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Re: railing design

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seaint(--nospam--at)seaint.org,Internet writes:
i have a handrail that has 1/2" X 1/2" verticals at 4" o.c. with a
nominal flat stock top horizontal.  in applying the code required 200 #
horizontal load what effective width is allowed.  another words how many
verticals can contribute?

another question is, what is the codefied deflection criteria?


I do not know of any specific requirements for the tributary width for the
200# loading condition.  Since the railing is made from individual pickets at
4" o.c. and not with primary posts, my first response would be to check it on
a 1'-0" long section, which uses 3 whole pickets.  If it didn't work, I could
justify to myself expanding it to 1'-4" and check it again because the area
of a concentrated load given in Table 16-A of UBC is 2-1/2 SF which is 1'-7"
square.  If a concentrated load can be distributed out in one table, it
should be able to be done in the other.  You have to use your own judgement
as to how far.  1'-4" would be my personal limit.

Another issue to wrestle with is do you use straight allowable stress design
values, or increase them 1/3 for temporary loading.  The actual load on a
handrail is very short in duration, like a wind load, so you may find self
justification in using an increase in allowable stress, but that is a
personal engineering judgment call you need to make.

I know of no limiting value for deflection.  You will have to let your
judgement be your guide.


__________________________________________________

Richard Lewis, P.E.
Missionary TECH Team
rlewis(--nospam--at)techteam.org

The service mission like-minded Christian organizations
may turn to for technical assistance and know-how.