107 research outputs found
Hybrid intelligence framework for optimizing shear capacity of lightweight FRP-reinforced concrete beams
No full textThis study rigorously assesses the shear capacity of fiber-reinforced polymer (FRP) reinforced concrete (RC) beams as a lightweight material alternative, scrutinizing the efficacy of the Eurocode and ACI design codes. Leveraging a dataset of 260 experimental FRP-RC beam cases, two distinct Artificial Neural Network (ANN) models were developed using the Levenberg-Marquardt algorithm. Beams with and without stirrups were considered, with parameters including beam width (b), depth (d), length (L), concrete compressive strength (fc′), FRP modulus of elasticity (Efr, Efs) and FRP reinforcement ratios (ρf, ρfs). Multi-objective optimization was deployed to integrate Genetic Algorithms (GA) and fmincon to optimize beam parameters for maximizing the shear capacity, Vc. Sensitivity analysis allowed to quantify the influence of each parameter, revealing that b and d significantly affect Vc, with sensitivity scores of 0.39 and 0.35, respectively. The optimization process, highlighted by a 3D scatter plot, dynamically illustrated trade-offs among key design parameters (ρf, ρfs, d), giving insights into the complex interplay in FRP beam design. The hybrid intelligence models reached superior predictive accuracy over traditional codes, achieving R2 values of 0.89. Notably, for beams without stirrups, model predictions closely matched experimental data, with a lower average ratio (1.02) compared to Eurocode (1.65) and ACI (1.58). Principal Component Analysis (PCA) has elucidated the intricate interactions among variables, thereby deepening insights into the structural dynamics of FRP-RC beams. Incorporating artificial intelligence, sophisticated optimization methodologies, and thorough statistical evaluations establishes a holistic approach for the structural examination of FRP-RC beams, providing improved precision and valuable viewpoints for the refinement of future designs
Mécanismes de transfert de masse dans le béton comme critère de durabilité : application in situ aux bétons de barrage
No full textUne étude visant à évaluer l'état de vieillissement des bétons d'ouvrages hydroélectriques à l'aide d'essais de perméabilité et d'absorption réalisés in-situ a été entreprise. Six bétons de barrage ayant différents rapports eau/ciment et différentes teneurs en air entraîné ont été confectionnés. Ils ont été utilisés comme bétons sains de référence pour nos études de simulation en laboratoire. Leurs propriétés mécaniques et leurs perméabilités ont été caractérisées. En parallèle, nous avons développé un essai de perméabilité à l'air et d'absorption d'eau in situ qui peuvent être utilisés de façon très simple en chantier sur les bétons de barrage. Ces techniques d'essais de chantier ont été mises à l'épreuve, d'une part en examinant la réponse des différents bétons confectionnés au laboratoire et d'autre part en comparant les résultats obtenus à ceux d'essais de laboratoire beaucoup plus classiques tels que la perméabilité à l'eau, la perméabilité à l'air, la perméabilité aux ions chlores, l'absorption d'eau par immersion et la porosimétrie par intrusion de mercure. Pour terminer, nous avons fait une série d'essais de chantier sur le barrage de Beauharnois et le barrage Heming. Nous avons pu mettre en évidence la sensibilité de ces essais à la variation de la qualité du béton mais aussi l'effet de l'humidité du béton sur la variabilité des résultats
Coupled effects of limestone powder and high-volume fly ash on mechanical properties of ECC
No full textOwing to its exceptional strain capacity, which can reach hundreds of times that of normal concrete, and its reduced crack width, engineered cementitious composites (ECC) are a very promising solution for mitigating many of the problems that generate colossal backlogs of deteriorated concrete structures worldwide. However, research is needed to develop more sustainable ECC with flexible formulation that uses local materials. This paper investigates the coupled effects of using limestone powder in ECC as partial or total replacement for silica sand aggregate, coupled with using high-volume fly ash as a binder. The compressive and flexural strengths and fracture toughness for the formulated ECCs were examined at 3, 28 and 90 days. The results of this study demonstrate that sustainable ECC for resilient structural applications can be produced. It is aimed that more flexible formulations of ECC using local materials with lower environmental footprint could emerge and contribute to more durable and sustainable civil infrastructure. (C) 2017 Elsevier Ltd. All rights reserved
Condition Assessment of Reinforced Concrete Bridges: Current Practice and Research Challenges
No full textOne quarter of bridges in Canada and the United States need repair. The present study provides a critical overview of the state-of-the-art existing condition assessment techniques for reinforced concrete bridges, with an emphasis on current practice in North America. The techniques were classified into five categories, including visual inspection, load testing, non-destructive evaluation, structural health monitoring, and finite element modelling. The potential applications of these technologies are discussed and compared, highlighting their primary advantages and limitations. The review revealed that quantitative assessment could be effectively achieved using several complementary technologies. It is shown that there is need for concerted research efforts to achieve automated data collection and interpretation analyses. Also, the configuration of monitoring systems was found to be paramount in effectively assessing bridge performance parameters of interest. The study suggests appropriate investigation methods for some bridge deterioration mechanisms. Knowledge gaps and challenges in this field are outlined in order to motivate further research and development of these technologies
Mitigating Portland Cement CO2 Emissions Using Alkali-Activated Materials: System Dynamics Model
No full textWhile alkali-activated materials (AAMs) have been hailed as a very promising solution to mitigate colossal CO2 emissions from world portland cement production, there is lack of robust models that can demonstrate this claim. This paper pioneers a novel system dynamics model that captures the system complexity of this problem and addresses it in a holistic manner. This paper reports on this object-oriented modeling paradigm to develop a cogent prognostic model for predicting CO2 emissions from cement production. The model accounts for the type of AAM precursor and activator, the service life of concrete structures, carbonation of concrete, AAM market share, and policy implementation period. Using the new model developed in this study, strategies for reducing CO2 emissions from cement production have been identified, and future challenges facing wider AAM implementation have been outlined. The novelty of the model consists in its ability to consider the CO2 emission problem as a system of systems, treating it in a holistic manner, and allowing the user to test diverse policy scenarios, with inherent flexibility and modular architecture. The practical relevance of the model is that it facilitates the decision-making process and policy making regarding the use of AAMs to mitigate CO2 emissions from cement production at low computational cost
Flexural toughness of sustainable ECC with high-volume substitution of cement and silica sand
No full textThis study explores the effects of high-content fly ash and limestone filler partial replacement for portland cement and silica sand, respectively on the flexural toughness parameters of engineered cementitious composites (ECC). Various groups of mixtures having variable fly ash/portland cement ratio and different levels of limestone filler were prepared. ASTM C1609, JSCE-SF4 and the Post-Crack Strength method were employed to appraise the flexural toughness parameters of the ECC mixtures at 3, 28 and 90-d. The results show that according to ASTM C1609, JSCE-SF4 and the Post-Crack Strength method, limestone filler did not significantly affect the flexural toughness, while the flexural toughness of ECC beams decreased when the fly ash content increased. Considering deflection capacity, specimens made with a FA/OPC ratio of 1.2 without limestone filler achieved higher ductility at all curing ages. Owing to its superior crack resistance and toughness compared to normal concrete, ECC with high fly ash content and limestone filler could be a sustainable alternative construction material in diverse civil engineering applications. ECC with enhanced ductility compared to normal concrete could offer increased crack resistance, durability and better resilience. (C) 2020 Elsevier Ltd. All rights reserved
Experimental and Analytical Investigation on Flexural Retrofitting of RC T-Section Beams Using CFRP Sheets
No full textThe large portfolio of aging highway bridges worldwide includes many reinforced concrete T-section beams with various levels of damage and degradation. However, there is currently dearth of research on the anchoring behavior of CFRP sheets used for strengthening such RC T-section beams. Moreover, there is a need for rational and accurate analytical models to predict the strengthening effect of CFRP sheets for RC T-section beams. In this study, eight RC T-section beam specimens strengthened with externally bonded CFRP sheets were tested under quasi-static loading. The failure mode, cracking resistance, yielding and ultimate capacity were examined. The effects of U-wrap spacing, flexural reinforcing ratio, and concrete compressive strength on the flexural behavior of the CFRP strengthened RC T-section beams were analyzed and discussed. New analytical models were developed to predict the cracking, yielding and ultimate load resistance of the RC T-section beams strengthened with CFRP sheets. The analytical models were validated through comparing its predictions with experimental results, and they demonstrated adequate accuracy. The findings could be deployed for the retrofitting of a large portfolio of aging highway bridges with deteriorated reinforced concrete T-section beams
Remote sensing of concrete bridge decks using unmanned aerial vehicle infrared thermography
No full textModeling Rheological Properties of Oil Well Cement Slurries Using Artificial Neural Networks
No full textMachine learning prediction of carbonation depth in recycled aggregate concrete incorporating SCMs
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