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- Experimental and analytical study of concrete structures reinforced with GFRP barsPublication . Escórcio, Patrícia Carlota Costa; França, Paulo Miguel MacedoThe rational use of natural, economic and social resources in order to ensure the sustainability and a long-term balance has become one of the largest global concerns. In the civil engineering field, the limited durability of steel reinforced concrete structures, especially in aggressive environments, and the high costs of the repair and maintenance operations have motivated the search for alternative materials and solutions to steel. One of these alternative reinforcements is the glass fibre reinforced polymer (GFRP) bars due to their immunity to corrosion, which is an important advantage when comparing to steel. However, several factors such as the novelty in the market, the high fabrication costs, the different design philosophies and the uncertainties of its behaviour with the concrete have been delaying the use of the GFRP bars in a larger scale. This thesis aims to contribute to the scientific knowledge of the GFRP reinforced concrete, as it studies its behaviour and design. The research work is mainly experimental and is based on a campaign with 24 full-scale reinforced concrete (RC) beams 4.30 m long and rectangular crosssection of 0.25 x 0.40 m2, divided into two groups with different purposes: - 18 beams to study the performance of different GFRP bar layouts as shear reinforcement; - 6 beams to assess the behaviour of a rehabilitation solution with GFRP bars to replace the deteriorated flexural steel reinforcement. The specimens of the first group were designed to fail due to shear with four different GFRP shear reinforcement solutions: 1) closed hoop GFRP stirrups, 2) two C shaped GFRP bars forming a stirrup, 3) two double headed GFRP bars and 4) two simple straight GFRP bars. Two shear reinforcement ratios with different spacing were also tested with the closed hoop GFRP stirrups. For each GFRP shear reinforcement layout, three different longitudinal stiffnesses were considered using steel and GFRP bars with different ratios. The beam specimens were tested until failure under a four point loading set-up and both the serviceability and the ultimate performance were analysed. The results were reported in terms of deflections, crack pattern, crack width, strains in the longitudinal and shear reinforcements, ultimate load capacity and failure modes. The different shear layouts were compared regarding their load carrying performance and their field implementation easiness. The design of the beams and their result predictions were made according to the existing guidelines and codes. It was concluded that the closed hoop stirrups and the C-stirrups were the most efficient and that the beams load capacity was highly underestimated by the GFRP codes. To improve the design formulas of these codes, different values for the limit strains and for the strut angle were proposed. The double headed bars as shear reinforcement were also efficient in the cases with higher longitudinal stiffness because it contributed to keep the integrity of the beam by exhibiting low deflections and crack widths. It was observed that a wide crack at the end of these bars highly compromises the anchorage function of the head. The solution of the simple straight bars was not effective because of the lack of anchorage length. The idea for the second group of beams was inspired on the RC structures with deteriorated bottom concrete due to the corrosion of the longitudinal steel reinforcement. Actually, no steel corrosion was considered in these specimens, but they were concreted in two phases to simulate the replacement of the deteriorated concrete, starting at the stage after its complete removal. The rehabilitation procedure consisted on the insertion of the longitudinal GFRP bars and the concreting of a new bottom layer in the beam. Two solutions with different GFRP longitudinal cross-section areas were designed according to the existing guidelines, one to restore the ultimate load capacity of the original beam, and the other to maintain the deflection of the original beam. The ends of the GFRP bars were conic heads to compensate their lower anchorage length. The rehabilitated beam specimens were subjected to 3 point bending tests until failure, and their service and ultimate behaviour were analysed. Results are presented in terms of deflection, crack pattern, mid-span crack width, reinforcement strains, ultimate flexural capacity and failure modes. It was concluded that this technique was effective for both the serviceability and ultimate limit states of the rehabilitated beam, as it was able to restore the deflection and the load capacity of the original beam, and that the existing GFRP design documents can be used. Although this was mainly an experimental research work, a simple but reliable two-dimensional finite element (FE) model was defined using ATENA software to simulate the tests, which helped to better understand some issues regarding the specimens behaviour and enabled to extrapolate some results of non-tested possibilities. The linear and nonlinear behaviour of all materials was adequately modelled by appropriate constitutive laws. Furthermore, numerical results were compared with the experimental results. Results show that, in general there was a good agreement between the overall modelling results and the experimental ones. The constructed models were able to predict the experimental behaviour in terms of ultimate capacity and load-deflection curves. Regarding the first group of beams, two additional stirrups spacing were modelled in order to clarify its influence in the shear capacity. It was simulated different longitudinal reinforcement ratios to assess its influence in the shear capacity. As a final remark, the results of the present work show that the use of GFRP bars is viable in RC structures, which contributes to more durable structures in long-term. This material can be used as longitudinal and shear reinforcement of new structures and as a rehabilitation solution to replace the corroded steel in deteriorated structures.
- Experimental study of a rehabilitation solution that uses GFRP bars to replace the steel bars of reinforced concrete beamsPublication . Escórcio, Patrícia; França, Paulo M.The corrosion of the steel reinforcement affects drastically the long-term durability of many reinforced concrete (RC) structures in the world, especially the ones near the sea. When this problem is detected at early stages, it is possible and important to repair the structure in order to restore its safety and avoid future hazards and more expensive interventions. The research work described in this paper is inspired on these cases as it proposes a rehabilitation solution to replace the tension steel reinforcement of a RC beam with GFRP bars, which is a material immune to corrosion. The experimental study consisted on six full-scale RC beams subjected to a three-point bending test until failure. The specimens had stirrups without the bottom branch and were casted in two phases to simulate the replacement of the corroded and cracked bottom concrete. Two different GFRP reinforce ment ratios were tested to assess the behaviour of the repaired beam regarding its service and ultimate states in comparison with the original beam with steel reinforcement. The results are presented and dis cussed in terms of flexural capacity, failure modes, deflection, crack pattern, mid-span crack width and reinforcement strains. It was concluded that the presented rehabilitation solution is easy to implement, can be designed according to general FRP design guidelines, and is able to restore the serviceability and ultimate limit states of the original RC beam.
- Application of the effective impulse approach to stairsPublication . Andrade, Pedro; Santos, José; Escórcio, PatríciaOne of the most commonly used simplified methods for predicting man induced vibrations in floors with high fundamental frequencies is the Effective Impulsive approach, first developed by the ARUP's company and later modified by the design guide SCI P354. Since the Effective Impulse approach was designed to be used in floors, its use in stairs can be arguable. To better understand the effectiveness of this method in stairs, in this paper are experimentally measured vibrations on a staircase with a poor dynamic behavior and then compared to the vibrations predicted using the Effective Impulse approach. The results indicate that this approach can be used, especially in the stair descends. The serviceability of the analyzed staircase was also verified by comparing the measured and predicted vibrations with the acceptable limits proposed by various authors and design guides.
- Pre-design of laterally supported stair stepsPublication . Santos, José; Andrade, Pedro; Escórcio, PatríciaIt is becoming increasingly common to design monumental staircases and their steps with elevated stiffness and low mass, obtaining high natural frequencies, off the range of frequencies that are excitable by pedestrians. However, this sometimes leads to unacceptable levels of vibration, with impulsive responses. In many cases the dynamic behaviour of steps is almost independent from the rest of the staircase, causing a phenomenon de signated as local vibrations, which could be much more severe than the global vibrations of the staircase. In order to avoid this problem, this paper presents a simplified expression to pre-design stair steps which guarantee that excessive vibrations will not occur, without the need to perform a dynamic analysis. The ex pression was deduced based on the results of an experimental campaign, several numerical analyses and a theoretical analysis. During this study it was necessary to define an acceptable limit of vibrations specific for this type of vibration, which affects mainly the feet of pedestrians. The expression deduced is easy to apply because it depends only of vertical stiffness of the step. Finally, the pre-design expression is also applied to the staircase used in the experimental campaign, and it was concluded that it would be easy to avoid excessive vibrations, with a negligible cost increase.
- Dynamics of the land use changes and the associated barriers and opportunities for sustainable development on peripheral and insular territories: The Madeira Island (Portugal)Publication . Castanho, Rui Alexandre; Lousada, Sérgio; Gómez, José Manuel Naranjo; Escórcio, Patrícia; Cabezas, José; Fernández-Pozo, Luis; Loures, LuísConsidering the complex dynamics, patterns, and particularities that peripheral and insular territories/regions present—e.g., as the fragility, they show to achieve a sustain able development and growth—a study that analyzes the land uses of this territories is seen as pivotal to identify barriers and opportunities for a long-term sustained devel opment. Contextually, a general analysis was carried out through case study research methods covering those territorial typologies of the insular territory of Madeira Island, Portugal. The study, which was carried out through GIS mapping tools, enabled us to identify the land use changes in the last decades over the territory—allowing to estab lish a relation and identification of the associated barriers and opportunities presented by the territories to face the emerging sustainable development challenges. The study reveals the evident limitations of “ultra-peripheral” territories not only by the physical spatial dimensions but also by the difficulty to reconvert land uses. Thus, the main actors and their policies over the territory are even more relevant and need to be conducted in a more reasonable way—considering the fragility of this regions; such actions present higher impact over the territory and over their inhabitants’ life’s quality standards and finally on the long-term sustainability.
- Estudo do comportamento de passagens superiores de peões com tabuleiro misto aço-betãoPublication . Escórcio, Patrícia Carlota Costa; Pedro, José Joaquim Costa Branco de OliveiraComo resposta às exigências do mundo actual, a projecção e construção de estruturas sofreram grandes alterações, assistindo-se à construção de estruturas cada vez mais esbeltas, integradas no ambiente circundante, transparentes, ousadas. Consequentemente a sua concepção constituí um desafio que é suportado por avanços na arte da engenharia, novos materiais e pela sensibilidade dos projectistas. Neste sentido as passagens superiores de peões não constituem excepção. São construídas desde os tempos remotos porém, hoje, querem-se mais ousadas, esbeltas, transparentes, integradas no ambiente circundante, económicas e eficientes, como forma de responder às exigências do mundo actual. Inicialmente forma de vencer obstáculos naturais, são hoje em dia, um meio para vencer a forte obstáculos inerentes as modificações da rede viária e à forte ocupação do espaço, fruto da crescente urbanização. Estas estruturas têm carregamentos baixos, o que possibilita a construção de vãos longos com esbeltas secções transversais, tornando-se estruturas muito flexíveis, com reduzida massa e rigidez, de que resultam frequências próprias de vibração baixas conduzindo a uma maior sensibilidade às vibrações. Com a construção das novas Vias Rápidas na ilha da Madeira, houve a necessidade de repor acessos pedonais por meio destas pontes. Apesar de existirem várias destas pontes, são essencialmente de dois tipos: de tabuleiro em treliça espacial mista ou tabuleiro do tipo “bi-viga” mista. Assim, no âmbito de um estágio na empresa Estradas da Madeira (RAMEDM, S.A.), procurou-se estudar uma ponte de cada um dos tipos mencionados, com intuito de compreender a acção pedonal, as suas características e formas de simular verificando a eficiência de ambos os modelos, os níveis de conforto que oferecem, e a segurança face aos valores limites apresentados nalguns regulamentos. Construíram-se modelos computacionais usando o programa SAP2000, nos quais se simulou quatro movimentos característicos da acção pedonal (andamento normal, andamento acelerado, jogging e corrida), através das respectivas funções de carga. Por já se encontrar construído, o tabuleiro em treliça mista foi ensaiado, de forma a validar o modelo computacional. Verificou-se que as frequências obtidas no modelo são próximas das reais. Verificou-se que ambos os modelos, apresentam um bom comportamento no que concerne às vibrações na direcção transversal, já que têm frequências de vibração suficientemente afastadas da gama excitável pela acção humana. Quanto às vibrações na direcção vertical, uma vez que ambos os tabuleiros têm frequências fundamentais coincidentes com as frequências de alguns dos movimentos simulados, verificaram-se acelerações acentuadas. O estudo destas estruturas mostrou em traços genéricos, que além das vantagens construtivas, ambos os modelos apresentam bom comportamento à acção pedonal.
- Interactions between surrounding landscape biodiversity and intermittent rivers in mediterranean environments – case study of the Caia RiverPublication . Kaletová, Tatiana; Raposo, Mauro; Pinto-Gomes, Carlos; Castanho, Rui Alexandre; Martin Gallardo, Jose; Loures, Luís; Castanho, Hermenegildo; Cabezas, José; Fernándes-Pozo, Luis; Naranjo Gómez, José Manuel; Lousada, Sérgio; Escórcio, PatríciaLandscape is a dynamic mosaic of various structures interacting together. Neglecting or overusing one part of this mosaic may boost up or damage the development of others. For instance, overgrazing may increase soil erosion process which may clog a river/stream. In this regard land use changes, climate change and landscape management may lead to increase the intermittency of the surface watercourses, as well as in the ecosystem services provided by riverscapes for humans. Therefore, the present research focus on the existing interactions between the Caia River, an intermittent river located in the Mediterranean region, and its surrounding agricultural and natural landscapes. The performed analyses considered the identification of the existing interaction between natural and agricultural landscapes with the Caia River defining the predictable ecosystem services provided by each element of the landscape and assessing the potential decrease of the ecosystem services provided in case of landscape changes, which according to the performed research might enclose significant impacts both in ecologic and socioeconomic terms.
- Numerical methods to predict vibration serviceability on high frequency stairsPublication . Andrade, P.; Santos, José; Escórcio, P.With the increasingly deepen knowledge on structural dynamic behaviour, nowadays, monumental staircases and their steps are usually designed with high stiffness and low mass, obtaining high fundamental frequencies, out of the interval of step frequencies excitable by the human walking. However, neglecting the structure's mass can also result in with high levels of impulsive responses. Furthermore, often the connection between the staircase and its steps experience an almost null rotational stiffness, which can cause local vibrations in steps, where the structural behaviour of two elements is nearly independent from each other. In this scenario, steps will most likely exhibit undesirable vibrations. Hence, intending to improve future designs, this paper compares different numerical methods that can be used to predict human induced vibrations in this type of structures, applying them to a real staircase with a high local liveness. The results showed that the footfall force time histories method could realistically predict the vibrations for almost all tested step frequencies, while the effective impulse could accurately estimate the vibrations for descents at different step frequencies. The walking models defined by Fourier coefficients only generated close vibrations for descents at 3.3 Hz.
- Assessing land-use changes in european territories: a retrospective study from 1990 to 2012Publication . Gómez, José Manuel Naranjo; Loures, Luís Carlos; Castanho, Rui Alexandre; Cabezas Fernández, José; Fernández-Pozo, Luis; Lousada, Sérgio António Neves; Escórcio, PatríciaThe need to understand what land use is has motivated the development of programmes that aims to identify it and quantify it—CORINE Land Cover (CLC) in 1985. From this official and open geodatabase—through the using of geographic information system (GIS) tools—the amount of area established for each land use has been identified in all the 28 member states of the EU. This mostly corresponds to agricultural and forestry uses. Between 1990 and 2012, it was possible to determine countries with variable land use models such as Finland, Latvia, Portugal and Spain—the rest of the states presenting stable land use models. Additionally, some countries are characterized by the predomi nance of one or two land uses. Contextually, the proposal aims to develop a retrospective study regarding the land-use changes in the EU territories from 1990 to 2012, through the available tools such as CLC.