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Some thresholds for grading British grown spruce to optimised strength classes using longitudinal resonance

Ridley-Ellis, Dan; Adams, Steven; Lehneke, Stefan



The main commercial species in the UK and Ireland is Sitka spruce (Picea sitchensis), which is graded in combination with a small amount of Norway spruce (P. abies). It is typically graded to the European strength class C16, but actually has superior strength and density, meaning that some performance capability is exchanged for trade convenience. When grading timber as part of the construction processes, rather than putting structural timber on the general market, it makes sense to use user-defined strength classes that better match the real properties of the timber and also allow better grading yields than the general grades. This paper is an illustration of the European method for calculating machine controlled grading settings (both EN 14081-2:2010+A1:2012 and draft revision FprEN 14081-2:2018), but with non-standard strength classes designed to maximise overall yield and timber potential. Grading thresholds are presented for a generic grading device based on longitudinal resonance, mass and moisture content. The yields with the current and revised standard are compared.


Ridley-Ellis, D., Adams, S., & Lehneke, S. (2018). Some thresholds for grading British grown spruce to optimised strength classes using longitudinal resonance.

Presentation Conference Type Conference Paper (Published)
Conference Name World Conference on Timber Engineering
Start Date Aug 20, 2018
End Date Aug 23, 2018
Acceptance Date Feb 20, 2018
Publication Date Aug 22, 2018
Deposit Date Sep 4, 2018
Publicly Available Date Sep 4, 2018
Keywords Grading; Sorting; NDT; Resonance; Sitka spruce; Norway spruce; User defined strength classes
Public URL
Contract Date Sep 4, 2018


MAT-02-01 Some Thresholds For Grading British Grown Spruce To Optimised Strength Classes Using Longitudinal Resonance FullPaper (1.1 Mb)

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