Efficiency of visual strength grading of timber with respect to origin, species, cross section, and grading rules: a critical evaluation of the common standards

Stapel, Peter; Kuilen, J.W.G. van de

doi:10.1515/hf-2013-0042

Cited by 24 publications

(20 citation statements)

References 2 publications

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“…Graders should follow specific rules to categorize the assessed lumber, which would in turn indicate its strength (Thelandersson and Larsen, 2003). Depending on the country or region, different rules are used for visual grading, which may result in differences in lumber yield and mechanical properties when compared to measured values (Stapel and van de Kuilen, 2014). Despite being adopted throughout the world due to its simplicity (Ridley-Ellis et al, 2016), visual grading presents disadvantages, such as the reliance on the grader's experience, being based on the assumption that lumber of similar appearance has similar mechanical properties, and the inefficiency due to the fact that physical properties such as wood density and strength are not taken into consideration during the assessment.…”

Section: Wood Properties and Expected Financial Gains By Sawmillsmentioning

confidence: 99%

White spruce wood quality for lumber products: priority traits and their enhancement through tree improvement

Hassegawa

Savard

Lenz

et al. 2019

Forestry: An International Journal of Forest Research

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White spruce breeding has traditionally focused on genetic improvement for high productivity, targeting mostly stem volume. However, new challenges, such as the effects of climate change on individual trees and ecosystems and the changing nature of forest products markets, require action to address these issues while providing improved stock for seed and seedling production. This work aims to define the relative importance of white spruce wood traits for the lumber industry, with the intent of guiding tree breeding programs. This manuscript examines: (1) wood features that are important for lumber, (2) the genetics of wood traits and their improvement and (3) the level of acceptance of raw material with optimal traits, as obtained from a survey conducted with sawmills. Stem diameter at stump height, wood density, bending strength and stiffness were determined as the most important properties for sawmills. Decay proportion, knot diameter, slope of grain and the proportion of compression wood were also determined as important for sawmills, but to a lesser extent. Breeding efforts aiming to produce lumber should focus on stems with improved growth that are capable of sustaining the production of dense wood in greater proportion.

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Section: Wood Properties and Expected Financial Gains By Sawmillsmentioning

confidence: 99%

White spruce wood quality for lumber products: priority traits and their enhancement through tree improvement

Hassegawa

Savard

Lenz

et al. 2019

Forestry: An International Journal of Forest Research

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“…Concurrently, we took into account that local defects such as knots become more frequent with board length and that timber strength accordingly decreases (Isaksson and Thelandersson 1995;Øvrum et al 2011;Rais and Van de Kuilen 2017). Similarly, the cross section of sawn timber might influence sawn timber's mechanical properties (Barrett and Fewell 1990;Denzler 2007;Stapel andVan de Kuilen 2013, 2014). The sawing pattern was identical to logs of all diameters, i.e., the amount of large boards (cross section 50 × 150 mm 2 ) was maximized.…”

Section: Discussionmentioning

confidence: 99%

Impact of spacing and pruning on quantity, quality and economics of Douglas-fir sawn timber: scenario and sensitivity analysis

Rais¹,

Poschenrieder²,

Kuilen

et al. 2020

Eur J Forest Res

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Controlling the long-term effect of management on the quantity and properties of individual boards is a fundamental challenge for silviculture. Within this basic study on Douglas-fir, we have investigated the sensitivity of the net present value (NPV) to three most common planting densities and a prominent pruning strategy. We therefore have applied an individual tree growth model, which represents intrinsic stem structure as a result of crown competition. The model extrapolated board strength development to the rotational age of 70 years, starting from real and comprehensive data recorded from experimental Douglas-fir plots at the age of 20 years. Total volume production increased from about 1600 m 3 ha −1 for 1000 and 2000 trees ha −1 to 1800 m 3 ha −1 for 4000 trees ha −1. The economic superiority of the lowest density stands increased considering the NPV at inflation-adjusted interest rates of 0%, 2% and 4%: Given an interest rate of 2% and no pruning, the NPV at 2000 was at about 50% of the one at 1000 trees ha −1. The NPV at 4000 trees ha −1 was even negative. Generally, artificial pruning was not effective. The revealed financial trade-off between growth and timber quality in young stands underlines the importance of silvicultural guidelines, which quantify the effect of management on yield per strength class and financial outcome.

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“…There is currently a diversity of standards for visual grading of timber that fit under the harmonised standard EN14081, and which vary in grading results (Stapel and van de Kuilen 2014). A common visual grading standard would be useful, from the perspective of ease of trade throughout Europe.…”

Section: European Visual Grading Standardmentioning

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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Efficiency of visual strength grading of timber with respect to origin, species, cross section, and grading rules: a critical evaluation of the common standards

Cited by 24 publications

References 2 publications

White spruce wood quality for lumber products: priority traits and their enhancement through tree improvement

White spruce wood quality for lumber products: priority traits and their enhancement through tree improvement

Impact of spacing and pruning on quantity, quality and economics of Douglas-fir sawn timber: scenario and sensitivity analysis

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

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