Visual and mechanical classification of the specie Cryptomeria japonica D. Don for using as glued laminated timber

Abstract

The objective was to evaluate the mechanical properties, the visual classification influence of Cryptomeria japonica D. Don at the mechanical performance to use it as glulam structural elements, comparing with the minimum requirements demanded by the Brazilian Standard ABNT NBR 7190 (1997) and European Standard EN 338 (2006). The tests for the characterization of the physical and mechanical properties of solid timber followed the recommendations of COPANT 461 (1972), 464 (1972), 555 (973) for density of timber, parallel compression to grain and bending, respectively; and ABNT NBR 7190 (1997) for the shear strength. The classification of the 80 laminate of timber with dimension of 6.0 x 1.5 x 220.0 cm were made by visual classification according to the American Standard ASTM D245 (2006) and by the modulus of elasticity - MOE (ASTM D4761 (2013)). Altogether, 20 beams of GLULAM were made, these formed by the combination of the laminated classified in the visual grades: Control (clear laminate), T1 (clear and special structural - SE), T2 (S1, S2, S3) and T3 (clear, SE, S1, S2, S3), the beams were evaluated by bending, tension perpendicular to grain and shear strength in the glued line. The results indicated the species as solid wood does not have the minimum resistance to be classified as C-20 by the ABNT NBR 7190 (1997), but the species was classified as structural grade in the C-16 by the EN 338 Standard. The GLULAM beams showed the minimum demanded values to the C-20 structural class according to the ABNT NBR 7190 (1997). The using of laminated with visually classified knots did not decrease the glulam beams strength when comparing to the beams made with laminated without knots.

Keywords:
Elasticity; Structural purpose; Visual grade