The relationship between bending and tension strength of Irish and UK spruce and pine

The correct characterisation of wood properties is fundamental for the best utilisation of resources. In Europe, grading is defined by strength classes that are determined based on either bending or tension tests. The European standards give equations to estimate characteristic strength in tension from characteristic strength in bending, and vice versa depending on which was tested. These equations are applied to all softwoods. The aim of this paper is to empirically determine the relationship between bending and tension strength properties using two conifer species grown in Ireland and the UK. The results show that the relationships change with species. The standard conversion underestimates, importantly, the performance of spruce for tension loads calculated for the most common bending strength class for Ireland and the UK, C16. The opposite occurs on the reverse conversion. Additionally, the study includes published data from continental Europe, to establish a new conversion that uses timber from a broader range of grades, and that adjusts the tension performance of Irish and UK spruce obtained from bending strength classes, ensuring safe values for desig

Experimental characterisation of the moment-rotation behaviour of beam-beam connections using compressed wood connectors

© 2021 The Authors. The widespread use of energy-intensive metallic connectors and synthetic adhesives in modern timber construction has negative implications for the end-of-life disposal or re-use of the structural timber components. Therefore, it is favourable to substitute metallic connectors and synthetic adhesives with bio-based alternatives such as wood-based connectors. Recent studies have shown that densified or compressed wood (CW) with superior mechanical properties could be suitable for the manufacture of wood-based connectors in the form of CW dowels and CW plates. This study experimentally examines the moment-rotation behaviour of semi-rigid type timber-CW beam-beam connections under pure bending. The study also assesses the suitability of current design rules to predict the moment capacity of timber-CW connections. The comparative study has shown that the moment capacity of the timber-CW connection can be conservatively predicted from the characteristic load-carrying capacity of the connections calculated using the EC 5 strength equations.European Regional Development Fund (ERDF) via Interreg North-West Europe grant 348 “Towards Adhesive Free Timber Buildings - AFTB”

Experimental investigation of the moment-rotation behaviour of beam-column connections produced using compressed wood connectors

Copyright © 2022 The Authors. The use of timber in construction in medium–high rise construction has increased in recent years largely due to the significant innovation in engineered wood products and connection technology coupled with a desire to utilise more environmentally sustainable construction materials. While engineered wood products offer a low-carbon solution to the construction industry, the widespread use of adhesive and metallic fasteners often limits the recyclability of the structural components at the end of life of the structure and it may be beneficial to reduce this where possible. To establish the possibility of an all-wood connection solution, this preliminary study examines a series of beam-column connections designs to evaluate the relative performance of the different designs, which are connected with modified or compressed wood (CW) connectors. The connection designs are formed between glued-laminated beam and column members in the first instance and later examined when connecting dowel-laminated timber (DLT) members. The results show that significant moment capacity and rotational stiffness can be achieved for connections solely connected using CW fasteners. Furthermore, the all-wood solution utilising CW fasteners to connect DLT members has also demonstrated significant moment capacity and rotational stiffness capacity without the use of adhesive and metallic components.Interreg North-West Europe (NWE) funded by the European Regional Development Fund (ERDF) for supporting their project Towards Adhesive Free Timber Buildings (AFTB) - Grant ID: NWE_348

Modulus of elasticity prediction through transversal vibration in cantilever beams and ultrasound technique of different wood species

Producción CientíficaThe prediction of the modulus of elasticity (MOE) of five species of different spectrum density woods, namely, Populus × euramericana I-214 (Poplar), Fagus sylvatica L. (Beech), Quercus pyrenaica L. (Oak), Paulownia elongata S.Y.Hu (Paulownia) and Pinus sylvestris L. (Scots pine) were examined through the natural frequency of vibration on cantilevered beams (transverse direction) and ultrasound (longitudinal direction). Cantilever beams are commonly used for other materials but limited information is available for wood materials tested in this manner. A total of 60 specimens with nominal dimensions of 40 × 60 × 1200 mm3 were tested, which were visually graded according to UNE 56544:2022 and UNE 56546:2022 as first class, and finally the global bending stiffness was obtained from a four-point bending test. Utilising this data, a regression model was presented to predict the MOE. Also, Picea sitchensis Trautv. & G.Mey (Sitka spruce) has been chosen as a blind species in order to validate the regression model of prediction of the MOE as a function of the dynamic MOE by ultrasound. Bending strength, modulus of elasticity and density were obtained according to the EN 408. In the prediction model using the dynamic MOE with vibrations, an r2 of 95.9% was achieved for the induced vibration technique which was found to be slightly higher than the model for the ultrasound prediction which had an r2 of 93.7%.Junta de Castilla y León- FEDER (VA095P17 y VA228P20

Photometric observations of distant active comets

We present CCD VR_C observations of 6 distant comets located at heliocentric distances of 3.4--7.2 AU. Time-series data were obtained on three nights in July, 2000 covering 16 hours. Each comet was observed after the perihelion, when a lower activity was expected. Contrary to expectation, we found well-defined circular comae and extended tails visible out to a few (3-5) arcminutes. We detected a quasi-cyclic light variation of C/1999 J2, while C/1999 N4 showed some hints of a more complex variation. C/2000 K1 was constant to +/-0.04 mag during the observing run. The standard V and R_C data were used to estimate nuclear diameters, while the colour indices implied a slighly reddish (V-R=0.68, C/2000 K1), a neutral (V-R=0.47, C/1999 N4) and a slightly bluish (V-R=0.25, C/1999 J2) coma. Simple fits of the surface brightness distributions are also presented enabling order of magnitude estimates of nuclear radii. Beside the time-series observations, further single-shot observations of three faint comets are briefly described.Comment: 8 pages, 5 figures, accepted for publication in A&

Review of state of the art of dowel laminated timber members and densified wood materials as sustainable engineered wood products for construction and building applications

Copyright © 2019 The Authors. Engineered Wood Products (EWPs) are increasingly being used as construction and building materials. However, the predominant use of petroleum-based adhesives in EWPs contributes to the release of toxic gases (e.g. Volatile Organic Compounds (VOCs) and formaldehyde) which are harmful to the environment. Also, the use of adhesives in EWPs affects their end-of-life disposal, reusability and recyclability. This paper focusses on dowel laminated timber members and densified wood materials, which are adhesive free and sustainable alternatives to commonly used EWPs (e.g. glulam and CLT). The improved mechanical properties and tight fitting due to spring-back of densified wood support their use as sustainable alternatives to hardwood fasteners to overcome their disadvantages such as loss of stiffness over time and dimensional instability. This approach would also contribute to the uptake of dowel laminated timber members and densified wood materials for more diverse and advanced structural applications and subsequently yield both environmental and economic benefits.Interreg North-West Europe (NWE) funded by the European Regional Development Fund (ERDF) supporting the project (Towards Adhesive Free Timber Buildings (AFTB) - 348)