Down pipes cast in concrete columns

[pwht1]

Hey all,

I've been asked to design a 700 long by 300 wide column (4.5m tall) with a 150 diameter down-pipe cast in the middle. This scenario seems a little odd to me but hey that's architects. Anyhow, I have no problems with do the basic moment/axial analysis and checking the reduced web shear capacity. I was just wondering whether anyone had done anything similar and come across any shrinkage/restraint issues due to the PVC pipe?

Thanks

 

[hokie66]

Restraint should not be an issue in a 4.5 metre tall column. Personally, I hate downpipes inside columns, for a variety of reasons, mostly to do with maintenance of the stormwater system. If you are forced into this situation, I think a 150 diameter downpipe deserves a larger column than 300. That only leaves 75mm maximum concrete over the pipe. You should consider how the pipe gets into and out of the column, as those details are often overlooked until the plumber botches things on site.

 

[csd72]

I agree with hokie, thats a big downpipe for a 300 column, even a 100 downpipe would be tight.

The problem is not so much the actual analysis but rather the compaction of the concrete in such slender sections.

Ensure cover to the downpipe is at least the same as everywhere else.

There may be fire rating issues with such thin parts.

Also if this is in a seismic area then this takes out a very big chunk of your confined concrete.

Not saying that this sort of thing cannot be done just that you need to consider everything, including those things that you normally take for granted.

 

[a2mfk]

Depending on your finishes and your axial load requirements, maybe you can talk the architect into using a steel column and then wrap the column and drain pipe in a fiberglass faux cover that can be stuccoed. Worse case scenario if they have to repair the pipe its not too bad to have to cut that out and replace it versus concrete.