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FW: FW: Reinforcement detailing in coupling beam

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-----Original Message-----
From: T. Eric Gillham PE [mailto:teric(--nospam--at)]
Sent: Saturday, October 27, 2001 11:34 AM
To: seaoc list
Subject: FW: FW: Reinforcement detailing in coupling beam

This message is too long to be posted to this list.


This sounds like a complicated situation - you say the steel column is
EXISTING?  What about the walls?

Short span R/C coupling beams have diagonal struts because the span to depth
ratio is such that compression and tension struts form between the walls in
the beam and dominate the behavior of the beam such that flexural action is
pretty much non-existent.

This being the case, you are essentially designing diagonal "columns", and
hoops spacing and detailing is a must if satisfactory peformance is to be
relied upon.  This also goes for the development of the main strut bars,
since they will yield in both tension and compression - in fact, as far as
development lengths for these bars into the abutting walls, I usually go at
least 1.2 times any UBC development length requirements.

This being the case, CONTINUOUS diagonal strut bars are required - they
cannot be cut and hooked any more than the vertical bars in a ductile R/C
column could be cut and restarted.

I am still confused as to the situation.  Is the wide flange section
required for carrying load across the opening, or are there other steel
elements (beams) framing into the existing WF col and that is why you wish
to keep it?

Perhaps if you gave some idea of the span of the opening, and whether the
walls are existing or not it might help.  If the walls and WF are existing,
it will be tricky indeed, since developing the diag strut bars (see above)
would require demolition of a rather large chunk of the existing wall and
repouring of it after the diag struts are installed.

Another way to look at it is whether the coupling beams are actually
required.  If you are cutting an opening in existing walls, can you get by
with just the cantilever action of the newly created (from 1 you are getting
2) walls?  If not, you may even want to look at using a steel coupling beam
anchored by thick plates at each wall end secured with a bunch of through

I'm having difficulty formulating a response, since I still cannot see the
picture quite clearly enough.



-----Original Message-----
From: Fariborz Tehrani [mailto:fmtehrani(--nospam--at)]
Sent: Saturday, October 27, 2001 10:26 AM
To: seaint(--nospam--at)
Subject: Re: FW: Reinforcement detailing in coupling beam

Thanks for your email and comment.
Here are some more information on this situation:
The steel column is existing WF10 and the wall
thickness is 18" at the lowest level and 10" at the
highest level.
The span is shorter than 4 times the beam depth, so
coupling action is applicable.
It's also notable that the steel column is at the
middle of the opening.
This column has not designed to carry any load other
than gravity. However at this situation, interaction
might occur between the coupling beam and the column.
Now, what would be happened to diagonal rebars? Shall
I transfer shear loads to the steel column? And in
that case, may I cut diagonal rebars at the column web
and provide standard hook or other means of
Thanks again for your help,

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