The current interest and growth of cross laminated timber (CLT) products has spurred interest in the manufacture of CLTs in the United States. The purpose of this paper is to explore the development of CLT materials from southern pine lumber commonly available in Virginia. A 5-layer CLT panel has been constructed using No. 2 southern pine lumber. Evaluation of mechanical properties, fire performance and acoustical performance were conducted. Results of these evaluations can guide the development and acceptance of CLT products in the International Building Code.
Sustainable solutions to building construction can help improve material utilization efficiency while providing economic development. This paper focuses on the development of low-grade hardwood CLT made with Yellow-Poplar (Liriodendron tulipifera) as an exemplar species. Analysis programs developed at Virginia Tech (CLT-VT) investigate whether design methods developed for softwood species are suitable for use with the mechanical properties of hardwoods to predict structural behaviour of CLT panels. The CLT-VT programs will include the analytical design methods defined in the CLT Handbook for floor/roof and wall systems, and beams/lintels [1]. The study will assist in further development of a sustainable building product while adding value to under-utilized low-grade hardwood lumber and creating a road map for the production of CLT materials from most every domestic wood species available in the United States.
This study examines if Cross-Laminated Timber (CLT) design methods approved for softwood species can be used with hardwood species, specifically low-grade hardwoods. Analytical predictions from researcher-generated computer programs will be compared to data from experimental evaluations of hardwood CLT. Successful completion will allow for an under-utilized timber resource to be incorporated into CLT production.
Cross-laminated timber (CLT) is a novel wood building material suitable for floor, roof, and wall assemblies in low and mid- rise construction as an alternative to concrete and steel. CLTs are considered to provide good seismic resistance, fast erection times, carbon sequestration, and a significant reduction in greenhouse gas emissions over other construction materials. Southern pine is an abundant forest resource, yet has not been commercially used for CLT manufacturing.
The purpose of this paper was to measure the bending and shear properties of CLT material fabricated using southern pine lumber compared to the ANSI/APA PRG-320 product standard. Bending strength, bending stiffness, shear strength, resistance to shear by compression loading strength, and resistance to delamination were measured according to ANSI/APA PRG-320, and test results were compared to the V3 grade values. Bending tests were conducted on jointed beams due to test length requirements. Bending strength, bending stiffness, and wood failure in resistance to shear by compression loading tests exceeded the published values for the V3 grade, while resistance to delamination did not meet the established criteria. The resistance to delamination results may have been effected by the uncontrolled moisture content of the lumber during fabrication of the CLTs. The application of glued laminated lumber standards to CLT products requires clarification in the orientation of loading directions for the resistance to shear by compression loading test and the measurement of all four sides of the resistance to delamination specimens. Increased scrutiny of moisture content quality control is highly encouraged for the production of CLTs.
