The use of a visual grading code of practice in the UK in the assessment of the mechanical properties of in situ structural timber elements

Bather, Michael ORCID: 0000-0002-6725-6815 and Ridley-Eliis, Dan J (2019) The use of a visual grading code of practice in the UK in the assessment of the mechanical properties of in situ structural timber elements. In: SHATiS'19 - Structural Health Assessment of Timber Structures, 2019-9-25 - 2019-9-27, Guimaraes, Portugal.

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Abstract

The estimation of the mechanical properties of in situ timber elements is an essential part of the structural appraisal of many existing buildings and structures. Currently, in the UK, this ap-praisal of load-bearing timber is generally carried out by a structural engineer based on a com-bination of engineering judgement and visual assessment; frequently making use of UK codes of practice for visual strength grading (CP112, BS4978 or BS5765). Despite their frequent use in this manner, these visual grading codes were not written for this purpose and were never intend-ed to be used in this way. The intended use of the codes is the strength grading of consignments of timber elements prior to their use in the construction industry. It is therefore necessary to consider the validly of the methodology of using the visual grading codes for in situ strength as-sessment. As a case study, 143 structural sized specimens of Norway spruce (Picea abies), sourced from the UK, were visually graded (using CP112) and then tested to destruction to ob-tain their mechanical properties. The results, when analysed, illustrate the weakness in predic-tion by visual grading. The key implication of this is that structural engineers in the UK should be made aware of the basis and limitations of using visual grading codes in the assessment of individual in situ structural timber elements, so that they do not overestimate the power of visual grading methods and the importance of visual grading indicators, but also do not unnecessarily under-evaluate the performance of timber in situ.

Item Type:	Conference or Workshop Item (Unspecified)
Uncontrolled Keywords:	timber grading, in situ assessment, Norway spruce
Divisions:	Faculty of Science and Engineering > School of Engineering
Depositing User:	Symplectic Admin
Date Deposited:	14 Jan 2022 14:40
Last Modified:	18 Jan 2023 21:16
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3146829