Bending capacity of pipe: Conversion from degrees/100 ft to kNm

[julian89]

Hi all!

I simply wish to convert a given bending capacity given in degrees/100 ft to kNm. How to do that?

Thanks!

Jules

 

[JStephen]

It sounds like you're converting a deflection to the applied moment that is required to cause the deflection?
The problem could be interpreted different ways, and it's unlikely the deflection is generated by a pure moment.
Regardless, it's a strength-of-materials beam design problem, approached by integration of the moment equation or reference to beam deflection equations in Formulas for Stress and Strain or other references.
Also note that for pipe with mechanical or push-on joints, the deflection may be accomplished at the joints rather than in the pipe.

 

[SnTMan]

What do you suppose is meant by "bending capacity"?

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[julian89]

@SnTMan, I'm actually not quite sure, but I think it's defined as the onset of yielding in the outermost fibre.

Simply put, I have been given data where the bending capacity (in pure bending) is given as 50°/100 ft. How to convert this to MKS units?

Jules

 

[SnTMan]

julian89, ahh, MKS units: 50deg / 30.49 m

No offense intended, but how do you think it is possible to do meaninful calculations on ill-defined quantities?

Maybe you'd have better luck in the piping forum: forum378

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[JStephen]

Do you actually know what the quantity is?
If not, some context would be helpful.
The "50 degrees/100 ft" sounds like how much you can bend the pipe into a curve (and that sound like pretty small pipe, maybe PVC or something). To convert that into metric units, you convert degrees to radians and feet to meters, and you'll have a value in radians/meter or whatever. If you don't know what that number means now, then you won't know what it means afterwards, either, but it'll be in different units at least.

See this page where they show "Therefore: Curve per 20’ length = 5.73°":

http://www.jmeagle.com/what-jm-eagles-recommended-curvature-its-gravity-sewer-pipe

This page shows minimum bending radius for a line of pipe products:

http://www.heritageplastics.com/technical-bulletins/longitudinal-bending-pvc-pipe/

And similar information here:

http://www.northernpipe.com/downloads/PipeDeflection.pdf

 

[julian89]

Thank you for replying guys,

I think I got it right. In my mind this was just a simple material mechanics problem concerned with converting the curvature/radius to bending moment. This can be done like so:

Should have posted this to the piping forums, my apologies.

Jules