Capacity of a traditional timber mortise and tenon joint

The safety and quality of traditional timber structures mostly depends on the conditions of their connections. A testing campaign has investigated the behaviour of mortise and tenon timber joint. The present paper addresses the quantification of the strength capacity of wood-wood mortise and tenon joint by physical testing of full-scale specimens. In addition, the performance of different non-destructive techniques (NDT) for assessing global strength is also evaluated. For this three non-destructive methods (ultrasonic testing, Resistograph and Pilodyn) are considered and the possibility of their application is discussed based on the application of simple linear regression models. New (NCW) and old (OCW) chestnut wood, obtained from structural elements belonging to old buildings, is used. Finally, a nonlinear model has been formulated and the predicted behaviour compared with the behaviour observed in the full-scale experiments, in terms of failure mode and the ultimate load. The study has shown very good agreement with the experimental values.(undefined

Compressive behavior and NDT correlations for chestnut wood (Castanea sativa Mill.)

The goal of the present work consists in the characterization of the mechanical behavior of chestnut wood under compression perpendicular to the grain. After a review of the problems usually involved in characterizing timber under this type of loading, a mechanical test was set-up. The timber specimens used in the testing program were divided in two groups: (a) new chestnut wood (NCW), which has never been used structurally even so it comes from logs that could be used as such; and (b) old chestnut wood (OCW), which were already used in structural elements from ancient constructions (date and precise origin unknown). The mechanical behavior of the specimens is discussed taking into account the orientation of the annual growth rings along the direction of the load. Correlations between mechanical properties and NDT (ultrasonic pulse velocity and drilling resistance) are also provided, taking into account the density of the wood.Fundação para a Ciência e Tecnologia (FCT) -SFRH/BD/6411/2001. Augusto de Oliveira Ferreira e Companhia Lda

Caracterização da resistência da madeira de castanho à tracção paralela ao fio

O objectivo do presente trabalho consiste na apresentação dos ensaios de tracção paralela ao fio realizados em provetes de Castanho, obtendo-se parâmetros que tentam descrever o seu comportamento mecânico, nomeadamente o módulo de elasticidade, o coeficiente de Poisson e ainda a resistência à tracção paralela ao fio. Estes parâmetros são particularmente relevantes quando se pretende efectuar análises numéricas de estruturas, como é objectivo futuro. Serão ainda analisadas as correlações existentes entre as propriedades físicas estudadas (propriedades mecânicas e densidade), com os resultados obtidos em ensaios não destrutivos realizados em laboratório: velocidade de propagação dos ultra-sons

Caracterização de propriedades da madeira de castanho na direcção perpendicular ao fio: recurso a técnicas destrutivas e não destrutivas de ensaio

A avaliação e a caracterização mecânica de provetes de madeira limpa de Castanho, à compressão perpendicular ao fio, são realizadas por meio de ensaios laboratoriais, com a determinação de parâmetros que descrevem o comportamento linear das madeiras, nomeadamente o módulo de elasticidade, o coeficiente de Poisson e ainda a resistência à compressão perpendicular ao fio. O comportamento mecânico dos provetes ensaiados é discutido atendendo à orientação das camadas de crescimento face à direcção de introdução da força. Igualmente é analisada a possibilidade de prever esse mesmo comportamento através de medições não destrutivas por meio da leitura da velocidade de propagação de ultra-sons, da utilização do Resistógrafo, do Pilodyn e da avaliação da massa volúmica

Do different sites in the same river have similar Trichoptera assemblages?

During the summer of 2001, trichoptera larvae were sampled with a kick-net in 15 sites belonging to 3 rivers of the Mondego River basin, in central-north Portugal. Simultaneously, 42 environmental variables were evaluated for each site. Twenty five species and genera of caddisflies were identified. The objective was to assess if trichoptera assemblages within a river tended to be more similar among each other than between rivers, giving the physical continuity of the habitat. Localities showed low segregation between all samples (MDS, CLUSTER and ANOSIM). The Alva River samples had the higher number of taxa and animals while the Ceira River samples had the lowest values. In terms of environmental characteristics, PCA showed high similarities between samples of the same river. However there was not total segregation of rivers. BIOENV analysis identified the set of parameters that best explain trichopteran associations per river. For the rivers, these variables were all related to habitat (e.g. pool quality, depth, substrate quality). The differences between the Alva and Ceira rivers seem to be related to the deterioration of the water quality in the Ceira river (increasing levels of sulphate, chloride and % of industrial, urban and degraded areas), which increased down the river.Durante el verano de 2001 se capturaron larvas de tricópteros en 15 puntos de muestreo pertenecientes a 3 ríos de la cuenca hidrográfica del Mondego, en el centro-norte de Portugal. Los muestreos fueron realizados con una red de mano (tipo "kicknet") y, simultáneamente, se evaluaron 42 variables ambientales para cada localidad. En total fueron identificadas 25 especies de tricópteros. El objetivo del estudio era evaluar si, dada la continuidad físico-química del habitat, las asociaciones de tricópteros de las localidades situadas en un mismo río son más semejantes entre sí que las pertenecientes a localidades de ríos diferentes. Los locales se presentaran poco segregados de acuerdo con los análisis MDS, CLUSTER y ANOSIM. Las muestras del río Alva tuvieron un número más elevado de taxa y animales mientras que las muestras del río Ceira tuvieron los valores más bajos. Desde el punto de vista ambiental el PCA reveló que las muestras de un mismo río eran más semejantes entre si. Sin embargo, no hubo segregación completa de ríos. El análisis BIOENV identificó el grupo de parámetros que mejor explican las asociaciones de tricópteros por río. Para los ríos, esas variables estaban todas relacionadas con el hábitat (e.g., calidad de las zonas lénticas, calidad de substrato y profundidad). Las diferencias entre los ríos Alva y Ceira parecen ser debidas al empeoramiento de la calidad de las aguas del río Ceira (mayores niveles de sulfato, cloro y porcentaje de degradación industrial y urbana) que aumentan río abajo

Water quality assessment of Portuguese streams: Regional or national predictive models?

http://www.sciencedirect.com/science/article/B6W87-4TY8WB4-2/2/5bab94f8490387f7a8da832e49003d6

Innovative architectural and structural design to preserve historical centers

Historical centers are important elements of our cities, representing their history and evolution. Many cities are facing the problem of having several vacant and degraded buildings needing intervention to avoid collapses. Also several examples of unforeseen events, like earthquakes, tsunamis, floods, etc., have severely damaged important historical cities. Beyond the risk of losing built heritage, these buildings represent public danger for citizens. Thus, in post-disaster scenarios it is urgent to protect historical buildings in order to prevent the propagation of damages. This paper presents a first efficiency assessment of using wood based systems in buildings needing urgent consolidation or damaged after disasters. Being light, easy to handle and install, as well as providing the sufficient load carrying to prevent the evolution of the damage and losses, wood and wood-based elements can be associated in different arrangements providing quick construction systems for the consolidation of damaged constructions

Isolamento e selecção de microrganismos com actividade biológica: produção de metabolitos bacterianos na protecção de madeira

Isolamento e selecção de microrganismos com actividade biológica: produção de metabolitos bacterianos na protecção de madeir

The role of spontaneous construction for post-disaster housing

Housing is crucial for living and well-being. Due to its vulnerability, one of the most severe consequences after natural disasters has been the destruction of houses, causing impressive numbers of homeless people. After those situations, it is imperative to start the reconstruction works and the provision of houses is a crucial task, since they can help to restore the livelihoods of the affected people. The urgency to supply housing quickly, has lead the formal construction sector to neglect user’s needs and expectations, and consequently has not conducted to successful solutions. Contrary to that, informal housing solutions have reached successful results in addressing the user’s cultural needs and expectations. Some studies have presented the advantages of spontaneous construction solutions, yet they seem to be ignored and contradicted by the formal construction sector. This study aims to present an assessment of the potentials of spontaneous construction solutions for post-disaster housing development

Water quality in the Mondego river basin : pollution and habitat heterogeneity

The "IMAR- Departamento de Zoologia, Universidade de Coimbra" and "Direcção Regional de Ambiente e Ordenamento do Território" started a partnership with the objective of establishing bases for the assessment of water quality in the Mondego river basin. Here we present the preliminary results of the study. We sampled 75 sites covering the Mondego river basin. At each site we took 18 physical and chemical measurements and sampled macroinvertebrates with a hand net. Site quality was assessed by the application of a biotic index (BMWP'), water chemistry and habitat heterogeneity. Fifty two percent of the sites had good biological water quality (based on BMWP' index). The strongly polluted sites were concentrated in the Lower Mondego region. Thirty three percent of sites had bad chemical water quality and 45% of the sites had low habitat complexity. Only 40% of the sites with low biological quality also had low chemical water quality. We concluded that (1) in general, the waters on the Mondego river basin do not suffer from strong water pollution and (2) low BMWP' values can be explained by low water quality or low habitat heterogeneity (natural or man-made).El "IMAR- Departamento de Zoologia, Universidade de Coimbra" y la "Direcção Regional de Ambiente e Ordenamento do Território" iniciaron una colaboración con el objetivo de establecer las bases para la evaluación de la calidad del agua en la cuenca hidrográfica del Río Mondego. En esta publicación presentamos los datos preliminares de ese estudio. Se muestrearon 75 localidades, repartidas por toda la cuenca del Mondego. En cada localidad se midieron 18 parámetros químicos y físicos y se muestreó la comunidad de macroinvertebrados acuáticos con una red de mano. La calidad ambiental fue calculada mediante la aplicación del índice biótico BMWP', por las características químicas del agua y por la heterogeneidad del hábitat. Un 51% de las localidades muestreadas tenían una buena calidad ambiental, de acuerdo con el índice BMWP'. Los sitios fuertemente contaminados estaban concentrados en la zona del Bajo Mondego. Un 33% de los locales tenían una calidad química mala, mientras que el 45% tenían una baja heterogeneidad del hábitat. Solamente un 40% de las localidades con baja calidad biológica también tenían baja calidad química. Concluimos que (1) en general, las aguas de la cuenca del río Mondego no sufre de contaminaciones fuertes, y (2) que los bajos valores de BMWP' pueden ser explicados por la baja calidad del agua o bien por una baja heterogeneidad del hábitat (por causas humanas o naturales)