Hi All,

As I was checking my lateral and vertical restraint loads I noticed that some of the lateral loads were too high for the given pipe support. I decided to check the displacement at the given support and noticed that the displacement is practically non-existent AND less than my modeled gap of 1/8" for the U-bolts. So my questions are:

1. If the displacement in the given direction is less than the modeled 1/8" gap, how is this fairly large force being generated? It should be zero since it never gets to be "restraint" by the U-bolt. Correct? (Displacement was only 0.045" and gap is 0.125")

2. The layout is for a Pipeline Receiver. As many of you know these layouts are extremely common and it is standard for the client so adding more flexibility to the layout is not a real option. Also, changing the support is not a real option either since this too is somewhat of a standard (placement and sizing). What other options/best practices for reducing support loads are typical or reasonable?

Thank you in advance.

The friction can crate lateral loads on support with very small movement. Check your friction coefficient at the supports. I additionally suggest you to check the geometry, densities etc... before getting into conclusion.

Some cases an unintentional support at the same location may cause similar scenario as well, they could be on the different location with the unintentional support node.

The software does not know if you are using U-Bolt or different type support, you are the one making judgement.

Ibrahim,

Friction ! of course, what a silly oversight on my part!. It does however open up other questions.

1. The pipe will be sitting on Teflon I-Rod so at the moment I'm using 0.1 for my friction coefficient and the lateral force is fairly large, is it reasonable to make the coefficient zero? And yes, I know that is a judgement call on my part but if asked I would say clearly that it is not ok to make it zero (does not represent real world) Am I missing something again?

2. I don't understand what you mean by "Some cases an unintentional support at the same location may cause similar scenario as well, they could be on the different location with the unintentional support node". Do you mean that the reaction at other nearby nodes can affect the specific support I'm looking at? I looked at the other nearby nodes and they are "ok" (within parameters, no lift-off, minimal movements, etc)

And yes, I'm aware that CAESAR has no clue what type of support I'm using and it up to me to model it correctly (again, standard by client and not much of a choice there) I mentioned U-bolt only to better explain the layout.

Thank you

1. I do not think you can make the friction zero with Teflon I-Rod. As far as I know teflon-stainless steel combination has the friction coefficient 0.1. In your case, I guess you use carbon steel, the coefficient should be even higher. I am away from my resources, you need to search the coefficient. If you require lower coefficient of friction (which is about 0.025 as far as I remember) you need to use roller supports.

2. Sometimes you unintentionally add a support, for the discussion say at node 100, you add another support for node 20 at this node. The support type at node 100 for Node 20 cannot be easily seen.

I additionally suggest you focus on the local stresses at Teflon I-rod supports. The local stresses can make you add local plate stiffener. There is an example at the image of the video on the web site below:

http://stoprust.com/i-rod-pipe-supports/

The use of Teflon I-rod is to protect the pipe against the crevice corrosion only. I guess your client is after this protection. If the side forces large, you either change the pipe route or change the support type.

Please remember the U-Bolts as supports can work in vertical(+/-) adequately, the side load resistance need to be proven by calculation. Check support displacement, if pipe fills the gap you have side force resistance that needs to be taken by the support (U-bolt in your case).

Please remember that the low friction coefficient of roller support is in the roll direction only.

Lateral loads are a function of friction times normal force. If you have significant lateral/axial loads in a properly modeled system, either your pipe and contents are extremely heavy, or you have thermal growth directly towards the support.