Please look at these combinations, GP1, GP1E1, GP1E2, GP1E3, GP1E4, the above is from Initial State Occasional GR and the below is from Initial State Occasional OP1; I got the different results of GP1E1 between 2 these Analysis Set; the same situation occurs with another combination; Is it right? And could you please explain this difference? The default combinations in autopipe do not include GP and GPE, please tell me which Initial State Occasional should be used in the case of GP and GPE. If the image below is hard to see, please look at the word file attached. Thank you so much
Bentley autopipe question.xlsx
Greetings Thang,
The short answer is that it is up to you what your initial state should be for all occasional load cases, either Gr or OPn (OP1- OP100).
The long answer, this discussion is all about Non-linear analysis. If you are not familiar with that concept, please take the time to review AutoPIPE help and various other WIKI pages on the subject. Knowing that non-linear analysis uses load sequencing, by default AutoPIPE will assign GR as the initial case to all occasional load case in a given analysis set. However you have the option to assign any operating case as the initial case to your operating loads in an analysis set. By doing so yes the results will be different because the load sequence has changed from Gr - E1 to, when using OP1, Gr - T1 - P1 - E1.
Another words, where is the pipe after applying Gr and then E1 load case, compared to applying Gr load case, then T1 load case, then P1 load case, and finally E1 load case. One should clearly understand that the results when using and not using an initial load case will be different.
To answer the question, which one is correct.... answer: which ever one you choose to use. Using Gr as an initial case to all occasional loads is a viable solution. However if your project documentation wants results for affects on the system due to all occasional loads occurring simultaneously with one or more operating conditions. You can set up your analysis sets to calculate these results to see which combination of operating condition and occasional load is the worst case scenario.
Regards, Mike Dattilio Design Analysis Engineering Group Senior Analyst Bentley Systems Inc=============================================================================
Answer Verified By: Mike Dattilio
Thanks for this answer, I'm confused with some concepts in autopipe, could I ask you?
Gr, OP1, OP... is Initial State Occasional, right? Is Gr(includes Gravity, GE and GTP) Non-operating Condition? Is OP1(Gravity, GTP, GTPE) Operating Condition?
Operating Condition is called when it include Thermal and Pressure in its combinations?
And if I use OP1 for calculating GP, GPE, this means I want to look at the result of GP and GPE in Operating Condition, right?
To answer your questions:
Q1. Gr, OP1, OP... is Initial State Occasional, right?
Answer: Yes these are initial cases to occasional loads.
Q2. Is Gr(includes Gravity, GE and GTP) Non-operating Condition?
Answer: No, Gr is not an operating condition and does not include E or TP as indicated in the question.
Let us stay on topic, a load case is Gr or T1 or P1 or E1. However when combined with other loads as defined by the nonlinear load sequence then they become an operating condition. GrE1, GrT1E1, GrT1P1E1.
Q3. Is OP1(Gravity, GTP, GTPE) Operating Condition?
Answer: See Q2 above.
Q4. Operating Condition is called when it include Thermal and Pressure in its combinations?
General comments, when creating combinations for nonlinear analysis, users only have 2 choices: 1. Gr (Gravity Load case only) or 2. Select an defined operating case (Op1..Op100).
Always best to look at the analysis summary to see what the settings are for:
1. Base load cases for nonlinear analysis
and
2. Non-Code Combination definitions that include occasional loads.
Remember to ignore all combinations with a single load case, and concentrate on the results for the operating conditions. Only consider the individual load cases when trying to understand the operating conditions