Flexural and shear performance of CLT panels made from salvaged beetle-killed white spruce

Abstract

This study aims to investigate the feasibility of CLT panels fabricated from salvaged dead standing trees after the beetle outbreak by evaluating the flexural and shear properties through mechanical tests and computational analysis. White spruce (Picea glauca (Moench) Voss) lumber salvaged from the dead and dying trees resulting from recent spruce budworm (Choristoneura fumiferana (Clem.)) activity were used to fabricate Cross-laminated timber (CLT) panels of three categories in terms of tree conditions: Category I─ live; Category II─ recently dead; and Category III─ dead for some time. A total of 17 three-layer CLT panels measuring 107 × 610 × 2438 mm were fabricated, 5 for Category I, 5 for Category II, and 7 for Category III. The CLT panels were tested with the third-point and mid-point bending tests following ASTM D198 for major-axis flexural and shear properties. The results indicated that the deterioration of dead, dying standing trees resulting from the budworm activity reduced the average bending strength and shear modulus of the CLT panels. The bending stiffness of the panels was not significantly affected. The CLT panels made from salvaged spruce lumber provided adequate flexural performance per current standard PRG 320–2019. The finite element model built with orthogonal constitutive law and progressive damage criteria simulated the flexural behaviors of the tested CLT panels. The model input modulus and strength were calibrated based on the tested MOE of laminations. The simulation results compared favorably with test data and provided reasonable estimates. The results of this study suggest that CLT panels fabricated from salvaged beetle-killed spruce satisfied the baseline performance requirement of the PRG 320 standard.