ISEP - Departamento de Engenharia Civil
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- 1º Ciclo de Palestras de Engenharia CivilPublication . Departamento de Engenharia Civil; Lopes, Duarte Barroso; Fontão, Eunice VilaverdeRealizou-se o I Ciclo de Palestras no Departamento de Engenharia Civil do Instituto Superior de Engenharia do Porto, sobre os seguintes temas: Revestimentos em Edifícios - dia 17 de Outubro de 2001 Zonas Costeiras - dia 14 de Novembro de 2001 Betão Reforçado com Fibras - dia 12 de Dezembro de 201 De que resultaram os textos das comunicações agora compilados. Na escolha dos temas considerou-se a sua actualidade e o facto de completarem os assuntos das aulas do curso de Engenharia Civil. No futuro prevê-se a realização de novos ciclos com temas diversos proporcionando a divulgação de conhecimentos e criando um espaço de diálogo com técnicos e investigadores. Não deve deixar de se referir, que estas palestras reflectem o empenho de docentes do DEC na actualização de conhecimentos em áreas científicas de elevado potencial e interesse para uma escola de engenharia de grandes tradições.
- Monitorização do comportamento de estruturas de betãoPublication . Félix, CarlosCom o presente trabalho pretende-se estudar sistemas de monitorização do comportamento de estruturas, com especial incidência nas estruturas de betão. Considera-se fundamental o conhecimento das potencialidades e limitações dos sistemas de medição actualmente existentes, de modo a permitir a sua correcta aplicação às estruturas, e consequente análise e interpretação do comportamento estrutural. A dissertação começa por apresentar uma descrição geral dos sistemas de monitorização de estruturas; introduzem-se os conceitos e a terminologia associados à metrologia e à caracterização dos instrumentos de medição, incidindo de modo particular sobre os instrumentos correntemente utilizados nas operações de monitorização. Em particular referem-se os instrumentos clássicos destinados à medição do deslocamento, da extensão, da temperatura, da pressão e da inclinação. O advento dos sensores de fibra óptica, e em particular dos sensores de Bragg, com características muito particulares de funcionamento, justificam uma referência especial na dissertação. Estes sensores têm sido aplicados com sucesso na monitorização de diversas estruturas, nomeadamente pontes e barragens, permitindo obter informação essencial acerca do seu comportamento ao longo do tempo. Descreve-se a aplicação pelo autor de sistemas de monitorização a estruturas de betão armado e/ou pré-esforçado, nomeadamente a duas passagens hidraúlicas, a uma ponte e a um viaduto. Relativamente a cada caso apresentado, descrevem-se as características das estruturas e do sistema de monitorização adoptado. Apresenta-se ainda uma interpretação sumária dos valores medidos em algumas dessas aplicações. Procede-se à análise do comportamento de uma das estruturas instrumentadas com base na medição efectuada em obra. Exemplifica-se deste modo as potencialidades dos sistemas de monitorização na interpretação do comportamento estrutural. A encerrar este trabalho, tecem-se algumas considerações genéricas acerca do trabalho realizado e apontam-se algumas sugestões tendo em vista o futuro desenvolvimento do tema.
- Analysis of the Out-Of-Plane Seismic Behavior of Unreinforced Masonry: A Literature ReviewPublication . Ferreira, Tiago Miguel; Costa, Alexandre A.; Costa, AníbalAlthough the issue of the out-of-plane response of unreinforced masonry structures under earthquake excitation is well known with consensus among the research community, this issue is simultaneously one of the more complex and most neglected areas on the seismic assessment of existing buildings. Nonetheless, its characterization should be found on the solid knowledge of the phenomenon and on the complete understanding of methodologies currently used to describe it. Based on this assumption, this article presents a general framework on the issue of the out-of-plane performance of unreinforced masonry structures, beginning with a brief introduction to the topic, followed by a compact state of art in which the principal methodologies proposed to assess the out-of-plane behavior of unreinforced masonry structures are presented. Different analytical approaches are presented, namely force and displacement-based, complemented with the presentation of existing numerical tools for the purpose presented above. Moreover, the most relevant experimental campaigns carried out in order to reproduce the phenomenon are reviewed and briefly discussed.
- Mechanical properties of chemically modified portuguese pinewoodPublication . Lopes, Duarte Barroso; Mai, Carsten; Militz, HolgerTo turn wood into a construction material with enhanced properties, many methods of chemical modification have been developed in the last few decades. In this work, mechanical properties of pine wood were chemically modified, compared and evaluated. Maritime pine wood (Pinus pinaster) was modified with four chemical processes: 1,3-dimethylol-4,5- dihydroxyethyleneurea, N-methylol melamine formaldehyde, tetra-alkoxysilane and wax. The following mechanical properties were assessed experimentally: Modulus of elasticity measured statically, stiffness stabilization efficiency in different climates (30 and 87% of relative humidity), modulus of rupture, work maximum load, impact bending strength, compression, tensile and shear strength at indoor conditions (65% of relative humidity). In both types of active principle of modification, cell wall or lumen fill, no significant changes on the bending stiffness (modulus of elasticity) were found. In the remaining properties analysed significant changes in the modified wood-material took place compared to unmodified wood control: - Cell wall modification was the most effective method to achieve high stiffness stabilization efficiency (up to 60%) and also increased compression strength (up to 230%). However, modulus of rupture, tensile, shear and the impact bending strength were reduced by both resins, but in a varying extent, where the N-methylol melamine formaldehyde endured less reduction than 1,3-dimethylol-4,5-dihydroxyethyleneurea resin. In the latter, reduction up to 60% can take place. - In the lumen fill modification: tetra-alkoxysilane has no effect in the mechanical properties. Although, a slight increase in shear strength parallel to the grain was found. Wax specimens have shown a slight increase in bending strength, compression, tensile and shear strength as well as in the absorption energy capacity.
- A simplified four-branch model for the analytical study of the out-of-plane performance of regular stone URM wallsPublication . Ferreira, Tiago Miguel; Costa, Alexandre A.; Vicente, Romeu; Varum, HumbertoDuring the last years, several studies have been made aiming to assess the out-of-plane seismic response of unreinforced stone masonry structures. This fact led to the development of a wide variety of models and approaches, ranging from simple kinematic based analytical models up to complex numerical simulations. Nevertheless, for the sake of simplicity, the out-of-plane seismic response of a masonry wall pier may be obtained by means of a simple single-degree-of-freedom system while still providing good results. In fact, despite the assumptions associated with such a simple formulation, it is also true that the epistemic uncertainty inherent with the selection of appropriate input parameters in more complex models may render them truly ineffective. In this framework, this paper focuses on the study of the out-of-plane bending of unreinforced stone masonry walls (cantilevers) by proposing a simplified analytical approach based on the construction of a linearized four-branch model, which is used to characterize the linear and nonlinear response of such structural elements through an overturning moment-rotation relationship. The formulation of the four-branch model is presented and described in detail and the meaningful parameters used for its construction are obtained from a set of experimental laboratory tests performed on six full-scale unreinforced regular sacco stone masonry specimens. Moreover, a parametric analysis aiming to evaluate the effect of these parameters’ variation on the final configuration of the model is presented and critically discussed. Finally, the results obtained from the application of the developed four-branch model on real unreinforced regular sacco stone masonry walls are thoroughly analysed and the main conclusions obtained from its application are summarized.
- Simulation of masonry out-of-plane failure modes by multi-body dynamicsPublication . Costa, Alexandre A.; Penna, Andrea; Arêde, António; Costa, AníbalThe seismic assessment of the local failure modes in existing masonry buildings is currently based on the identification of the so-called local mechanisms, often associated with the out-of-plane wall behavior, whose stability is evaluated by static force-based approaches and, more recently, by some displacement-based proposals. Local mechanisms consist of kinematic chains of masonry portions, often regarded as rigid bodies, with geometric nonlinearity and concentrated nonlinearity in predefined contact regions (unilateral no-tension behavior, possible sliding with friction). In this work, the dynamic behavior of local mechanisms is simulated through multi-body dynamics, to obtain the nonlinear response with efficient time history analyses that directly take into account the characteristics of the ground motion. The amplification/filtering effects of the structure are considered within the input motion. The proposed approach is validated with experimental results of two full-scale shaking-table tests on stone masonry buildings: a sacco-stone masonry façade tested at Laboratório Nacional de Engenharia Civil and a two-storey double-leaf masonry building tested at European Centre for Training and Research in Earthquake Engineering (EUCENTRE).
- Mestrado em Engenharia Civil: Dissertação, Projeto, Estágio. Anuário 2015Publication . Félix, Carlos; Abreu, Tiago; Jacob, Ângelo; Trigo, José Castro; Pinto-Faria, JoséA unidade curricular (UC) de Dissertação, Projeto, Estágio (DIPRE) desenvolve-se no segundo semestre do último ano letivo do curso de Mestrado em Engenharia Civil (MEC) do Instituto Superior de Engenharia do Porto (ISEP). No decorrer desta UC os estudantes do MEC têm a oportunidade de se dedicar em exclusivo ao desenvolvimento de um tema do seu interesse que preencha os requisitos estabelecidos para a obtenção do grau de mestre. Este trabalho pode ser realizado em meio académico, usualmente em formato de dissertação ou de projeto, ou em ambiente empresarial, no âmbito de um estágio, resultando, neste caso, a produção de um relatório de estágio. A presente publicação identifica e apresenta os resumos de todos os trabalhos de DIPRE realizados pelos estudantes do MEC do ISEP, no ano letivo 2014/2015. Pretende-se, desta forma, promover e difundir, de modo mais eficaz, estes trabalhos, bem como os resultados que têm vindo a ser alcançados, junto da comunidade técnica e científica. Esta iniciativa resulta de uma reflexão sobre o volume de informação que tem vindo a ser produzido e da excelência que alguns destes trabalhos atingem. Espera-se, de forma convicta, que a sua divulgação contribua para o avanço tecnológico na área da Engenharia Civil e para a efetiva melhoria dos processos, estabelecendo referências para trabalhos futuros. Os resumos dos trabalhos de DIPRE, em formato de dissertações, de projetos ou de relatórios de estágio, estão organizados no presente anuário segundo as subáreas científicas ou ramos em que se organiza o MEC, nomeadamente, Construções, Estruturas, Gestão da Construção e Infraestruturas, seguindo a ordem alfabética dos seus autores.
- Efficiency of strengthening techniques assessed for existing masonry buildingsPublication . Diz, Sérgio; Costa, Aníbal; Costa, Alexandre A.The Azores archipelago is a zone with a vast cultural heritage, presenting a building stock mainly constructed in traditional stone masonry. It is known that this type of construction exhibits poor behaviour under seismic excitations; however it is extensively used in seismic prone areas, such as this case. The 9th of July of 1998 earthquake was the last seismic event in the islands, leaving many traditional stone constructions severely damaged or totally destroyed. This scenario led to an effort by the local government of improving the seismic resistance of these constructions, with the application of several reinforcement techniques. This work aims to study some of the most used reinforcement schemes after the 1998 earthquake, and to assess their effectiveness in the mitigation of the construction’s seismic vulnerability. A brief evaluation of the cost versus benefit of these retrofitting techniques is also made, seeking to identify those that are most suitable for each building typology. Thus, it was sought to analyze the case of real structures with different geometrical and physical characteristics, by establishing a comparison between the seismic performance of reinforced and non-reinforced structures. The first section contains the analysis of a total of six reinforcement scenarios for each building chosen. Using the recorded 1998 earthquake accelerograms, a linear time-history analysis was performed for each reinforcement scenario. A comparison was then established between the maximum displacements, inter-storey drift and maximum stress obtained, in order to evaluate the global seismic response of each reinforced structure. In the second part of the work, the examination of the performance obtained in the previous section, in relation to the cost of implementing each reinforcement technique, allowed to draw conclusions concerning the viability of implementing each reinforcement method, based on the book value of the buildings in study.
- Experimental characterization of the out-of-plane performance of regular stone masonry walls, including test setups and axial load influencePublication . Ferreira, Tiago Miguel; Costa, Alexandre A.; Arêde, António; Gomes, Ana; Costa, AníbalStone masonry is one of the oldest and most worldwide used building techniques. Nevertheless, the structural response of masonry structures is complex and the effective knowledge about their mechanical behaviour is still limited. This fact is particularly notorious when dealing with the description of their out-of-plane behaviour under horizontal loadings, as is the case of the earthquake action. In this context, this paper describes an experimental program, conducted in laboratory environment, aiming at characterizing the out-of-plane behaviour of traditional unreinforced stone masonry walls. In the scope of this campaign, six full-scale sacco stone masonry specimens were fully characterised regarding their most important mechanic, geometric and dynamic features and were tested resorting to two different loading techniques under three distinct vertical pre-compression states; three of the specimens were subjected to an out-of-plane surface load by means of a system of airbags and the remaining were subjected to an out-of-plane horizontal line-load at the top. From the experiments it was possible to observe that both test setups were able to globally mobilize the out-of-plane response of the walls, which presented substantial displacement capacity, with ratios of ultimate displacement to the wall thickness ranging between 26 and 45 %, as well as good energy dissipation capacity. Finally, very interesting results were also obtained from a simple analytical model used herein to compute a set of experimental-based ratios, namely between the maximum stability displacement and the wall thickness for which a mean value of about 60 % was found.
- Longshore Transport Estimation on Ofir Beach in Northwest Portugal: Sand-Tracer ExperimentPublication . Fernández-Fernández, Sandra; Baptista, Paulo; Martins, Virgínia A.; Silva, Paulo A.; Abreu, Tiago; Pais-Barbosa, Joaquim; Bernardes, Cristina; Miranda, Paulo; Rocha, Mariana V. L.; Santos, Fábio; Bernabeu, Ana; Rey, DanielThis work aims to shed some light on longshore sediment transport (LST) in the highly energetic northwest coast of Portugal. Data achieved through a sand-tracer experiment are compared with data obtained from the original and the new re-evaluated longshore sediment transport formulas (USACE Waterways Experiment Station’s Coastal Engineering and Research Center, Kamphuis, and Bayram bulk formulas) to assess their performance. The field experiment with dyed sand was held at Ofir Beach during one tidal cycle under medium wave-energy conditions. Local hydrodynamic conditions and beach topography were recorded. The tracer was driven southward in response to the local swell and wind- and wave-induced currents (Hsb=0.75mHsb=0.75m, Tp=11.5sTp=11.5s, θb=8−12°θb=8−12°). The LST was estimated by using a linear sediment transport flux approach. The obtained value (2.3×10−3m3⋅s−12.3×10−3m3⋅s−1) approached the estimation provided by the original Bayram formula (2.5×10−3m3⋅s−12.5×10−3m3⋅s−1). The other formulas overestimated the transport, but the estimations resulting from the new re-evaluated formulas also yield approximate results. Therefore, the results of this work indicated that the Bayram formula may give satisfactory results for predicting the longshore sediment transport on Ofir Beach.