Hi all,

I have read the article about "Beam Element Models and the ASME B31 Codes" in COADE Mechanical Engineering News, June 2000 which was written by John C. Luf.

The article's opinion is:

"Typically, when busily engaged in creating a model, the analyst goes from point to point (from fitting to fitting or support point to support point) and does not necessarily give thought to the issue of whether additional data nodes are required. Ordinarily this might result in an incorrect model, which would give incorrect results.I am sure that a lot of people go along from support to support without any added considerations. However, this can lead to some incorrect results"

My question is: Should we add middle nodes when we create the model in CII (fitting-fitting, support-support, fitting-support) ?

BR.

That depends fully on your model and the results you want to have. If you want to see deflection in the middle of the span, yes you do need to add extra nodes.
There are also some other situations where additional nodes may be necessary, but it's too complicated to tell that in a short answer here. Understanding of the beam theory is necessary when making a CII model.

Dear corne,

Can you explain more about "There are also some other situations where additional nodes may be necessary" ?

Thank you,

With Best Regards.

My opinion is :
If you have a strait pipe, example with a lenght 1000 mm and set at beginn and end one node, then you becomes the same global static mechanical pipe behaviour as with one more node in the middle of this element.

The general practice is to give a node between 2 supports, so that the deflection can be calculated at that point and minimum deflection criteria can be checked as per your project spec.
The number of nodes entirely depends on how complex analysis you are performing on the piping system and the responses you need to study. For studying responses in dynamic analysis, you need to specify more nodes depending on the pipe size and span. One of the example is paper on "Mass-Lumping technique for Seismic analysis of piping"- John Lin / Adolph Molin, which specifies criteria for distance between two consecutive lumped mass. This will be the spacing between the nodes.

Regards,