Timber grading potential of Douglas fir in the Republic of Ireland and the UK

Gil-Moreno, David; Ridley-Ellis, Daniel; Harte, Annette M.

doi:10.1080/20426445.2019.1617984

Cited by 12 publications

(9 citation statements)

References 4 publications

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“…As first observation, the characteristic values of the several grades generally achieved the values of the strength classes tabled in the European standardization (EN-338 2016). In particular, regarding bending strength, which is often the limiting property for the assignment to a strength class (Nocetti et al 2013, Stapel & Van De Kuilen 2013, Gil-Moreno et al 2019), the visual grades showed a far higher characteristic strength for the highest class: 62.1 MPa and 59.5 MPa for visual-1 and visual-2 respectively, compared to the required value of the class of 45 Mpa, while the machine grading showed a slightly lower value (44.5 MPa). However, this was above the 90% of the class value (namely 98.9%), which is the requirement to be met in the second step of the verification during the development of the machine settings (EN-14081-2 2018): each verification sample (part of a country in our case) should reach the 90% of the characteristic strength value of the class.…”

Section: Validation Of Visual Grading Rules and Machine Settingsmentioning

confidence: 99%

Validation of visual and machine strength grading for Italian beech with additional sampling

Brunetti¹,

Aminti²,

Nocetti³

et al. 2021

iForest

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The typical variability of wood properties, higher than for other construction materials, requires a thorough knowledge of its mechanical performance. To make the use of wooden structural products safe and at the same time efficient, a proven methodology for the selection of the raw material is also crucial. As a general rule, the initial sampling is of vital importance to develop effective strength grading processes, but it is rarely verified with additional samples, besides those already included during the development of the grading procedure itself. Here, a new source of sawn timber was collected to verify the original sampling and to validate the visual and machine strength grading early developed for Italian beech. The new pieces were graded, destructively tested and the characteristic values of the graded material were calculated. The dispersion of the new data was found to be entirely included in that of the original data, proving an effective sampling of the resource variability. The correlations between properties were very similar comparing the original and the new sample, with the exception of the correlations between the dynamic modulus of elasticity and both bending strength and stiffness, which were lower in the new sample. The characteristic values of the graded new material were generally higher than the characteristics values of the corresponding strength classes as tabled in the technical standard. Only for one grade in the machine grading the strength reached 98.9% the class value, anyhow above the 90% required by the procedure of the checking of existing settings in a particular location, as provided by the related standard. In conclusion, the earlier development of the strength grading of Italian beech confirmed to be correct and safe.

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Section: Validation Of Visual Grading Rules and Machine Settingsmentioning

confidence: 99%

Validation of visual and machine strength grading for Italian beech with additional sampling

Brunetti¹,

Aminti²,

Nocetti³

et al. 2021

iForest

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“…One kind of long-standing indicating property (IP) used to predict wood properties is knot indices, which is familiar for visual grading, but also, in a different form, part of grading by machines using principles such as X-rays, and optical mapping of the wood surface. In recent years, the use of non-destructive techniques based on the measurement of dynamic modulus of elasticity (E dyn ) has also become broadly applied (Gil-Moreno et al 2019b;Krajnc et al 2019b;Ridley-Ellis et al 2018) since it is relatively easy to apply and usually gives strong relationship with mechanical properties, even in logs and standing trees (Gil-Moreno and Ridley-Ellis 2015;Llana et al 2020;Wang 2013). Knot index and E dyn are used in the current study as representative examples of IP, but there are also others in common use.…”

Section: Introductionmentioning

confidence: 99%

“…Sitka spruce has similar properties to Norway spruce, and these are graded together as a species combination known as British spruce, recognised in the standards EN13556 and EN14081-1 (species code WPCS). Timber from Ireland and the UK is often graded using the same rules (Gil-Moreno et al 2019b) due to the similar growing conditions that result in comparable timber characteristics. Scots pine is a native minor species, and although it can perform better than spruce, and achieve high yields of C20 (Moore (1) 0,k et al 2008;Fátharta et al 2020), there is currently little information on the wood properties of the species grown in these countries.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2022

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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 design.

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“…The present investigation is dedicated to the silvicultural influence of the tree species mixture on the strength grading. Bending or tensile strength are often the limiting timber property in European strength grading, which is related to knot size and is in turn strongly influenced by silviculture (Gil-Moreno et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Timber tensile strength in mixed stands of European beech (Fagus sylvatica L.)

Rais¹,

Kovryga²,

Pretzsch

et al. 2022

Wood Sci Technol

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The conversion to climate-stable, resilient and productive forests has resulted in an increasing share of mixed stands. Different growth conditions and silvicultural treatments lead to an increased scatter in strength compared to what is expected from monoculture experience. The study (i) quantified the magnitude of variation in strength of European beech timber from stands of different composition and (ii) showed the impact of grading on the characteristic strength value of timber coming from those stands. Strength grading models and machine settings for hardwood tensile classes on over 900 European beech (Fagus sylvatica L.) boards were derived. One model used only the dynamic modulus of elasticity (Edyn), and a more complex model used a knot value in addition. Afterwards, 407 boards from pure beech stands as well as mixed stands of beech with Douglas fir (Pseudotsuga menziesii (Mirb.) Franco), Norway spruce (Picea abies (L.) Karst.), sessile oak (Quercus petraea (Matt.) Liebl.), and Scots pine (Pinus sylvestris L.) were graded and analyzed for their material properties from tension tests parallel to grain. Although a variance components analysis attributed only 4.2% of the variation to mixture, the ungraded timber showed significant strength differences between the pure and the beech-pine stands (65.2 versus 46.6 MPa). The yield of the material graded to the highest class in a class combination was higher in pure beech stands. The required characteristic strength values were mostly met for boards from the pure stands; while boards from the beech-pine mixed stands hardly ever reached the required values. To reduce strength variation and guarantee reliable timber products, strength grading should consider the various growth situations in forests when sampling material for the derivation of settings.

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Timber grading potential of Douglas fir in the Republic of Ireland and the UK

Cited by 12 publications

References 4 publications

Validation of visual and machine strength grading for Italian beech with additional sampling

Validation of visual and machine strength grading for Italian beech with additional sampling

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

Timber tensile strength in mixed stands of European beech (Fagus sylvatica L.)

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