Seismic restraint - supp detail to meet stiffness in CII mod

We provide quite fine gap 1/2 mm gap in seismic restraints near to equipment nozzle; we chk the same in ensured or not by physically at site.

But, no one is checking the stiffness in support detail meets the stiffness modelled in Caesar-II or not for seismic static or dynamic analysis; is it a lapse in design!

In nuke design, we had checked as per Sec-III NF code each and every support for stiffness and stress reqt; why the practice is so lax in today's SMART generation, where people are modelling 0.5" pipe in 3D, but designing the same with work share quality way, where a process plant owner does not know who is designing the piping or civil structure - may be a school dropout in third world through layered sucontacting!

reg,
sam

Third world is a big word to use on this forum, fellow!!

Refrain from these specific remarks!!

Its a technical forum and not a place to write all this stuff!!

Dear Sam,

I'd like to ask that the way we(as a stress analyst) are able to check the support stiffness. What method or data do you use?

We(and CAESAR II) assume that support will be rigid, and put 1E+10 stiffness in the analysis, but sometimes it's not correct especially in dynamic analysis.

Support vendor usually don't have or provide specific values, so as a rule of thumb, I just put more brace or stiffner to the support looked relatively weak.

CAESAR II model of structural input may help with this?

Yes sam you are right "no one is checking the stiffness in support detail meets the stiffness modelled in Caesar-II " .

There is a technical paper published in hydrocarbon processing on "Improve design for pump suction nozzles" in which nozzle loads were checked by predicting the first adjustable support base plate’s stiffness.

basically I would say the support stiffness plays an important role near nozzles and one must consider it accurately to check the nozzles loads specially for rotating equipments.