HELLO :

when we take in account SAM , seismic anchor movements, on equipments and structures attached to piping systems is necessary add inertial loads U1 to verify occasional stresses according with ASME B31.3 ?

Streses OCC < 1.33 SHot
W+P1+U1+SAM < 1.33SHot ?

Normally SAM are considered self-limiting displacement that make secondary streses , why we do not compare these with allowable secondary streses SA?

thanks

Mery CARACAS, VENEZUELA

Inertial loads are collapsing loads... SAM loads are displacement loads....

They are two distnictly different loads with different allowable stresses....

Read B31.3 carefully....

So U loads are OCC less than or = to 1.33 Sh

and SAM is a displacement stress so it can be compared against EXP try T+D < = EXP

Mery,

In the future, please use the button above to post a "new topic", instead of "post a poll". A "poll" is a series of questions for which you provide a set of answers for people to select from.

Clarification:

Occasional loads must be summed with other collapse loads for proper evaluation.

You say "Stresses OCC < 1.33 SHot"

I say "Stresses SUS + Stresses OCC < 1.33 SHot"

As you say, U1 is inertia loads from seismic event and this is force driven “Primary Stress(SUS, OCC)”.
SAM is the stress from displacement, that is, strain driven Secondary Stress(EXE).
When you consider this movement as D1 in Caesar II , you will have load combination as below;

1 W+P1+T1(OPE)
2 W+P1+D1+T1(OPE)
3 W+P1(SUS)
4 L1-L3(EXE)
5 L2-L3(EXE) ---- this is total secondary stress from thermal expansion and SAM

If a piping is connected between two buildings or tall equipments and the building movement due to seismic cannot be ignored, two stresses(occasional and displacement ) need to be evaluated separately.

Not to get too picky (Sun Wee)...

D1 should probably be plus and minus.

If we are talking only about stress evaluation (and not structural response, as in restraint loads) and if we are looking at a linear system, I might run D1 by itself and then add that stress to the expansion stress range to take care of this +/- approach.

Dave, I agree with you.

Assumed D1 has already plus/or minus sign in CAESAR II input data field from civil/structure.

Mery's question is "why do we compare the stress from seismic anchor movement to SA(secondary stress allowable in B31.3)?"

?????????
W+P+T ==> (OPE) normal condition
P ==> Operating Pressure

W+P (SUS)
P ==> design pressure

D ==> displacement from earthquake +/-
This ist not OPE load case !

Your
W+P1+D1+T1 (OPE) ??????????

For this stress you have a higher stress limit
as at normal condition .

Ohliger,

Except for the new Appendix P, B31.3 has no allowable limit set for operating stress. I believe Sun Wee's interest in the W+P1+D1+T1(OPE) load case was for the structural response of the system (Loads on restraints & deflections) rather than the stresses.

I find it interesting that you distinguish between operating pressure and design pressure in your load case definitions. My understanding is that design pressure is used to set the component specification (wall thickness to prevent burst) but for structural and stress evaluation, the expected (operating) conditions are used.

Dave
So do it ASME Class1,Class 2 and german nuclear Rule KTA.
Best Regards

Dave,

The design presure should be the same as or greater than the expected max operating pressure the pipe may have. stress evaluation due to design pressure should be checked too, since the pipe may be overstressed when the design pressure is the max operating pressure.

Regards,

Jack

It is not always the case that the design pressure is the greatest pressure. The design pressure is that pressure, which in combination with the coincident temperature of the condition, governs the wall thickness or pressure rating. You could for example have a lower pressure higher temperature condition which governs the wall thickness, as well as another higher pressure lower temperature operating condition which does not. Also note that you can have occasional variations in pressure and temperature.