Visual and machine strength grading of European ash and maple for glulam application

Andriy Kovryga, Philipp Schlotzhauer, Peter Stapel, Holger Militz, Jan Willem G. Van De Kuilen

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)


Medium dense hardwoods (HWs) show higher tensile strength (TS) values than softwoods (SWs). These advantages cannot be utilised effectively because HW grading is not well developed. The aim of the present paper was to analyse the utilisation potential of European ash (Fraxinus spp.) and maple (Acer spp.) grown in Central Europe, which were graded by different methods. The visual grading characteristics of 869 HW boards were determined and the dynamic modulus of elasticity (MOE dyn ) and X-ray attenuation (XRA) were measured by an industrial scanner. The specimens were subsequently tested in tension according to EN 408:2010 and according to German visual grading rules show strength values of 28 MPa and 30 MPa, respectively. Machine strength grading and for a combination of manually assessed boards and MOE dyn give rise to higher strength data. MOE dyn , in particular, results in lamella data with 62 MPa for ash and 42 MPa for maple. There is good agreement with recently presented HW tensile profiles. Machine grading with a multisensor system allows better strength prediction compared to the MOE dyn or visual strength grading. Best performance is achieved by a combined grading approach.

Original languageEnglish
Pages (from-to)773-787
Number of pages15
Issue number8
Publication statusPublished - 2019


  • dynamic MOE
  • glulam
  • grading of hardwoods
  • hardwoods
  • machine grading
  • mechanical properties of hardwoods
  • multisensor system
  • optimisation
  • strength profiles
  • tensile strength
  • visual strength grading
  • X-ray attenuation (XRA)

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