Hollow Core Concrete Beam Analysis

[HZStruct]

Hello,
I am looking to analyze a rectangular beam with circular void in the middle as a structural member, similar to a ductbank or a pipe encasement. Are there any good design resources that go over analysis of hollow core concrete beam members? Any recommended approaches for analyzing a hollow concrete member?

Thanks in advance!

 

[Greenalleycat]

What are you trying to do with the Hollowcore? Are you in a seismic zone?

 

[HZStruct]

What are you trying to do with the Hollowcore? Are you in a seismic zone?

Yes, in a region with seismic, but unsure why that affects the analysis of a beam with a void. To clarify, the beam would be the encasement and is not a Hollow core plank. The beam would span between supports.

 

[Greenalleycat]

Ok, just want to make sure as Hollowcore flooring generally performs terribly in seismic zones and is a topic of significant scrutinty here

SESOC

www.sesoc.org.nz

 

[KootK]

My approach would be:

1) Execute a flexure design that keeps the compression block above the void.

2) Execute a shear design that uses only the concrete to the sides of the void.

I don't know of any resources that specifically deal with a mildly reinforced concrete beam with a longitudinal void.

There's stuff for HC plank and bridge box girders but both of those situations would be substantially overkill for what you're doing.

 

[Greenalleycat]

I can imagine you'll need a very good contractor to make this work - they'll need to get the steel nice and tidy to match your drawings

 

[HZStruct]

My approach would be:

1) Execute a flexure design that keeps the compression block above the void.

2) Execute a shear design that uses only the concrete to the sides of the void.

I don't know of any resources that specifically deal with a mildly reinforced concrete beam with a longitudinal void.

There's stuff for HC plank and bridge box girders but both of those situations would be substantially overkill for what you're doing.

Thanks for the response. I agree with this approach. After some more research, I am going to check the depth of compression block is above the void. If it is, I would do a typical beam analysis. If the compression block is within the void, I would do a T-beam analysis.
Checking the shear based on the "webs" alone makes sense to me. Thanks!

 

[EngDM]

How are you planning on forming the void? I'd be tempted to stick a steel pipe in there with some nelson studs.