Browsing by Author "Oliveira, M. J."
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- Automation and optimization of in-situ assessment of wall thermal transmittance using a Random Forest algorithmPublication . Bienvenido-Huertas, David; Rubio-Bellido, Carlos; Luis Perez-Ordonez, Juan; Oliveira, M. J.Reducing energy consumption and greenhouse gases emissions is among the main challenges of building sector. It is therefore crucial to know the characteristics of envelopes. There are experimental methods to determine thermal transmittance, but limitations are presented. By using techniques of artificial intelligence, this article solves the limitations of current methods by predicting correctly the thermal transmittance value of ISO 6946 and the building period of a wall with monitored data. The methodology used is extrapolated to any country: 163 real monitorings and 140 different typologies of walls have been combined to generate the dataset (22,820 items). The results show the optimal operation of the Random Forest algorithm because both the thermal transmittance of ISO 6946 and the building period are determined by using the most common methods: the heat flow meter method and the thermometric method. This study makes progress towards more automatized processes to characterize thermal transmittance.
- Strategies to mitigate shrinkage in an intermediate strength self-compacting concretePublication . Oliveira, M. J.; Bettencourt Ribeiro, Antonio; Branco, Fernando G.Self-compacting concrete (SCC) is a concrete that does not require vibration for casting and consolidation. It is able to flow under its own weight, completely filling the formwork and achieving full consolidation, even in the presence of congested reinforcement. SCC possesses special technical features and properties that recommend its application in a considerable amount of applications. Nevertheless, an inadequate behavior of the material at early ages has been observed in some situations, due to shrinkage. Shrinkage has a significant importance in the design, construction and in-service performance of concrete structures. The regulatory requirements were derived from experience with traditional concrete, which is not always suitable for SCC. In addition, the option of using new materials, such as binders with large amount of pozzolanic or latent hydraulic additions, strongly limits the validity of existing rules. In order to contribute for a better understanding of the major drawback of this material-its high potential shrinkage, experimental research was carried out using different commercial shrinkage-compensating products. This study focuses on the use of a shrinkage reducing admixture and an expansive agent. The results obtained demonstrate the efficiency of the individual or combined use of these products and allowed identifying three different strategies to control the shrinkage, with distinct levels of efficiency.