1,720,996 research outputs found
TVTδ Concept for Long-Span Glass–Steel Footbridges
No full textTransparency and structural lightness are inspiring ideas in the design of footbridges. Glass is the most performing transparent
material to be used for structural purposes because of its high compressive strength, chemical stability, and absence of fatigue and viscosity
phenomena at room temperature. However, its fragility constitutes a challenging limit in structural applications. This research provides and
discusses a specific concept named TVTδ (Travi Vitree Tensegrity) for lightweight long-span beam-like footbridges made of structural glass.
Hence, two design approaches of fail-safe design (FSD) and damage avoidance design (DAD) are applied to guarantee adequate safety levels
and postcracking serviceability, respectively, with low damages on the main components. FSD provides the adoption of structural collaboration
between glass and steel. Following DAD, glass is segmented into triangular panels, and reciprocal diffuse prestress is performed by
steel tendons. This strategy assures low rehabilitation costs because only collapsed elements should be replaced once failed. At ultimate limit
state (ULS), the TVTδ footbridge attains a global ductile behavior in which the yielding of steel tendons occurs before any fragile failure.
Such result is achieved through a hierarchic calibration of the chain of failures. In glass panels, which are mostly precompressed, the buckling
failure, representing the main risk, is delayed by the mutual stabilization of the panels’ compressed edges with steel clamping. However,
because an accidental event may cause a localized or diffuse brittle failure of glass components, the system is designed to maintain a residual
load bearing capacity in this scenario. At the serviceability limit state (SLS), the TVTδ footbridge is highly stiffened by the presence of glass
panes, partially encased in metallic frames. Crack initiation is delayed by precompression
An Artificial Neural Network for the prediction of the structural and foundational attention class of bridges according to the Italian Guidelines
No full textThe state of conservation, maintenance and monitoring of bridges has gained attention in the last decade over the world especially in Italy, where a large number of structures are present and, multiple cases of collapses of bridges have recently occurred. To address this problem and to provide a prioritization on bridges where detailed safety assessments are necessary, in 2020 the Italian Ministry of Transport and Infrastructure issues Guidelines, based on a multi-level and multi-risk approach. Six levels of assessment are foreseen: the first three must be applied to all bridges (Levels 0-2), while the last three (Levels 3-5) only for the bridges which are characterized by high risk deriving from the analyses of the previous levels. Focusing on the first three levels, Level 0 consists of a census of all the existing bridges, collecting registry data mainly deriving from the existing documentation. Level 1 consists of visual inspections, which are used to point out the conservation status of the bridge and the surrounding area. Level 2 provides for a risk-based classification starting from the data previously collected. Levels 0-2 must be applied indiscriminately to all bridges. Thus, to prioritize inspections, it could be helpful to have a tool capable to predict the state of conservation of bridge and to assess the associated risks, starting from data gathered with census. For this reason, this paper proposed an Artificial Neural Network (ANN) capable to assess the level of degradation and structural and foundational risk level of existing bridges, using a reduced set of information derived from Level 0 activities. This tool can be used to: I) rationally schedule the inspections, starting from structures that could have a higher probability to be heavily degraded, II) support managing and planning activities at territorial level, promptly furnishing information about the structural and foundational risk of the bridges
Temporal reliability evolution of a prestressed girder with post-tensioned tendons subjected to corrosion
No full textThis paper presents a methodology for the assessment of time-dependent reliability of post-tensioned (PT) girders. As possible lack of consistent maintenance efforts and the constraints of economic and temporal resources become increasingly apparent, there is a need to comprehend their remaining service life, intricately tied to the gradual evolution of their reliability over time. In this study, the primary focus is directed towards a combination of extreme load failure mechanisms and tendon corrosion. The proposed methodology is applied to a scenario involving a simply supported prestressed girder with PT tendons. The analysis takes into account the progressive reduction in bending capacity over time due to the adverse effects of tendon corrosion. Diverging from conventional approaches found in existing literature, the time-to-corrosion model embeds not only the chloride concentration in voids present in the grout injection but also considers the thermodynamic conditions necessary for the development of corrosion. A sensitivity analysis of the input variables is performed to identify the most influential parameters over time. The study shows that considering both chloride concentration and thermodynamic conditions can lead to a more realistic residual structural life. It is concluded that the consideration of the thermodynamic conditions is essential to avoid overly conservative safety assessments, which could lead to a poorly optimized management and sustainability of bridges
Design and analysis of automated rack supported warehouses
Full text linkBackground: The lack of codified standards for the design of automated rack supported warehouses forced engineers to use personal experience and commonly accepted rules. Objective: This paper investigates the efficacy of applying Eurocodes’ rules for the design and analysis of automated rack supported warehouses. Structural performance, construction feasibility and economic effort are considered. Method: A typical case study building was designed following the two approaches proposed by Eurocodes: elastic and dissipative. Results: The satisfaction of the capacity design requirements, used for dissipative approach, was not always possible. Analyses showed the development of non-uniform collapse mechanisms and yielding patterns. Conclusion: Specific design rules and analysis techniques shall be developed accounting for the structural performance of automated rack supported warehouses
Investigation of reinforced concrete bridges by using a dual-polarized high-frequency GPR
No full textGround penetrating radar is a non-invasive technique that, amongst the various available state-of-the-art methods, is capable of accurately locating both metallic and nonmetallic buried objects. The main object of this paper is to describe the application of a GPR strategy to the non-destructive testing of concrete structures, particularly bridges, where there is a need to identify, quantify and categorize structural reinforcements. The new C-Thrue radar, developed by IDS GeoRadar, was used to investigate two bridges near Pisa (Italy). The acquisition of dense and regular grids was used to provide a full reconstruction of the geometry of the investigated area. Moreover, through the use of sensors in different polarizations, and dedicated data processing techniques, the C-Thrue radar enables the creation of spatially correlated data sets that represent scanned 3-D volumes of the ground, allowing demonstrable benefits in overall assessment of the required structural parameters
Trustworthy AI for infrastructure monitoring: a blockchain-based approach
No full textIn the field of Artificial Intelligence (AI), there is an increasing focus on enhancing trustworthiness especially in critical sectors such as in the management of civil infrastructure. This paper proposes the adoption of a framework based on Hybrid Distributed Ledger Technology (Hybrid-DLT) as a technological solution for improving trustworthiness. We detail three specific applications in the sector of critical infrastructure maintenance: Explainable AI (XAI) for risk classification, structural defects recognition, and real-time monitoring through IoT. The proposed approach employs tamper-resistant ledgers for tracking key processes such as dataset collection, model training, and inference generation, thereby ensuring non-repudiability for recorded actions and enabling auditability. We demonstrate how this strengthens the explainability mechanisms of AI models and enables the production of verifiable data lineage and certified inferences. Our framework can be applied to existing AI solutions, enhancing their trustworthiness
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