Hi,

I have a query regarding the pipe support loads for skewed piping systems. I can see from some of the previous discussions of this forum that we can use the 'Local Element Forces' to calculate the guide and limit loads (by adding the local forces of the two adjacent elements which has the common restraint node in them)

Please refer the following for an earlier discussion on Coade's forum.

http://65.57.255.42/ubbthreads/ubbthread...=true#Post37478


Caesar's Global-to-Local transformation utility can also be used
for this calculatiion purpose.

The thing I wonder about here is whether we can use this same method (using the summation of local element forces) for calculating the Rest loads? Or, Is it correct to use 'Restraint Summary (FY)' for the purpose of finding out Rest loads?

I raise this query because the Rest load always acts in vertical direction for a horizontally skewed piping system in both gloabl and local coordinates.

Thanks for your time on answering my query & Have a nice week ahead!

Regards

Dear All,

If any of you have experience in extracting support loads for a skewed piping system, please share your suggestions on my query above!

Cheers

Can you explain better.

If you have horizontal skewed piping system, you read vertical loads from restraint summary.

If you have long horizontal skewed run you also can rotate entire model around Y and read the guide and limit stop loads from restraint summary.

If your question was other than I understand, please be more specific.

Regards,

Dear Danb,

Thanks for your reply. If we have a long horizontal skewed line, then it might be effective to rotate the model about global Y and read the guide and limit loads directly from restraint summary as you suggested. But I have a system (in the turret of an FPSO), where lot of pipes are at different angles to each other. In that case, it might be time consuming to rotate the model for each and every restraint. Especially in the case of FPSO modification projects (which I am dealing with at present), we don't have such luxury of long skewed pipes

Also in case of pipe supports on Tee's (welded shoes or trunnions under Tee for instance) of skewed piping, it is then a tricky thing to manipulate the local element forces to get the effective restraint loads. It is because the same restraint node (at the middle bottom of tee) exists in 3 different elements of the same Tee and these elements have different local coordinate systems!

Probably the most efficient thing to do for such systems is to get Caesar II, ver. 5.30, which has the local restraint summary feature added to it.

Thanks again for your response & Have a nice weekend

Cheers

Just be aware that the new report gives you the restaint loads as defined in the attached element's local coordinate system. Restraints, which are points, don't have a coordinate system.

That's cool, I always preferred rotating the model rather than summing the node elements as I was not confident of getting it right 100% of the time, esp in peak times. Having the restraint report for nodes *in local coordinates) is a great addition.

The other thing I would like to see in CII is related to skewed systems. As well as specifying rotation by degress, it would be good if you could rotate a model by specifying an element to be in line with on of the axes, rather than working out what the angle is then rotating.