Nondestructive evaluation of timber: the new Brazilian code for the design of timber structures

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Title: Nondestructive evaluation of timber: the new Brazilian code for the design of timber structures

Author(s): Almir Sales, Marcela Candian, Viviane de Salles

Publication: RILEM

Volume: 43

Issue: 1

Appears on pages(s): 213-221

Keywords: Timber structures, Timber structures, Grading, Ultrasound, Transverse vibration

Date: 12/1/2009

Abstract:
The grading of structural timber members allows for their greater efficiency and quality. This grading can be done by means of nondestructive methods that improve the evaluation process. Timber grading makes it possible to augment the k mod,3 coefficient, resulting in greater structural reliability. The purpose of this work was to calibrate the modification coefficient (k mod,3) of the Brazilian NBR 7190:2007 code for the Design of Timber Structures. The modification coefficients are numbers that govern the estimation of a property of a material as a function of phenomena that may occur permanently or during a certain period of the service life of the building, being that the coefficient k mod,3 leads in consideration if the wood is of first or second-class quality. The experimental procedure involved a study of structural members of Eucalyptus grandis and Pinus sp., which were graded by ultrasound and transverse vibration techniques to determine the dynamic modulus of elasticity (Ed). The members were visually graded and static bending tests (MOE) were conducted concomitantly. The results indicated that the transverse vibration technique yielded higher modification coefficient (k mod,3) values than the ultrasound technique, since it grades the material at values closer to those obtained in static bending.


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