prone areas are concerned, damage limitation under seismic loads must be ensured while paying attention on the issues related to the environmental sustainability of the construction, ranging from its ecological footprint to the thermal efficiency. Masonry infills in framed reinforced concrete buildings are especially important in this context. In fact, they are vulnerable to earthquakes and greatly impact on the environmental sustainability of the building because they employ a significant amount of construction materials and influence its energy consumption throughout the lifetime. In light of this, the main novelty of the present work is concerned with a new deformable joint for masonry infills in framed reinforced concrete buildings. A detailed description of such innovative system for masonry infills is provided, together with numerical and experimental investigations about its mechanical and thermal behavior. The proposed joint is made of recycled plastic material, namely Regenerated Polypropylene Homopolymer. Geometry and manufacturing process of the proposed joint are initially described. Then, stress–strain relationships for the plastic material are obtained from uniaxial tensile tests at different temperatures. An assembly of fired hollow clay bricks and plastic joints is also tested under in-plane cyclic load, and a phenomenological model is thus proposed to simulate the experimental hysteretic behavior. Finally, experimental tests and finite element-based numerical simulations are performed to investigate the thermal performance of masonry infills with plastic joints.
Advances in FRP Composites in Civil Engineering, 2011
An innovative method to connect existing orthogonal masonry walls through aramidic FRP bars is pr... more An innovative method to connect existing orthogonal masonry walls through aramidic FRP bars is presented. The proposed technique has the objective of mobilizing and maximizing the collaboration of intersecting structural elements, thus increasing the overall strength and stiffness of masonry buildings under horizontal forces. The method was experimentally tested to prove its applicability and effectiveness.
Masonry buildings represent a large and important portion of the existing building stock in sever... more Masonry buildings represent a large and important portion of the existing building stock in several countries. They are still being built and nowadays they are mainly used as residential buildings, offices or for other activities. Most of these buildings are not designed to withstand earthquake-induced forces, therefore seismic safety assessment represents a crucial task to estimate risk level and eventually define retrofit measures. This task is hampered by the many uncertainties affecting the acquired data on plan and elevation geometry, material properties, connections between walls and roof, connections between walls and walls, seismic actions. The present paper intends to give a contribution in dealing with such uncertainties by applying a global probabilistic analysis on different masonry structural units. Such approach is based on the Italian seismic code and relies on a simplified non-linear assessment method. Purposely developed codes have been used for deriving the equivalent bilinear constitutive laws of floors and of the entire structural unit. Afterwards, a fully probabilistic Monte Carlo-based analysis has been performed by including and consistently modeling all uncertainties affecting the structural response. Capacity-demand ratios and failure probabilities have been evaluated for every considered structural unit. The subsequent sensitivity analyses have allowed for identification and quantification of the effect of all considered variables on the global response. Some interesting remarks on results obtained have been developed in order to progress towards a reliable and simple assessment procedure
This paper introduces the first attempts to develop a simplified method called ESM (Effective Sen... more This paper introduces the first attempts to develop a simplified method called ESM (Effective Sensitivity Method) to help managing the seismic assessment of uncertain structural systems. The G-function describing the capacity of structural systems is often available only through numerical models. Here, the case of masonry building clusters (MBC) is studied, for which an ad-hoc analytical procedure (Monti and Vailati, 2009; Vailati et al. 2015) is used to describe the response. The confidence is estimated with a first order sensitivity analysis, assuming that the design point is at the mean values of the basic variables and that their estimates are independent. The proposed analytical procedure allows to quantify the confidence in the outcome of the probabilistic assessments of a structural system by calibrating a coefficient α, used to attain specified fractiles of the output variable of interest. The practitioners are given appropriate values of α under table form, depending to the...
A simplified pushover method for rapidly assessing the seismic capacity of shear-type frames is p... more A simplified pushover method for rapidly assessing the seismic capacity of shear-type frames is presented. The frame global force-displacement capacity is described as a trilinear curve passing through three limit states (LS): Damage LS (DLS), Life safety LS (LLS), and Collapse LS (CLS). The global LSs are obtained consequently to the attainment of story-level, element-level, and section-level LSs. All LS capacities are described through closed-form equations. The validity of the proposed method is verified by applying it on several reinforced concrete (RC) frames with a varying number of stories. The results obtained with such an analytical procedure show a good match with those obtained from pushover based on finite element method (FEM) analysis models, in terms of both global force-displacement capacity curves and story displacements at various LSs. The proposed method has the potential to be conveniently applied in large-scale vulnerability/risk assessment studies, where the qua...
The NTC 2008 allows us, considering buildings in a built-up area, to conduct a simplified analysi... more The NTC 2008 allows us, considering buildings in a built-up area, to conduct a simplified analysis in which to not take into account the variation of the axial force in masonry-walls and the torsional behavior. Furthermore, another simplification comes from the opportunity of studying the building by analyzing and verifying separately each floor. However, regulations require to perform this analysis by a non-linear method, and hence without giving details on how to perform it. In this regards, in the following paragraphs we propose a non-linear procedure which, in accordance with current regulations, gives us the opportunity to assess the sismic reliability of a Structural Unit (SU), in the case of rigid floors in their own plane
Practice Periodical on Structural Design and Construction, 2021
AbstractThe double-concave curved-surface slider isolators are tribological systems composed of t... more AbstractThe double-concave curved-surface slider isolators are tribological systems composed of the assemblage of three rigid bodies that include two concave spherical plates and a straight cylinde...
Bridges are essential to infrastructure and transportation networks, but face challenges from hea... more Bridges are essential to infrastructure and transportation networks, but face challenges from heavier traffic, higher speeds, and modifications like busway integration, leading to potential overloading and costly maintenance. Structural Health Monitoring (SHM) plays a crucial role in assessing bridge conditions and predicting failures to maintain structural integrity. Vibration-based condition monitoring employs non-destructive, in situ sensing and analysis of system dynamics across time, frequency, or modal domains. This method detects changes indicative of damage or deterioration, offering a proactive approach to maintenance in civil engineering. Such monitoring systems hold promise for optimizing the management and upkeep of modern infrastructure, potentially reducing operational costs. This paper aims to assist newcomers, practitioners, and researchers in navigating various methodologies for damage identification using sensor data from real structures. It offers a comprehensive review of prevalent anomaly detection approaches, spanning from traditional techniques to cutting-edge methods. Additionally, it addresses challenges inherent in Vibration-Based Damage (VBD) SHM applications, including establishing damage thresholds, corrosion detection, and sensor drift.
Still nowadays masonry structures represent most of the global built environment in seismic regio... more Still nowadays masonry structures represent most of the global built environment in seismic regions. Despite their diffusion and long age, their dynamic behavior under earthquake loads is still extremely hard to predict, since it depends on several site-dependent factors, such as local empirical expertise, that are difficult to generalize. Furthermore, considerable and often economically disproportionate efforts are usually required to achieve a sufficient knowledge level for characterizing the basic variables affecting their response. The problem is challenging and the recent earthquakes have highlighted the extreme urgency to provide structural engineers with reliable yet simple procedures to seismically assess such buildings. This work intends to propose a new approach for dealing with ex-isting masonry structures, by expressing their seismic vulnerability in terms of failure probability, using only two (or three, if needed) sim-plified non-linear deterministic analyses, where the standard devia-tions of a selected number of variables are appropriately combined. The method has been applied to five Structural Units, where two types of wall connections and four masonry types were considered. Numeri-cal models are purposely developed in spreadsheets, to calculate the base shear/displacement response of each floor and then build the global response of the equivalent SDOF system. For the purpose of comparison, the proposed approach was validated against a fully probabilistic analysis by including all uncertainties affecting the struc-tural response. The probabilistic response of each considered structural unit is rep-resented through Capacity/Demand (C/D) ratios and exceedance prob-abilities. Sensitivity analyses are used to quantify and rank the effects of each variable on the global response. The viability of the overall procedure is commented upon, with due attention to the ensuing er-rors, which are deemed to be more than acceptable, given that only a few analyses have to be carried out
The challenge against the waste of resources in the world of construction industry, starts from t... more The challenge against the waste of resources in the world of construction industry, starts from the seismic and thermal retrofitting of existing buildings with low environmental impact innovative technologies. When the buildings are especially vulnerable, for instance in the case of double-layer infills -often without thermal insulation -it's really hard to achieve satisfactory performance levels without resorting to radical interventions. In these cases the interaction with the building internal activities is unavoidable and forms a further design constraints. This work shows an innovative technology based on recycled plastic parts, optimized for the double-layer infills of existing buildings in which the maintaining of the internal activity is fundamental for the successful of the intervention. The system with recycled plastic joints is aiming at improving thermal and seismic performances, avoiding the residents relocation, consistently reducing the demolitions of existing infills and using plastic from recycled waste. Such system was preliminarily tested on a real-scale double-layer infill equipped with two joint lines under horizontal force at the testing laboratory of materials and structures (LPMS) of the University of L'Aquila. On the basis of this previous experimental tests, the present study proposes the calibration of a macroelement and a later numerical modelling of a multi-storey frame representative of r.c. buildings of the 80's. The results of the retrofitted configuration with plastic joints were compared with bare frame and infilled frame with different macroelement available for traditional infills.
In this study, a direct displacement-based method is proposed for the design of hysteretic dissip... more In this study, a direct displacement-based method is proposed for the design of hysteretic dissipative bracings to be applied to gravity-load-designed (GLD) reinforced concrete (RC) frames. The direct, i.e., non-iterative, design procedure aims at limiting the interstorey drifts of the GLD frame to prevent damage in the existing columns, thanks to the added stiffness and damping of the bracings. The method is based on a simplified yet accurate representation of the braced frame, through a so-called stick model, whose elements stiffness and damping are obtained by equivalent linearization of each braced storey. The method allows obtaining an optimal design of the bracing system at each storey, both in terms of stiffness and damping. The design method efficiency has been validated by comparing the performance of three GLD RC frames retrofitted with bracing systems designed with two other methods available in the literature.
I centri storici sono comunemente il risultato di una serie di eventi succedutisi nel tempo che d... more I centri storici sono comunemente il risultato di una serie di eventi succedutisi nel tempo che danno luogo a una stratificazione temporale e spaziale di sistemi aggregativi di costruzioni che presentano, agli occhi dell’analista strutturale, una profonda complessità che rende ardua la valutazione della loro vulnerabilità sismica.. Per la prima volta, nel 2003, l’OPCM 3274 introduce il concetto di aggregato edilizio, proponendo un metodo di riconoscimento delle sue Unità Strutturali, nonché di modellazione ed analisi di queste, fondato sulla consapevolezza che “in questi casi lo studio assume una natura convenzionale”. Nonostante ciò, si fornisce al professionista uno strumento agevole per gestire tale complessità, attraverso una serie di ipotesi semplificative, al tempo stesso imponendo, però, il ricorso all’analisi non lineare di ogni singola Unità Strutturale. Essendo la normativa di natura prestazionale, essa non fornisce indicazioni su come eseguire tale analisi. Il lavoro di q...
Modern approaches in buildings design strive to fulfill multiple performance requirements simulta... more Modern approaches in buildings design strive to fulfill multiple performance requirements simultaneously. Accordingly, as far as buildings in earthquake-prone areas are concerned, damage limitation under seismic loads must be ensured while paying attention on the issues related to the environmental sustainability of the construction, ranging from its ecological footprint to the thermal efficiency. Masonry infills in framed reinforced concrete buildings are especially important in this context. In fact, they are vulnerable to earthquakes and greatly impact on the environmental sustainability of the building because they employ a significant amount of construction materials and influence its energy consumption throughout the lifetime. In light of this, the main novelty of the present work is concerned with a new deformable joint for masonry infills in framed reinforced concrete buildings. A detailed description of such innovative system for masonry infills is provided, together with numerical and experimental investigations about its mechanical and thermal behavior. The proposed joint is made of recycled plastic material, namely Regenerated Polypropylene Homopolymer. Geometry and manufacturing process of the proposed joint are initially described. Then, stress–strain relationships for the plastic material are obtained from uniaxial tensile tests at different temperatures. An assembly of fired hollow clay bricks and plastic joints is also tested under in-plane cyclic load, and a phenomenological model is thus proposed to simulate the experimental hysteretic behavior. Finally, experimental tests and finite element-based numerical simulations are performed to investigate the thermal performance of masonry infills with plastic joints.
Advances in FRP Composites in Civil Engineering, 2011
An innovative method to connect existing orthogonal masonry walls through aramidic FRP bars is pr... more An innovative method to connect existing orthogonal masonry walls through aramidic FRP bars is presented. The proposed technique has the objective of mobilizing and maximizing the collaboration of intersecting structural elements, thus increasing the overall strength and stiffness of masonry buildings under horizontal forces. The method was experimentally tested to prove its applicability and effectiveness.
Masonry buildings represent a large and important portion of the existing building stock in sever... more Masonry buildings represent a large and important portion of the existing building stock in several countries. They are still being built and nowadays they are mainly used as residential buildings, offices or for other activities. Most of these buildings are not designed to withstand earthquake-induced forces, therefore seismic safety assessment represents a crucial task to estimate risk level and eventually define retrofit measures. This task is hampered by the many uncertainties affecting the acquired data on plan and elevation geometry, material properties, connections between walls and roof, connections between walls and walls, seismic actions. The present paper intends to give a contribution in dealing with such uncertainties by applying a global probabilistic analysis on different masonry structural units. Such approach is based on the Italian seismic code and relies on a simplified non-linear assessment method. Purposely developed codes have been used for deriving the equivalent bilinear constitutive laws of floors and of the entire structural unit. Afterwards, a fully probabilistic Monte Carlo-based analysis has been performed by including and consistently modeling all uncertainties affecting the structural response. Capacity-demand ratios and failure probabilities have been evaluated for every considered structural unit. The subsequent sensitivity analyses have allowed for identification and quantification of the effect of all considered variables on the global response. Some interesting remarks on results obtained have been developed in order to progress towards a reliable and simple assessment procedure
This paper introduces the first attempts to develop a simplified method called ESM (Effective Sen... more This paper introduces the first attempts to develop a simplified method called ESM (Effective Sensitivity Method) to help managing the seismic assessment of uncertain structural systems. The G-function describing the capacity of structural systems is often available only through numerical models. Here, the case of masonry building clusters (MBC) is studied, for which an ad-hoc analytical procedure (Monti and Vailati, 2009; Vailati et al. 2015) is used to describe the response. The confidence is estimated with a first order sensitivity analysis, assuming that the design point is at the mean values of the basic variables and that their estimates are independent. The proposed analytical procedure allows to quantify the confidence in the outcome of the probabilistic assessments of a structural system by calibrating a coefficient α, used to attain specified fractiles of the output variable of interest. The practitioners are given appropriate values of α under table form, depending to the...
A simplified pushover method for rapidly assessing the seismic capacity of shear-type frames is p... more A simplified pushover method for rapidly assessing the seismic capacity of shear-type frames is presented. The frame global force-displacement capacity is described as a trilinear curve passing through three limit states (LS): Damage LS (DLS), Life safety LS (LLS), and Collapse LS (CLS). The global LSs are obtained consequently to the attainment of story-level, element-level, and section-level LSs. All LS capacities are described through closed-form equations. The validity of the proposed method is verified by applying it on several reinforced concrete (RC) frames with a varying number of stories. The results obtained with such an analytical procedure show a good match with those obtained from pushover based on finite element method (FEM) analysis models, in terms of both global force-displacement capacity curves and story displacements at various LSs. The proposed method has the potential to be conveniently applied in large-scale vulnerability/risk assessment studies, where the qua...
The NTC 2008 allows us, considering buildings in a built-up area, to conduct a simplified analysi... more The NTC 2008 allows us, considering buildings in a built-up area, to conduct a simplified analysis in which to not take into account the variation of the axial force in masonry-walls and the torsional behavior. Furthermore, another simplification comes from the opportunity of studying the building by analyzing and verifying separately each floor. However, regulations require to perform this analysis by a non-linear method, and hence without giving details on how to perform it. In this regards, in the following paragraphs we propose a non-linear procedure which, in accordance with current regulations, gives us the opportunity to assess the sismic reliability of a Structural Unit (SU), in the case of rigid floors in their own plane
Practice Periodical on Structural Design and Construction, 2021
AbstractThe double-concave curved-surface slider isolators are tribological systems composed of t... more AbstractThe double-concave curved-surface slider isolators are tribological systems composed of the assemblage of three rigid bodies that include two concave spherical plates and a straight cylinde...
The recent earthquakes that occurred in Central Italy, in L’Aquila in 2009 and in Amatrice in 201... more The recent earthquakes that occurred in Central Italy, in L’Aquila in 2009 and in Amatrice in 2016, have shown once again how infill panels and partitions, widely used as non-structural elements in reinforced concrete frames, are significantly vulnerable when subjected to seismic actions. Moreover, they highly affect the structural behavior and seismic response of typical multi-story buildings, strongly influencing their repair costs due to the inevitable damage they usually undergo during seismic events. Therefore, they should be designed to withstand earthquakes forces, both in-plane and out-of-plane, so to ensure the safety of the occupants. In addition to seismic performance, infill panels play the primary role of providing comfort to occupants, through adequate thermal and acoustic insulation. In this paper, an innovative solution of earthquake-safe and eco-friendly infill panels is presented, which are at the same time thermally and acoustically efficient, thus avoiding waste of energy and respecting the environ-ment. The proposed innovative technology proposed here is tested with different surface finishes, boundary conditions and temperature. A comparison of the pro-posed technology with respect to conventional infill typologies is provided, hig-hlighting pros and cons.
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Papers by Marco Vailati