Hello everybody here,

I need an advice regarding seismic load, I need what load case combination should be given to civil for structural design. For now I gave them the (W+T1+P1+U1), but it has a very big load.

Thank you.

That is the load you want to give them. This is an operating case with seismic, and since you won't have any warning preceeding the earthquake, this is your most likely scenario.

thanks richard,

regarding how to properly set-up load case combination with seismic uniform load applied system and active rigid snubbers are used as support?

If you're setting this load case up to give to your structural group, then you have two options:

1) W+P1+T1+U1 (OCC), snubbers will be activated because the case is "occasional".

or

2) W+P1+T1+U1 (OPE), but on the [Load Case Options] tab, check the checkbox to activate snubbers.

Do a search on this forum using the word snubber or snubbers, there are some added considerations when using a snubber in a static analysis...

Frohle Weinachten!

Hello John,

I have read you post before regarding how to interpret and create a load case combination to properly define snubbers on the static analysis--->>>


1) Place a node(s) where the snubber(s) is to be attached to the system.
2) Run the required operating cases i.e., W + T + P + (F for spring can if req’d) + D (if req’d)
3) Note the displacements linear and rotation that occur at the snubber node(s).
4) Call out snubbers attaching them to the piping node(s) and then cnode them to a fictitious node.
5) Then go to the displacements input screen and input the operational displacements for the cnode.
6) Finally set up your load cases….
CASE 1 (OPE) W+D1+T1+P1

CASE 2 (SUS) W+P1

CASE 3 (OCC) W+D1+T1+P1+U1(Case for algebraic summation)

CASE 4 (EXP) L4=L2-L1

CASE 5 (OCC) L5=L3-L1 (Results in U1 loads/ stresses alone)

CASE 6 (OCC) L6=L2+L5 (Weight + Pressure + U1 loads)

--->>>Is this method still applicable or simply we just activate the snubber on the load case tab for W+T1+P1+H+U?

Im just confused which one to do. Thanks and regards,

Eterp

The snubber must be active in the load case editor for the "U" case, however when doing a static solution you must incorporate the OPE displacements at the snubber locales otherwise you will have the snubbers restricting more than just the "U" loads.

Recently I received a call on my mobile over just this issue, my friend was looking at an existing system with snubbers on it and his CAESAR II model was giving him eneormous loads on his snubbers that made no sense. When he "released" the snubbers by imposing the OPE dislacements they then only picked up his Seismic G loads.

Ow I see, Thanks john that make sense now because I also have enormous load on the system and Im really confused.

Thanks again for this clarification.

Best Regards,
Eterp

You should not really see an enormous load???? Look at the restraint summary at the snubber. You should see little if any load for the OPE report with the snubbers active because you are displacing them to match the OPE displacement.

Then when you have your OPE + Occasional load the restraint report should show only the load acting on the snubber due to the Occasional load (Seismic G I presume)