FCT: DEC - Documentos de conferências internacionais
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- Seismic Behavior of Slab-Column Connections Using High Performance Fiber Reinforced ConcretesPublication . Ramos, António; Isufi, Brisid; Marreiros, Rui; DEC - Departamento de Engenharia CivilSignificant research efforts have been devoted to achieving high performance of slab – column connections subjected to lateral loading. Solutions such as using stirrups and headed studs have been shown to work well. With the development of concrete materials with enhanced properties, new possibilities have arisen to employ solutions that are easy to apply and cause less congestion of reinforcement. A total of nine tests on flat slab specimens subjected to combined gravity and lateral loading are discussed, including two new specimens with High Performance Fiber Reinforced Concrete (HPFRC) over a limited region near the column. The main experimental variables were the flexural reinforcement ratio and the punching shear improvement method: none, headed studs, High Strength Concrete (HSC) or HPFRC. It is shown that excellent behavior is achieved with a relatively small amount of HPFRC, extended up to 1.5 times the effective depth of the slab from the face of the column. Punching was completely avoided until the end of the loading protocol (6% drift) for the specimens with HPFRC, whereas reference specimens without punching shear reinforcement failed at 1% drift and specimens with HSC reached 3% drifts. Additionally, the use of HPFRC led to an increased unbalanced moment transfer capacity and lateral stiffness, though this effect was more pronounced for specimens with lower flexural reinforcement ratio.
- Effect of Bio Heating Oil from Biodiesel Production on Rheological Behaviour of BitumenPublication . Cabette, Marina; Pais, Jorge; Micaelo, Rui; DEC - Departamento de Engenharia Civil; CERIS - Polo NOVA
- Discontinuous hydromechanical modelling of concrete dam foundationsPublication . Freitas, Gonçalo; B. Farinha, M. Luísa; M. Azevedo, Nuno; R. de Almeida, João; Sá, Magda; S. Leitão, Noemi; DEC - Departamento de Engenharia CivilThe analysis of the hydromechanical behaviour of concrete dam foundations requires coupled models which account for the role of deformation in fluid flow and the stability of the rock mass. In this study the hydromechanical analysis is performed by means of an explicit time stepping small displacement algorithm, Parmac3D-Fflow, based on a discrete representation of the discontinuities. In order to evaluate the practical importance of stress-sensitive fluid flow in rock mass discontinuities a case study is presented of an arch-gravity dam, 83 m high. Especial attention is given to boundary conditions, drainage system simulation and sets of mechanical and hydraulic parameters that may control flow and stress behavior. This paper presents the results of the application of a 3D discontinuum hydromechanical model for the analysis of the behaviour of the dam foundation. In this hydromechanical model the hydraulic behaviour is simulated assuming that seepage takes place along channels located at the edges of the triangular interface elements which simulate the various discontinuities. In the study presented here the main emphasis is on the simulation of the drainage system and on the results of sliding stability analysis. Conclusions are drawn regarding the safety factors obtained using the traditional method of strength reduction and other methods in which the hydrostatic load is gradually increased.
- Hybrid use of HPFRC in slabPublication . Ramos, António Pinho; Isufi, Brisid; Marreiros, Rui; Marchão, Carla; DEC - Departamento de Engenharia Civil; CERIS - Polo NOVAPunching shear reinforcement has already proved to be a reliable solution to improve the deformation capacity of flat slab – column connections subjected to seismic actions. Alternative approaches are becoming attractive with the development of materials such as High-Performance Fibre Reinforced Concrete (HPFRC) with better performance in tension and compression compared to conventional concrete. Motivated by the promising results obtained during an experimental campaign on hybrid HPFRC flat slabs under monotonic centred vertical loading, this paper investigates the possibility of using HPFRC to improve the behaviour of flat slabs under lateral loading (such as during earthquakes). Four reversed horizontal cyclic loading tests, under constant gravity loads, are presented. The flexural reinforcement ratio, the extent of HPFRC zone from the face of the column and the gravity load were the experimental variables considered. Results show that HPFRC can be a promising alternative to conventional punching shear reinforcement in slab column connections subjected to seismic actions, leading to increased deformation capacity. Furthermore, the results show that even a small extent of the HPFRC zone (up to 1.5 times from the face of the column) can lead to significant benefits in terms of seismic behaviour of slab – column connections, opening the possibility for an optimization of use of HPFRC.
- Dynamics of tensegrity solar Façades operating as mechanical energy harvestersPublication . Miranda, Raffaele; Babilio, Enrico; Singh, Narinder; Villamil, Diana P.; Santos, Filipe; Fraternali, Fernando; CERIS - Polo NOVA; DEC - Departamento de Engenharia CivilDeployable sunscreens with tensegrity architecture have been recently proposed for dynamic solar façades of buildings working on low energy consumption. Such structures are aimed at ensuring well-being indoor conditions while using reduced electrical-grid energy. The present paper studies the dynamical response of the tensegrity shading screens recently appeared in the literature, by studying structures formed by modular panels suitably assembled to form an origami pattern. The origami tensegrity façade is activated by stretching or releasing selected cables. Its energy-harvesting ability arises from the action of piezoelectric effects under the opening/closure motion of the origami panels, and wind-induced fluctuations. The dynamic response of the origami panels is simulated through a fully tensegrity model, with the aim of estimating their energy harvesting ability. The given results show that the overall tensegrity façade can daily produce a quantity of electric energy equivalent to the electric power produced by more than 200 squared meters of photovoltaic panels, and about 90 squared meters of rooftop wind turbines.
- Rheology of grouts for masonry injectionPublication . Baltazar, Luis G.; Henriques, Fernando M A; DEC - Departamento de Engenharia CivilGrout injection technique applied in a multiple leaf masonry walls aims at increasing the compactness of the masonry and, therefore, improving their monolithic behaviour by bonding the separated segments together without compromising the architectural value of the masonry building. The success of the injection grouts depends mainly on their rheological properties. This means that the flow properties of fresh grouts are as important as their properties in the hardened state, since they govern the ability of the grout to flow and fill the voids within masonry. In practice, the variability of voids within masonry requires ability to fine tune the rheological properties of the grout, in order to optimal fill all voids with grout. So, models were developed with the main purpose of predict and control the rheological properties of grouts just performing simple flow tests traditionally used in the field. It is well known that flow tests commonly performed (such as Marsh cone and slump test), which try to describe the workability of cementitious materials, only give a qualitative result that can not be expressed in physical rheological units. However, the proposed models allow calculating a physical parameter (e.g. viscosity) instead of an empirical one (e.g. fluidity). This research shows the effect of grout design variables on the properties of natural hydraulic lime grouts based on the correlation between rheometry measurements and simple flow tests. Furthermore, the proposed models can be very useful to smooth the grout design methodology, since these models enable the prediction of rheological properties of the grout without the need for expensive and complex equipment, such as rheometers or viscometers.
- Environmental benefits and mechanical performance of cement mortars with tungsten mining residues incorporationPublication . Almeida, Joana; Santos Silva, António; Ribeiro, Alexandra B.; Faria, Paulina; CENSE - Centro de Investigação em Ambiente e Sustentabilidade; DCEA - Departamento de Ciências e Engenharia do Ambiente; DEC - Departamento de Engenharia CivilSecondary mining resources have been largely applied for the development of alternative building products. Additionally, its reuse versatility increases the potential on the future circular economy generation. Herein, mining residues from Panasqueira mine were applied in the formulation of cement-based mortars, according to EN 196-1 standard.Mechanical performance of mortars was analysed after the replacement of the conventional binder (cement) by mining residues in 10, 25 and 50 % (v/v). As expected, compressive and flexural strength decrease when compared to the reference mortar (100 % cement) in all cases. This decrease was more significant in terms of compressive strength (between 27 % and 71 %), when compared to flexural strength results (between 18 % and 56 %). Furthermore, an environmental approach of secondary mining resources incorporation on mortars, regarding Portugal and Poland data, was carried out. The savings in terms of primary resources may promote to minimise energy impacts. When mining residues replace cement in 10 % is possible to save 0.3 or 1.9 Mt of cement production and 0.14 or 0.89 CO2 Mt emissions, in Portugal and Poland, respectively.
- Characterization of agro-wastes to be used as aggregates for eco-efficient insulation boardsPublication . Cintura, Eleonora; Nunes, Lina; Faria, Paulina; DEC - Departamento de Engenharia CivilThis work derives from the awareness of the environmental impacts caused by the construction sector. Since building products are one of the main causes of this issue, the incremental use of local natural eco-friendly materials can moderate this problem, guaranteeing lower energy consumption for production and transport. Nowadays, research is increasingly focused on the possibility of using bio-wastes to produce several materials and products such as plasters, bricks, boards, binders and glues. They can secure both more sustainable building practices and contribute to solve the problems of disposal of wastes, another cause of the environmental impacts. The present work focuses on the characterization of some bio-wastes to assess their viability as aggregates for eco-efficient insulation boards. Knowing the properties of the raw materials allows making a more conscious choice of composite formulations according to the final requirements of the boards. For this reason, the bio-wastes from agricultural practices (agro-wastes) were studied individually. To evaluate their properties, the analysis was carried out according to RILEM Technical Committee 236-BBM, “Bio-aggregate-based building Materials” document, past literature studies and European Standards. The considered properties were loose bulk density, grain size distribution and thermal conductivity. Four agro-wastes were chosen: spent coffee grounds, grapes press waste, olives press waste and hazelnut shells. Maritime pine (Pinus pinaster Ait.) chips were included as control material. They have been considered both for their potential use to produce insulation composites and for their world production, focusing on Euro-Mediterranean countries. This region was chosen taking into account where the future research will be carried out and the advantages of employing local materials. In addition, buildings of Euro-Mediterranean countries have historically low insulation performance due to the mild climate; however, climate change and other factors have led to the recognition by the users of some periods of poor indoor hygrothermal comfort. The bibliographic research allowed identifying a gap as concerns the characterization of these agro-wastes. Both the testing methods and the properties of the considered materials are presented and discussed. In addition, the obtained results are compared with the ones of already studied materials, such as rice husk, hemp shiv and cork. Results show that the chosen materials do not have excellent insulating properties if considered individually but may probably be used to produce eco-efficient boards. The combination of them with other materials could guarantee building composites with good thermal insulation performances. The spent coffee ground differs greatly from the other bio-wastes and it seems to be more appropriate as a fine aggregate. Future research will deepen these studies and develop composites having adequate characteristics as insulation boards.
- A study on hygrothermal conditions in intermittently heated or unheated bedrooms in southern EuropePublication . Ranesi, Alessandra; Posani, Magda; Veiga, M. Rosário; Faria, Paulina; DEC - Departamento de Engenharia Civil; CERIS - Polo NOVAIndoor hygrothermal parameters have an important role in the assessment of indoor air quality (IAQ) and comfort. In fact, the perception of air quality is strongly influenced by temperature (T) and relative humidity (RH). In Northern Europe, due to the severe climate conditions during winter, it is common to adopt continuous heating to guarantee sufficient thermal comfort in residential buildings. On the contrary, in Southern European countries, due to the specific climate, economy and culture, a permanent heating practice in winter is generally not adopted. Consequently, the indoor climate in Northern and Southern Europe is expected to be quite different, and this discrepancy should be taken into account when designing retrofit interventions aimed at improving indoor comfort and lowering energy demands. In particular, when studying the properties of interior coating materials, T is commonly set between 20-25 °C and RH in the range 33-75%. These are considered acceptable and common indoor conditions for continuously heated buildings, but they might be not representative of Southern European reality. For the present study, four residential buildings were chosen in the city of Lisbon. The indoor air T and RH were continuously recorded for one bedroom in each building during wintertime. The bedrooms are characterized by a floor surface of 7.5-10 m2, the occupancy of one person during an average of eight hours, natural ventilation and the presence of one window North/Northwest oriented and with manually-regulated shading. All rooms were monitored under operational conditions, with users adopting intermittent heating (room heaters) or no heating at all. The main differences between the case studies concern the floor where the apartments are located and the constructive characteristics of the buildings. The indoor hygrothermal conditions obtained in the monitoring campaign are discussed in this paper and indoor thermal comfort is evaluated. Finally, despite the differences between the case studies, an approximation of the overall indoor T and RH fluctuations is provided.
- Agriculture and Sustainable Tourism for the Consolidation of Peace in ColombiaPublication . Cintura, Eleonora; Nunes, Lina; Faria, Paulina; DEC - Departamento de Engenharia CivilNowadays different organizations carry on international cooperation programs to boost relationships with the most disadvantaged parts of the world. These projects allow people and countries to work together for a common aim. They also allow improving knowledge in different fields, sharing information and favouring a mutual exchange between the involved parts. This paper describes a cooperation program carried on between Italy and Colombia. It reports a small part of this experience related to sustainable architecture, the use of natural building materials and vernacular architecture in Colombia. The aim is both to give some theoretical information concerning these themes and to describe the experimental part of this project. It reports the understanding of the population of these issues and the perception of their traditional architecture.