Characterization and structural performance in bending of CLT panels made from small-diameter logs of loblolly/slash pine

The main objective of this work was to study the structural viability of using small-diameter logs of Uruguayan Loblolly/Slash pine, mainly from thinning operations, to design cross-laminated timber (CLT) panels. A visual grade named “CTH” (coniferous thinning) was proposed, and 45 specimens of sawn timber boards were tested, resulting in 51% lower bending strength than that of the minimum strength class C14. Subsequently, 20 CLT panels were manufactured and experimentally tested, the results showed that the bending strength of the CLT panels was 43% above that of the individual layers. Additionally, the structural performance of the CLT panels for use in floors was calculated, and the thickness-span relationship depending on strength class and imposed load are presented. Results showed than the use of CTH timber to design CLT floors implies a volume (m3/m2) 17% higher than that using C24 timber

Pliego de condiciones técnicas para la madera estructural en la edificación en Uruguay

El documento indica los requisitos que deben cumplir la madera y los productos de ingeniería de madera para ser utilizados con fines estructurales en arquitectura e ingeniería civil en Uruguay. Se presenta información sobre tipo de productos, especies de madera cultivadas en Uruguay, calidad visual, clases resistentes, de uso y de servicio, tratamientos protectores, control de calidad, recepción y almacenaje entre otros temas

estado del arte y propuesta para generar un cuerpo normativo para madera estructural

El documento pretende brindar información que facilite la toma de decisiones al momento de redactar los documentos técnicos necesarios para la conformación de un cuerpo normativo para madera estructural en Uruguay. La metodología incluyó la revisión del estado del arte en los países referentes en el desarrollo de códigos de estructuras de madera, y en los países de la región, la discusión con expertos internacionales sobre sus experiencias y motivos para la elección del formato de cálculo de estructuras de madera en sus respectivos países y el establecimiento de recomendaciones para la generación de un paquete normativo nacional que acompañe a la norma de cálculo estructural. Los resultados del trabajo permitieron concluir que sería pertinente para Uruguay considerar la adopción del cuerpo normativo europeo, en particular el Proyecto de estructuras de madera, Eurocódigo 5, y concentrar esfuerzos en la redacción de anexos nacionales, con información técnica referente a la madera y productos de ingeniería de madera de procedencia uruguaya, y en la redacción de manuales con ejemplos prácticos y documentos técnicos que difundan el conocimiento y permitan adoptar la tecnología de construcción con madera

Demonstrating innovative wood-based materials and products in green public procurement: the co-design of the BASAJAUN demo building following the New European Bauhaus values and principles

Upscaling the use of wood products in new built and renovation can contribute to transform the built environment into a large-scale carbon sink and help to unlock the low-carbon, circular economy. This case study describes the co-design of a residential wood building in a new school complex in rural southern France. The purpose was to maximise the use of wood in the building design, in response to green public procurement (GPP) criteria set by the regional authority. The 4-years project was carried out by a large consortium of research centres, architects, engineers, manufacturers, construction companies and public bodies. A series of innovative wood-based products and system solutions were designed, tested and manufactured for integration in the building, including: i) a main industrial prefabricated glulam structural timber, ii) a façade system using biocomposite profiles, and iii) a structural insulation panel for roof components and interior partitions. Additional innovations included: iv) a pulp-based insulation foam, v) thermoplastic composite materials, and vi) coatings with less harmful biobased agents. A digital twin model of the value chain was developed, and LCA addressed the environmental benefits. The NEB Compass assessment of the co-design highlights the role of the coordination team to steer all phases, including the formal approval procedures of innovative solutions for use in the public building. Thorough planning and follow-up with all parties was essential to ensure that all components fulfilled the required performance levels and could be correctly installed by the contractor. The transdisciplinary team made it possible to address all technical, budgetary and managerial challenges of the complex design and construction process. The final demo building represents a successful showcase for the New European Bauhaus (NEB) movement on how wood innovation can bring together all relevant stakeholders to co-create beautiful, sustainable and inclusive solutions for the big green transformatio

Strength grading of sawn timber in Europe: an explanation for engineers and researchers

This paper is a concise explanation of the normative background to strength grading in Europe, addressing important aspects that are commonly misunderstood by structural engineers and timber researchers. It also highlights changes that are being made to the standards to: incorporate requirements of the construction products regulations; add improvements to the system to accommodate the latest knowledge and technology; and widen the application of the standards. Where designs need to be optimised, there is an opportunity to use the system more intelligently, in combination with the latest technology, to better fit design values to the true properties of the timber resource. This can bring a design enhancement equivalent to effort improving other aspects of the structure, such as connectors and reinforcement. Parallel to this, researchers working on other aspects of structural improvement need to understand what grades really mean in respect of the properties of the timber, in order to correctly analyse the results of testing. It is also useful to know how techniques used in grading can assist with material properties characterisation for research. The amount of destructive testing involved in establishing machine grading settings and visual grading assignments presents a barrier to greater use of local timber, and diversification of commercial species, so it is important that any researcher assessing the properties of such species should consider, from the outset, doing the research in a way that can contribute to a grading dataset at a later date. This paper provides an overview of what is required for this

Relación entre parámetros de producción y propiedades estructurales de madera laminada encolada de Eucalyptus grandis

La oferta actual de maderas uruguayas ha incentivado la producción de vigas de madera laminada encolada sin adaptar la tecnología original destinada a elementos de carpintería. La inexistencia de normativa sobre requisitos de fabricación permite producir y comercializar componentes que siendo no estructurales, son consumidos como tales por usuarios desconocedores de las características del producto. El objetivo del trabajo fue establecer la relación entre los parámetros de fabricación de madera laminada encolada de Eucalyptus grandis y sus propiedades estructurales, adaptando la tecnología en Uruguay. La metodología involucró modificar los parámetros de producción de una empresa y ejecutar ensayos de caracterización. Los parámetros adoptados incluyeron: adhesivo poliuretánico; diente estructural de longitud 15 mm; presión de ensamble de 10 MPa y de 1,2 MPa en uniones dentadas y vigas respectivamente; y control de tiempos de prensado en láminas y vigas. Los resultados de los ensayos mecánicos y de integridad de encolado indicaron que fue posible fabricar madera laminada estructural. Las propiedades de flexión y densidad de las vigas se correspondieron con las respectivas de la clase resistente GL24h de la norma europea EN 14080. Estos resultados contribuyen a la redacción de una norma uruguaya de madera laminada encolada estructural de Eucalyptus grandis.&nbsp

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Embedment Strength of Low- and Medium-Density Hardwood Species from Spain

The embedment strength is a key parameter in the design of timber connections with metal fasteners. This property can be determined by the equations given by design codes such as the Eurocode 5, which are based on the European Yield Model proposed by Johansen, and it depends on the value of timber density among other parameters. These equations provided by design codes are based on experimental tests performed mainly in softwood species; thus, the objective of this work is to evaluate the embedment strength of two low- and medium-density hardwood species from Spain (poplar—Populus x euroamericana; beech—Fagus sylvatica) in the parallel and perpendicular to grain directions. Four different experimental test configurations were carried out according to EN 383 for each species using two different fasteners: (i) a 9 mm-diameter screw and (ii) a 12 mm-diameter bolt. Results of embedment strength were evaluated according to three different determination methods, and later compared with the current equations provided by Eurocode 5 (EC5) and new ones proposed in the draft of the new Eurocode 5 (prEC5). Results showed that current equations overestimated perpendicular to grain embedment strength for the cases studied, while the equation proposed in prEC5 for screws fitted best perpendicular to grain embedment strength. However, it underestimated the parallel to grain one because it does not consider any difference due to load-to-grain angle (α). Finally, ratios between experimental parallel and perpendicular to grain embedment strength were studied (k90), showing 30% and 44% higher values than the theoretical values resulting from k90 equations of EC5 and prEC5 for beech with screws and bolts, respectively, and 4% and 49% higher than the theoretical values for poplar with screws and bolts, respectively

Experimental and numerical evaluation of the structural performance of Uruguayan Eucalyptus grandis finger-joint

The aim of this study was to evaluate the structural performance of finger-joints made of Uruguayan Eucalyptus grandis and two types of adhesives. A numerical model for bending strength and stiffness prediction was developed. Model inputs were experimentally determined from tests on wooden specimens and from the literature. Finger-joints glued with two types of adhesives (one-component polyurethane -PUR- and emulsion polymer isocyanate-EPI-) were tested in bending and the failure modes were evaluated. Results show that adhesive type did not influence the stiffness of the finger-joint, but the bending strength. Specimens glued with PUR showed higher strength than those glued with EPI. A 3D model, using Comsol Multiphisic software, was developed to simulate the finger-joint behavior. Adhesive-wood interaction in the finger-joints was modelled using the Comsol Thin Elastic Layer module, defined by the elastic properties of the adhesives. The numerical results showed no differences on the stiffness of the joints regardless of adhesive type. Results agreed with those obtained from experimental tests, with a maximum error of 7%. Models predicted the bending strength with an error of 6% with respect to the experimental values. Different finger configurations were analysed, and the optimal geometry (20 mm-length, 6.2 mm-pitch and 1.0 mm-tip-thick) to attain the maximum strength for Uruguayan Eucalyptus was found