REHABEND 2016

Producción CientíficaEl Hostal-Parador “San Marcos” de la ciudad de León ha sido objeto de diversas ampliaciones y reformas parciales en los últimos cincuenta años hasta que, en 2010 y 2011, se acometió una restauración integral del conjunto de edificios, con sus ampliaciones sucesivas. La estructura horizontal dispuesta a lo largo de la segunda mitad del siglo XX consistió en la realización de forjados con viguetas metálicas y un material muy pobre de relleno, a base de cenizas y placas de aislamiento ligero. En la última reforma proyectada se pretendió conseguir, entre otras cosas, una mayor capacidad portante de tales forjados, añadiendo y conectando debidamente una losa superior de hormigón ligeramente armado. Solución simple y económica, frente a otras alternativas de refuerzo más costosas. Ante la ausencia de normativa para estructuras mixtas de forjado en España, esta ponencia expone el planteamiento empleado para resolver el problema, con las escasas indicaciones de EHE y un criterio clásico de resistencia de materiales. Se presta especial atención a la definición empleada para las tensiones tangenciales a resistir por el hormigón y el engarce con las viguetas metálicas existentes

REHABEND 2016

Producción CientíficaEl objetivo principal de este trabajo es el perfeccionamiento del ensayo no destructivo de velocidad de propagación de ondas ultrasónicas sobre madera aserrada de coníferas de gran escuadría y uso estructural (MEG), y la interpretación de los resultados obtenidos. Para ello se han escogido dos especies de madera ampliamente utilizadas (Pinus sylvestris L. y Pinus radiata D. Don) y un aparato de ondas sónicas Fakopp Microsecondtimer©, por sus cualidades para emplearlo sobre estructuras construidas con acceso limitado. Por medio de la realización de ensayos en laboratorio sobre un abanico de ángulos conocidos, se ha estudiado la influencia que tiene el ángulo entre la dirección de la fibra y la de las ondas ultrasónicas al realizar ensayos indirectos; en la práctica los únicos posibles en la mayoría de estructuras en servicio. Se ha optimizado el postproceso analítico de resultados para la generación de un modelo de ajuste (ecuación general) en función del ángulo, obtenido por la regresión de datos reales medidos en laboratorio para las especies y el equipo empleado. Se determinan también los ángulos de aplicación más homogéneos y fiables para la realización de este tipo de ensayo indirecto en obra

Congreso Latinoamericano REHABEND 2014

Producción CientíficaLa termografía infrarroja se ha incorporado en fechas relativamente recientes al grupo de técnicas instrumentales consideradas no destructivas que, de forma habitual, se utilizan en la inspección de estructuras históricas de madera. Esta técnica permite visualizar la temperatura de la superficie de los objetos de forma remota y sin ningún tipo de contacto, lo cual la convierte en un método estrictamente no destructivo. A pesar del potencial que atesora, las prestaciones que actualmente proporciona en el campo de las estructuras de madera son bastante limitadas, quizás por no haberse profundizado lo suficiente en su funcionamiento. En esta comunicación se analizan los principios físicos que subyacen en la termografía infrarroja, así como del comportamiento termodinámico de la madera, para determinar sus posibilidades en la evaluación no destructiva de estructuras de madera. Mediante una serie de ensayos llevados a cabo en laboratorio se ha fijado, por un lado, la emisividad de la madera, propiedad imprescindible para el uso adecuado de esta técnica. Por otro lado, se ha abierto una nueva vía para caracterizar físicamente la madera mediante la estimación cuantitativa de su densidad, y se ha comprobado el alcance de la termografía infrarroja para detectar los defectos subsuperficiales que puede padecer este material

Congreso Latinoamericano REHABEND 2014

Producción CientíficaEn este trabajo se presenta la caracterización estructural de madera de Pinus pinaster Ait. rechazada visualmente para uso estructural según la norma UNE:56544:2010. Se trabajó con 160 viguetas (1200 x 60 x 40 mm) divididas en 3 grupos: 55 piezas de madera maciza, 55 piezas de vigas tipo dúo (adhesivo epoxi), y 55 piezas de madera tipo dúo reforzadas longitudinalmente con fibra de carbono (SIKAWRAP-230 C/45) situado en su centro y paralelo a la cara de la pieza. Los 3 grupos fueron ensayados (EN-408:2011) para determinar las propiedades resistentes: densidad, módulo de elasticidad (MOE) y resistencia a la flexión (MOR). Los resultados obtenidos muestran un aumento considerable en las propiedades resistentes en las vigas reforzadas, consiguiéndose aumentos de más del 25% en el MOE y de prácticamente el 90% en el valor del MOR respecto a la madera maciza original

Infrared thermography for wood density estimation

Infrared thermography (IRT) is becoming a commonly used technique to non-destructively inspect and evaluate wood structures. Based on the radiation emitted by all objects, this technique enables the remote visualization of the surface temperature without making contact using a thermographic device. The process of transforming radiant energy into temperature depends on many parameters, and interpreting the results is usually complicated. However, some works have analyzed the operation of IRT and expanded its applications, as found in the latest literature. This work analyzes the effect of density on the thermodynamic behavior of timber to be determined by IRT. The cooling of various wood samples has been registered, and a statistical procedure that enables one to quantitatively estimate the density of timber has been designed. This procedure represents a new method to physically characterize this material.Junta de Castilla y León (grant VA006A07

Morphology and Material Composition of the Mouthparts of Stromatium unicolor Olivier 1795 (Coleoptera: Cerambycidae) for Bionic Application

The novelty of this study is the deep analysis of the morphologic, geometric and mechanical performance of longhorn beetle larvae mouthparts. Furthermore, a metal nano identification of jaw reinforced parts was made. Background and Objectives: Analysis of insect mechanical properties has shown an important application in the develop of bionic technologies such as new materials, industrial machines and structural concepts. This study aims to determine the mechanical and geometric properties of longhorn beetle (Stromatium unicolor Olivier 1795) larvae mouthparts to improve the development of innovative cutting tools. In addition, this study obtains a nano identification of metals in the cuticle of the mouthparts, which will enable the development of new nontoxic and sustainable preservation agents against xylophagous insects based on nanoparticles. Materials and Methods: five third-larval-stage samples of Stromatium unicolor were used to study its mandible morphologic, geometric and mechanical properties. To this end, mouthparts were analyzed by several microscopic techniques using a scanning electron microscope, a stereomicroscope and an optical microscope. Composition analysis was performed using with two Analytical-Inca X-ray detectors, dispersive energy spectroscopy and dispersive wavelength spectroscopy. Results: The main geometric parameters of the insect jaw are the edge angle (β = 77.3°), maximum path depth of the insect (120 μm), length (800 µm) and mouthpart movement, which were identified and measured. The chemical analysis results of the jaw tissues shows the presence of zinc and manganese. Conclusions: The geometry and angles of the mouthparts can be applied in the fabrication of bionic self-sharpening cutting tools. Molecular compounds that form the reinforcing elements in the jaws can be used to develop wood preservatives based on nanometals and metal absorption and metabolism inhibitor

Internal GFRP Reinforcement of Low-Grade Maritime Pine Duo Timber Beams

This paper presented an experimental structural-scale test campaign used to analyze the flexural behavior of low-grade maritime pine (Pinus pinaster Ait.) duo timber beams reinforced with an internal glass fiber-reinforced polymer (GFRP) sheet. For this purpose, thirty (30) unreinforced duo beams and thirty (30) duo beams internally reinforced with a unidirectional GFRP sheet with an areal mass of 1200 g/m2 were produced and tested. The addition of a low GFRP reinforcement ratio (1.07%) in the tension zone of the duo beams provided an average improvement of 8.37% in bending stiffness (EI) and an increase of up to 18.45% in ultimate moment capacity. In addition to this improved bending behavior, the internal GFRP reinforcements seemed to decrease the influence of wood singularities and wood heterogeneity on mechanical properties, which allowed for better characteristic values to be reached and for the achievement of results with less variability.Ministerio de Ciencia e Innovación (grant BIA2012-31233)Junta de Castilla y León (grant VA051A10-2

Internal reinforcement of laminated duo beams of low-grade timber with GFRP sheets

The purpose of this work is to study the flexural behaviour of Populus euroamericana I-214 low-grade glulam timber beams, internally reinforced with Glass Fibre Reinforced Polymer (GFRP). To this end, 30 unreinforced beams and 60 reinforced beams, with two ratios of GRFP reinforcement, were produced and tested. Results show an improvement in the flexural behaviour of reinforced beams, with noticeable increases in stiffness (MOE) and ultimate moment capacity (MOR). By using relatively low reinforcement ratios (1.07%, 1.6%) in the tension zone, we have measured an average improvement of 12.1% and 14.7% in stiffness, and an increase up to 23% in moment capacity. GFRP reinforced seems to reduce the influence of timber heterogeneity and singularities (knots, cracks . . .), which translates into less scattered results and better characteristic values.Ministerio de Ciencia e Innovación (project BIA2012-31233)Junta de Castilla y León (project VA051A10-2

Acoustic detection and localisation system for Hylotrupes bajulus L. larvae using a MEMS microphone array

Producción CientíficaA novel system for acoustic detection of the presence of xylophagous insect larvae inside structural timber beams is presented. It is based on an extensive array of MEMS microphones that allows the acoustic detection and localisation of the larvae when they are active. In a first phase, the activity of the larvae is continuously detected by means of frequency filtering and a sliding energy estimator, and after that, a set of short-duration segmented signals is generated, which obtains the spatial localisation of the larvae, by means of a shaping algorithm based on delay-sum beamforming techniques. The tests carried out demonstrate that it is possible to detect and locate multiple larvae of Hylotrupes bajulus L. inside structural-sized pieces of wood of Pinus syilvestris L., as well as their internal trajectory. In the future, the system could address the identification of the specific type of xylophage responsible for the deterioration by using machine learning or equivalent techniques, based on the temporal and frequency information of the detected sound events. The aim of this work is to control unintentional infestions in the international timber trade, in the assembly and the use of infested timber and, in all cases, to be able to carry out selective, targeted and localised treatments and to verify their success.Junta de Castilla y León - UE-FEDER (VA228P20

Assessment of machine learning algorithm-based grading of Populus x euramericana I-214 structural sawn timber

The efficiency of visual grading standards applied to structural timber is often inappropriate, and timber properties are either under or over-graded. Although not included in the current UNE 56544 visual grading standard, machine learning algorithms represent a promising alternative to grade structural timber. The general aim of this research was to compare the performance of machine learning algorithms based on visual defects, non-destructive techniques and sawing systems (“cut type”) with UNE 56544:1997 visual grading in order to predict the qualifying efficiency of Populus x euramericana I-214 structural timber. Visual evaluation, ultrasound and vibrational non-destructive testing, and sawing systems register (radial, tangential and mixed) were applied to characterize 945 beams. In addition, in order to retrieve actual physical-mechanical values, density and static bending destructive testing (EN-408:2011 + A1:2012) was also carried out. Several machine learning algorithms were then used to grade the beams, and their predictive accuracy was compared with that of visual grading. To do so, three scenarios were considered: a first scenario in which only visual variables were used; a second scenario in which “cut type” variables were also included; and a third scenario in which additional non-destructive variables were considered. Results showed a poor level of performance of UNE 56544:1997, with an apparent mismatch between the strength values assigned for each visual grade (established by the EN 338 standard) and the actual values. On the opposite, all algorithms performed better than visual grading and may thus be deemed as promising timber strength grading tools.Junta de Castilla y León (project VA047A08