Filling the Knowledge Gaps in Mass Timber Construction.

2023-07-14T19:18:29+10:00

As mass timber construction evolves from a niche product to a mainstream, there is an urgent need for focused research activities to support the industry and avoid duplication or overlap of work being done internationally. To identify and prioritise the future of mass timber research agenda, this article pursues responses to the following questions: What is the current state of knowledge and where are the remaining research needs in mass timber construction? For example, newcomers to mass timber often believe it is imperative to research fire performance, fire resistance, or sound transmission when these areas have been extensively explored and are now widely seen as resolved. Consequently, the focus has shifted, towards answering new research questions, including explorations of carbon storage, and life cycle analysis durability. There is already a growing research activity in mass timber, involving several research centres worldwide, that would benefit from some guidance on research needs. Thus, defining new trends and research gaps that help avoid replicating research. A more nuanced discussion on knowledge gaps and industry research needs is also timely, to truly capture and disseminate information on the full potential of engineered-wood products as an innovative construction material, which helps reduce the use of carbon-intensive conventional building materials. To answer the above-mentioned research questions, this study has consulted experts at an international conference, and seven key research areas have been identified and presented as the results.

Evaluating the Effect of Inner Layer Grain Orientation on Dimensional Stability in Hybrid Species Cross- and Diagonal-Cross-laminated Timber (DCLT)

2023-08-11T14:38:42+10:00

Wood deformation due to moisture adsorption and desorption in the cell wall components challenges the dimensional stability of multi-layer wood-based panels. This is a common issue in timber products with single board products and parallel glued layers (such as Glued-laminated Timber; GLT). Orienting the inner layers of timber products at an angle, like plywood and Cross-laminated Timber (CLT), with the perpendicular (90°) orientation of the inner layers, helps minimize overall shrinkage and swelling of the composite panel. However, due to the perpendicular orientation of the layers, Cross-laminated Timber (CLT) exhibits a lower out-of-plane bending stiffness than a parallel-layered Glued-laminated Timber (GLT) panel. An optimized modified orientation of the inner layers in a diagonal direction could improve dimensional stability compared to GLT while developing a better structural performance than CLT. This study evaluates the dimensional stability of small specimens of four-layer Diagonal-Cross-laminated Timber (DCLT) with a hybrid layup consisting of a high-density hardwood species, black locust, in the top and bottom layers, and a low-density softwood species, eastern white pine, in the asymmetric inner layers. The results show that increasing the inner layer fiber orientation angle improves the dimensional stability of the panels. While the dimensional change in the length of the panel (longitudinal) is negligible, by varying the inner layer angle-ply from 0° to 90°, the percentage changes in width (tangential), thickness (radial), and volume reduced respectively from 3% to 0.8%, 1.6% to 0.4% and 5.1% to 1.3%. Since the dimensional tolerances of the CLT due to the moisture content in the manufacturing process and the in-service conditions have already been established in the design and building standards, the result of this study can be helpful for the construction industry to predict the potential dimensional change (%) and corresponding required tolerances for DCLT panels when used in building structures.

Mass Timber Construction Journal

Filling the Knowledge Gaps in Mass Timber Construction.

Evaluating the Effect of Inner Layer Grain Orientation on Dimensional Stability in Hybrid Species Cross- and Diagonal-Cross-laminated Timber (DCLT)