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Shear flow adjacent to web

Shear flow adjacent to web

Shear flow adjacent to web

(OP)
Me and my college mate are looking for an efficient method of calculating shear flow in a large concrete member's 'flange' between two voids, to ensure the whole member still acts integrally. We have two walls (acting as webs) integral with a roof slab (acting as a top flange). See attached.

For simplicity sake, let's say the structure is 10m long, 5m wide and 5m high, with 0.5m thick members all round.

What is the best method in determining reinforcement requirements around these void/s to ensure load is transferred longitudinally and hence the flange still acts 'integrally' with the web, as there is a small disconnect obviously from the web for a short distance. One void is directly on the inside face of the web and the other is a little further in.

Can anyone advise on how to best to check our section is adequate, in terms of shear flow between the voids? If we use a FE model, we could extract a horizontal shear stress, but is this then to be checked against allowable shear stress of concrete? Just wondering where the longitudinal rebar would come into play?

Thanks!

RE: Shear flow adjacent to web

The transfer of shear is generally considered as a uniform linear distribution. You can easily run a FEM model to get a better elastic distribution; at first 'crack', I'm not sure how meaningful, the FEM study will be. I always thought Pom was an adjective.

Dik

RE: Shear flow adjacent to web

(OP)
Hi Dik,

Pom in this context is referring to a person from England (slang term!).

Thanks for the input. Do you have any suggestions on how best to justify the flange is adequately functioning either side beyond the void?

AP

RE: Shear flow adjacent to web

Quote (OP)

Pom in this context is referring to a person from England (slang term!).

...knew that, and, it's generally used as an adjective.

Dik

RE: Shear flow adjacent to web

Quote (OP)

Do you have any suggestions on how best to justify the flange is adequately functioning either side beyond the void?

The holes don't seem to be too substantial and I would run reinforcing on each side of them to match the bars 'cut'. You can do a FEM model that may give you a better idea of the load 'flow' around the openings. The rest of the diaphragm is sufficiently stiff that it will function with the openings pretty much as if it were solid.

Dik

RE: Shear flow adjacent to web

(OP)
Thanks Dik.

I assume by 'cut' you mean the rebar that would otherwise continue longitudinally where the void is - trimmer bars as we call them here!

RE: Shear flow adjacent to web

OP: Yup... A recognised manner of determining the stresses around the openings would be FEM; unless you are challenged on the method, replacing discontinuous bars (cut bars) with an equivalent As is normally the way it is done. Make sure you extend all bars a minimum of 2' beyond the corner. Some engineers swear by diagonal bars at the corner... I almost never use them... just congests the area under high stress.

Dik

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