Restraint Summary

Hi everybody,

please,i will like to know why the moment in my restraint summary are all zeros. i do have a Y restraint.

Thanks for ur help.

You probably have no moment restraint, or no load causing a moment. There is not enough information in your post. Please clarify.

Hi oatty

There are six degree of freedom, 3 translation ( X , Y, Z) 3 rotation ( Rx, Ry, Rz)

when you block translation movement you will get Force Fx or Fy or Fz as per blocked movement.
When you block rotation & translation like "ANCHOR" or feed displacement x,y,z,Rx,Ry,Rz, then you will get force & moment.

Regards

Habib

Hi Oatty,

As shr explain rightly, you should have some restrain in the rotational direction then only you will have moment in that direction. In your case your Y-restraint is blocking only translation movement & allowing the rotational movement. Hense in your restraint summary report you are not getting the moment value.

Regards,
RK

Thanks, everyone. these will really help me.

Thanks once again.

I am modeling a buried pipeline of which the battery limit is before a monoblock which is before the bend that takes the pipeline underground. The piping group wants displacements at the battery limit from me. The problem is there is an anchor at that node. Should I remove the anchor to have displacement at that node? or is there any way I can of going about it?

Thanks,
Oatty

Hi everybody,

I am modeling a buried pipeline of which the battery limit is before a monoblock which is before the bend that takes the pipeline underground. The piping group wants displacements at the battery limit from me. The problem is there is an anchor at that node. Should I remove the anchor to have displacement at that node? or is there any way I can of going about it?

Thanks,
Oatty

Add the anchor after you "bury" the model.

Hi oatty

Traditionally underground-aboveground interface point consider as anchor for stress analysis hence displacement considered 0,0,0,0,0,0.

Anchor you mention is physically is there or just considered for analysis?

If it is physical one no issue. If that is not a proper anchor point in that case you may remove that anchor & have to model above ground piping till first anchor support to get interface displacement.

In my opinion if system is not highly critical then considering anchor at interface should be acceptable.

Regards

Habib

SHR,

Your statement ... "Traditionally underground-aboveground interface point consider as anchor for stress analysis hence displacement considered 0,0,0,0,0,0."..... is misleading and not correct.

A pipeline passing from above ground to buried will ultimately have a point some distance along the buried portion from the ground transit, known as the 'virtual anchor' where soil friction prevents any further axial expansion. This is the point from which above ground movement should be considered. In some cases the resulting above ground movement can be very significant and if ignored will cause damage or failure.

Hi MoverZ

Thanks for your comments.
So far we assume interface as anchor but yes I accept the virtual anchor concept suggested by you.
Is there any simple way to roughly calculate virtual anchor location to get approximate interface displacement in case we do not perform caesar underground piping analysis ?

Regards

Habib

There are many generic ways to predict the virtual anchor point. All are approximate and often ignore soil properties etc., so not too useful. Try googling 'pipeline virtual anchor'. There are lots of math solutions available.

Hi MoverZ

Thanks for your response.
Appreciate if you can share some technique, attached in this forum or can send me.

Regards

Habib
habibur21@gmail.com

thanks Habib for ur help

Assuming the interface is node 10 and the next node is 20. Can I have a Y restraint at 20 and without an anchor at node 10?

And what if the interface is a flange? what can i do to have a displacemnet for the piping guys.

Thanks,
Oatty

Hi MoverZ

thanks for u contributions,
u are right about the virtual anchor point but are u saying there is no need for an anchor at the interface becos of this?

thanks.

Hi oatty

Interface is a flanged or welded connection should not make much differences.
In your underground piping if any anchor or so called virtual anchor present close to interface you may rough estimate the interface displacement values.
In case virtual anchor is far away from interface you have to consider underground piping as well as above ground piping until first anchor or at least until first partial anchor to figure out approximation values of interface displacement.

Regards

Habib

hi Habib,

thanks for ur help so far, but i can't really understand this statement(In case virtual anchor is far away from interface you have to consider underground piping as well as above ground piping until first anchor or at least until first partial anchor to figure out approximation values of interface displacement.)

Thanks
Oatty

Hi oatty

To make the thing simple...

Since your pipe is going underground I guess temperature is quite less so there is no much movement expected at interface, I think consider the interface as Anchor. For the above ground piping provide additional flexibility ( May be add one additional elbow) to cover up interface movement accuracy.

You might attach sketch of above ground & underground piping mentioning Diameter, thickness, temperature & pressure to comment better for your particular case.

Regarding my previous statement, since underground & aboveground pipe is connected so if you only consider underground piping to find interface movement it will not be so accurate, because above ground piping also affect the interface movement.


Regards

Habib

Email habibur21@gmail.com