ZIGZAG WALL ABOVE

[ASergio]

Hello Everyone,

Does anyone have an idea of how to best(most economically) design this pick up structure.

As per the attached, there is a concrete wall above with about two stories of load. The wall is long and is supported by multiple supports and is functioning as a deep beam. However for one of the spans there is a zigzag.

Is there a way to continue to design this indeterminant deep beam with some additional calculations? The slab below is currently too thin to support the line loads; ignoring deep beam behavior. Additionally, one could split the indeterminant deep beam into three segments, with the middle "zigzag" cantilevering off the ends of the other two through shear, however the large cantilever spans would led to perhaps unrealistic results.

I have additionally included my thoughts of required additional rebar in the slab above and below, but would appreciate feedback from others.

 

[Tomfh]

Can’t the walls just cantilever beyond their respective columns, with the link wall spanning between them?

 

[HTURKAK]

The left and right deep beams are cantilevers with back spans and the third zigzag one, just transfering tributary slab loads as tip loads to cantilever ends . Your STM model is not clear and additional slab rebars are not meaningful.
The easiest way is , FEM modelling.

...

He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[ASergio]

Hello All,

Thank you for the replies, however as explicitly mentioned in my initial post, I am cognisant that the problem could be decomposed into one simply supported deep beam and relying on cantilever for the primary member.

Though the cantilever bars would resist ultimate collapse, they would not engage until significant cracking occurs. Consider the cantilever is larger and the offset even smaller; surely that would not be the rational approach.

If anyone out there knows how to better solve this I am eager to see. Not sure how to model this in FEM with the software in my possession: ETABS/SAFE.

 

[KootK]

Though the cantilever bars would resist ultimate collapse, they would not engage until significant cracking occurs. Consider the cantilever is larger and the offset even smaller; surely that would not be the rational approach.

You have that backwards my friend. The cantilever option is the way to go precisely because it will be the stiffest load path of those that are available to you. Heed the advice of the experienced gentlemen above.

What you are attempting is to do is to affect a cross diaphragm moment connection between the walls on the opposite sides of the zig zag. It bears some similarity to the virtual outrigger concept: Link. It's a creative solution and there's a theoretical load path there to be had but, ultimately, it's ill advised for the following reasons:

1) It's likely to fall apart on you in the detailing of the connections.

2) The load path that you are proposing will be more flexible than the cantilever approach.