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RC beam supported on a Deep beam

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greznik91

greznik91

Structural
Feb 14, 2017
186
I have a RC deep beam - B1 in attached image (dimensions: b/h = 300/1800 mm)
I have a standard beam - B2 in attached image (dimensions: b/h = 300/600 mm)
Both beams are connected with RC slab as shown in image.

Beam B2 is supported on deep beam B1 - 1 m away from B2 support. Beam B2 is heavily loaded, so design reaction Rd on deep beam is large (approx. 300 kN)

Im wondering how should I do analysis and what to consider. I dont want to overlook important things.

I know I should also add extra stirrups = 'hanging reinforcement' in an area of B1 where B2 is supported.

What do you think about my deep beam model?

Thoughts?

dbeam_kf2n6m.png
 
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I'd just consider making it a normal beam with a thinner 'wall' over if your typical beam width can be accomodated. But otherwise I don't see any issues with what your are proposing from a gravity load perspective. Code deep beam provisions usually state some minimum level of reinforcement in both orthogonal directions over the full depth of the deep beam, vs reinforcement concentrated at the base that might come out of using a strut and tie model like shown.
 
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OP said:
I know I should also add extra stirrups = 'hanging reinforcement' in an area of B1 where B2 is supported.
Click to expand...

Yup, I also consider that to be the thing of most importance here. The best technical answer for the design of the deep beam is strut and tie of course. I'm a realist though. I'd accept something simpler and faster like the reduced lever arm method if it were my stamp going on this.
 
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I'd personally do strut-and-tie as this should be a relatively simple setup for the model and makes a good exercise in S&T design if it's not something you break out regularly.

KootK said:
reduced lever arm method
Click to expand...

I'm not familiar with this term but I think I know what you mean. Are you basically considering that the wall is just a non-deep beam and designing it accordingly?

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
 
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TME said:
Are you basically considering that the wall is just a non-deep beam and designing it accordingly?
Click to expand...

What you're doing is acknowledging that a Bernoulli assumption would produce a non-conservative flexural reinforcing demand and compensating for that by using a reduced flexural lever arm based on analogous elastic models. Toss in a few detailing measures and you've got a design that's nearly as reliable as STM at 1/10 th of the design effort. I my opinion, hand calculated strut and tie is a bit overkill for a problem that isn't much fancier than "deep beam". A guy's gotta justify his fee/existence after-all. The concrete codes of most jurisdictions contain explicit provisions for this.

c01_ixiudo.jpg
 
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