Technical Approaches to NLT in Progress
Subsequently to establishing an NLT technical committee in April 2018, COFI and the Japan 2×4 Home Builders Association has been working together on several Nail Laminated Timber (NLT) test programs. One technical project is to confirm NLT bending performance. From September 5th to 12th 2018, a series of bending tests were conducted at the HOWTEC* laboratory to NLT beams. The test specimens consisted of 2×8 and 2×10 SPF with 8m span (with butt joints), 2×6, 2×8 and 2×10 SPF with 3.7m span (without butt joints) and 2×6 Sugi with 3.7m span (without butt joints). The main objective of these tests was to accumulate basic data for the future evaluation by the MLIT** designated bodies. The project leader is the renowned University of Tokyo professor Dr. Inayama, who developed these tests after a thorough review of the Canadian Design & Construction Guide of the NLT, published by the Binational Softwood Lumber Council and Forestry Innovation Investment. Dr. Inayama pointed out that the key element of the bending performance evaluation is to analyze the mechanism of bending stress transfer across the butt joints. Additional NLT technical work is being conducted to confirm fire resistive performance. The final test for the performance evaluation (seeking Ministerial Approval for fire resistivity) is scheduled in mid-November. As reported in this blog on August 23, 2018, the fire resistive approval is the key to promote NLT after the Japanese Building Standard Law is amended in 2019.
*HOWTEC: Japan Housing and Wood Technology Centre
**MLIT: Ministry of Land, Infrastructure, Transport and Tourism