Cranked concrete beam 1

[hoshang]

Hi all,
What considerations one should take in analysis and design of concrete cranked beams? If my query isn't clear, I can upload images. I searched this forum for cranked concrete beams, but without success.

 

[driftLimiter]

pictures please

 

[hoshang]

Hi
Please find the attached image:

 

[Greenalleycat]

Is this beam taking lateral loads? How much gravity load? Why does it have to be cranked like this?

 

[BHHH]

Are there any columns along that line? Or only along gridline 5?

 

[Just Some Nerd]

Seems like an awfully large cantilever if the columns are as per that screenshot

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Why yes, I do in fact have no idea what I'm talking about

 

[KootK]

What considerations one should take in analysis and design of concrete cranked beams?

1) Torsion.

2) Detailing for flexural and torsional continuity at the knuckles.

3) The impact that #1 and #2 may have on deflection performance.

 

[hoshang]

Is this beam taking lateral loads? How much gravity load? Why does it have to be cranked like this?

This beam is taking lateral loads.
Gravity load: floor self-weight+ light-weight partition+ tile+ floor live load.
For architectural purposes.

Are there any columns along that line? Or only along gridline 5?

The red squares are columns.

 

[HTURKAK]

The contribution of this beam to LFRS will be negligible.. but will help to reduce the deflection of slab..
I would consider this beam as architectural element and provide minimum code specified reinf.











Tim was so learned that he could name a
horse in nine languages: so ignorant that he bought a cow to ride on.
(BENJAMIN FRANKLIN )

 

[jayrod12]

If the columns are only as per plan, then that beam really isn't doing anything but adding load to the outside edge of your cantilever slab. You'd need to have outrigger beams from the columns for it those beams to be effective in the least.

 

[driftLimiter]

Agreed with jayrod12 here. Its more of a rib than a beam unless it has a stiff element to react on at the ends.

 

[HouseBoy]

Agree with jayrod and DL too AND .... I wonder how those stair openings are going to affect the cantilever behavior.

 

[hoshang]

I'm sorry for late answer

1) Torsion.

2) Detailing for flexural and torsional continuity at the knuckles.

3) The impact that #1 and #2 may have on deflection performance.

Thanks. Can you elaborate more on 3?

You'd need to have outrigger beams from the columns for it those beams to be effective in the least.

I'm sorry but I can't catch this.

Its more of a rib than a beam unless it has a stiff element to react on at the ends.

By stiff element to react on at the ends (as per you), is it outrigger beams from the columns (as per jayrod12)?

I wonder how those stair openings are going to affect the cantilever behavior.

In your opinion how those stair openings are going to affect the cantilever behaviors'?
Another question came into mind. Do you think the column layout as per the picture is the best configuration?
Should other columns be added at specific positions?

 

[hoshang]

Hi
I'd appreciate any thoughts.

 

[jayrod12]

So you disappear for a month, come back with no answers or thought put into our recommendations/comments, and then expect an immediate response. That's not how this works.

Based on the questions you're asking, I think you need to have a mentor at your company aid you. We aren't here to design your building for you, but rather here for help on specific issues you're having. Currently your issue seems to be "I don't know how to do any of this design and layout, please do it for me." That's not what we're here for.

 

[dik]

As HTURKAK notes... just added load to the cantilevered slab. If concrete, I'd add control joints at the 'cranked' portions (no torsion).

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[EngDM]

The weight of that beam is only going to make for a heavier slab to pick it up since by the looks of it the beam is completely unsupported and is essentially just line loading the edge of the slab. It might help with the deflection as the slab approaches it but that's about it.

 

[dik]

That's why I noted, "If concrete..."

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[hoshang]

So you disappear for a month, come back with no answers or thought put into our recommendations/comments, and then expect an immediate response. That's not how this works.

I redo my sorrow. I did have my excuses for not being attendant since my last response.

Based on the questions you're asking, I think you need to have a mentor at your company aid you. We aren't here to design your building for you, but rather here for help on specific issues you're having. Currently your issue seems to be "I don't know how to do any of this design and layout, please do it for me." That's not what we're here for.

I'm sorry, but this is not for design. It's here to exchange opinions. In this case, you may recommend adding a column somewhere. Another one may solve the same position without adding a column. So the pros and cons behind each recommendation may be discussed.
dik & EngDM
Thanks for your recommendations.

 

[jayrod12]

I'm sorry, but this is not for design. It's here to exchange opinions. In this case, you may recommend adding a column somewhere. Another one may solve the same position without adding a column. So the pros and cons behind each recommendation may be discussed.

I apologize for my frustration, but I don't think you're quite getting what I'm getting at. We all gave you a bunch of comments/considerations earlier. You haven't done anything with any of those.

Why are you asking about this beam if it's not to help you in the design? I'm just not sure what you're after.