Stress analysis

[aaloui]

hi every body,


Reason of the Classification of stresses in the convential combinations given by ASME 31.3 as well as by EN 13480-3 for the comparison with the respective allowed material stresses .

That combinations are the following :

Stresses due to sustained and expansions loads
Stresses due to sustained and occasional loads

for example why the combination of the stresses due to expansions and occasional loads ist not required ? or for example the stresses due to the combination of the 3 stresses type together ?

im asking this because i think that the 3 kind of load cases can occur simultaneously however the ASME as well as the european norms have required just the combinations written bellow .


thanks for giving me an answer.

 

[C2it]

Sustained and expansion cases are not usually combined.

The codes segregate primary stresses - called sustained - those that cause direct failure, and secondary - expansion / displacement stresses - those that cause failure by fatigue but are self limiting by local yielding.

Combination of occasional loads is tricky. Normally wind and seismic are combined with sustained stresses, but there is often an argument for considering adding to expansion stresses. To be agreed with the Client / Insurance body.

Sustained, expansion and occasional can be 'summed' under B31.3 by aplying the 'liberal' allowable stress equation.

 

[if7005]

Kindly ask the ASME comittee B31.3 code of conduct about that. And, why operating-stress case defined just in recently edition, not in early issued...
Operating combined with occasional stress may be allowed in the future

 

[aaloui]

thank you very much "C2it (Petroleum)" for the answers , it looks like logic , i thought also about it .