I understand that the expansion stress and sustained stress calculated by auto-pipe take into account the pipe lifting off supports during operating case (as each operating case is defined in separate analysis set as per 31.3 option). But what about occasional stresses? As per default analysis set, the earthquake loads are defined in an analysis set with more than one temperatures. Does it mean that when using "Multiple Analysis set (31.3)" option, the seismic stresses will be combined with "worst hot sustained stress of all operating cases" or hot sustained stress corresponding to the defined "initial case for occasional loads" or "sustained case corresponding to cold rested position".
Am I right in thinking that I should combine only one temperature case with earthquake loads in an analysis set if I want to combine hot sustained stress with pure occasional stress. (as lift off check is not possible for an analysis set with more than 1 temperatures)
Just found the following on help file :
" Note that if there are multiple analysis sets available then category maximums like (SUS), (EXP), (OCC) etc. takes the maximum stress across all analysis sets. Example: Consider a model with two analysis sets with different options. Analysis set 1 has default sustained combination "GR + MaxP{1}" and analysis set 2 has default sustained combination "GR + MaxP{2}". Assume that the stress value for "Gr + MaxP{1}" for a point is 100 psi and the stress value for "Gr + MaxP{2}" for the same point is 200 psi. When calculating the stress for the default Occasional combinations which includes category maximum (SUS), then AutoPIPE will take in to consideration the maximum sustained stress across both the analysis sets i.e. (SUS) will be equal to 200 psi for all the combinations for both the analysis sets. Similar approach is applied for user defined code combinations."
I think that explains it. Since the occasional combinations included (SUS), therefore, it combines maximum sustained stress across both the analysis sets with pure occasional loads.
Manu,
Glad that you were able to figure it out. AutoPIPE does take in to consideration the maximum sustained stress across at a given point all analysis sets (hot or cold) for calculating occasional stresses. Your answer would help other users with same / similar question.
Regards,
Bilal Shah