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- Improving the earthquake resilience of primary schools in the border regions of neighbouring countriesPublication . Estêvão, João M. C.; Morales-Esteban, Antonio; Sá, Luis F.; Ferreira, Mónica A.; Tomás, Bruno; Esteves, Carlos; Barreto, Vítor; Carreira, Ana; Braga, Alfredo; Requena-Garcia-Cruz, Maria-Victoria; Romero-Sanchez, Emilio; de-Miguel-Rodriguez, Jaime; Segovia-Verjel, Maria-Luisa; Blanco, Beatriz Zapico; Oliveira, Carlos SousaThis work summarises the strategy adopted in the European research project PERSISTAH. It aims to increase the resilience of the population, focusing on the existing primary schools in the Algarve (Portugal) and Huelva (Spain) regions. Software was developed to assess the seismic safety of these schools, considering different earthquake scenarios. Seismic retrofitting measures were studied and numerically tested. Some of them were also implemented in the retrofitting activities of two case study schools (one in each country). It was found that the adopted ground motion prediction equations (GMPEs) considerably affect the results obtained with the software, especially for offshore earthquake scenarios. Furthermore, the results show that the masonry buildings would be the most damaged school typologies for all the scenarios considered. Additionally, a set of guidelines was created to support the school community and the technicians related to the construction industry. The goal of these documents is to increase the seismic resilience of the population. Different activities were carried out to train schoolteachers in seismic safety based on the guidelines produced, obtaining positive feedback from them.
- Verificação experimental do nível de precisão do método dos elementos de fibras de contactoPublication . Estêvão, João Manuel Carvalho; Carreira, A. S.A obtenção de soluções analíticas de sistemas dinâmicos com distribuição contínua da massa apresenta uma elevada complexidade. Os problemas práticos envolvem, normalmente, um processo de discretização com maior ou menor número de graus de liberdade. Nestes problemas discretos, a massa do sistema dinâmico é concentrada num número finito de nós. Contudo, este processo de discretização origina soluções que correspondem somente a uma aproximação da solução exata, pois a massa está distribuída de uma forma contínua. O número mínimo de graus de liberdade a considerar na resolução deste tipo de problemas depende muito da sua natureza, e do método adotado para a análise da estrutura. O método dos elementos de fibras de contacto (MEFC) é um novo método de análise de estruturas, que pode ser usado na análise dinâmica de sistemas dinâmicos contínuos, pois recorre a micromodelos das estruturas. Para melhor entendermos a capacidade deste novo método nos resultados da análise dinâmica de uma estrutura, foi realizada uma comparação entre os valores obtidos via experimental e os obtidos pelo MEFC. Os resultados obtidos parecem indicar que este novo método pode conduzir a valores muito próximos dos obtidos por via experimental.
- Using the new Fibre Contact Element Method for dynamic structural analysisPublication . Estêvão, João Manuel Carvalho; Carreira, A. S.In literature, there are many methods proposed for structural analysis based on discrete element formulations, mainly for nonlinear problems. One of these new methods is the Fibre Contact Element Method (FCEM). Many of these methods have been used for structural dynamic analysis problems. However, there are some questions about their precision in capturing the dynamic elastic response of structures when comparing to methods based on continuous models, like the well known Finite Element Method (FEM). For this reason, the results obtained with FCEM were extensively compared with FEM results and with laboratorial tests, to better understand the performance of this new method in capturing the elastic dynamic response of structures. Results indicate that this kind of discrete methods are able to determine the vibration modes of a structure with equal or better precision level than the obtained with FEM. FCEM was also used to capture the dynamic response of a reinforced concrete frame with infill walls, as a way to show the method capabilities in reproducing the dynamic behaviour of structures that have an almost continuous mass distribution.
- Use of vibration measurements to determine the most suitable locations to improve sound insulation in buildingsPublication . Rosão, Vitor; Carreira, A. S.In the present work in situ sound insulation measurements were performed, according to the applicable standards of ISO 140 series, and vibration measurements of the separator elements in question (floor, ceiling, side walls). We intend to compare the results of direct measure-ments of sound insulation with the results of the predictions of sound insulation, based on the vibration measurements, to verify the feasibility of using vibration measurements to determine the most suitable locations of sound propagation (floor, ceiling, side walls) to act in order to improve, where it is needed, sound insulation in buildings. The principles of sound propaga-tion considered in EN 12354 series standards are used, e.g., 5 major structural paths, depend-ing on the sound radiating element in the receiver compartment [1) partition wall, 2) ceiling, 3) floor, 4) wall left side, 5) wall right side] and 2 major airborne path [1) openings in the par-tition element, 2) openings in other elements]. Different Radiation Factors, to convert vibra-tion of elements in sound are also considered, depending on the radiation element type and on the frequency in question.
- Using non-destructive testing for the determination of mechanical properties in rc structures: a case studyPublication . Braga, Alfredo Manuel Gonçalves Silva; Carreira, A. S.; Estêvão, João M. C.One of the goals of the PERSISTAH project is the seismic assessment of primary school buildings existing in the regions of Algarve (Portugal) and Huelva (Spain). One of the building typologies existing in Algarve is the so called “P3 Schools”. Each school is composed by a combination of independent modules, which can be combined in different manners, depending on the number of classrooms of each school. Unfortunately, no structural designs were found, which was a common issue identified for some of the Algarve school typologies. So, no information was found about the geometry, details or even the materials used in these school buildings. Also, no destructive or semi-destructive testing could be carried out. Fortunately, the architecture exhibits apparent reinforced concrete columns and beams. For this reason, a campaign of non-destructive testing was carried out in different schools in order to allow the seismic assessment of these school buildings. The adopted procedures are presented in detail is this paper. A pachometer was used to identify the position and the number of rebars. A correlation between the results of the Ultrasonic Pulse Velocity test (UPV) and the results of the Schmidt hammer test procedure is discussed.
- Análise comparativa de medições de vibração e de isolamento sonoro em edifíciosPublication . Rosão, Vitor; Carreira, A. S.No presente trabalho foram efetuadas medições de isolamento sonoro in situ, de acordo com as normas aplicáveis da série ISO 140, e medições de vibração dos elementos separadores em causa. Pretende-se comparar os resultados das medições diretas de isolamento sonoro com os resultados das previsões de isolamento sonoro, tendo por base as medições de vibração, de forma a verificar a viabilidade de aplicação desta metodologia na determinação mais rigorosa dos caminhos de propagação sonora entre espaços e da definição mais rigorosa, eficaz e direcionada das intervenções de melhoria de isolamento sonoro a efetuar, quando necessárias.
- Experimental test methodology to evaluate sound propagation paths between interior spaces of buildingsPublication . Gervásio, Nuno; Carreira, A. S.; Rosão, VitorWhen is detected in situ the existence of poor sound insulation, typically the non-compliance with the acoustic requirements of buildings, between two spaces – source and receiver - and if we want to solve the problem, it is necessary to know which sound paths most contribute to the difference of sound levels between these spaces. However, the classical sound insulation measurement does not make this distinction, it only provides the difference in sound levels. In order to overcome this difficulty, a new test methodology is proposed to estimate the sound propagation paths between building rooms, generated by sound sources located in the interior. The proposed methodology is based on the use of vibration measurements of structural elements (slabs) and non-structural elements (parti-tion walls) to estimate the sound field in the receiver space, together with sound measure-ments to estimate the sound field in the source space. With this alternative methodology to determine the sound insulation of a space, it is intended to obtain more rigorous results with respect to: i) determination of the contribution of each of the structural paths, in a certain sound isolation, in order to define the sound paths in which an acoustic rehabilita-tion intervention is most effective; ii) determining the possible existence of airborne paths that contribute to the reduction of sound insulation. In order to validate the proposed methodology, in situ sound insulation measurements were carried out, according to the applicable standards of ISO 16283 series, and vibration measurements of the separator el-ements (floor, ceiling, side walls) of interior spaces in existing buildings.
- Utilização de ensaios dinâmicos na avaliação da segurança de estruturas: caso de estudoPublication . Laranja, Roberto; Carreira, A. S.; Estêvão, João M. C.A vibração induzida por máquinas rotativas é um problema que pode afetar o regular funcionamento de um sistema estrutural bem como o conforto dos utilizadores expostos, dado que o ser humano é sensível às vibrações, designadamente quando são ultrapassados determinados níveis de aceleração. Isso pode originar a sensação de desconforto e problemas de saúde, pelo que é da maior importância a medição desses níveis de vibração. Além disso, a vibração continuada poderá originar fenómenos de fadiga nos sistemas estruturais. Neste trabalho, é apresentado um caso de estudo onde é ilustrada a utilização de ensaios dinâmicos in situ, nomeadamente como forma de apoio à realização da avaliação da segurança última e em serviço de um edifício industrial em betão armado, que apresentava indícios de existirem anomalias estruturais, e onde os trabalhadores sentiam as vibrações induzidas pelas máquinas da fábrica
- Caracterização da propagação de vibração através de estruturas de edifícios de betão armadoPublication . Carreira, A. S.; Neves e Sousa, AlbanoEste artigo descreve os parâmetros que controlam a propagação da vibração através de estruturas de edifícios de betão armado para frequências abaixo de 200 Hz. A influência das propriedades dos materiais e das dimensões dos elementos estruturais foi avaliada com modelos de elementos finitos validados experimentalmente, considerando cinco tipos de funções de transferência de aceleração: i) da fundação para o primeiro piso; ii) entre pisos intermédios; iii) do último piso para a cobertura; iv) entre troços do mesmo piso intermédio; e v) entre troços da cobertura. Os resultados mostram que a transmissão de vibração depende não tanto do número de pisos mas mais de parâmetros como a espessura da laje, no caso da transmissão da vibração num pavimento, ou a esbelteza dos pilares, no caso da propagação de vibração das fundações para o primeiro piso. Observa-se que, apesar da amplitude de vibração ser maior para elementos estruturais mais flexíveis, os elementos mais rígidos transmitem efectivamente mais energia devido a um menor efeito dissipativo. Os resultados também mostram que a atenuação piso-a-piso é aproximadamente constante para todos os pisos excepto a cobertura, onde a atenuação diminui por via da redução do número de caminhos de dissipação de energia.
- Prediction of low frequency sound fields in buildings near railway linesPublication . Neves e Sousa, Albano; Lopes, Isabel; Carreira, A. S.The design of new buildings in the vicinity of railway lines must consider protection against noise and vibrations induced by railway traffic. However, the prediction methods available involve heavy numerical models which have frequency limitations. In this paper a prediction method combining finite elements (FEM) with natural mode analysis is presented for use in reinforced concrete buildings with heavy walls. The method considers 2D FEM models of the railway, ground and buildings to identify the transfer function of vibration from the railway to building foundations. Also 3D models of the buildings are considered to identify the transfer functions of vibration from foundations to walls and floors. Finally, as the impedance of heavy walls and floors is much higher than the acoustic impedance of air, the numerically assessed vibration fields of walls and floors are used to calculate sound fields in rooms by means of natural mode analysis. A set of in situ measurements were made in two different situations in order to calibrate the prediction method and also to identify the factors which most affect vibration and sound transmission.