Embedment strength of LVL and cross-banded LVL manufactured from blending hardwood and softwood species

Abstract

This paper experimentally evaluates the embedment strength of Laminated Veneer Lumber (LVL) and cross-banded Laminated Veneer Lumber (LVL-C) manufactured from blending spotted gum (Corymbia citriodora subsp. variegata-SPG) veneers with hoop pine (Araucaria cunninghamii-HP) veneers. Nominal 3.0 mm thick veneers were rotary peeled from small diameter (less than 30 cm) native forest sourced SPG logs and commercial plantation grown HP logs. For each species, the veneers were classified into three grades based on their dynamic Modulus of Elasticity (MOE). Six LVL and four LVL-C panels (1.2 m × 0.9 m × 12-ply) were manufactured using four different construction strategies by mixing (i) the number of veneers from each species, (ii) the veneer grades and (iii) the veneer orientations (cross-banding). A total of 240 embedment tests, using three different dowel diameters, were performed using the half-hole test method described in the ASTM D5764-97a. This paper compares (i) 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. 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 products. Overall, the mixed species LVL and LVL-C showed significantly higher embedded strengths than only softwood LVL products. LVL-C samples exhibited a very ductile behaviour for all load-to-grain angles and dowel diameters.