Affect of Cast in Pipes in a 1m thick Raft Slab on shear

100mm? or 500mm?... 500mm is getting up there... 300mm would be better.

...likely not an issue if you provide added reinforcing to accommodate shear and flexure. Can do a small FEM study to see if any stress risers, but, should be able to reinforce to accommodate this.

Dik

Jlaurence said:

I have read the presence of the pipes can be ignored...

Click to expand...

Pipes can be ignored. If this was not true, buried electrical ductbanks which are lightly reinforced and often subjected to vehicle traffic would be a disaster.

dik, sorry for poor communication 100mm diameter cast in pipes cast in an L shape with 400mm of concrete ontop and 500mm of concrete below (see the section).

There is a 10 storey building being supported on-top of this slab, with considerable loads on some of the columns. In the range of 5000-10000kN (ULTIMATE).

As SRE noted... you shouldn't have any issues, but, you should check stress conditions at the pipes... Try to keep them midway between columns and centred in the mat.

Dik

I agree that the pipes can be ignored as long as they are away from the columns, and at or near middepth.

SRE, I don't see the relevance of your ductbank detail to the OP's mat foundation for a 10 storey building.

hokie - The heavily loaded foundations (including mat foundations) of our electric generating stations are filled with embedded piping (process water, fire protection, lubricating oil, etc.), much of it >>100 mm diameter... no problems, over many decades.

I used the ductbank example since it has a large amount conduit for it's size and is lightly reinforced.
Gets loaded as a beam when a roadway (in our area - with poor soil) settles but the adjacent road shoulders don't settle.
Easy to find a representative picture of a ductbank on the web.

No doubt a better example can be found.

Also, I made my post 8 minutes before the OP told us the foundation was for a 10 storey building.

You'll lose maybe 1/9 of your shear capacity which is surely not a problem unless you've got a bunch of pipes right near a column.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

Thanks for the replies. You have all been very helpful.

Jlaurence:

Join Pat's Pub and buy us a beer... It's hot (somewhere) and we're thirsty...

Dik