When evaluating the racking load of a plywood-sheathed shear wall of North-American type wood framing, considering the effect of wall parts above and/or below the door and window openings, all the calculation methods proposed by R.L. Tuomi and others in the past seem to troublesome. Therefore, we propose a simplified calculation method based on the following two assumptions (Fig. 1): (1) Only the component in the direction along the perimeter of a plywood-sheathing is considered for the slip resistance of each nail, whereas the component perpendicalar to the perimeter is neglected. (2) Slip resistances of nails at intermediate studs are negligible. In this paper, we compare the values, estimated by our method, of the racking load of a wall unit without openings with the results of full-scale and 1/3-scale tests, and with the values estimated by other methods to determine the accuracy of the values calculated by our method. Conclusions: (1) With the simple assumptions, our method estimates slightly smaller values of racking loads than those by other methods. (2) However, when using an exponential equation as the relationship between shear force and slip in nails, our method brings about the best agreement with the test results. This seems to indicate that our assumptions are not inappropriate. (3) We think that a bilinear equation might make the analysis of plywood-sheathed walls with openings easier than an exponential equation. Although our method estimates a slightly smaller racking load than that in the test when using a bilinear equation, we think that our method might be more useful than other methods estimating larger values than the tests.
