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Re: What a Structural Engineer Should Memorize

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A couple of quick extras:

An inch of 3/16" weld will hold about 2.7kips
concrete shear allowable w/o stirrups is about 25psi
unreinforced concrete has a bending stress of about 250psi
a collar tie 1/3 down from the ridge of a roof will halve the allowable span of the rafter
Drift loads for 25-30psf ground snow are almost never less than 60psf, nor more than 100psf
If the contractors lips are moving, he's lying about something on the job site.

Dave Adams wrote:
Hello list,
I've been compiling a list of facts & tidbits that I believe structural engineers should commit to memory in an effort to bolster an ability to think on their feet when confronted in the field or receiving that emergency phonecall.  Things that give a good "global" picture of what solutions might be practical for a given situation before actually running numbers.  These bits of information are never intended as the means & ends, but basically a starting point for discussing possible solutions to a problem.
Some of the things that I've got on my list include:
1.  The basic allowable shear value of ONE 16d common nail in Doug Fir is about 140 lbs.
2.  The basic allowable withdrawal value of ONE 16d common nail in Doug Fir is about 40 lbs/inch of penetration.
3.  The basic allowable single-shear value for ONE 5/8" diameter A307 machine bolt for a steel-to-steel connection is about 3 kips.
4.  The total wind pressure for a single-story building design in 70 mph/Exp. C is about 20 psf.
5.  The total seismic design load in UBC Zone 3 for a wood-framed building will be about 0.30*W.
Obviously there are other considerations, such as the fact that toe-nails and end nails must have their allowable values reduced, but the purpose of the list is just to give us a BASIC starting point for thinking through s solution to a field issue.  The final numbers are rounded off and I felt that the lateral loading figures should be bumped up a little when thinking a solution through.  There are certainly many more bits of info that are helpful to commit to "quick-recall" memory and I'd like to hear if anyone else would like to contribute to the list.
Dave K. Adams, S.E.
Lane Engineers, Inc.
Tulare, CA

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