Friction effect on SUS stress

Dear Friends,

Dear Richard, I tried to search this topic,but not the same doubts what we face,So,request to provide your valuable result.

While compressor nozzle analysis,I noticed following,I need your help to clear my doubts.Please express your thoughts,

1) As vibration analysis & as per vendor suggestion, design gr. providing special supports like clamp support,we are not modeling in CAESAR these clamp supports,If I need to model clamp in CAESAR, need to model as X,Y,Z with friction factor Mu=0.3,that will generate huge load, as we can not put clamp in Teflon / graphite pad. How to consider in three direction Friction for clamp support?

2) After changing the friction factor Mu=0.1 in vertical +Y, SUS stress is nothing going to affect,however Expansion stresses are reduced.

Question is if Pipe rest on civil beam with clamp than it;s weight,fluid weight,insulation all are taking by the support i.e called Sustained load, than why it is not help to reduce the SUSTAINED load/stress both?

3)If the friction force is less than Mu*Fy, there shall not be displacement at that node,still we can see displacement in the restraint summary due to the stiffness used in CAESAR configure set up.

My knowledge says that this force shall be ""stiffness * Displacement""" only, which is called "non-sliding".

But,I calculated manually, that force is not matching with CAESAR output.So, how CAESAR is working for such cases.

I wish to get clear my questions & hope to have answers from all of experts here.


Thanks in advance.

Dear Friends, Richard , Dave

Await the answers.


Regards
SND

Awaiting the reply from Experts,Dave & Richard.

If anyone can provide his understanding, please share/highlight the solution.


Regards
SND

Typically a clamp would be modeled as only Y and Z (assuming the pipe is in X) with friction. A clamp will not restrain the thermal growth of the pipe. If you try this in c2, you will see huge loads.



Friction acts normal to the support direction. So if your support is a Y (or +Y), friction acts in the XZ plane. The load from the pipe, acting on the support won't completely reduce the moments in the pipe elements. Most Code stresses are governed by moments.




There is a good discussion on this question in the Technical Reference section of the documentation (User's Guide for v.6.10 and later, Technical Reference Manual for v.5.31 and earlier).

You should not use the clamp as a stopper as the pipe
Will possibly just slide. Also, i think you can just use restraint +Y
Since you did not mention that your clamp is guided or welded on a structure.

If you want to model the vibration control clamp, typically you will need to estimate the hold down force(Fn=friction force/friction factor)and apply the force (the minimum required preload)to the clamp support.