Markov chain-based stochastic modeling of chloride ion transport in concrete bridges

Over the last decade, there has been an increasing interest in models for the evaluation and prediction of the condition of bridges in Canada due to their large number in an advanced state of deterioration. The models are used to develop optimal maintenance and replacement strategies to extend service life and optimally allocate financial and technical resources. The main process of deterioration of concrete bridges in Canada is corrosion of the reinforcing steel due to the widespread use of de-icing salts. In this article, numerical models of the diffusion process and chemical reactions of chloride ions in concrete are used to estimate the time to initiation of corrosion and for the progression of corrosion. The analyses are performed for a range of typical concrete properties, exposure and climatic conditions. The results from these simulations are used to develop parametric surrogate Markov chain models of increasing states of deterioration. The surrogate models are more efficient than physical models for the portfolio analysis of a large number of structures. The procedure provides an alternative to Markov models derived from condition ratings when historical inspection data is limited

Savoir d’où l’on vient : connexions entre les savoirs expérientiels des étudiant.e.s au deuxième cycle en travail social et leur expérience de formation pratique

Les savoirs expérientiels représentent des connaissances issues de l’expérience. Il s’agit d’une source de savoir controversée pour les intervenant.e.s en travail social, bien que de plus en plus considérée pertinente. Toutefois, leurs impacts sur le cheminement académique des futur.e.s travailleuses sociales et travailleurs sociaux (T.S.) demeurent méconnus. Ce projet de mémoire vise donc à explorer les connexions entre les savoirs expérientiels des étudiant.e.s et leur parcours de formation pratique. Toutes les personnes rencontrées étudient ou étudiaient au programme de deuxième cycle en travail social de l’Université de Montréal (UdeM). Ce projet s’inscrit au cœur de la vaste recherche « Dans quelle mesure la maîtrise en travail social peut promouvoir les apprentissages transformationnels : possibilités et limites » menée par Edward Ou Jin Lee à Montréal. Nous avons conduit des entretiens qualitatifs semi-dirigés, deux (2) de groupe et quatre (4) individuels, pour un échantillon final de treize (13) personnes. Un cadre théorique anti-oppressif et l’analyse thématique de Braun et Clarke ont guidé l’analyse. Trois thématiques principales ont été identifiées lors de cette recherche : (1) le profil sociodémographique largement privilégié des étudiant.e.s en travail social ; (2) la nature complexe, identitaire, intersectionnelle et interrelationnelle de leurs savoirs expérientiels ; (3) leurs perceptions critiques de la formation pratique, notamment sur les enjeux d’adéquation entre le programme et le terrain, l’importance d’offrir des espaces d’échange entre étudiant.e.s et la place de la justice sociale dans la formation. Ces perceptions s’appuient fortement sur les savoirs expérientiels des participant.e.s, particulièrement ceux liés à une expérience professionnelle d’intervention.Experiential knowledge is knowledge derived from experience. Although a perceived controversial source of knowledge, it is increasingly considered relevant in the field of social work. However, its impact on the education of future social workers remains largely unknown. Thus, this project aims to explore the connexions between the students' experiential knowledge and their field education journey. All the people interviewed are or were graduate students in the social work program at the Université de Montréal (UdeM). This project is part of the larger research project " Social work graduate field education: exploring the potential for transformative learning and institutional change " conducted by Edward Ou Jin Lee at UdeM. We conducted semi-structured qualitative interviews, two (2) focus groups and four (4) individual interviews, resulting in a final sample of thirteen (13) participants. An anti-oppressive theoretical framework and Braun and Clarke’s thematic analysis guided the analysis. Three main themes were identified during this research: (1) the largely privileged socio-demographic profile of social work students, (2) the complex influence of identity, along with the intersectional and interrelational nature of their experiential knowledge, and, (3) their critical perceptions of field education, especially on the issues of the inadequacy between the program and the field, the importance to provide spaces for informational exchange between students, and the place of social justice within the graduate program. These perceptions are strongly based on the experiential knowledge of the students, particularly experiences related to professional intervention

Updating of chloride ingress models using core data measurements

A large proportion of concrete bridges in North America are reaching the end of their service life. An important factor that accelerates deterioration is the amount of salts used during winter months. The chloride ions from the salt enter the concrete and destroy the passive-oxide layer that protects the reinforcing steel from corrosion. The TransChlor® software is used to simulate the time history of chloride ion ingress into a typical concrete bridge. A climate model is used to simulate the exposure of the structure to winter conditions. A probabilistic method is used to propagate the uncertainty on material properties in the model and to obtain the distribution of chloride ion concentrations. A procedure for updating the distribution is proposed using data from core samples at two depths (25/50 mm) and for the two types of exposure (splash/direct). The procedure is shown to be very efficient in reducing bias and variance from model predictions

The application of coupled finite-discrete element method in analyzing soil-structure interaction problems

A framework to couple the Finite and the Discrete element methods is proposed in this study. The framework takes advantage of both approaches to investigate different soilstructure interaction problems. The structural elements in the problems are modeled using finite elements whereas surrounding soil is modeled using discrete elements to reflect the discontinuous nature of the granular material. The coupled framework is then used to model three soil-geogrid interaction problems including geogrid pullout test, strip footing on geogrid-reinforced sand and geogrid reinforced fill over void. The numerical results show the efficiency of the coupled framework to model the interlocking effect between the soil and the geogrid sheet. New insights into the nature of the interaction between the soil and the geogrid at the microscopic scale are also presented

“Not Just an Apartment Building”: Residents’ Quality of Life in a Social Housing Co-operative

ABSTRACT The objective of this study was to examine the impact that two social housing complexes have had on their residents' quality of life. These two complexes, known as Tannery Court Co-operative Ltd., target a specific segment of the affordable housing market: non-elderly singles. A mixed-methods approach was used to assess the quality of life of residents. The data collection strategy used semi-structured interviews conducted with the help of a questionnaire. A total of 43 interviews were completed at the two building sites. Analysis of interview and questionnaire data identified six areas of improvement in residents' quality of life. These are life in general (an overarching dimension), housing (the focus of the Tannery Court intervention), neighbourhood (including safety and appearance), food, self-confidence (an enabling dimension for future development of projects and goals among the residents), and financial situation (a key dimension because of its multiple impacts on other aspects of life).   RÉSUMÉ L'objectif de cette recherche était d'évaluer l'impact des deux complexes de logements coopératifs Tannery Court sur la qualité de vie des résidants. Ces complexes ciblent un segment particulier du marché du logement social, les célibataires d'âge actif et vivant en deçà du seuil de la pauvreté. Cette étude utilise une méthodologie mixte pour évaluer la situation et la qualité de vie des résidants. La stratégie de cueillette de données s'appuie sur des entrevues semi-dirigées effectuées à l'aide d'un questionnaire. Au total, nous avons complété 43 entrevues. Six aspects de la qualité de vie se sont améliorés de façon significative. Il s'agit de la vie en général (une dimension globale), le logement (l'objectif premier visé par l'équipe de Tannery Court), le quartier de résidence (dimensions importantes de la localisation d'un complexe comme la sécurité et l'apparence) la confiance en soi (une dimension clé pour le développement futur de projets et d'objectifs pour les résidants), la nourriture (en raison de l'accès à des électroménagers) et la situation financière (une dimension majeure étant donné son impact sur les autres composantes de la vie)

Quantifying the effects of modeling simplifications for structural identification of bridges

Several long span prestressed segmental box girder bridges were built in the early 1980’s and many of them are affected by long-term residual deformations. Although models have been proposed to describe their structural behavior, several uncertainties remain. This paper examines the effects of errors introduced by model simplifications on predicted values. These results are used to improve the estimation of parameter values using model-based data-interpretation strategies. The procedure is illustrated for the Grand-Mere bridge located in Canada. This bridge is affected by excessive long-term vertical displacements. Model simplifications such as the degree of complexity of a model are found to have an important influence on prediction errors. Representing these errors by zero-mean independent Gaussian noise does not adequately describe the relationships between errors observed in this case study. Estimated errors are used during the interpretation of ambient vibration acceleration data recorded on the structure. The interpretation approach employed is based on error-domain model falsification. The study provides ranges of parameter values that can subsequently be used to characterize more accurately aspects such as long-term creep and shrinkage behavior

Assessing the Condition of Reinforced Concrete Bridge Using Visual Inspection Ratings

The evolution of the state of a structure is characterized by deterioration. This is mainly due to corrosion of the steel reinforcement and damage from mechanical solicitations. The maintenance of existing infrastructures involves a good grasp of their condition and a high level of expertise on the part of the project managers. An accurate assessment of the bridge state condition is required to plan maintenance and repair activities for better durability, and to maintain the level of service of the road network. In this paper, an effective management framework for bridge is proposed using field observations from visual inspections. Each element of the bridge was evaluated separately by a visual inspection from which were derived ratings to quantify the structural performance and the material condition. The element ratings were also combined to obtain an overall rating for the bridge considering its defects and impact on the behavior of the complete structure. The modelling approach proposed in this work can better represent the deterioration of concrete-built bridges when the defect is visible. A representative structure in Quebec was studied to illustrate how to apply the methodology for the assessment of a real structure condition at specific times

Quantifying the Effects of Modeling Simplifications for Structural Identification of Bridges

Several long-span, prestressed, segmental box girder bridges were built in the early 1980s and many of them are affected by long-term residual deformations. Although some models have been proposed to describe their structural behavior, several uncertainties remain. This paper examines the effects of errors introduced by model simplifications on predicted values. The results are used to improve the estimation of parameter values using model-based data-interpretation strategies. The procedure is illustrated for the Grand-Mere Bridge located in Canada. This bridge is affected by excessive long-term vertical displacements. Model simplifications such as in its degree of complexity are found to have an important influence on prediction errors. Representing these errors by zero-mean independent Gaussian noise does not adequately describe the relationships among the errors observed in this case study. Estimated errors are used in the interpretation of the ambient vibration acceleration data recorded on the structure. The interpretation approach employed is based on error-domain model falsification. This study provides ranges of parameter values that can be used subsequently to characterize more accurately aspects such as long-term creep and shrinkage behavior. (C) 2014 American Society of Civil Engineers

Human subcortical brain asymmetries in 15,847 people worldwide reveal effects of age and sex

The two hemispheres of the human brain differ functionally and structurally. Despite over a century of research, the extent to which brain asymmetry is influenced by sex, handedness, age, and genetic factors is still controversial. Here we present the largest ever analysis of subcortical brain asymmetries, in a harmonized multi-site study using meta-analysis methods. Volumetric asymmetry of seven subcortical structures was assessed in 15,847 MRI scans from 52 datasets worldwide. There were sex differences in the asymmetry of the globus pallidus and putamen. Heritability estimates, derived from 1170 subjects belonging to 71 extended pedigrees, revealed that additive genetic factors influenced the asymmetry of these two structures and that of the hippocampus and thalamus. Handedness had no detectable effect on subcortical asymmetries, even in this unprecedented sample size, but the asymmetry of the putamen varied with age. Genetic drivers of asymmetry in the hippocampus, thalamus and basal ganglia may affect variability in human cognition, including susceptibility to psychiatric disorders