Connection Performance of Mass Timber Panels Made from Thermally Modified and Unmodified Strands

Abstract Increasing wildfire risk in the Western United States has driven efforts to utilize small-diameter timber from thinning operations. Developing economically viable products from these materials helps reduce forest fuel loads and mitigate catastrophic fires. One promising approach is producing structural composite lumber and cross-laminated panels using timber strands. However, utilizing this material requires an understanding of the connection performance of strand-based mass timber panels and the impact of thermal modification on strands. A series of connection-level tests were conducted to evaluate the product’s performance, including dowel withdrawal, dowel bearing, and lateral resistance tests. The strand-based panel was tested in both its initial and thermally modified states to compare their performance. In addition, differences between the unidirectional material and a cross-laminated version were assessed. Withdrawal testing indicated that the material’s withdrawal strength was lower than predicted by density but remained comparable to similar engineered wood products. Dowel bearing results closely followed density-based predictions for small diameters but diverged for larger dowels, a trend consistent with other strand-based engineered wood products. The lateral resistance tests confirmed the applicability of the European yield model with predicted values based on dowel bearing results aligning well with lateral resistance results. Overall, few significant differences were observed between thermally modified and control materials, suggesting that thermal modification may effectively mitigate moisture effects without substantially impacting connection performance.