Combined axial loading and pressure induced stresses
Combined axial loading and pressure induced stresses
(OP)
I have an application where a vertical tube (2 in OD) is subjected to combined presure and axial loading. At one point, the tube has an opening for a branch (also of 2 in. OD) to form a tee. This tee is of a welded construction and formed from tubes. How do I analyse the effect of the opening?





RE: Combined axial loading and pressure induced stresses
RE: Combined axial loading and pressure induced stresses
stress1 = (F/A) + pressure + [i * (Mbending / Z )]
stress2 = (F/A) + pressure - [i * (Mbending / Z )]
with:
1/ F = axial force , > 0 , if tensile and negative if compressive.
2/ i = stress intensification factor , between 1 to about 5. (But there are tables in B31.1 or B31.3)
3/ Mbending = total bendig moment,
Allowable is : S from code if sigma1 and/or sigma 2 are > 0.
Otherways , there is buckling ( which is never checked by ANSI 31.3, it is the design responsability to check it , by adding extra guides,.. ), and one has to use the ASME VIII div 1 , procedure, i.e, calculate A and find out the allowable compressive stress B in psi.
RE: Combined axial loading and pressure induced stresses
My apologies , forgot to tell you in my above answer
to use this:
( pressure * Mean radius)/ ( 4* thickness )
[INSTEAD of ( pressure) alone !!!]
this is the longitudinal component due to pressure= 0.5* the circumferential one.
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For: mean radius , Area= A ,and modulus of resistance
Z , introduce Corroded thickness and deduct also mill tolerance of pipe/tube which is -12.5 % or -10 % of the
pipe/ tube Nominal thickness.
For (i) = keep the nominal thickness, this is more conservative..
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Note:
Another more elegant (but time consuming) approach if system looks overstressed is to use stress classification as per ASME VIII div.2.
e.g. segregate stresses into primary , secondary , peak , etc..Each type or combination therof has a different allowable...
Caesar or FE pipe could do this , if so instructed.