Mechanical Characteristics of Custom CLT Layups Laminated by Ponderosa Pine Harvested from Restoration Programs
Abstract
National forest restoration programs aimed at effective mitigation of catastrophic wildfires and pest outbreaks in Western region of the United States yield a substantial amount of small diameter Ponderosa pine logs. Lumber produced from these logs is considered low-value due to lower mechanical properties compared to commercially harvested lumber. US Forest Service is seeking a value-added market for this material to offset the high costs of the forest restoration operations. Cross laminated timber (CLT) is considered one of the potential markets for the material. This study was a part of a larger project aimed at determination of feasibility of utilizing CLT fabricated from restoration harvested Ponderosa pine in a class of low-rise modular mass-timber construction. A CLT layup was designed based on the design requirements of a modular construction system determined in a parallel study. The mechanical characteristics of that layup were empirically verified through mechanical tests on prototype panels, three fabricated at a pilot-plant line at Oregon State University and two at an industrial manufacturing line. In all prototypes, grades No. 1, 2, 3 and ungraded laminations were assigned to all layers randomly. Standard ASTM D198 methods for long- and short-span flatwise bending tests were conducted to derive effective moment capacity, effective stiffness, and shear capacity of the layups. Optical measurement based on digital image correlation was used to derive effective shear rigidity of the specimens. There was no significant difference between the results obtained from the prototypes fabricated in the pilot-plant compared to those fabricated in an industrial setting. The outcomes of mechanical tests indicate that the prototype CLT panels exceeded the structural requirements. The effective moment capacity, stiffness, and shear rigidity were higher than the values estimated by the shear analogy method. Shear capacity was lower than predicted. It is concluded that the restoration program PP CLT layups can be custom designed to meet mechanical requirements for structural elements in certain class of modular buildings.
Downloads
Published
Issue
Section
License
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.
