1,721,004 research outputs found
Pont ferroviaire sur l’Aar en ville de Soleure
Get PDFCe présent rapport synthétise le projet de master que j’ai effectué durant le semestre d’automne 2021 à l’EPFL. Il s’agit d’un projet purement académique ; il n’a pas pour but d’être utilisé par des professionnels. L’ouvrage-thème de mon projet de master est le pont ferroviaire sur l’Aar à Soleure. Comme le suggère la table des matières, le projet de master est scindé en 2 parties : 1. Examen de l’ouvrage existant 2. Projet d’intervention Ce rapport de synthèse a pour but de donner un aperçu aussi exhaustif que possible de tout ce qui a été abordé. Il cherche à être représentatif du travail qui a été effectué pour ce projet de master. En plus du présent rapport de synthèse, les documents suivants sont inclus dans le dossier du projet de master : • Étude historique • Convention d’utilisation actualisée • Base de projet actualisée • Examen de l’ouvrage, partie 1/2 • Projet d’intervention, partie 2/2SGCMC
Pont sur le Torrent d’Allèves : examen et projet d’intervention
No full textEn Suisse, le travail des ingénieurs civils constitue de plus en plus en l’analyse d’ouvrages existants. Ce travail d’analyse est très différent de celui lié à la construction de structure neuve. En effet, il s’agit de vérifier qu’un ouvrage remplit toujours bien sa fonction en utilisant des méthodes d’analyse souvent plus complexes. L’examen doit nécessairement être plus avancé et détaillé qu’une structure neuve car les coûts d’intervention sont très onéreux. En outre, la planification de l’intervention doit être finement étudiée afin de limiter les nuisances sur les usagers de l’ouvrage. Le renforcement d’une structure existante s’avère souvent peu efficace avec les méthodes traditionnelles qui engendrent des coûts disproportionnés. Au cours des dernières années, de nouveaux matériaux ont été développés et des méthodes innovantes ont été appliquées lors d’intervention avec grand succès. Le composé cimentaire fibré à ultra-haute performante (CFUP) fait partie de ces nouvelles technologies, car les exceptionnelles propriétés mécaniques et la durabilité de ce matériau conviennent parfaitement au renforcement d’un ouvrage. Ce projet de Master à l’EPFL étudie le pont du Torrent d’Allèves situé sur la route d’importance nationale du Grand-Saint-Bernard en Valais. Construit en 1962 lors de l’aménagement des voies d’accès au tunnel, cet ouvrage multi-poutres mesure 114 mètres de long. Il dispose de nombreuses travées irrégulières et de deux joints Gerber en mauvais état. En 1986, d’importants travaux ont été menés pour éviter l’effondrement de la travée entre ces joints. Encadré par le Prof. Brühwiler et le Dr Bertola, le projet consiste premièrement en l’examen de la structure existante. Puis, un projet d’intervention visant le renforcement et l’amélioration de la durabilité de l’ouvrage est élaboré. La dalle de roulement sera notamment renforcée au moyen d’une couche de CFUP, matériau extrêmement performant et novateur. Avant de développer ces deux sujets techniques, l’influence historique et culturelle de la route du Grand-Saint-Bernard est étudiée.SG
Passage supérieur sur l’autoroute A1 à Bavois. Vérification de la structure existante et dimensionnement d’un nouvel ouvrage en CFUP armé
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Strategies for a More Sustainable Management of Existing Concrete Structures
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Measurement-system design for structural identification
No full textIn developed countries, the management of existing civil infrastructure is challenging due to evolving functional requirements, aging and climate change. Due to conservative approaches in construction design and practice, infrastructure often has hidden reserve capacity and this has potential to improve decisions related to asset management. For example, improved knowledge of behavior of load capacity through bridge measurement can be exploited to extend lifetimes and optimize retrofit designs.
The assessment of bridge reserve capacity requires predictions of structural behaviour under actions. This behaviour is influenced by several parameters that are difficult to estimate, such as material properties. Field measurements, collected through load testing, may help in the identification of unknown parameter values and this process is called structural identification. Then, the reserve capacity is assessed using the updated behaviour model.
The design of measurement systems is usually carried out by engineers using only qualitative rules of thumb. However, finding the optimal design is difficult due to redundancies in information gained from sensors. Suboptimal sensor configurations are often selected by engineers, reducing the information collected during monitoring. This thesis proposes a range of quantitative methodologies for measurement-system design in order to improve structural-identification performance.
Measurement-system design for structural identification depends on the actions applied during measurements. This aspect is often neglected in sensor-placement algorithms. A methodology is presented to maximize the information gain of measurement systems when multiple static load tests are involved.
The optimal design of measurement systems depends on multiple conflicting performance criteria such as information gain and cost of monitoring. A multi-objective approach for measurement system design thus leads to more informed decision making when several performance criteria are important. A framework is proposed that quantitatively accounts for multiple objective functions to recommend measurement systems based on asset-manager preferences.
Monitoring is justified only when asset-manager decisions regarding bridge safety can be influenced by the information gain during load testing. A methodology is introduced to quantitatively assess whether monitoring information has the potential to influence reserve-capacity assessments and the value of information is assessed probabilistically.
These proposals have been tested and verified with three case studies of full-scale bridges and one case study of a retaining wall in an excavation. Proposed methodologies for measurement-system design outperform other approaches and qualitative engineering rules of thumb. Sensor-performance predictions have then been corroborated using field measurements. Furthermore, the excavation case study demonstrates that the selection of the most informative data sets is crucial when sensor information is used to update complex models.
This thesis demonstrates that rational methodologies to design measurement systems enhance the performance of structural identification, leading to better asset-management decisions. More generally, the measurement-point-selection methodologies proposed in this thesis have the potential to help maximize the information extracted from large data sets collected by the Internet of Things at city scale.IMA
Combining monitoring information and UHPFRC strengthening to extend bridge service duration
Get PDFpeer reviewedAs many bridges are approaching the end of their supposedly theoretical service duration, finding novel technical solutions to extend their service duration is crucial, also for reasons of sustainability. In this article, two strategies (structural performance monitoring, and strengthening with ultra-high-performance fiber-reinforced cementitious composite (UHPFRC)) are introduced to avoid prematurely replacing structures. The case study of the Ferpècle road bridge (Valais, Switzerland) is presented since the two strategies were combined in 2023 to extend its service duration. This bridge is one of the first prestressed concrete bridges in Switzerland. Built in 1958, the structure consists of a single girder with a 34.5-meter span resting on abutments in the form of reinforced concrete piers. As the deck has a width of only 5.3 meters, bridge owners have decided to widen it to 7.9 meters in order to include two road lanes and a pedestrian way. Despite its good condition, the bridge must be strengthened as its load-bearing capacity (bending moment at mid-span) would be largely insufficient with the new deck width. To increase its load-bearing capacity while widening the bridge deck by 50%, an intervention with UHPFRC has been made. The innovative intervention enables clamping the abutments with the bridge deck to modify the static system to obtain a semi-rigid frame to reduce the bending moment at midspan. Two load tests using the latest sensing technologies, before and after the intervention, have enabled the quantification of the design capacity and the validation of this pioneering intervention. This case study demonstrates the potential of novel technologies to extend bridge service duration, thereby improving the sustainability of the construction sector.13. Climate actio
Distributed fiber-optic sensor-based methodology for performance evaluation of prestressed concrete girder bridges
No full textpeer reviewedBridges are exposed to high environmental actions, which could affect their structural capacities. Additionally, many existing concrete bridges were not designed for current traffic demands. This means that structural verifications of current standards are often not verified, putting structural integrity at risk. Data-informed structural-assessment methodologies are essential to ensure structural safety. Structural health monitoring aims to detect damage by monitoring the structural response over time. This approach generates large datasets over the years that renders data processing and interpretation challenging. Moreover, only the relative variation of the structural behavior is usually monitored, meaning that initial structural deficiencies cannot be seen. On the opposite, structural performance monitoring (SPM) aims to evaluate current bridge conditions using a data-informed framework. This study proposes a new methodology for SPM based on distributed fiber-optic datasets during static load tests for concrete girder bridges. The datasets provide information to understand both global and local structural behavior, such as load distribution between girders, support conditions, impacts on secondary elements, and extrapolate displacements. Applied to the Ferpècle Bridge, a prestressed concrete structure in Switzerland, built in 1958 and strengthened with ultra-high-performance fiber-reinforced cementitious composite in 2023, distributed fiber-optic sensor with a low spatial resolution (strain measurements every 2.6 mm) reveals detailed information on three-dimensional girder responses, support conditions, and load distribution and enables accurate data-driven deflection predictions. The methodology provides new insights into structural behavior, allowing for more refined structural safety assessments
Transforming the Static System of Prestressed Concrete Bridges Using UHPFRC
No full textpeer reviewedThe rehabilitation of existing bridges should always be the first investigated solution because it usually reduces construction costs, environmental impacts, and traffic disruption. Nonetheless, bridges are too often replaced due to the lack of effective structural strengthening schemes. The latter reason is particularly true for short-span, simply supported structures that cannot plastically redistribute additional loads. Ultrahigh-performance fiber-reinforced cementitious composites (UHPFRCs) and their technology offer new solutions for enhancing the performance of existing reinforced concrete bridges. The UHPFRC technology allows for the rehabilitation and strengthening of the deck and girder of bridges due to its high mechanical properties and high durability. Conventional UHPFRC interventions are realized by casting an additional layer on the deck, but this solution enables only limited improvement in the case of simply supported structures. This manuscript presents the innovative strengthening concept for short-span concrete bridges with UHPFRCs, consisting of clamping supports to modify the boundary conditions and, thus, the static system. This intervention was recently realized on a prestressed concrete bridge with a single span of 35 m built in 1958 in Switzerland. The bending structural capacity increased by 47%, allowing for the widening of the deck from 5.3 to 7.9 m. Load tests were performed before and after the intervention, and data collected validated the strengthening scheme. Life-cycle cost and environmental analysis showed significant savings (42% and 55%, respectively) compared to the previously proposed deconstruction-reconstruction solution. This case study demonstrates the potential of this strengthening strategy for managing short-to medium-span bridges, respecting sustainable and cost-effective infrastructure management
Structural performance monitoring for concrete girder bridges with distributed fiber optic sensors
Get PDFpeer reviewedThe alarming frequency of bridge collapses in recent years underscores the critical need for advanced monitoring strategies tailored to existing infrastructure. Many concrete bridges, built decades ago, now face increasing traffic demands and environmental stressors that threaten their structural integrity.
This study investigates the use of distributed fiber optic sensors (DFOSs) with high spatial resolution (independent strain measurements every 2.6 mm) during static load tests to assess the structural performance of concrete girder bridges. The goal is to gain a deeper understanding of their condition using data-driven approaches. The fiber optic technology provides detailed strain profile information that gives insights into global bridge behavior, such as stress distributions, support conditions and static responses. It also allows the detection of cracks along the fiber path and other localized effects that may remain undetected without a calibrated numerical model.
This method of structural performance monitoring is applied to a prestressed concrete bridge in Switzerland. Static load tests have been performed on a full-scale bridge in Switzerland and the resulting distributed strain datasets allow the accurate understanding of bridge behavior, including deflection extrapolation and crack detection. The results underline the potential of DFOS to develop novel data-driven solutions for extending the service life of structures
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