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Re: Inclined Diaphragms

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>Usually, existent software accepts only horizontal diaphragms. Which is the
reason of >this? and how  are considered the inclined diaphragms, for
example, most of the roofs, in >the seismic analysis?

>Thank you

>Alberto Guida

Alberto:

Since you are asking about horizontal diaphragms, I am assuming that you are
dealing with rigid diaphragms (e.g. concrete slab/deck).  Most FEM software
does assume a horizontal rigid diaphragm, and this is adequate for many
cases.  If you are modelling a roof diaphragm, with a slope for drainage, I
would think that assuming it was horizontal would be OK, since the slopes
are typically less than 1/4" per foot.

Now, if you are talking about a pitched roof, with say a 1:3 ratio, then
assuming a rigid horizontal diaphragm would not be all that good of an idea.
You can still model it, though, using shell elements available though a
general purpose FEM program such as SAP2000, RISA3D or (ugh) STAAD.  Just
remember, though, that applying the inplane horizontal loading gets
trickier, since you won't be able to apply the load (or displacement for
that matter) at the centroid of the diaphragm.

Does this answer your question?

T. Eric Gillham PE
GK2 Inc.
PO Box 3207  Agana, Guam  96932
Email - gk2(--nospam--at)kuentos.guam.net
Ph:  (671) 477-9224
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