Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: Cold-Formed Joist Lap Splice Question

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Maybe it doesn't need fasteners at all. These are Z sections so one member
bears against the other enforcing deflection compatibility. How is it
achieved? Who cares? Is it broke?

Regards,

Bill Allen, S.E.
ALLEN DESIGNS
Laguna Niguel, CA


> -----Original Message-----
> From: Zachary Goswick [mailto:ZachG(--nospam--at)angusyoung.com]
> Sent: Tuesday, August 17, 1999 2:40 PM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: FW: Cold-Formed Joist Lap Splice Question
>
>
> I have to add a little more to this discussion.  I do not
> think that the
> way that AISI is doing this is the correct analysis.  In order to be a
> continuous beam, the moment must be transferred from the single member
> to the double member and act in the same manner.  Does this
> happen.  The
> way AISI looks at it is as if the beam were a simple member with a
> cantilever end.  Consider the deflection for a moment with
> unequal laps.
> The cantilever end wants to deflect upward due to the load on the rest
> of the member.  In this case it is forced down by the other
> member which
> it laps onto.  The cantilever end wants to deflect
> differently than the
> member that it laps onto.  In order for the cantilever to
> deflect in the
> same manner as the beam it laps onto, the moment must be
> added into the
> splice.  I think the technically correct way to do this analysis is to
> add the vertical shear with the shear in each bolt due to the
> moment(which will vary)and any axial shear that may be involved.  This
> gets into a complicated analysis if you are lapping Z-members because
> the neutral axis shifts where your lap is, especially if you have
> different gauge members.  I used to work for a pre-engineered metal
> building manufacturer.  They considered the beam to be continuous as
> AISI does, but I confirmed it with the Research and Development
> department that it was not the technically correct way to analyze the
> connection.  It is one of those things that has worked for years so it
> is considered to be OK.
>
>