La madera en la construcción de entramados inclinados de viviendas unifamiliares. Situación actual en España

Structural timber is playing an increasing role in the market and construction of domestic roofs, pushed by existing regulations, governmental policies and the development of new timber products and subproducts. This paper presents a range of timber construction systems used in roofs, analysing their structural performance and determining their positive and negative aspects. The paper focuses on two heavy timber frame systems: couple roof (“par e hilera”) and ridge-loaded roof (“par y picadero”) that are being widely used with respect to light frame systems. Eventually the thermal performance of the presented systems is evaluated in comparison with a traditional ventilated roof made of ceramic and bricks, according to the Spanish Building Construction Regulation (Código Técnico de la Edificación). This analysis shows that timber roofs present a similar thermal response that the traditional ceramic one, and allow a signifi cant reduction in construction time.La madera estructural está encontrando un nicho importante de mercado en la construcción de entramados inclinados de madera, impulsada por las normativas vigentes, las políticas gubernamentales y los nuevos productos y subproductos de la madera. En el presente artículo se presentan los diferentes sistemas constructivos en madera empleados en entramados inclinados, analizando su comportamiento estructural y determinando las ventajas y desventajas de cada uno de ellos. Se incide en los sistemas de entramado pesado de par e hilera y par y picadero, que son los que están teniendo una mayor acogida en la construcción de entramados inclinados en madera, frente al sistema de entramado ligero. Finalmente se compara el comportamiento térmico de los diferentes sistemas constructivos de madera presentados con el de un sistema tradicional de cubierta ventilada de teja curva cerámica sobre tabiquilla según el CTE (Código Técnico de la Edificación). En este análisis se comprueba que la madera tiene un comportamiento térmico igual al sistema tradicional de teja y en además permite abaratar en tiempos de montaje

Influence of Timber Moisture Content on the Ultrasonic Wave Velocity Measurement of Tectona grandis L.F. and Cupressus lusitanica M from Costa Rica

Ultrasound is a reliable non-destructive method commonly used to evaluate the state of a piece of wood. The effect of the moisture content (MC) on the timber wave velocity, which is different de-pending on the wood species, must be considered. MC adjustment factors are important if accurate and comparable results are to be achieved. Thus, the goal of this study is to define a model that allows obtaining the adjustment factor to predict the standard velocity (12% of MC (V12) from ve-locity obtained at different MC for two Costa Rican commercial species: Tectona grandis L.F (teak) and Cupressus lusitanica M. (cypress). This effect was studied on small clean specimens during the desorption stages, from the fiber saturation point to the oven-dry state, controlling the specimen’s mass and MC on 62 specimens. With this data, the rate of change in ultrasound velocity per MC was modeled. Thus, the applicability of already published moisture adjustment models for conifers and hardwood tropical species was proved. The results showed that the proposed model coefficients adjust better than the ones obtained from the wood science literature, which makes them suitable to describe ultrasound velocity in different moisture conditions (VH).Universidad de Costa Rica/[330-C0-242]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de QuímicaUCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Arquitectur

Methodology to analyze the degradation of structural timber in acidic atmospheres

The atmospheric composition varies according to geographic locations. In Costa Rica, part of the infrastructure is affected by corrosive atmospheres caused by volcanic activity and tropical climate humidity. The aim of this research is to propose a robust methodology to establish the influence of acid agents on the mechanical performance of structural Tectona grandis and Cupressus lusitanica specimens exposed to this environment. This research contemplates different acid pollution degrees and on-site and in laboratory analysis; Dynamic Elasticity Modulus Edyn, apparent Elastic Modulus Eapp, and chemical composition changes are the response variables. Among the highlighted results during the initial experimental stage, it was observed an estimated decline rate of 5-7% in Edy and 8-11% in Eapp, with a tendency of 3% more decrease in Cypress than in Teak. The acidic atmosphere remained between 0.5ppm and 1 ppm of SO2 gas concentration, and pH values of acid rain were 3.92±0.33 on average. In addition, specimens were sensitive to color change (∆E*>17) which can be considered for architecture design purposes. Since this environmental accelerates natural degradation, the proposed methodology seems suitable for monitoring wood degradation based on a six-month tracking study.UCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de ArquitecturaUCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Ingeniería Químic

Use of Artificial Neural Networks as a Predictive Method to Determine Moisture Resistance of Particle and Fiber Boards Under Cyclic Testing Conditions (UNE-EN 321)

Determining internal bond strength and thickness swelling after cyclic aging tests in humid conditions is essential to assess moisture resistance of particle and fiber boards. However, because operating procedures for these types of tests take at least 3 wk, their use in daily finished product control is impractical. To solve this problem, an artificial neural network was used as a predictive method to determine these values from the board properties of thickness, density, and moisture content in conjunction with thickness swelling and internal bond strength values obtained before the aging cycle. Using 113 boards, an artificial neural network was designed consisting of two separate feedforward multilayer perceptrons applying the hyperbolic tangent as the transfer function. Training was conducted through supervised learning after the input data had been normalized. In the testing group, the network attained a determination coefficient of 0.94 for internal bond strength and 0.92 for thickness swelling

Desarrollo metodológico mediante análisis experimental de la valoración de la degradación en situación de incendio de uniones carpinteras en estructuras de madera laminada encolada

En situación de incendio, los elementos estructurales de madera laminada encolada (?MLE?) sufren una degradación térmica que les lleva a una pérdida de sección portante. El Código Técnico de la Edificación cuantifica esta pérdida en 0,55 - 0,70 mm/min por cada cara sometida a carga, según especie y densidad, pero no propone una metodología específica para el cálculo de uniones carpinteras en situación de incendio. Para conocer el comportamiento de este tipo de uniones en situación de incendio, la Plataforma de Ingeniería de la Madera Estructural (PEMADE) de la Universidad de Santiago de Compostela, el Instituto de Ciencias de la Construcción Eduardo Torroja y el Centro Tecnológico CIDEMCO-Tecnalia han realizado conjuntamente una serie de ensayos experimentales sobre probetas ensambladas con unión carpintera del tipo cola de milano. Se han sometido las probetas a cargas térmicas variantes en el tiempo siguiendo la norma ISO 834-1, tal y como indica el CTE. Se registró usando termopares la variación de la temperatura a lo largo de la duración del ensayo. En este trabajo se expone en detalle la metodología desarrollada para realizar los ensayos, así como los primeros resultados obtenidos. In a fire event, glued laminated timber ("GLULAM") elements suffer a thermal degradation that produces in them a decrease of bearing section. Spanish technical building normative (?CTE?) quantify this decreasing from 0.55 to 0.70 mm / min according to species and density, but does not propose a specific methodology for calculating carpenter joints in a fire situation. In order to understand the behavior of such joints in a fire situation, the Platform for Structural Timber Engineering (PEMADE) of University of Santiago de Compostela; Institute of Science Construction Eduardo Torroja and Technology Center CIDEMCO-Tecnalia conducted together a series of experimental tests on glulam specimens assembled with a carpenter union type called ?dovetail?. Specimens were subjected to thermal loads varying in time according to ISO 834-1, as indicated by the CTE. Thermocouples were inserted in the specimens, recording the temperature variation along the length of the test. This paper details the methodology developed for the test and the first results

Variation throughout the tree stem in the physical-mechanical properties of the wood of Abies alba Mill. from the Spanish Pyrenees

This study analyses the variation of main physical-mechanical properties of wood along the longitudinal and radial directions of the tree for Abies alba Mill. growing in the Spanish Pyrenees. Small clear specimens were used to study the properties of volumetric shrinkage (VS), density (?), hardness (H), bending strength (MOR), modulus of elasticity (MOE), maximum compressive strength parallel to the grain (MCS) and impact strength (K). Several models of properties variation in the longitudinal and radial directions were analyzed. Main trends of variation of properties throughout the tree stem were identified although none of them could be fitted to predictive statistical models. Along the longitudinal direction, the properties studied followed a downward trend from the base to the crown, which was not significant in all cases, indicating that no differences in quality existed. Throughout the radial direction the trend is upward for the first 40-50 growth rings, after which it slopes downwards, more gently at first until rings 70-75 and then more steeply. This behaviour is related to variation in wood structure from the pith to the bark, depending on whether the wood is juvenile, sapwood or heartwood, and to wood maturity and microfibril angle. Authors encourage carrying further studies on other populations of A. alba in the Spanish Pyrenees to check if the trends found in this study apply to other provenances

Signaling pathways involved in liver injury and regeneration in rabbit hemorrhagic disease, an animal model of virally-induced fulminant hepatic failure

Management of fulminant hepatic failure (FHF) continues to be one challenging problem, and experimental animal models resembling its clinical conditions are still needed. Rabbit hemorrhagic disease (RHD) fullfils many requirements of an animal model of FHF. This work investigated changes in MAPK, NF-κB, AP-1 and STAT pathways during RHD-induced liver injury. Rabbits were infected with 2 × 104 hemagglutination units of an RHD virus isolate. Apoptosis was documented by the presence of caspase-3 activity and substantial PARP proteolysis at 36 and 48 h postinfection (pi). Infection induced a marked and maintained expression of TNF-α from 12 h pi, while there was only a transitory increase in IL-6 expression. Expression of phosphorylated (p)-JNK, p-p38 and p-ERK1/2 was significantly elevated at 12 h pi. At 48 h pi p-JNK expression was maintained at a maximum level, while that of p-p38 returned to normality and there was no p-ERK1/2 expression. Activation of NF-κB and AP-1 and increased expression of VCAM-1 and COX-2 were observed. No significant changes were detected in activation of STAT1 and STAT3, while SOCS3 expression increased significantly. The current findings suggest that activation of JNK is an essential component in liver injury mediated by the RHD virus and that lack of activation of STAT3, probably mediated by SOCS3 over-expression, would contribute to the inhibition of the regenerative response. Data show the presence of molecular mechanisms contributing to liver damage and the lack of regeneration and they support the usefulness of this model to investigate novel therapeutical modalities in FHF

Los discos de oro del Museo Arqueológico de Asturias: algunas observaciones sobre la orfebrería prehistórica

Se presenta un estudio detallado de dos discos de oro de procedencia desconocida que permanecen depositados desde mediados del s. xx en el Museo Arqueológico de Asturias. Pese a la abundante bibliografía sobre estas piezas, hasta el momento no se había realizado un análisis arqueométrico y arqueometalúrgico de las mismas. Los resultados permiten inferir observaciones interesantes acerca de su composición, manufactura y secuencia tecnológica de elaboración, así como sobre la posible procedencia del oro, confirmando, con los paralelos reconocidos para la decoración de estas placas, de una clara raigambre atlántica.Los ejemplares de las Islas Británicas se asocian con inhumaciones campaniformes. Para los objetos en estudio se consideró una cronología más moderna dada la ausencia de evidencias similares en Asturias. Sin embargo, la reciente identificación de las típicas cerámicas en espacios de transformación de mineral de cobre en el territorio central asturiano posibilita una nueva consideración, reforzada con los más recientes hallazgos áureos de similar cronología en la Península Ibérica que se reconocen como parte del ajuar de inhumaciones campaniformes. Todos los argumentos refuerzan la propuesta de la existencia de redes de intercambio entre las Islas Británicas y el continente a lo largo de aquel periodo

Registro de paisajes de interés cultural de Andalucía: criterios y metodología

La importancia que están adquiriendo los estudios y prácticas sobre el paisaje hacen de este recurso espacial uno de los grandes protagonistas de todas las políticas públicas que tienen incidencia territorial. Por otro lado, los compromisos adquiridos al reconocer el Convenio Europeo del Paisaje obligan a las instancias públicas a dar respuestas a situaciones y problemas que precisan reflexión previa y metodologías de análisis rigurosas al tiempo que flexibles en relación con este objeto de estudio. Además, en los estudios sobre paisaje, la categoría de paisajes culturales o patrimoniales, asimilables a los paisajes protegidos del Convenio, ofrece una nueva escala en la que entender los valores de los bienes culturales. Superados como paradigma de la tutela patrimonial, los conjuntos históricos y los entornos se revelan insuficientes para una responsabilidad de protección que se fija ahora en la escala general del territorio. Esto motiva no sólo un cambio de escala, sino también un cambio en la concepción de la propia protección. Este artículo pretende, a través de la presentación de los paisajes de interés cultural, proporcionar nuevas claves, métodos y temas de debate sobre cómo entender y gestionar el patrimonio cultural y hacer de éste un verdadero factor de calidad de poblaciones y territorios