Japanese 2×4 Building Code to Specify High Performance Shear Walls
When designers take the prescriptive design approach for wooden buildings, shear wall multipliers are the indicator that are popularly used to determine the seismic load resistance. In the PFC building code, a shear wall multiplier 3.5 has been the highest value given to a shear wall with 9-mm thick Class 1 JAS plywood sheathing fastened with the CN50 nails at 100 mm spacing. In the past 3 years, MLIT has been reviewing the shear wall ministerial approvals with the multiplier higher than 3.5 and has been seeking the possibility to include those specifications in the code. The reviewed approvals include those obtained by the APA the Engineered Wood Association. As a result, it has been decided to specify in the PFC code the shear walls with the multiplier as high as 4.8. The code revision draft defines 4.8 for the walls with 12mm-thick Class 3 OSB and Class 1/Class 2 plywood sheathing fastened with CN65 nails at 50mm spacing. Using these high shear wall factors would enable the architects to design PFC houses with remarkably higher seismic resistance than currently achievable in the code. It is important to note that shear wall factors approved in the past remain effective even after the new code becomes enacted. The revised code is scheduled to be released in December 2017.