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Re: Cranked Beam supported at blockwalls

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I'm sure it can be done, but I haven't done it.  The torsion translates into simple bolt shear at the wall.  Each bolt will have shear in a different direction.  The AISC manual has a similar treatment for bolts in a shear-tab.  All that said, why not simply header off the span?  Run a beam from wall wall 2 to wall 3.  And then one from wall 1 to the previous beam.  You can then cantilever over the second beam (see below).

    __________________________<wall 1
|                    |                       |
|        _______|_____________|
|        |            |      ^cantilever |
|        |            | < wall 1 to beam1
|____ |_______|____________ |
|             ^beam 1 (wall 2 to 3) |
^wall 2                                    ^wall 3

You didn't give dimensions, this may not be practical.

Good luck,

Jake Watson, S.E.
Salt Lake City, UT

On 4/15/07, refugio rochin <fugeeo(--nospam--at)> wrote:
I have a scenario that I am losing sleep over.
So, I think I would like some opinions from the "been there done that" peoples.

Between two perpendicular wall segments, sketch below

__________________________<wall 1
|                     |                       |
|        _______|                        |
|        |     ^                              |
|        | <  cranked beam           |
|____ |                                    |
|                                             |
^wall 2                                    ^wall 3

there is a cranked beam (torsion beam).  Between the cranked beam and
wall 3 is a floor, suspended by the cranked beam and the wall.  In
between the cranked beam and wall 2 is a stair. which lands at the
portion of the cranked beam terminating into wall1.  total length of
wall 1 is about 28 feet.  the stair lands about midway.

the floor uses office live loading 50 psf, and is a joist and deck floor.

Now, wall 2 ends just past the beam and also has a beam landing on it
supporting one wall of load and a roof and one floor length. of the
same joist and deck floor.  It is a 12" solid grouted block wall below
into an 8" block wall above.  The wall 1 is an 8" block wall solid
grouted below, into an 8" block wall above.

Now, I can design a beam internally to the walls which takes the
cranked beam ends and the torsion loads.  However, my main concern is
what the blockwalls can take.  I can provide the beam loads tomorrow
morning.  My calculations show it can be done, but perhaps I am
missing some elements of surprise...  I am happy to share my calcs
with an engineer that would be so happy to gander and give me their

cranked beam size:  10"x 24" with 4 #5 bars top and bott, and 4
intermediate #5 bars spaced in pairs...  wall 1 beam is 8"x 48"beam w/
14 #5 bars and #3@3"o.c. stirrups.  wall 2 beam is a conjoined beam
12"x 26" beam + 8"x 16" beam.  The 12x 26 beam has 4 #5 bars top and
bott and 4 intermediate #5 bars and the 8x16 portion has 8 #5 bars
which round it out.  there are two sets of #3@3"o.c . stirrups which
are overlapped about 8 inches.

Best Regards,
Refugio Rochin

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