Embedment strength of mixed-species laminated veneer lumbers and cross-banded laminated veneer lumbers

Abstract

This paper experimentally evaluates the embedment strength of laminated veneer lumbers (LVL) and cross-banded laminated veneer lumbers (LVL-C) manufactured from blending spotted gum (Corymbia citriodora) or white cypress pine (Callitris glaucophylla) veneers with hoop pine (Araucaria cunninghamii) veneers. Nominal 3.0 mm thick veneers were rotary peeled from small diameter (less than 30 cm) native forest sourced spotted gum and white cypress pine logs, and plantation grown hoop pine logs. 12-ply × 1.2 m (long) × 0.9 m (wide) LVL and LVL-C panels were manufactured using ten different construction strategies by mixing (i) the number of veneers from each species, (ii) the modulus of elasticity of the veneers and (iii) the veneer orientations (cross-banding). A total of 672 embedment tests, using three different dowel diameters and four different load-to-grain orientation angles, were performed using the half-hole test method described in the ASTM D5764-97a. This paper (i) compares the proportional limit strength, 5%-offset embedment strength and maximum embedment strength across the different construction strategies adopted in the study, and (ii) discusses the results in terms of load-to-grain angle and dowel diameter. More importantly, the test results are also compared to the embedment strength prediction equations detailed in the Eurocode 5 to determine their suitability for mixed-species LVL and LVL-C products. Overall, the mixed-species LVL and LVL-C showed significantly higher 5%-offset embedment strengths than single-species commercial softwood LVL products. The effect of the cross-banded veneers on the embedment strength was not found to be significant. However, the LVL-C samples exhibited a highly ductile behaviour for all load-to-grain angles and dowel diameters when compared to the LVL samples. The experimentally determined 5%-offset and maximum embedment strengths for the mixed-species LVL were on average equal to and 7% higher than the predicted values given in Eurocode 5.