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

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

Abstract

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.

Citation

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

• Conference Name: World Conference on Timber Engineering
• Conference Location: Seoul, Republic of Korea
• 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: http://researchrepository.napier.ac.uk/Output/1291789