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Re: Story Drift: 1994 UBC vs. 1997 UBC

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Bill,
I reviewed your calc's on your website and have the following comments:

1. When I created this model in Excel I found that the units of the terms do 
not balance. The first term, for example, 8fvh^3/EAb is not intended to be 
converted to comparable units as Mathcad would do automatically. This is one 
of those examples that I wrote about in the Mathcad / Excel Thread.  
I received a number of responses to my previous threads as to how the units 
balanced and one or two list members sent me a complete breakdown as to how 
to the Algebra from 5wl^4/384EI converted to this formula above. The problem 
was that Mathcad converted the units which inflated the results - the results 
should be in the following units:
fv = psi
h = ft
E = psi
A = in^2
b = ft
The inclination is to convert feet to inches and, in this case, would inflate 
the answer by a factor of 12.

The next issues is the Load per nail that you use. This should be the actual 
nail load based on the actual shear in the panel rather than the allowable 
capacity of the plywood - therefore, your load per nail should be somewhat 
less. This is moot since you might be assuming that your demand is equal to 
your capacity in this example.

I might be wrong on this one, but the t for a non-structural grade 3/8" thk 
panel should be 0.298" rather than 0.373. I did not take the time to check my 
spreadsheet, but this is what I get off the lookup tables. Again, I might be 
the one who is wrong here.

The nail elongation term is another one where the units are not suppose to 
balance. the results are to be in inch-feet but assumed inches. Again, this 
is an emperical formula and nobody to date has been able to tell me why 
constants of 1/feet was not used to clarify this. This might yield an error 
of 12 times in Mathcad.

If you are interested in the translation from the normal simple span 
deflection formula to the first term of this deflection formula (the 
deflection in the chords) I can provide it to you.

Let me know if I have made this clear - I think others are making the same 
mistakes.

Dennis