To all Engineers,

Let me share your valuable comments on my problem,
We are working on one of the Thermal Power Plant PJT (CFBC) located in Seismic zone-4, We have passed all stresses as well as all nozzles for all the systems. Now my client is asking for the consideration of SAM (Seismic Anchorage Movements analysis) in the analysis, however Contract and Code don’t says regarding to the same. All the supports items also procured, and also we don’t want to do this, Please advice us how to avoid it.

If we do SAM analysis, my stress value as well as Nozzle loading will be affected, Please share your valuable experience regarding stress analysis without considering SAM.

We will appreciate in advance to all your response!


Regards
Vikram Kapse

SAM will be a effect, if you do a multiresponse analysis.
This the case you have different spectrums in one direction on your supports.
Then Caesar do automatical made a SAM calculation.
Or you have a pipe between 2 buildings with different dynamic response.
Then you can give anchor movements on the nodes.

Vikram,

Since it is a Thermal Power plant, You should be using B31.1
Now Consideration of SAM is generally decided at an early stage in the project and agreed with the Client.
Regarding Code reference, It never says directly anyone to use SAM, but there is a reference in the Non-Mandatory appendix.II 3.4 about using Moments due to SAM.
There are two ways of handling this problem :
1. Doing Static analysis and considering SAM as displacement D1 and then combining SAM with other thermal displacements in Thermal stress. The allowable will be SA
2. Doing Dynamic analysis (Response spectra analysis) and where SAM is considered in occasional stress along with sustained.

SAM cannot be avoided because failures during an earthquake is primarily because of SAM which causes Fatigue racheting. Now there has been a discussion whether SAM would cause fatigue...I am still not clear with it.....Discussion on this by Mentors is appreciated..

Regards,

Dear Ohlinger and SKK,

First of all thanks to your response.
One thing I want to mention, I did complete analysis as static equivalent, I already tried as mentioned point 1 by SKK (1. Doing Static analysis and considering SAM as displacement D1 and then combining SAM with other thermal displacements in Thermal stress. The allowable will be SA) and due to this my system failing in Stresses as well as in Nozzle loadings. This is the reason at this stage of project we don’t want to do SAM, b’cose all the vendors like tbn, blr, htrs, cndrs, pumps etc. we already negotiated & agreed our present loadings, if we do SAM then nozzle loading is again needs to be approved by vendors and same is very time taking activity. So Please advice how to convince my Client regarding SAM b’cose there was not any initial agreement with Client.

Please advice there is any other ways without doing SAM, how I convinced my Client, Please share your experience or we need to do the same.

ASME Section III Division 1
NC- 3655 Consideration of Level D Service Limits for anchor movements:
c 2 * Mam*Do/2I < 6Sh
Fam/Am < Sh

Here no combination with temperature load case T or weight W or P !