Condition Assessment of Concrete Bridge Decks Using Ground and Airborne Infrared Thermography

Applications of nondestructive testing (NDT) technologies have shown promise in assessing the condition of existing concrete bridges. Infrared thermography (IRT) has gradually gained wider acceptance as a NDT and evaluation tool in the civil engineering field. The high capability of IRT in detecting subsurface delamination, commercial availability of infrared cameras, lower cost compared with other technologies, speed of data collection, and remote sensing are some of the expected benefits of applying this technique in bridge deck inspection practices. The research conducted in this thesis aims at developing a rational condition assessment system for concrete bridge decks based on IRT technology, and automating its analysis process in order to add this invaluable technique to the bridge inspector’s tool box. Ground penetrating radar (GPR) has also been vastly recognized as a NDT technique capable of evaluating the potential of active corrosion. Therefore, integrating IRT and GPR results in this research provides more precise assessments of bridge deck conditions. In addition, the research aims to establish a unique link between NDT technologies and inspector findings by developing a novel bridge deck condition rating index (BDCI). The proposed procedure captures the integrated results of IRT and GPR techniques, along with visual inspection judgements, thus overcoming the inherent scientific uncertainties of this process. Finally, the research aims to explore the potential application of unmanned aerial vehicle (UAV) infrared thermography for detecting hidden defects in concrete bridge decks. The NDT work in this thesis was conducted on full-scale deteriorated reinforced concrete bridge decks located in Montreal, Quebec and London, Ontario. The proposed models have been validated through various case studies. IRT, either from the ground or by utilizing a UAV with high-resolution thermal infrared imagery, was found to be an appropriate technology for inspecting and precisely detecting subsurface anomalies in concrete bridge decks. The proposed analysis produced thermal mosaic maps from the individual IR images. The k-means clustering classification technique was utilized to segment the mosaics and identify objective thresholds and, hence, to delineate different categories of delamination severity in the entire bridge decks. The proposed integration methodology of NDT technologies and visual inspection results provided more reliable BDCI. The information that was sought to identify the parameters affecting the integration process was gathered from bridge engineers with extensive experience and intuition. The analysis process utilized the fuzzy set theory to account for uncertainties and imprecision in the measurements of bridge deck defects detected by IRT and GPR testing along with bridge inspector observations. The developed system and models should stimulate wider acceptance of IRT as a rapid, systematic and cost-effective evaluation technique for detecting bridge deck delaminations. The proposed combination of IRT and GPR results should expand their correlative use in bridge deck inspection. Integrating the proposed BDCI procedure with existing bridge management systems can provide a detailed and timely picture of bridge health, thus helping transportation agencies in identifying critical deficiencies at various service life stages. Consequently, this can yield sizeable reductions in bridge inspection costs, effective allocation of limited maintenance and repair funds, and promote the safety, mobility, longevity, and reliability of our highway transportation assets

Specimen Size Effect on Shear Behavior of Loose Sand in Triaxial Testing

Triaxial tests are widely used to determine the behavior and strength characteristics of soils without due attention to the differences in specimen size. Several drained and undrained monotonic triaxial compression shear tests are performed on three different specimen sizes of the same sand to investigate the influence of specimen size and scale effect on the shear behavior. The test results indicate that the behavior of loose sand is strongly influenced by the specimen size, with larger specimens exhibiting a stiffer behavior during isotropic compression, and mobilizing smaller shear strengths and effective friction angles. Triaxial testing also involves many sources of errors that could significantly affect shear strength parameters if not corrected. Extensive errors are investigated and it is found that negligence in making corrections accounting for these errors will result in an overestimation as much as 42% and 15 degrees in the critical shear strength and critical state friction angle, respectively. Furthermore, the measured critical state parameters and shear strengths are employed to compare the static and seismic slope stability of an earth embankment dam, calibrate a critical state soil constitutive model, study the soil behavior under shallow foundations, and evaluate liquefaction triggering and failure of retaining structures. The results show that all of these analyses are significantly affected by the strength parameters of the same soil determined from different specimen sizes. While using small size samples for determining shear strength parameters might result in un-conservative design, the choice of a large sample size is consequently a more accurate representation of soil strength conditions and field deformations

Studying the QCD medium in proton-proton collisions using PYTHIA

It is believed that in the first microsecond after the big bang, the universe was in a state known as the Quark-Gluon Plasma (QGP), where quarks and gluons were asymptotically free. Signatures of QGP like jet quenching and elliptic flow have been observed in heavy-ion collisions at RHIC and LHC experiments. The aim of this study was to investigate the possibility of QGP formation in proton-proton (p-p) collisions. PYTHIA was used to simulate the p-p collision at center-of-mass energies of √s = 200 GeV and √s = 13 TeV corresponding to the available energies of the current collider experiments. The ratios between the near-side and away-side yields associated with the high transverse momentum particles were calculated and compared for the low and high multiplicity events as a function of transverse momentum in order to search for such phase. For LHC energies at high multiplicity, away-side yields show suppression in comparison to near-side yields. This indicates that there is a possibility of creating QGP at high-energy high-multiplicity p-p collisions

MAT-713: EVALUATION OF NDT TECHNIQUES FOR CONCRETE BRIDGE DECKS USING FUZZY ANALYTICAL HIERARCHY PROCESS

Considering the colossal backlog of deteriorating bridges, transportation agencies need to systematically evaluate bridge deck conditions in order to optimize the timing, scope, and approach of preventive maintenance, repair, and replacement. Over the last few years, there have been growing interest among bridge infrastructure stakeholders in using non-destructive methodologies for bridge inspection, evaluation, and maintenance. Nondestructive testing (NDT) techniques can provide needed information about the “under-the-surface” deteriorated condition of bridge decks. This paper examines the most common NDT technologies for assessing bridge decks. Each technology was rated based on five performance measures: capability to detect subsurface defects, speed of data collection, simplicity of analysis and interpretation, accuracy of results, and cost of measurement. The study has particular emphasis on reinforcement corrosion, delamination, and internal cracking. The information sought to identify the significance of the factors affecting the analysis process was collected through a survey questionnaire. In order to incorporate the imprecise information and vagueness of human judgment in the decision-making, the fuzzy analytical hierarchy process (FAHP) is employed, as per the fuzzy preference programming method. Results demonstrate the capabilities of each technology and its ability to address bridge challenges. In order to assist bridge engineers and decision makers, recommendations were made with respect to the selection of the most appropriate technologies to identify specific deterioration mechanisms

MAT-714: CONDITION ASSESSMENT AND DETERIORATION PREDICTION TOOLS FOR CONCRETE BRIDGES: A NEW LOOK

Structural problems created by corrosion, ageing, aggressive environments, material defects and unforeseen mechanical or seismic loads can compromise the serviceability and safety of bridges. The importance of an effective bridge-management system (BMS) cannot be overstated, especially in light of the recent collapse of bridges in North America and elsewhere. Several technologies are available for assessing the condition of concrete bridges and a number of deterioration models are used to predict future bridge conditions and estimate associated funding requirements. This paper critically reviews the different available condition assessment and deterioration prediction approaches for concrete bridges. The potential applications of condition assessment technologies with particular focus on their advantages and limitations are presented. The various types of deterioration models are discussed and compared. The findings indicate that: (i) non-destructive testing (NDT) methods and structural health monitoring (SHM) systems can play a major role in effectively evaluating the conditions of concrete bridges; (ii) mechanistic models for deterioration prediction embrace a reliability-based approach that can provide bridge owners and maintenance personnel with an improved tool to assess bridge conditions and to make decisions regarding their maintenance; and (iii) automated data collection and interpretation analysis is needed for improved BMS. The challenges associated with the different technologies and models are outlined. Furthermore, to empower bridge asset managers in making more informed decisions, recommendations are made on the selection of appropriate evaluation and prediction models that meet desired service goals

Commande par modes glissants d'ordre supérieur et observateur grand gain de la génératrice asynchrone double alimentation d'une éolienne

International audienceLe rendement d'une éolienne dépendant essentiellement de la puissance du vent, de la courbe de puissance de la turbine et de l'habilité de la génératrice à répondre aux fluctuations du vent, cet article propose alors une stratégie de commande robuste de la génératrice asynchrone double alimentation d'une éolienne qui permet d'optimiser sa production énergétique (rendement). Pour ce faire, il est mit en œuvre un observateur grand gain pour estimer le couple aérodynamique et des commandes par mode glissant d'ordre supérieur. La stratégie globale ainsi proposée a été validée sur une éolienne tripale de 1.5 MW en utilisant le simulateur FAST

Health related quality of life among adolescents with sickle cell disease in Saudi Arabia

INTRODUCTION: Increased life expectancy due to recent medical advances has increased the need to understand more fully the quality of life (QoL) in patients with sickle cell disease (SCD) and factors predicting disease adaptation .The objectives of this study were to assess the impairment of health related quality of life (HRQoL) domains in a sample of Saudi Arabian adolescents with SCD. METHODS: A non-probability sample composed of Saudi adolescents with SCD (n=180) aged 14-18 years and comparable age and gender matched healthy controls (n=202). Socio-demographics and disease related data were obtained through personal interview with parents/legal guardians and reviewing patients medical records. Self-administered "Short Form-36" questionnaire was used to assess HRQoL of the included groups. RESULTS: HRQoL showed significant deterioration in adolescents with SCD especially in role physical, general health, and bodily pain domains irrespective of the gender, while female adolescents with SCD demonstrated significant deterioration in emotional wellbeing. Those with SCD-complications showed worse scores along the physical, general health, and emotional wellbeing domains. HRQol scores were negatively associated with increasing age, female gender, rural residence, low family income, presence of disease-related complications and frequent hospital admissions as revealed by multivariate regression analysis. CONCLUSION: Saudi adolescents with SCD experience deterioration along all domains of HRQoL especially the physical. Disease related complications and socio-demographic correlates are significant determinants to worse HRQoL among the included adolescents with SCD

The Effect of Thickness And Accelerated Aging on Opalescence of Different Ceramic Materials

Purpose: The objective of the study was to evaluate the effect of ceramic material type and thickness on opalescence before and after accelerated aging. Materials and methods: 180 all-ceramic slices were divided into three groups (n=60) according to the ceramic material (InCoris TZI, Empress CAD HT, and Empress CAD LT). Each group was further subdivided into four subgroups (n = 15) according to their thickness (0.5 mm, 0.8 mm, 1 mm and 1.2 mm).). CIE Lab coordinates were measured for each slice against black and white backgrounds using intraoral spectrophotometer and OP was calculated. All specimens were subjected to accelerated aging using autoclave (134 ºC, 0.2 MPa for 5 h) and OP was calculated after accelerated aging. Repeated ANOVA combined with a Tukey-post hoc test were used to analyze the data obtained (P ≤ 0.05). Results: The results showed that ceramic material type and thickness have significant effect on opalescence with OP values (from 4.4±1.2 to 7.1±1.7) for InCoris TZI, (from 4.1±0.28 to 5.7±0.36) for CAD HT, and (from 5.9±0.7 to 8.7±4.6) for CAD LT, while the effect of accelerated aging was not statistically significant. Conclusion: The dental ceramic type affected the opalescence with Empress CAD HT showing the highest OP values. Increasing the thickness caused an increase in the opalescence of leucite reinforced glass ceramic, while it decreased the opalescence of zirconia. Therefore, manufactures should develop all-ceramic materials that can simulate the opalescence of natural teeth especially in esthetic ceramic restoration with lower thickness