NLT Structural Evaluation in Progress
We understand that North American building codes do not require any special evaluation procedures such as “alternative solutions” when a designer wishes to use NLT as a structural member. In Japan, this is partially true, but the NLT with butt joints requires a different solution. In order to verify if such an NLT behaves similarly to the NLT without butt joints under the bending stresses, a structural evaluation process is required.
COFI and the Japan 2×4 Home Builders Association are jointly working for obtaining a structural evaluation certificate from HOWTEC*, one of the MLIT**-designated performance evaluation bodies. Under the guidance from the evaluation committee members, we conducted butt-joint structural element tests at Gunma Prefectural Forestry Laboratory in Gunma Prefecture on September 24th and 25th, 2019. This was the 4-point loading bending test to the simplified specimens with 3 layers and one butt joint. Specimens were fabricated with 2×12 Canadian SPF and 2×6 Sugi (Cryptomeria japonica). After collecting data, we are confirming if our numerical modelling works accurately on the rotational rigidity at the butt joint. We are targeting December this year by which time the HOWTEC issues the structural evaluation certificate on the NLT with butt joints.