Dear Richard Ay,


I have a query here ,need your help about snubber input.

I input in spreadsheet: node 30, xsnubber, cnode to 35 ,give 35 a displacement -10,-5,5,
(the displacement is the hot displacement of node 30,for static seismic analysis purpose)

OPE case 1(hot case), i did not active snubber,

Then ,I want to analysis steam hammer in dynamic model, i want to use the same snubber,
is there any difference between input a snubber in dynamic anaylysis editor and input a snubber in spreed sheet?
noticed that in dynamic analysis editor, no cnode displacement is needed,but i had input a cnode displacement in spreadsheet.
I did a test using this two ways, got a same result.
Hope you can know what i mean,

Best Regards,

whm

Dear Whm,

Our Nuclear Powerplant experienced people will reply your query better.

I am just suggesting one solution; check whether it works.

Snubber is active only in 'OCC' load case. Have you included D1+T1 within that to take care of operating case position of piping at snubber attached node?

In this forum, June,27,2001 John.C. Luf's reply in how to use thermal movement in static seismic analysis with snubber may be of help to you.

regards,

sam

Dear sam,

I have read John's reply before, I only active snubber in load case W+T1+D1+P1+U1/-U1(OPE)in order to know the load on snubber properly, Though it's a OPE case ,but the snubber works. So I don't think snubber only work in "OCC" load case now.

My question is to knew the difference between input snubber in spreedseet and in dynamic editor when doing dynamic analysis.

can you help me ?

Dear whmwhm,

You can enter snubber either in input processor or in dynamic processor - both are same. In both the cases, (opt) Cnode is available.

By activating snubber in some load case, we consider snubber as rigid restraint. Otherwise, by default, OCC loadcase activates snubber & other loadcase types inactivate the snubber.

By opting the 'staic load case for nonlinear restraint status' in dynamic analysis control parameters(see pages 8-3 & 8-4 of user manual) the hot operating position, not by cnode movement you have described, you can provide the thermal movement. If your loadcase opted is 'OPE' loadcase type, then activate snubber in that particular loadcase.

regards,

sam

Dear sam;

As you have said: By activating snubber in some load case, we consider snubber as rigid restraint. Otherwise, by default, OCC loadcase activates snubber & other loadcase types inactivate the snubber. (the manual say the same)

In above words, what "rigid restraint" really mean? Dose it mean the sofeware will ignore the stiffness you input for the snubber if the load case is not an OCC case?
I active the snubber in load case W+T1+D1+P1+U1/-U1(OPE),So i think it is an OPE case ,not an OCC csae, results show that the software use the stiffness value that i input for the snubber. So i was confused, the software actually do not consider snuber as "rigid" restraint in the above my loadcase.

Best Regards,
whm

"In above words, what "rigid restraint" really mean?" It means the snubber as active with the stiffness you have inputted. For snubber, the stiffness is entered by yourself unlike other types of rigid restraints where the default restaint stiffnesses are generally taken, unless we specifically input the same.

Take resonable snubber stiffness from some vendor.

regards,

sam

By default, snubbers modeled in the piping input for static analysis are only active if the load case is designated as "OCC". However, you can over-ride this behavior when you setup the load cases. Go to the [Load Case Options] tab, scroll it to the right until you find the Snubber column. Check or uncheck the boxes to activate or deactivate snubbers on a load case by load cases basis.

Dear Richard Ay,

when i use snubbers for static analysis,
suppose node 200 is the node that i want to set snubber, the Cnode is 201,
....
L5 W+D1+T1+P1+H (ope)
....

first run for L5 displacements of node 200
give 201 the above displacements(D1).Set Xsub for node 200, Cnode to 201, ....
....
L5 W+D1+T1+P1+H (ope)
L6 W+D1+T1+P1+H+U1 (ope) active snubber when setup this load case
.....

OK, then rerun, In some modules, everything is ok,The result show Cnode 201 have "Displ. Reaction",in case L6, and the number is the same with the load on node 200. but, in some modules, the the displ.Reaction of Cnode201 is zero, There are must some problem in it ,but i can't find why?
Can you help me ?

Best Regards,

I assume by "modules" you mean "load cases"?

Be careful here, because back in 2001, you had to activate snubbers by specifying that the load case was OCC. There was no Load Case Options tab, and therefore no checkbox to activate snubbers. Make sure you're activating the snubbers in the appropriate load cases.

yes, i am sure i have activat snubber in L6 everytime,but some times results seems not right,if you have interests ,i can send you an simple module, which have the same problem,very appreciate your time!

Ps,i use CII 4.50, this verison of sofeware have "Load Case Options tab" ,and there are checkbox to activate snubbers.

Regards,

Ok, e-mail me your _a and _j files for this job. Send them to "ray at coade.com"