Climate change is associated with significant variations of temperature, atmospheric humidity, an... more Climate change is associated with significant variations of temperature, atmospheric humidity, and carbon dioxide concentration levels. These changes potentially produce a double negative effect on the safety and the life cycle of civil engineering structures: increased climatic actions and rate of material degradation. In fact, changes in these variables affect the service life of reinforced concrete and steel structures by acting on the rate of carbonation and corrosion. Corrosion has a detrimental effect especially on the seismic vulnerability influencing strength, ductility and affecting the dynamic response and consequently the failure of reinforced concrete structures. Particularly bridges, as structures directly exposed to the weather effects, are more susceptible to these phenomena. In this paper, a framework to quantitatively account for the effects of climate change on carbonation-induced corrosion is proposed, focusing on the loss of concrete passivity, and thus widespread corrosion. Different scenarios for the expected variations in CO 2 concentrations and temperature are analyzed and seismic risk indexes are evaluated through a real case study of bridge located in the province of Massa-Carrara (Italy).
Reinforced Concrete (RC) technology is moving towards new frontiers improving its sustainability ... more Reinforced Concrete (RC) technology is moving towards new frontiers improving its sustainability and durability through innovative materials. In particular, the application of Glass Fiber Reinforced Polymer (GFRP) bars, in lieu of steel reinforcement, shows excellent performance, especially in aggressive environments However, current international design guides and standards are quite conservative, particularly for the shear reinforcement, and this makes the technology less competitive both in terms of the amount of material used and especially in terms of construction. This research aims to analytically compare and experimentally validate the formulations of some international standards on shear capacity in case of reduced shear reinforcement and when the number of stirrups is less than the minimum recommended by the standards itself. The sample beam tests considered two different flexural GFRP reinforcement ratios to assess their role in shear capacity resulting in different collapse mechanisms: longitudinal GFRP bar rupture and concrete crushing. The experimental results were used to compare the North American ACI, French AFGC, and Italian CNR shear capacity design approaches. Analytical capacity expressions are discussed with some remarks aiming at structural optimization.
This paper illustrates the results of an experimental campaign performed on a scale prototype of ... more This paper illustrates the results of an experimental campaign performed on a scale prototype of a base dissipator called Mini Tribological ROCKing Seismic Isolation Device. This device allows a smooth, controlled and damped rocking by means of frictional layers and viscous elastic springs, which aim to decouple the frequencies of the superstructure, dissipate energy during motion and re-centering the system once the action is removed. Four superstructures are tested-a shear type frame, braced and unbraced, a multi-storey frame and a SDOF oscillatorwith 96 ambient vibration and impulsive tests. An analytical model is illustrated and validated by the experimental tests. The reduction of relative displacement demand is analyzed for all the cases together with the reduction of the acceleration demand, showing positive effects of the base dissipator on the dynamic behavior of all the superstructures.
Within this work, the causes of collapses and damages occurred in masonry artefacts have been eva... more Within this work, the causes of collapses and damages occurred in masonry artefacts have been evaluated to properly identify suitable monitoring and restoration methods. In this regard, a comprehensive literature review has been performed. Based on the results, the moisture has found to be a critical parameter, which affects the structural health of masonry artefacts. Diverse non-destructive methods were employed to measure the moisture and monitor the materials involved: the Infrared Thermography, the Electrical Resistivity Tomography and the Ground Penetrating Radar, the Laser Scanning and Digital Terrestrial Photogrammetry, the Global Navigation Satellite Systems, the Unilateral Nuclear Magnetic Resonance, the Laser-Induced Fluorescence technique, the Acoustic Imaging and the Acoustic Tomography, the Geographic Information System and on-site survey process as well as computer modeling of the structure with specific FEM software. Finally, the implementation of tie-beams, Fiber Rei...
This study deals with the identification of the mechanical behavior of chemical anchors embedded ... more This study deals with the identification of the mechanical behavior of chemical anchors embedded in masonry walls. 108 pull-out tests are carried out in five types of masonry walls built with clay brick or vertically perforated units with cement mortar. Different parameters are taken into account: embedment depths, masonry type, anchor position (injection either in brick units or in mortar joints). The axial load capacity and the failure mode are observed for each test. The results are examined by means of elastic and plastic models assessing the efficiency of anchors installed in headers, stretchers or mortar joints. The anchors injected in mortar joints are shown to have much greater pull-out capacity than that found for anchors in bricks. Passing from 90 to 160 mm of embedment depth, a minimum increase by 40% of pull-out strength is observed. The most common failure modes are the sliding failure, which occurs for short anchors or weak masonry, and mixed sliding/cone failure, for ...
IABSE Congress, Ghent 2021: Structural Engineering for Future Societal Needs
Recent collapses due to hydrogeological soil instability caused by extreme climate events recall ... more Recent collapses due to hydrogeological soil instability caused by extreme climate events recall the attention on a large-scale monitoring of the road infrastructures, particularly bridges and viaducts. Several studies focus the attention on both hydraulic and structural issues. In-depth systematic investigations do not suit this purpose because of time and cost investments usually carried out from local authorities. Increasing needs of available fast, low cost and reliable methods to investigate the performance of the road and bridges pushed towards new applications. The use of Fast-Falling Weight Deflectometer, conceived for airport pavements, is here applied as a non-destructive test to evaluate the stiffness of the deck and embankment of a bridge. The- Fast Falling Weight Deflectometer can produce a broadband, constant and replicable dynamic force, providing data in real time. An experimental campaign is here described on a case study of single span bridge.
IABSE Conference, Seoul 2020: Risk Intelligence of Infrastructures
Risk management plays a crucial role in the stakeholders’ decision making because it is directly ... more Risk management plays a crucial role in the stakeholders’ decision making because it is directly related to safety, serviceability and economy. There is now a growing concern about how to relocate known risks into an acceptance threshold: this implies the evaluation of several options obtained from hazard scenarios considering the related consequences. In parallel, practitioners usually rely on standard tools for risk assessment, and on structural codes to compute performances. Although this approach is currently widely implemented, this research shows that hazardous situations can arise in properly designed infrastructures, due to errors in management. This paper deals with such issue, also highlighting a gap in current codes that could contribute to losses caused by unforeseen failure modes. In this study, a preliminary FMEA assessment was performed to identify the failure modes that required a deeper quantitative analysis. In a second step, a quantitative analysis was implemented...
Abstract This contribution comes from the investigations carried out on recent flooding events oc... more Abstract This contribution comes from the investigations carried out on recent flooding events occurred in Italian suburban areas. Those events, regarding minor roads, cause unexpected failure modes of existing bridges with reduced span (less than 10 m), whose construction and maintenance are not properly covered by standards. Three failure scenarios are here considered: the dragging effect on vehicles when they are crossing bridges (A), the erosion effect due to the overtopping of the bridge (B), and the erosion and the floating effect caused by upward buoyant force from Archimedes’ principle on the bridge slab (C). The described mechanisms of failure are paradigmatic to identify not only the structural collapses but also the service failure. In this sense, the ‘resilience’ of the small bridge is defined, in view to propose technical indications for maintenance and consolidation activities.
IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management
In the last years, extreme rainfalls have caused many collapses of bridges. In Italy several of t... more In the last years, extreme rainfalls have caused many collapses of bridges. In Italy several of those were short span’s ones that failed during or after extreme events of this nature. This work presents a method for inspection survey and its results regarding a campaign on 71 bridges, located in Tuscany (Massa Carrara, Italy). This area was affected by a big flood that took place in 2014 and also two earlier ones in 2012 with only 15 days apart one from the other, leading to a huge disrupting situation for the population’s daily life and consequent economical loss. Concerning this issue, the local stakeholders showed an increasing interest for sustainable methods for monitoring the built environment, thus the results of this research have been made available for integration on the Civil Protection Emergency Plan (CLE) and can be used in a decision-making prioritization list of actions. The framework uses a Gis- based approach combined with a quick survey technique. This method balan...
Transportation Research Record: Journal of the Transportation Research Board
Infrastructure plays a key role in society. Recent collapses of bridges have underlined their imp... more Infrastructure plays a key role in society. Recent collapses of bridges have underlined their importance for road functionality, causing disruptions to commuters and emergency vehicles. Major issues arise on rural roads, where the lack of redundancy leads to the isolation of entire communities. Actual approaches to assess the resilience of countryside roads rely on the availability of specific datasets, limiting their practical application; this issue is typically related to traffic data. This research aims to propose innovative algorithms to assess the road network’s vulnerability in rural areas, including a novel traffic data collection process and its calibration. The aggregate metric is called Detour-Impact Index (DII) and compares user costs before and after a disruptive event. The method uses traditional network-impact metrics in combination with a new algorithm that allows us to gather quantitative traffic data starting from qualitative information. User travel time showed go...
In this paper, the use of Fast Falling Weight Deflectometer (Fast-FWD) is analyzed as a non-destr... more In this paper, the use of Fast Falling Weight Deflectometer (Fast-FWD) is analyzed as a non-destructive and quick test procedure to evaluate the efficiency of short-span bridges. The Fast-FWD is an instrument that can produce a broadband dynamic force up to an impact value of 120 KN: The impact is constant and replicable, providing accurate action measures of bridge stiffness in a truly short period (30 ms). In this paper, a single-span reinforced concrete bridge is investigated, using the Fast-FWD. The considered bridge, approximately 12.0 m long and 15.5 m wide, was in critical condition. The bridge is in a suburban principal road near to the City of Cagliari in Sardinia (Italy), with an Annual Average Daily Traffic of 13,500 vehicles/day, and was suddenly closed, creating serious problems for urban mobility. In these conditions, the investigation through other standard techniques is time-consuming and labor intensive. For this reason, it is important to introduce methods that can...
Recent failures in road networks highlight their vulnerability towards natural hazards, particula... more Recent failures in road networks highlight their vulnerability towards natural hazards, particularly to extreme weather events. This paper proposes a method to evaluate the safety of road networks in case of collapse of one or more bridges. In addition, relevant consequences in terms of safety of human life, direct and indirect cost are crucial aspects to consider. The framework described here is based on the knowledge of road and river network, of the individual bridges and of the traffic data. However, this approach can be generalized in case of interruption of road network due to other causes. An algorithm has been developed to extract traffic data from Google and elaborate it throughout a procedure based on the application of the USA Highway Capacity Manual. This consents to have a quantitative definition of the road traffic directly from the users and to get updated traffic data. The maps are processed throughout a GIS software and, thanks to the application of a routing algori...
Structural irregularity is a crucial issue in assessing seismic vulnerability of both new and exi... more Structural irregularity is a crucial issue in assessing seismic vulnerability of both new and existing buildings. European technical codes provide simple criteria to define irregularities in plan and in elevation, amplifying the seismic actions and/or introducing torsional effects. Nevertheless, this approach only considers geometrical irregularity. For existing buildings, another source of irregularity comes from the non-uniform distribution of the material strength. In particular, for existing reinforced concrete (r.c.) structures, it is possible to detect significant spread of the concrete compressive strength not only from different structural elements but also from different parts of the same member. In this work, non-linear static analysis is performed on two case-studies of r.c. buildings characterized by geometrical and mechanical irregularity. The resistance of each column is determined with an extensive experimental campaign with in situ and laboratory test (about 600 in situ tests). The results are analyzed considering both local and global effects in terms of resistance of the single elements and of the entire buildings. In this sense, shear and bending failure mechanism are taken into account. The effect of storey flexibility is also considered in the models. Fragility curves are calculated for the buildings with random distribution of the compressive strength of the columns. The results are then compared with the approaches proposed by the Eurocodes evaluating in the standard approach proposed by technical codes is conservative or not.
In this work, numerical analyses on the Volterra's ancient walls are performed to understand the ... more In this work, numerical analyses on the Volterra's ancient walls are performed to understand the causes of a collapse occurred after an extreme rainfall (2014) and to identify the mechanical parameters that most influenced it. The stretch of collapsed wall is modelled with finite elements by distinguishing the material composing the multi-leaf wall. Non-linear static analyses are carried out with the DIANA software considering different levels of hydraulic head up to reach the collapse of the structure. The impact on the failure modes of the involved parameters, such as tensile strength, fracture energy and shear strength, are discussed. Tensile strength is found as the most relevant parameter in the failure mode. Finally, a 3-dim model is presented, and the results show a very good agreement with the failure mode actually occurred in terms of both failure modes and displacement fields. The safety evaluation is performed in the as-built and the retrofitted configuration, consisting in the wall restrained by tie-rods. The results show a significant increasing of the safety level of the retrofitted configuration showing a considerable improvement not only in terms of limit equilibrium but also in terms of structural capacity of the wall.
The seismic rehabilitation of existing R.C. and masonry buildings is a topical issue in Civil Eng... more The seismic rehabilitation of existing R.C. and masonry buildings is a topical issue in Civil Engineering. A useful technique consists in the introduction of the external bracing system. This kind of intervention can be improved through the introduction of dissipative links, investigated here with the help of some examples. The links are made of common steel profiles: length, geometry and positioning are considered as design parameters. A general procedure of link-bracing optimization is proposed by applying a set of identical external restraints. The adopted dissipative links allow a cheaper and more effective design both in terms of ULS and of DLS: the damages are addressed in a small area allowing easy replacement of the links in case of an earthquake.
Climate change is associated with significant variations of temperature, atmospheric humidity, an... more Climate change is associated with significant variations of temperature, atmospheric humidity, and carbon dioxide concentration levels. These changes potentially produce a double negative effect on the safety and the life cycle of civil engineering structures: increased climatic actions and rate of material degradation. In fact, changes in these variables affect the service life of reinforced concrete and steel structures by acting on the rate of carbonation and corrosion. Corrosion has a detrimental effect especially on the seismic vulnerability influencing strength, ductility and affecting the dynamic response and consequently the failure of reinforced concrete structures. Particularly bridges, as structures directly exposed to the weather effects, are more susceptible to these phenomena. In this paper, a framework to quantitatively account for the effects of climate change on carbonation-induced corrosion is proposed, focusing on the loss of concrete passivity, and thus widespread corrosion. Different scenarios for the expected variations in CO 2 concentrations and temperature are analyzed and seismic risk indexes are evaluated through a real case study of bridge located in the province of Massa-Carrara (Italy).
Reinforced Concrete (RC) technology is moving towards new frontiers improving its sustainability ... more Reinforced Concrete (RC) technology is moving towards new frontiers improving its sustainability and durability through innovative materials. In particular, the application of Glass Fiber Reinforced Polymer (GFRP) bars, in lieu of steel reinforcement, shows excellent performance, especially in aggressive environments However, current international design guides and standards are quite conservative, particularly for the shear reinforcement, and this makes the technology less competitive both in terms of the amount of material used and especially in terms of construction. This research aims to analytically compare and experimentally validate the formulations of some international standards on shear capacity in case of reduced shear reinforcement and when the number of stirrups is less than the minimum recommended by the standards itself. The sample beam tests considered two different flexural GFRP reinforcement ratios to assess their role in shear capacity resulting in different collapse mechanisms: longitudinal GFRP bar rupture and concrete crushing. The experimental results were used to compare the North American ACI, French AFGC, and Italian CNR shear capacity design approaches. Analytical capacity expressions are discussed with some remarks aiming at structural optimization.
This paper illustrates the results of an experimental campaign performed on a scale prototype of ... more This paper illustrates the results of an experimental campaign performed on a scale prototype of a base dissipator called Mini Tribological ROCKing Seismic Isolation Device. This device allows a smooth, controlled and damped rocking by means of frictional layers and viscous elastic springs, which aim to decouple the frequencies of the superstructure, dissipate energy during motion and re-centering the system once the action is removed. Four superstructures are tested-a shear type frame, braced and unbraced, a multi-storey frame and a SDOF oscillatorwith 96 ambient vibration and impulsive tests. An analytical model is illustrated and validated by the experimental tests. The reduction of relative displacement demand is analyzed for all the cases together with the reduction of the acceleration demand, showing positive effects of the base dissipator on the dynamic behavior of all the superstructures.
Within this work, the causes of collapses and damages occurred in masonry artefacts have been eva... more Within this work, the causes of collapses and damages occurred in masonry artefacts have been evaluated to properly identify suitable monitoring and restoration methods. In this regard, a comprehensive literature review has been performed. Based on the results, the moisture has found to be a critical parameter, which affects the structural health of masonry artefacts. Diverse non-destructive methods were employed to measure the moisture and monitor the materials involved: the Infrared Thermography, the Electrical Resistivity Tomography and the Ground Penetrating Radar, the Laser Scanning and Digital Terrestrial Photogrammetry, the Global Navigation Satellite Systems, the Unilateral Nuclear Magnetic Resonance, the Laser-Induced Fluorescence technique, the Acoustic Imaging and the Acoustic Tomography, the Geographic Information System and on-site survey process as well as computer modeling of the structure with specific FEM software. Finally, the implementation of tie-beams, Fiber Rei...
This study deals with the identification of the mechanical behavior of chemical anchors embedded ... more This study deals with the identification of the mechanical behavior of chemical anchors embedded in masonry walls. 108 pull-out tests are carried out in five types of masonry walls built with clay brick or vertically perforated units with cement mortar. Different parameters are taken into account: embedment depths, masonry type, anchor position (injection either in brick units or in mortar joints). The axial load capacity and the failure mode are observed for each test. The results are examined by means of elastic and plastic models assessing the efficiency of anchors installed in headers, stretchers or mortar joints. The anchors injected in mortar joints are shown to have much greater pull-out capacity than that found for anchors in bricks. Passing from 90 to 160 mm of embedment depth, a minimum increase by 40% of pull-out strength is observed. The most common failure modes are the sliding failure, which occurs for short anchors or weak masonry, and mixed sliding/cone failure, for ...
IABSE Congress, Ghent 2021: Structural Engineering for Future Societal Needs
Recent collapses due to hydrogeological soil instability caused by extreme climate events recall ... more Recent collapses due to hydrogeological soil instability caused by extreme climate events recall the attention on a large-scale monitoring of the road infrastructures, particularly bridges and viaducts. Several studies focus the attention on both hydraulic and structural issues. In-depth systematic investigations do not suit this purpose because of time and cost investments usually carried out from local authorities. Increasing needs of available fast, low cost and reliable methods to investigate the performance of the road and bridges pushed towards new applications. The use of Fast-Falling Weight Deflectometer, conceived for airport pavements, is here applied as a non-destructive test to evaluate the stiffness of the deck and embankment of a bridge. The- Fast Falling Weight Deflectometer can produce a broadband, constant and replicable dynamic force, providing data in real time. An experimental campaign is here described on a case study of single span bridge.
IABSE Conference, Seoul 2020: Risk Intelligence of Infrastructures
Risk management plays a crucial role in the stakeholders’ decision making because it is directly ... more Risk management plays a crucial role in the stakeholders’ decision making because it is directly related to safety, serviceability and economy. There is now a growing concern about how to relocate known risks into an acceptance threshold: this implies the evaluation of several options obtained from hazard scenarios considering the related consequences. In parallel, practitioners usually rely on standard tools for risk assessment, and on structural codes to compute performances. Although this approach is currently widely implemented, this research shows that hazardous situations can arise in properly designed infrastructures, due to errors in management. This paper deals with such issue, also highlighting a gap in current codes that could contribute to losses caused by unforeseen failure modes. In this study, a preliminary FMEA assessment was performed to identify the failure modes that required a deeper quantitative analysis. In a second step, a quantitative analysis was implemented...
Abstract This contribution comes from the investigations carried out on recent flooding events oc... more Abstract This contribution comes from the investigations carried out on recent flooding events occurred in Italian suburban areas. Those events, regarding minor roads, cause unexpected failure modes of existing bridges with reduced span (less than 10 m), whose construction and maintenance are not properly covered by standards. Three failure scenarios are here considered: the dragging effect on vehicles when they are crossing bridges (A), the erosion effect due to the overtopping of the bridge (B), and the erosion and the floating effect caused by upward buoyant force from Archimedes’ principle on the bridge slab (C). The described mechanisms of failure are paradigmatic to identify not only the structural collapses but also the service failure. In this sense, the ‘resilience’ of the small bridge is defined, in view to propose technical indications for maintenance and consolidation activities.
IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management
In the last years, extreme rainfalls have caused many collapses of bridges. In Italy several of t... more In the last years, extreme rainfalls have caused many collapses of bridges. In Italy several of those were short span’s ones that failed during or after extreme events of this nature. This work presents a method for inspection survey and its results regarding a campaign on 71 bridges, located in Tuscany (Massa Carrara, Italy). This area was affected by a big flood that took place in 2014 and also two earlier ones in 2012 with only 15 days apart one from the other, leading to a huge disrupting situation for the population’s daily life and consequent economical loss. Concerning this issue, the local stakeholders showed an increasing interest for sustainable methods for monitoring the built environment, thus the results of this research have been made available for integration on the Civil Protection Emergency Plan (CLE) and can be used in a decision-making prioritization list of actions. The framework uses a Gis- based approach combined with a quick survey technique. This method balan...
Transportation Research Record: Journal of the Transportation Research Board
Infrastructure plays a key role in society. Recent collapses of bridges have underlined their imp... more Infrastructure plays a key role in society. Recent collapses of bridges have underlined their importance for road functionality, causing disruptions to commuters and emergency vehicles. Major issues arise on rural roads, where the lack of redundancy leads to the isolation of entire communities. Actual approaches to assess the resilience of countryside roads rely on the availability of specific datasets, limiting their practical application; this issue is typically related to traffic data. This research aims to propose innovative algorithms to assess the road network’s vulnerability in rural areas, including a novel traffic data collection process and its calibration. The aggregate metric is called Detour-Impact Index (DII) and compares user costs before and after a disruptive event. The method uses traditional network-impact metrics in combination with a new algorithm that allows us to gather quantitative traffic data starting from qualitative information. User travel time showed go...
In this paper, the use of Fast Falling Weight Deflectometer (Fast-FWD) is analyzed as a non-destr... more In this paper, the use of Fast Falling Weight Deflectometer (Fast-FWD) is analyzed as a non-destructive and quick test procedure to evaluate the efficiency of short-span bridges. The Fast-FWD is an instrument that can produce a broadband dynamic force up to an impact value of 120 KN: The impact is constant and replicable, providing accurate action measures of bridge stiffness in a truly short period (30 ms). In this paper, a single-span reinforced concrete bridge is investigated, using the Fast-FWD. The considered bridge, approximately 12.0 m long and 15.5 m wide, was in critical condition. The bridge is in a suburban principal road near to the City of Cagliari in Sardinia (Italy), with an Annual Average Daily Traffic of 13,500 vehicles/day, and was suddenly closed, creating serious problems for urban mobility. In these conditions, the investigation through other standard techniques is time-consuming and labor intensive. For this reason, it is important to introduce methods that can...
Recent failures in road networks highlight their vulnerability towards natural hazards, particula... more Recent failures in road networks highlight their vulnerability towards natural hazards, particularly to extreme weather events. This paper proposes a method to evaluate the safety of road networks in case of collapse of one or more bridges. In addition, relevant consequences in terms of safety of human life, direct and indirect cost are crucial aspects to consider. The framework described here is based on the knowledge of road and river network, of the individual bridges and of the traffic data. However, this approach can be generalized in case of interruption of road network due to other causes. An algorithm has been developed to extract traffic data from Google and elaborate it throughout a procedure based on the application of the USA Highway Capacity Manual. This consents to have a quantitative definition of the road traffic directly from the users and to get updated traffic data. The maps are processed throughout a GIS software and, thanks to the application of a routing algori...
Structural irregularity is a crucial issue in assessing seismic vulnerability of both new and exi... more Structural irregularity is a crucial issue in assessing seismic vulnerability of both new and existing buildings. European technical codes provide simple criteria to define irregularities in plan and in elevation, amplifying the seismic actions and/or introducing torsional effects. Nevertheless, this approach only considers geometrical irregularity. For existing buildings, another source of irregularity comes from the non-uniform distribution of the material strength. In particular, for existing reinforced concrete (r.c.) structures, it is possible to detect significant spread of the concrete compressive strength not only from different structural elements but also from different parts of the same member. In this work, non-linear static analysis is performed on two case-studies of r.c. buildings characterized by geometrical and mechanical irregularity. The resistance of each column is determined with an extensive experimental campaign with in situ and laboratory test (about 600 in situ tests). The results are analyzed considering both local and global effects in terms of resistance of the single elements and of the entire buildings. In this sense, shear and bending failure mechanism are taken into account. The effect of storey flexibility is also considered in the models. Fragility curves are calculated for the buildings with random distribution of the compressive strength of the columns. The results are then compared with the approaches proposed by the Eurocodes evaluating in the standard approach proposed by technical codes is conservative or not.
In this work, numerical analyses on the Volterra's ancient walls are performed to understand the ... more In this work, numerical analyses on the Volterra's ancient walls are performed to understand the causes of a collapse occurred after an extreme rainfall (2014) and to identify the mechanical parameters that most influenced it. The stretch of collapsed wall is modelled with finite elements by distinguishing the material composing the multi-leaf wall. Non-linear static analyses are carried out with the DIANA software considering different levels of hydraulic head up to reach the collapse of the structure. The impact on the failure modes of the involved parameters, such as tensile strength, fracture energy and shear strength, are discussed. Tensile strength is found as the most relevant parameter in the failure mode. Finally, a 3-dim model is presented, and the results show a very good agreement with the failure mode actually occurred in terms of both failure modes and displacement fields. The safety evaluation is performed in the as-built and the retrofitted configuration, consisting in the wall restrained by tie-rods. The results show a significant increasing of the safety level of the retrofitted configuration showing a considerable improvement not only in terms of limit equilibrium but also in terms of structural capacity of the wall.
The seismic rehabilitation of existing R.C. and masonry buildings is a topical issue in Civil Eng... more The seismic rehabilitation of existing R.C. and masonry buildings is a topical issue in Civil Engineering. A useful technique consists in the introduction of the external bracing system. This kind of intervention can be improved through the introduction of dissipative links, investigated here with the help of some examples. The links are made of common steel profiles: length, geometry and positioning are considered as design parameters. A general procedure of link-bracing optimization is proposed by applying a set of identical external restraints. The adopted dissipative links allow a cheaper and more effective design both in terms of ULS and of DLS: the damages are addressed in a small area allowing easy replacement of the links in case of an earthquake.
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Papers by Mario Puppio