Resilience analysis of large scale networks using the D-spectrum method

Infrastructure systems are crucial for the development of communities because they provide essential services to the habitants. Here we focus on the transportation network, which is designed to provide a continuous service to the community. Due to its decisive role in the economy, governments and policy makers have been investing in developing strategies to increase the resilience of this kind of infrastructure against disruptive events. In the literature, several methods to evaluate networks’ reliability and resilience can be found. The applicability of these methods is limited to small networks due to the computational complexities. In this paper, the case of city-scale road transportation networks is tackled. The case study considered in this work is the transportation network of a virtual, city called ‘Ideal City’. First, the road map of the city is transformed into an undirected graph with 15012 nodes and 19614 edges. A non-random gradual removal of the edges has been applied until the network’s failure point is reached. The edge removal process is related to the failure probabilities of the edges when the network is exposed to a certain hazard. In fact, the effect of hazards on the transportation network is not direct. The hazard exposes the building structures on the road sides to a failure risk. These structures if collapsed would cause the adjacent roads to be blocked and thus lose functionality due to the debris falling from the structures. For this purpose, a building infrastructure is modeled and the relationship between the level of damage of building and the amount of debris falling on the adjacent roads is developed. A Monte Carlo approach is used to generate failure permutations of edges considering their failure probabilities. The network reliability is then calculated using the Destruction Spectrum (D-spectrum) approach. In addition, the network’s edges have been ranked from the most to the least important by applying the Birnbaum Importance Measure (BIM). Due to the large size of the network, a number of computational problems have arisen. Therefore, several coding algorithms have been developed to allow evaluating both the reliability and the BIM indexes while avoiding computational errors. The results obtained in this study are used to identify the vulnerable components of the network. The vulnerable components are the ones that should be focused on to improve the overall resilience of the infrastructure. The analysis concept adopted in this study is applicable to all network-based infrastructure systems such as water, gas, transportation, etc. Future work will be oriented towards applying the methodology to other network-based infrastructure systems

RELIABILITY AND COMPONENT VULNERABILITY ANALYSIS OF CITY-SCALE NETWORKS: APPLICATION TO THE TRANSPORTATION SYSTEM OF A VIRTUAL CITY

Infrastructure systems are crucial for the development of communities as they provide essential services to the habitants. To improve the resilience of such systems, their intrinsic properties need to be understood and their resilience state needs be identified. In the literature, several methods to evaluate networks’ reliability and resilience can be found. However, the applicability of these methods is restricted to small-size networks due to several computational limitations. In this paper, the case of large scale networks is tackled. The transportation network of a virtual city is considered as a case study. First, the road map of the city is transformed into an undirected graph. A random removal of the roads is applied until the network’s failure point is reached. The network reliability is then calculated using the Destruction Spectrum (D-spectrum) approach. A Monte Carlo approach has been developed to generate failure permutations, which are necessary for the evaluation of the D-spectrum set. In addition, the Birnbaum Importance Measure (BIM) has been adopted in this study to determine the importance of the network’s components. Due to the large size of the network, several computational problems have been faced. To solve the problems, two coding algorithms have been introduced in the paper to evaluate both the reliability and the BIM indexes for large scale networks. The analysis concept adopted in this study is applicable to all network-based systems such as water, gas, transportation, etc

A new framework to estimate the probability of fire following earthquake

Fire following earthquake has been recognized as a very significant risk in the past decade. Several studies have been performed by researchers to develop analytical and experimental methods to assess the economic and life losses due to fire after an earthquake event. While the outcome of these efforts has resulted in significant advances, an accurate and simplified framework to be utilized by practicing engineers is still lacking. In this paper, a new methodology to predict the probability to have fire following a seismic event considering the building seismic damage is proposed. Earthquake was considered as the main hazard, whereas blast and fire were assumed as a cascading hazards. Bayesian approach was used to estimate conditional probability of fire caused by an earthquake. A hospital building has been assumed as case study, while a LPG tank located nearby the structure has been considered as potential source of blast and ignition. A physical-based simulation was used to evaluate intra-structure ignition probability due to leakage and/or breaks of the gas pipelines. Several parameters were considered to model the occurrence of intra-structure ignitions such as structural and non-structural damage, earthquake intensity, buildings geometry and occupancy and earthquake scenario time. proposed framework is considered a significant step to accurately predict fire risk following a seismic event with affordable time and it can be an alternative solution to the statistical ignition model currently being used in many fire following hazard methods

Experimental Investigation of the Static and Dynamic behaviors of 3D-Printed Shell Structures

Over the last years, several optimization strategies were conducted to find the optimal shape minimazing internal stress or total weight (volume) of shell structures. In recent times, this structure typology gained a great importance among researchers and the scientific community for the renowed interest in the form-findind optimization of column-free space solution for large span roofing constructions. In the present paper, a form-finding of a shallow grid shells was introduced basing on the multy-body rope approach (MRA) for the definitions of vault shapes and different hole percentage. In order to obtain an experimental validation, a physical model was reproduced at the laboratory scale performing ad hoc measurements to compare the observed respect to the simulated behaviour. A 3D printing procedure based on the Fuse Deposition Modeling (FDM) technique in polylactide (PLA) material was used to realise form-works of the cement based blocks of the scaled prototype. Several static and dynamic load configurations are investigated, collecting into a sensitivity analysis the parameters which mainly affect the structural behaviour. To simulate earthquake ground motion an assigned frequency range as dynamic input to the structure was provided by a shaking table. Finally, some preliminary considerations of the dynamic response of the model were provided testing the robustness of the form-finding approach when horizontal load are taken into account

The Digital Living Archive and the construction of a participatory cultural memory in the DARE-UIA project (Digital Environment for collaborative Alliances to Regenerate urban Ecosystems in middle-sized cities)

Living Archives perform a function of social memory sharing, which contributes to building social bonds, communities, and identities. This potential lays in the ability of Living Archives to put together an archival function, which allows with the conservation and transmission of memory, with an artistic, performative and creative function linked to the present. As part of the DARE-UIA (Digital environment for colaborative alliances to regenerate urban ecosystem in middle-sized cities) project, the creation of a living digital archive made possible to create a narrative that would consolidate the cultural memory of the Darsena district of the city of Ravenna. The aim of the project is to stimulate the urban regeneration of a suburban area of a city, enhancing its cultural memory and identity heritage, through digital heritage tools. The methodology used involves various digital storytelling actions necessary for the overall narrative using georeferencing systems (GIS), storymaps and 3D reconstructions for a transversal narration of historical content such as personal and institutional historical photos and to enhance the industrial archeology heritage of the neighborhood. The aim is the creation of an interactive and replicable narrative in similar contexts to the Darsena district in Ravenna. The Living Archive, in which all the digital contents are inserted, finds its manifestation towards the outside with the form of a museum spread throughout the neighborhood, making the contents usable on smartphones via QR codes and totems inserted on-site, creating thematic itineraries spread around the neighborhood. The construction of an interactive and engaging digital narrative has made possible to enhance the material and immaterial heritage of the neighborhood by recreating the community that has historically always distinguished it

Resilience assessment of large scale water distribution networks: a simulation approach

The capacity of a community to react and resist to an emergency situation is strictly related to the proper functioning of its own infrastructure systems. This paper proposes a simulation oriented approach to evaluate the resilience of large scale water distribution networks. The case study used in this research is the water network of a large scale virtual city. The water network is modeled using the software EPANET 2.0 with the help of an integrated Matlab toolbox. The network consists of 16000 junctions and 19000 water pipes buried under the road network of the city. A series of earthquake scenarios is applied to the water network and the damage induced by the earthquakes has been determined using fragility function. The failure of the system occurs when the water flow and the water pressure go below a certain threshold. The resilience of the network is then evaluated using two indices: (1) the number of users without water, (2) the drop in the total water supply

Development of a Multi Modular platform for seismic engineering courses and research

Small-scale shaking tables are usually employed in seismic engineering for studying structural models' dynamic behavior and for investigating innovative solutions, as active and passive structural control systems. In an increasingly complex and dynamic world, the ability of responding community natural disasters, such as those induced by earthquakes, is also becoming a pressing issue. With the aim of supporting the research in the field of resilience and emergency management, with particular reference to earthquakes, this paper has the main goal of illustrate the development of a multi modular platform to be used by students during dynamic and seismic courses. Indeed, another peculiarity of this platform, with respect to literature, is that the system has been entirely developed by undergraduate students at the Politecnico di Torino, for both the unidirectional and bidirectional applications. Virtual reality is also an additional tool that can enrich the possible applications of the proposed shaking table in the seismic engineering research field. Indoor and outdoor virtual environments have been developed for reproducing the emergency conditions, where the human response to earthquake shaking can be explored by employing both ground shaking and floor response records as well. The project under consideration is rooted in the perspective of realizing a vibrating table capable of simulating the earthquake and, through instrumentation, measuring the stress characteristics and deformation. Specifically, it is an instrument designed to replicate a seismic event seismic on structural model of a reduced scale, such as a building, a bridge, or, at a larger scale, a portion, e.g. a district, of an urban area. With the prototype of a shaking table herein proposed it is possible to reproduce a seismic event on a model of structure and to execute hybrid simulations. The university experience of students in understanding the intricacies of real structural systems results consequently improved by visualizing their complex behavior when subjected to earthquake loading

Seismic vulnerability of historical artifacts: experimental test and analytical formulation through evolutionary algorithm

Historical artifacts represent a crucial aspect for societies and therefore it should be preserved from natural disasters (e.g. earthquakes). Artifacts such as statues are often made by fragile material, while present irregular shapes and different slenderness levels. Furthermore, a complete and accurate dynamic characterization can be achieved through the use of complex models. Indeed, friction is a crucial aspect which affects the behaviour of historical artefacts during dynamic excitations. Several studies investigated how friction is influenced from other parameters, such as artefact’s geometry and motion characteristics. The paper investigates the relationship between the input velocity and dynamic friction coefficient through experimental dynamic test performed by shaking table. High and low velocity conditions are analyzed for free standing cylindrical concrete sample. Three input time histories with different maximum amplitude and predominant frequency are adopted to analyze various shaking conditions. The experimental campaign is aimed at determining the main factors which affect the dynamic friction while creating a consistent output dataset. Finite Element Models are implemented for modelling the dynamic behaviour of the artefact and then validate the obtained results

Progressive Collapse Analysis of the Champlain Towers South in Surfside, Florida

Since the Ronan Point collapse in the UK in 1968, the progressive collapse analysis of residential buildings has gradually drawn the attention of civil engineers and the scientific community. Recent advances in computer science and the development of new numerical methodologies allow us to perform high-fidelity collapse simulations. This paper assesses different scenarios that could have hypothetically caused the collapse of the Champlain Tower South Condo in Surfside, Florida, in 2021, one of the most catastrophic progressive collapse events that has ever occurred. The collapse analysis was performed using the latest developments in the Applied Element Method (AEM). A high-fidelity numerical model of the building was developed according to the actual structural drawings. Several different collapse hypotheses were examined, considering both column failures and degradation scenarios. The analyses showed that the failure of deep beams at the pool deck level, directly connected to the perimeter columns of the building, could have led to the columns’ failure and subsequent collapse of the eastern wing of the building. The simulated scenario highlights the different stages of the collapse sequence and appears to be consistent with what can be observed in the footage of the actual collapse. To improve the performance of the structure against progressive collapse, two modifications to the original design of the building were introduced. From the analyses, it was found that disconnecting the pool deck beam from the perimeter columns could have been effective in preventing the local collapse of the pool deck slab from propagating to the rest of the building. Moreover, these analyses indicate that enhancing the torsional strength and stiffness of the core could have prevented the collapse of the eastern part of the building, given the assumptions and initiation scenarios considered

Monitoring human body motions during earthquakes

This work aims at establishing laboratory requirements and testing conditions in order to understand the physical and emotional stability of people during a ground shaking. Several individuals with different human characteristics (gender, age, height, etc.) are considered in the test. Two different laboratory setups are presented. A position device (Kinect) and video targetless tracking algorithm has been used to collect the human body position during the shaking. A two and a three dimensional shaking tables are used to generate artificial earthquakes with different frequency bands. In addition, a well detailed virtual reality setting is applied to the testing site in order to illustrate the real environment. During the experiment, a special attention has been given to the factor of “surprise”, which is necessary to ensure a natural reaction of the individuals. The result of the experiment proved common behaviors among the individual samples during the shaking. This work is considered a first step towards a large test campaign, which is necessary to obtain comprehensive statistics on this topic