École Polytechnique Fédérale de Lausanne
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Experiments on the flexural behavior of full-scale PC box girders with service damage strengthened by prestressed CFRP plates
No full textTwo full-scale PC box girders with typical damage were derived from an in-situ bridge that was in service about 20 years, to understand the strengthening effects of prestressed CFRP plates for the entire bottom slab, casting of a RC layer in composite action with the entire top slab and steel plates anchored on the webs of the shear span. The flexural tests were conducted on the two full-scale PC box girders with and without strengthening measures, and comparative analysis was conducted regarding flexural capacity, failure mechanism, rigidity, ductility and overall structural behavior. The test results showed that the strengthening measures improved the girder rigidity by 40 % before reaching cracking state and increased the yielding and ultimate capacity by 39 % and 28% respectively. The theoretical analysis was conducted to discuss failure modes for PC box girder strengthened by prestressed CFRP plates. Theoretical equations are derived to calculate the flexural capacity of strengthened PC box girder according to typical failure modes. Good agreement with tested results was obtained. The strengthening design of the prestressing CFRP plate was verified by application in a PC box girder bridge.MC
Mining Effective Strategies for Climate Change Communication
No full textWith the goal of understanding effective strategies to communicate about climate change, we build interpretable models to rank tweets related to climate change with respect to the engagement they generate. Our models are based on the Bradley-Terry model of pairwise comparison outcomes and use a combination of the tweets’ topic and metadata features to do the ranking. To remove confounding factors related to author popularity and minimise noise, they are trained on pairs of tweets that are from the same author and around the same time period and have a sufficiently large difference in engagement. The models achieve good accuracy on a held-out set of pairs. We show that we can interpret the parameters of the trained model to identify the topic and metadata features that contribute to high engagement. Among other observations, we see that topics related to climate projections, human cost and deaths tend to have low engagement while those related to mitigation and adaptation strategies have high engagement. We hope the insights gained from this study will help craft effective climate communication to promote engagement, thereby lending strength to efforts to tackle climate change.INDY
Predicting the effect of non-uniform fiber distribution on the tensile response of ultra-high-performance fiber reinforced concrete by magnetic inductance-based finite element analysis
No full texton-uniform fiber distribution can significantly reduce the extension of multiple-cracking and favor crack local-izations in Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) members under tension with important implication on the sought durability. This work aims at fostering the coupling between a novel Non-Destructive Technique, namely Magnetic Inductance Method (MIM), and Finite Element Method (FEM) to predict the effect of nonuniform fiber distribution on the micro-cracking response of UHPFRC samples under tensile loading.First, uniaxial tensile tests on 5 dumbbell samples of UHPFRC with 3.8% of steel fibers showed that tensile ductility is much affected by the degree of uniformity of the fiber distribution. Thus, FEM analysis was performed with the Concrete Damaged Plasticity model (CDP) in Abaqus software, where the UHPFRC tensile law was scaled by a field variable based on the fiber orientation factor and the fiber efficiency factor (li0 and li1) measured by Magnetic Inductance Method (MIM). The field variable scales the UHPFRC tensile law between an upper and a lower bound of the tensile law estimated by a fiber pull-out model and a cohesive law for concrete matrix, respectively. The accuracy of the proposed MIM-FEM method was verified against the experimental results by considering the load-displacement curve, the asymmetric displacement, the crack pattern, the fracture energy, and the evolution of the microcrack opening. Based on the presented results, the proposed MIM-FEM method can map and quantitatively analyze the effect of non-uniform fiber distribution for UHPFRC members under tension, thus providing potential application value for infrastructures, pre-casting and architectural applications more broadly.MC
The Biopolitics of Habitability in a Persistent Company Town. Rethinking the Industrial Cities and Their Productive Habitats
No full textCompany towns are cities founded during the Industrial Revolution by single enterprises operating as employers and landlords, enforcers of security, promoters of social harmony, and providers of services and goods for workers to enhance the living and health conditions of the production sites and the surrounding settlements. In the second half of the twentieth century, existing company towns encompassed a transition process, which contributed to a radical change in the modes of living, in most cases caused by the disappearance of the industry that had ceased its industrial activities in the area. Where today production has not ceased, the company's power in the territory is still discernible. My work hypothesises that these companies adopt postmodern spatial and social control dynamics to shape the conditions of habitability. I use the city of Dalmine, funded in 1906 in Northern Italy, to corroborate this hypothesis. Dalmine represents a curious archetype of an Italian company town, where the company is today still actively contributing to the construction of the town's identity through educational and social programs freely offered to the citizens. The analysis of the 100 years of welfare programs recorded in the private business archives of Fondazione Dalmine allows grasping how the dynamics of spatial, social and body control have changed over time, following changes in the company's biopolitical strategies.LAB-URespondent: Paolo Scrivano, Politecnico di Milano
Computational Approaches to Digitised Historical Newspapers (Dagstuhl Seminar 22292)
No full textHistorical newspapers are mirrors of past societies, keeping track of the small and great history and reflecting the political, moral, and economic environments in which they were produced. Highly valued as primary sources by historians and humanities scholars, newspaper archives have been massively digitised in libraries, resulting in large collections of machine-readable documents and, over the past half-decade, in numerous academic research initiatives on their automatic processing. The Dagstuhl Seminar 22292 "Computational Approaches to Digitised Historical Newspaper" gathered researchers and practitioners with backgrounds in natural language processing, computer vision, digital history and digital library involved in computational approaches to historical newspapers with the objectives to share experiences, analyse successes and shortcomings, deepen our understanding of the interplay between computational aspects and digital scholarship, and discuss future challenges. This report documents the program and the outcomes of the seminar. DagRep, Volume 12, Issue 7, pages 112-179DHLA
Knowledge-Aware Cross-Modal Text-Image Retrieval for Remote Sensing Images
No full textImage-based retrieval in large Earth observation archives is difficult, because one needs to navigate across thousands of candidate matches only with the proposition image as a guide. By using text as a query language, the retrieval system gains in usability, but at the same time faces difficulties due to the diversity of visual signals that cannot be summarized by a short caption only. For this reason, as a matching-based task, cross-modal text-image retrieval often suffers from information asymmetry between texts and images. To address this challenge, we propose a Knowledge-aware Cross-modal Retrieval (KCR) method for remote sensing text-image retrieval. By mining relevant information from an external knowledge graph, KCR enriches the text scope available in the search query and alleviates the information gaps between texts and images for better matching. Experimental results on two commonly used remote sensing text-image retrieval benchmarks show that the proposed knowledge-aware method outperforms state-of-the-art methods.ECE
Improvement of fixed railway tracks using fatigue-resistant cementitious fibre reinforced composite material
No full textMCSGIS-G
Von Bettlach nach Grenchen über die restaurierte Brücke Witi – ein junger Baustoff weist den Weg
No full textIn der Landwirtschafts- und Schutzzone Witi macht eine Informationstafel auf die historische Brücke über den Witibach aufmerksam: «103 Römerbrücke. Diese Brücke, die im Volksmund ‹Römerbrücklein› heisst, geht wohl kaum auf die Zeit ihres Namens zurück. Sie ist ein Zeuge eines mittelalterlichen Wegsystems durch die Aareebene vor der Versumpfung.» Die denkmalgeschützte Natursteinbrücke besitzt einen hohen Zeugniswert und wurde 2020/2021 sorgsam restauriert.MCSGIS-G
Minimum Cost Intervention Design for Causal Effect Identification
No full textPearl's do calculus is a complete axiomatic approach to learn the identifiable causal effects from observational data. When such an effect is not identifiable, it is necessary to perform a collection of often costly interventions in the system to learn the causal effect. In this work, we consider the problem of designing the collection of interventions with the minimum cost to identify the desired effect. First, we prove that this problem is NP-hard, and subsequently propose an algorithm that can either find the optimal solution or a logarithmic-factor approximation of it. This is done by establishing a connection between our problem and the minimum hitting set problem. Additionally, we propose several polynomial-time heuristic algorithms to tackle the computational complexity of the problem. Although these algorithms could potentially stumble on sub-optimal solutions, our simulations show that they achieve small regrets on random graphs. 32 pages, 10 figures, ICML2022BA