Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation

Olsson, Anders; Oscarsson, Jan; Serrano, Erik; Källsner, Bo; Johansson, Marie; Enquist, Bertil

doi:10.1007/s00107-013-0684-5

Cited by 84 publications

(83 citation statements)

References 3 publications

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“…Shown local MOE variations are based on strains that originate from DIC (black curve), and FE_FAM (purple curve). In addition, Figure 4 also includes the local bending MOE (blue curve) calculated using the above-mentioned grading method [5] for a comparison.…”

Section: Bending Stiffness Variation Along Boardsmentioning

confidence: 99%

“…The local MOE calculated using the suggested FE_FAM model comply very well with those obtained based on data from DIC. Bending MOE variation along board B2 obtained using data of DIC (black curve), the suggested FE_FAM (purple curve) and the grading method in [5] (blue curve). Each value on the curves represents the average bending MOE over a distance of 50 mm.…”

Section: Bending Stiffness Variation Along Boardsmentioning

confidence: 99%

“…This is done by utilizing the so-called tracheid effect, which is dependent on scattering and reflection of light within wood fibres [3,4]. Knowledge of local fibre orientation obtained by tracheid effect scanning have been utilized in a previously developed machine strength grading method [5]. Although the mentioned method enables rather accurate prediction of bending strength [6], it is based on simplifying assumptions on the interior fibre orientation and when calculating local bending MOE.…”

Section: Introductionmentioning

confidence: 99%

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Modelling Local Bending Stiffness of Norway Spruce Sawn Timber Using Scanned Fibre Orientation

Olsson

Johansson

et al. 2018

The 18th International Conference on Experimental Mechanics

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Strength of structural timber depends to a high degree on the occurrence of knots and on the local fibre deviation around such defects. Knowledge of local fibre orientation, obtained by laser scanning, have been utilized in a previously developed machine strength grading method. However, that method was based on rather crude assumptions regarding the fibre orientation in the interior of boards and a mechanical model that does not capture the full compliance of knotty sections. The purpose of the present study was to suggest and verify a model by which local bending stiffness can be predicted with high accuracy. This study included development of a model of fibre orientation in the interior of boards, and application of a three-dimensional finite element model that is able to capture the compliance of the board. Verification included bending of boards in laboratory and application of digital image correlation to obtain strain fields comparable to those obtained by finite element simulation. Results presented comprise strain fields of boards subjected to bending and calculated bending stiffness variation along boards. Comparisons of results indicated that models suggested herein were sufficient to capture the variation of local bending stiffness along boards with very high accuracy.

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Section: Bending Stiffness Variation Along Boardsmentioning

confidence: 99%

Section: Bending Stiffness Variation Along Boardsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modelling Local Bending Stiffness of Norway Spruce Sawn Timber Using Scanned Fibre Orientation

Olsson

Johansson

et al. 2018

The 18th International Conference on Experimental Mechanics

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“…The tracheid effect has often been used, also in industrial processes, to determine the in-plane fibre angle on wood surfaces (e.g. Olsson et al 2013;Olsson and Oscarsson 2017).…”

Section: Laser Scanning and The Tracheid Effectmentioning

confidence: 99%

Growth layer and fibre orientation around knots in Norway spruce: a laboratory investigation

Briggert

Olsson

et al. 2017

Wood Sci Technol

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The strength of structural timber largely depends on the occurrence of knots and on the local material directions in the surroundings of such knots. There is, however, a lack of methods for establishing a full dataset of the local material directions. The present research aims at the development and application of a laboratory method to assess the geometry of growth layers and the orientation of fibres in a high-resolution 3D grid within wood specimens containing knots. The laboratory method was based on optical flatbed scanning and laser scanning, the former resulting in surface images and the latter, utilizing the tracheid effect, resulting in in-plane fibre angles determined in high-resolution grids on scanned surfaces. A rectangular solid wood specimen containing a single knot was cut from a tree in such a way that it could be assumed that a plane of symmetry existed in the specimen. By splitting the specimen through this plane through the centre line of the knot, two new specimens with assumed identical but mirrored properties were achieved. On one of the new specimens, the longitudinal-radial plane was subsequently scanned, and the longitudinal-tangential plane was scanned on the other. Then, by repeatedly planing off material on both specimens followed by scanning of the new surfaces that gradually appeared, 3D coordinate positions along different growth layers and 3D orientation of fibres in a 3D grid were obtained. Comparisons between detected fibre orientation and growth layer geometry were used for the assessment of the accuracy obtained regarding 3D fibre orientation. It was shown that the suggested method is well suited to capture growth layer surfaces and that it provides reliable information on 3D fibre orientation close to knots. Such knowledge is of great importance for understanding the properties of timber including

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“…Olsson et al 2013), microwave (e.g. Denzler and Linsenmann 2014) and ultrasound (Yaitskova 2014) scanning.…”

Section: New Types Of Ipmentioning

confidence: 99%

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

2016

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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.

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Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation

Cited by 84 publications

References 3 publications

Modelling Local Bending Stiffness of Norway Spruce Sawn Timber Using Scanned Fibre Orientation

Modelling Local Bending Stiffness of Norway Spruce Sawn Timber Using Scanned Fibre Orientation

Growth layer and fibre orientation around knots in Norway spruce: a laboratory investigation

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

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