Design of Wood Diaphragms with Openings

Abstract

The existence of openings in diaphragms causes concentration of shear forces around the openings and the generation of axial forces in the framing. In 1981, the Applied Technology Council developed the only guidelines for designing diaphragms with openings. The procedure for determining the shear around the opening, however, is complicated and has not been experimentally verified. Accordingly, simplified equations for determining the shear forces in diaphragms with openings are derived in this paper. The application of the membrane-to-brace replacement method to diaphragms is also discussed. Horizontal loading tests are conducted on three floor diaphragms designed to the same load. The ultimate loads are almost the same, regardless of the existence of the opening. The observed unit shear around the opening is close to the calculated value. The observed deflection is smaller than the value calculated on the basis of the nominal stiffness for the materials and the fasteners by 14–28%. It can be said from these results that all the methods perform well as a practical design tool.