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Re: Plywood shear wall, nailing, deflection
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- Subject: Re: Plywood shear wall, nailing, deflection
- From: <Mlcse(--nospam--at)aol.com>
- Date: Thu, 16 Jul 1998 04:11:02 EDT
In a message dated 98-07-15 11:26:05 EDT, you write: << Assuming the shear to the wall is 2.79 kips.Uplift does not exceed 4.5 kips and so I am planning to use one Simpson Strong-tie's PHD5 holddown at each end. The header is a 5-1/8"x12 glulam beam. To minimize the drift I am planning to using with 8d at 3" BN o.c. Here are the values I used to calculated the deflectoin: max shear = 443 plf height = 8 ft width wall = 6.4 ft chord member area = 19.25 in^2 da = 0.047 in en = 0.023 in effective thickness of plywood = 0.535 in E, chord member = 1700000 psi G, plywood = 90000 psi Here is the result: deflection = 8*v*h^3/E*A*b + v*h/G*t + 0.75*h*en + h/b*da deflection from bending = 0.00866 in. 1.46% deflection from shear = 0.0736 in. 12.4% deflection from nail slip = 0.453 in. 76.2% <<------- deflection from holddown slip = 0.0587 in. 9.9% sum of deflections = 0.594 inches This deflection is still exceeding the drift limit. But I used Rw=6 not 8 to calculate the base shear. I have two questions: 1) Why is the nail slip accounts about 3/4 of the total deflection? 2) Do I need to require pre-drill the nail holes (4xs) to prevent the nail splitting the 4xs? Thanks Sam Chang, SE Cupertino, CA >> Sam, Double check your math; I get 0.75*h*en = 0.75 (8)(.023) = 0.138 <<< 0.453 Revised drift = 0.2789" << than .005h = .005*8*12 = 0.48 inches. You may want to use 10d commons since they have less slip than the 8d and I would not worry to much about splitting the 4x6 posts. In your drift calculation, remember that the the equation is for a statically applied load. Some sources recommend that you use a 1.25 multiplier to account for the approximate cyclic deflection. Michael Cochran
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