Coupling Beam- ShearWall 1

[Akhilkp]

Hi All,

I would like to know your views about the coupling beam design and coupling shear wall connection.

i am having a stair core as shown below screenshot.

Do you think a coupling beam between two walls as shown in the images are good?

I believe that since the walls are out of planes, coupling between these walls are not a good idea. Do you agree or not ?

(However i have to provide a beam to support the slabs. And it can be as deep as 1200mm).

Is openings / Sleeves are allowed to provide in the coupling beams ? If yes , where is the ideal location and approximate allowable sizes ?

Any comments and tips are really appreciated

Thanks
Akhil

 

[KootK]

I'd use the coupling beams but treat them as though they cantilever from CW5. That will make for some delicate detailing at the free ends of the cantilevers. I think that the best location for penetrations would be midheight of the beams at either end of the beams. Top centre and bottom centre would be my next choices. Essentially, you're trying to avoid the diagonal compression struts that will form in the beams.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Akeee]

Because of CW5 is a full wall you will not have a lot of stress/force in you bottom coupled beams like the level expected in this kind of elements because the hole core/tube cannot deform as much as usual one's. This is because the tube is not "broken" in two parts of C walls sections that bend and rotate the beams that connect them, here if only you have a lot of torsional moment in the core maybe your beams will have some moment and shear force in them but i cant tell that if i dont see the full formwork plan.
About the location i agree with KootK, somewhere in the midle will be fine, you have to ancorate the reinforment from the beam so i will suggest at least 1 m left or right of RC wall.
How high is the building ? Number of story's? beucase from what thickness you have there is at least 10story tall building.
Let me show you a example, this is a central core of a 12 story building, PGA 0.30g:

Now this are the bending moments in the bottom RC coupled beams from E-V earthquake attack:

As you can see there are almost none bending moment.

Now in the same building lets look at this:

These are 2 isolated walls with RC coupled beam in the same direction as the one above.

As you can see is a big difference between 20 and 350 kNm bending moment.

Try it for youself in your case and tell us what you found out.

 

[Yt.]

Without experience, i may say that this coupled beams may be controlled by shear and the openings at the beam may need a strut and tie approach. If the beam result over demanded it will act as a energy dissipator if it's properly anchored.