MLIT Releases CLT Design Guide Draft
February 8th of this year, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) released a draft for CLT design stresses, structural design guide and char margin for fire safety. After MAFF*1 established the CLT material standard (JAS3079) in 2013, MLIT and the Forestry Agency announced the CLT roadmap in 2014. Compared with the cases where the other new building elements are accepted in the building code, the road map assumed quite an accelerated schedule. The photo shows the full-scale shake table test conducted at E-Defence*2 on January 19th this year. The objective of this test was to collect the structural safety criteria for drafting the design guide. However, nobody predicted at that time the design guide draft would be released this quickly. The draft excludes the prescriptive approach, but stipulates the structural calculation procedures that would allow engineers to follow without doing the time history response analysis which is quite a time and money consuming approach. The data for assigning the design stresses have been collected at the laboratories of BRI*3 and FFPRI*4. Char margins were proposed in this draft so that the CLT buildings can be categorized under “Quasi Fire Resistive Structures”. After the public comment procedures, the design guide is scheduled to officially be announced in April. COFI Tokyo sent a comment that MLIT should establish a scheme to designate overseas CLT. This is because the draft requires the CLTs either be graded to JAS or be approved under Article 37 of Building Standard Law. Article 37 approvals are famous for its high costs and time consuming procedures.
*1 Ministry of Agriculture, Forestry and Fisheries
*2 World-largest 3D shake table facility in Miki City, Hyogo Prefecture
*3 Building Research Institute
*4 Forestry and Forest Products Research Institute