Metal pipe stiffness.
Metal pipe stiffness.
(OP)
Could anyone inform me how to calculate the pipe bending stiffness and pipe hoop stiffness for metallic pipes. I have found formula's for the above but the reference material I have suggests that these formula's are for non-metallic pipes. Please help.





RE: Metal pipe stiffness.
Actual collapse loads may depend on out of roundness or other mechanical factors for which different materials may have different tolerance values.
Can you furnish more information as to what formulas you have and what exactly it is that you are actually trying to accomplish with your formulas?
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Metal pipe stiffness.
I would complete the analysis in general terms, place a theoretical distributed load across the span and do the Bending Moment Diagram. Given the strength of material, you can easily derive an expression for shear, bending moment and deflection based on geometry of the pipe and the theoretical load.
Try finding a textbook from first year engineering static courses. Typically such a problem is worked out in detail from first principles as an example.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Metal pipe stiffness.
Go to www.standards.org.au and invest.
Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng
www.waterhammer.bigblog.com.au
RE: Metal pipe stiffness.
Pipe bending stiffness = EI/(0.139r^3)
Where:-
E = pipe material modulus of elasticity
I = pipe wall moment of inertia per unit length.
I found this in reference material for thermoplastic piping. Nowhere in the reference material is pressure mentioned. Would applied pressure affect the pipe bending stiffness significantly? Obviously there would be some effect but at this time I am unaware of how much.
RE: Metal pipe stiffness.
The "I" value for a pipe assumed to be circular would be
"I"= Pi* (Do^4-Di^4)/(64)
where Do=outer diameter of pipe
Di= inner diameter of pipe
hope this helps
regards
desertfox
RE: Metal pipe stiffness.
I think the bending would come from the weight of the pipework not the internal pressure.
If one asssumes that a straight pipe subject to equal internal pressure is supported on simple supports all I can see is that the forces due to pressure would cancel out and your left with the weight of the pipe to cause sagging between the supports or am I missing something?
regards
desertfox
RE: Metal pipe stiffness.
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com
RE: Metal pipe stiffness.
True but we need to establish that.
Regards
desertfox
RE: Metal pipe stiffness.
Every bit of information that comes through makes the muddy water clearer. The problem that I am trying to solve is transverse to the pipes longitudinal axis. However the X setion of the object for which I am trying to solve is more like a c section. A pipe with strengthening flanges if you will.
RE: Metal pipe stiffness.
I believe you are also correct in your hunch that flexible pipes can become in effect stiffer when they are pressurized, and maybe even able to carry more ring or other load in this condition; however, I believe this strengthening effect is most often ignored in many basic designs (after all, pipelines must initially in many cases carry loads before they are pressurized, and also commonly become de-pressurized at times thereafter.)
RE: Metal pipe stiffness.
If you just had a point load at the top of an arch, M = P * e/2, E according to your material and I according to your shape "U" in a cross section a-a, you'd have something like this,
bending stress would be M * c/I and deflection would be M/EI.
The other bottom half of the pipe would tend to reduce M and the deflection by allowing Fr and Fl to be greater than zero, so this Moment calc. is a bit conservative.
BigInch
-born in the trenches.
http://virtualpipeline.spaces.msn.com