Revision of Shear Wall Multiplier Notifications
Under the prescriptive building code in Japan, seismic resistivity of shear walls is indicated as shear wall multiplier in MLIT* notifications. As for the wall specifications not listed in the notifications, building material manufacturers and housing companies obtain numerous ministerial approvals for their own respective shear wall multipliers. Those approvals are reflecting the strong demand in the industries to use shear walls not listed in the notifications. The building guidance division of MLIT has therefore started a technical survey aiming to revise the notifications by expanding the wall variations. The survey includes the shear wall tests that MLIT asked housing industry associations to conduct. Japan 2×4 Home Builders Association, for instance, recently tested a plywood-sheathed shear wall fastened with longer nails at a narrower schedule than in the notifications (photo). Another benefit of revising the notifications is to apply so-called “summation rule” of the multipliers. The summation rule allows the designers to calculate a shear wall multiplier by summing up two different multipliers; i.e.) 2×4 wall sheathed with Class 2 JAS plywood (multiplier 3.0) + gypsum board (multiplier 1.1) = 4.1. This rule does not apply to some of the approved multipliers** but to those in the notifications. Once the notifications are revised, designers will benefit from wider array of shear wall variations wherein multipliers can be added to one another.
Note: *Ministry of Land, Infrastructure, Transport and Tourism
**Summation rule can apply for OSB sheathed shear walls approved for APA