Percorrer por autor "Santos, Pedro"
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- Energy Efficiency and Sustainability in an Aquaponic Greenhouse Supported by IoTPublication . Galvão, João; Santos, Pedro; Aires, Luis; Ribeiro, Vânia; Neves, FilipeThe increasing demand for agricultural crops and the necessity to reduce environmental impacts from traditional agriculture have led to the emergence of sustainable production systems such as hydroponics and aquaponics. These soil and pesticide-free systems require less water and fertilizers but need electrical energy and controlled greenhouse environmental conditions to be highly productive. This work presents a monitoring and management system for environmental parameters inside an aquaponic greenhouse, that allows the manager to assess in real-time the working status of the aquaponic system, helping in the detection of critical conditions that require a quick decision. This system was developed to measure, through IoT sensors network, the temperature and the relative humidity of the air, the temperature, pH and the electrical conductivity of the water that contains the dissolved nutrients that feed the growth of the plants. It is possible to visualize the measured parameters via the Internet, on a dashboard, in a mobile application and store these variables in a database. To further increase the sustainability of the aquaponic greenhouse, the electricity consumed during its activity will be produced locally by photovoltaic technology. The technologies proposed in this work may promote the emergence of small models of greenhouses, implemented by communities and populations, reducing production energy costs and transportation resources.
- Factors affecting bond between new and old concretePublication . Santos, Pedro; Julio, Eduardo Nuno Brito SantosThe bond strength of concrete-to-concrete interfaces, of reinforced concrete (RC) members with parts cast at different ages, is highly influenced by the curing conditions. Therefore, the monolithic behavior is dependent on these conditions. Current design codes only consider: a) the concrete compressive strength; b) the normal stress at the interface; c) the amount of reinforcement crossing the interface; and d) the roughness of the substrate surface. Because the curing conditions of both substrate and added concrete are ignored, the influence of the differential shrinkage is neglected. The influence of the differential stiffness due to the mismatch between the Young’s modulus of both materials is not considered either. This paper presents an experimental study conducted to assess the influence of differential shrinkage and stiffness on the bond strength of new-to-old concrete interfaces. Both parameters were shown to have a significant influence on the bond strength and failure mode of concrete-to-concrete interfaces.
- INFLUENCE OF CONCRETE DENSITY AND STRENGTH ON THE BOND STRENGTH OF COMPOSITE MEMBERSPublication . Saldanha, Rui; Santos, Pedro; Júlio, EduardoThe present paper addresses the influence of both material density and strength in the adhesion between concrete layers cast at different ages. A Normal Oensity Concrete (NOC), a LightWeight Aggregate Concrete (LWAC) and an Ultra High Durability Concrete (UHDC) were considered. The latter is characterized by presenting enhanced durability properties. Nevertheless, the production of the UHDC presents both economical and environmental disadvantages. In order to minimize the impact of its use and, simultaneously, take advantage of its properties, it is proposed to use it only in the cover layer of structural members, being the bulk produced in ordinary concrete. An experimental study was conducted to characterize the adhesion between UHDC/NOC and UHDC/LWAC by means of the Modified Slant Shear Test (M-SST). This new bond test was developed by the authors to always ensure adhesive failures in composite specimens. Two different surface conditions were selected for the interface: i) smooth surface, as-cast against steel formwork; and ii) surface obtained by casting against a plastic wavy formwork. Experimental results are discussed and conclusions are drawn.
- A modified slant shear test designed to enforce adhesive failurePublication . Saldanha, Rui; Júlio, Eduardo; Dias-da-Costa, Daniel; Santos, PedroPresently, there are several tests available to evaluate the adhesion between concrete layers cast at different times. Among these, the Slant Shear Test (SST) has a wide spread use, mainly for being sensitive to the roughness of the interface surface, one of the most influencing parameters in this scope, but also because of the simplicity of the experimental setup. However, the major drawback of this test is the fact of being often obtained cohesive (monolithic) failures, therefore providing a lower bound of the interface strength, which is related with the concrete compressive strength. To definitely solve this issue, i.e., to enforce adhesive (interface debonding) failures in all situations, the 'Modified Slant Shear Test' (M-SST) was herein designed and developed. Both numerical and experimental tests have been conducted to validate this new method. All relevant conclusions are presented. In summary, it can be stated that the M-SST always enforces adhesive failure, therefore allowing to accurately assessing the adhesion of concrete-to-concrete interfaces.