Interpretation of stresses at points

RE: Interpretation of stresses at points

Maciej Rydlewicz - CS Softdesk — Fri, 23 Apr 2021 07:07:07 GMT

Witam,

Zostaną dodane do raportu pomiędzy punktami węzłowymi. Zapraszam do kontaktu bezpośrednio będzie szybciej łatwiej.

In English on request of Mike: These points are added to the stress report if stress in between regular model nodes, if necessary only. Stress is calculated for interim points but isn't reported if it isn't necessary, i.e. isn't bigger than in boundary nodes of element.

RE: Interpretation of stresses at points

Piotr Łukowicz — Fri, 23 Apr 2021 07:01:59 GMT

Dzień dobry,

Miałbym pytanie o to w jaki sposób te punkty, jeżeli wystąpią, będą oznaczone?

Pozdrawiam,

Piotr Łukowicz

RE: Interpretation of stresses at points

Mike Dattilio — Thu, 22 Apr 2021 13:01:21 GMT

Greetings Piotrek,

What could be different between these 2 points that would affect the sustain calculations?

With out being able to review the actual model, one should be able to assume that the following would be the same between the 2 end points of a bend component:

Pc = defined pressure
do = Outside pipe dia
en = nominal thickness on drawings
i = Sif calculation
Z = section modulus for a pipe

However the following could be different:

Ma = resultant moment from the sustained mechanical loads

This would explain the difference in the reported results.

Regards,
Mike Dattilio
Design Analysis Engineering Group
Senior Analyst Bentley Systems Inc
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RE: Interpretation of stresses at points

Piotr Łukowicz — Thu, 22 Apr 2021 07:15:22 GMT

Thank you for your reply,

I would like to clarify, though.

Analyzing code stresses for the previosly mentioned pipe:

I understand that point S20 F+ and S21 N- refer to the pipe between them.

I assume that code (EN 13480 in this case) stresses for the combination GR + Max P{1} are calculated using:

And are a single value for the entire pipe, as the code considers elements as a whole, unlike general stresses which can be found also for intermediate points.

Am I right and if so, why are these values (shown above) slightly different? Is it because of the precision of AutoPipe calculations?

Kind Regards,

Piotrek

Proen

RE: Interpretation of stresses at points

Piotr Łukowicz — Thu, 22 Apr 2021 06:55:27 GMT

Dziękuję za odpowiedź.

Kind thanks for your reply.

RE: Interpretation of stresses at points

Mike Dattilio — Wed, 21 Apr 2021 20:35:13 GMT

Greetings Piotr,

Ahh.. now I understand your question,

Please noted that every node point has a +ve (downstream) and -ve side (up stream). If the results are the same on both sides of the node point then only one set of results are reported. However if there is a difference, then both sides of the node point results are reported.

With regards to elbows, they are comprised of 4 node points (TIP, Near, Far, and Mid) A bend component really starts on the +ve side of the Near point and ends at the -ve side of the far point. For locations outside of the bend (i.e. both -ve side of the Near and +ve side of the Far) will be considered straight pipe.

Therefore to answer your question

"Which component do they refer to, if a point is located for example between a pipe and an elbow?"

Answer:

Straight pipe stresses are calculated on the outside of a bend component and Bend pipe stresses are calculated on the a bend component.

As you know AutoPIPE will report stress at defined node points. There is a feature in the program where users can define intermediate points, see the following AutoPIPE help section:
Help > Contents> Search Tab> enter "Intermediate stress points" (include the quotes), press List Topics button, double click on the selected topic from the list provided to see more information.

Keep in mind that you can add additional node points (ex. S20 to S22), however suggest that you do not place a node point at the exact location as the bend's Near or Far point. Doing so may result in error message "E732-3: Not enough clearance to fit bend..". This message will prevent you from analyzing the model.

Regards,
Mike Dattilio
Design Analysis Engineering Group
Senior Analyst Bentley Systems Inc
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RE: Interpretation of stresses at points

Maciej Rydlewicz - CS Softdesk — Wed, 21 Apr 2021 15:09:31 GMT

Panie Piotrze,

Proponuję jedno z dwóch rozwiązań:

1. Można zaznaczyć opcję Intermediate stress points - tzn. wpisać ile punktów ma dodać (zagęścić siatkę MES) AutoPIPE. Jeśli naprężenia będa większe w tych pośrednich punktach - to zostaną umieszczone w raporcie. Jeśli nie - to nie będzie ich w raporcie. Opcja dostepna jest w Model Options > Results (prawa strona, poz. 13 od góry);

2. Ręczne wstawienie dodatkowych punktów na prostce. Zwykle to się stosuje jeśli na odcinku prosty ma Pan spoinę i trzeba zorientować się co w niej się dzieje.

RE: Interpretation of stresses at points

Piotr Łukowicz — Wed, 21 Apr 2021 05:49:17 GMT

I assume the selected point lays between the elbow and the pipe. How can I find ot what are the values of stresses for the straight between this point and point S22?

Regards,

Piotrek

RE: Interpretation of stresses at points

Mike Dattilio — Tue, 20 Apr 2021 15:06:50 GMT

Greetings, Piotr,

As you know, an AutoPIPE model is made up of pipe spools or fitting (i.e. elbow, tee, etc..). Your comment "AutoPipe shows calculated values of stresses at points which are located at joints between pipes and fittings", is confusing because there is nothing between the 2 items.

Please provide a screen shot of exactly what you are talking about.

Regards,
Mike Dattilio
Design Analysis Engineering Group
Senior Analyst Bentley Systems Inc
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