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Re: 1997 NDS Equation Error?

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Mr. Madden I have found the same error in the AITC Timber Construction Manual 4th edition, page 7-448 The
equation is given correctly as per the NDS but the example with numbers extend the square root line as you
had found in the table. Design of Wood Structures 4th edition design examples are per the NDS equation.

The equation is most likely correct. The tables and AITC examples may be wrong. I have not calculated the
answers for the specific problems. We need the derivation.

The k1 k2 and k3 equations are for the modes II, III and IV. The varying capacity solutions are based on the
plus and minus equation that is used to solve for the variable in a quadratic equation. Short of deriving the
equations I see that there must be a term outside of the square root to satisfy the quadratic equation form.
This means that the NDS equation satisfies that requirement if one does not extend the square root line over
the remainder of variables that are now not part of the square root.

See the equation break down on page 6 of "Technical Report No. 12" titled "General Dowel Equations for
Calculating Lateral Connection Values" by "American Forest & Paper Assoc." and "American Wood Council"

David Merrick, SE
Sacramento, Ca
MRKGP(--nospam--at)pacbell.net

>
> --------------------------------------------------------------------------
> 31                               Message:0031                           31
> --------------------------------------------------------------------------
> From: Gerard Madden <gmadden(--nospam--at)duquette-eng.com>
> To: "'SEAINT(--nospam--at)SEAINT.ORG'" <SEAINT(--nospam--at)SEAINT.ORG>
> Subject: 1997 NDS Equation Error?
>
> In light of the anchor bolt design values for wood mudsills thread, I
> created a spreadsheet to calc the values. When comparing the values with
> those of 1997 NDS Table 8.2E, I was noticing that my numbers where not
> matching those for 7/8" and 1" Diameter bolts with 2X mudsills.
>
> The problem lies in the equation for k1 in section 8.2.1 (page 53). My NDS
> shows the Square Root Symbol Stopping short of the -Re(1+Rt) value in the
> denominator. If I include that value within the square root sign, my table
> matches Table 8.2E
>
> Is the k1 equation incorrect or is the table wrong? For 3X and 4X members,
> the mode Zii does not govern and therefore I cannot compare other values
> within the table.
>
> thanks,
> -gerard
>
> Gerard Madden, PE
> Design Group Manager
>
> Duquette Engineering
> 10 South Third Street
> San Jose, CA 95113
> T: 408.494.0944 - ext 102
> F: 408.494.0940
> E: gmadden(--nospam--at)duquette-eng.com
> w: www.duquette-eng.com
>


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