Applies To Product(s): AutoPIPE, Version(s): 2004, XM, & V8i Environment: N/A Area: Loads Subarea: Original Author: Bentley Technical Support Group Comments, Questions, and Answers Item #1: How to perform a Pressure analysis? Answer: AutoPIPE V8i 096.06.01.xx performs a pressure analysis when the following settings are enabled: Load Static Analysis sets select and modify any analysis set Enable the check-box to the left of "Calculate pressure extension cases, e.g. P1, P2, etc" as shown below: Please see the online help for details on this option / setting. Item #2: When should I perform a Pressure Analysis? Answer: A pressure analysis should be performed when some significant strain due to pressure a) Systems with expansion joints. b) Low modulus piping e.g HDPE or FRP or any plastic c) Large pressure on steel piping systems e.g 500psi d) Large diameter e.g =30" diameter with moderate pressure e.g. 30 psi To include the pressure thrust then you must select “Calculate pressure extension cases” and should also include a pressure stiffening case. This will pump the system with pressure and calculated the pressure thrust and corresponding movement under pressure. Item #3: From FAQ #67: "Note: P1 force does not include the capped internal pressure force. However this pressure force PiAi can be manually subtracted from the Local - X P1 force to give a true P1 axial force i.e Total P1= P1- PiAi" Answer: It is true that P1 case does not directly apply cap force. It does that indirectly by apply pressure strain that accounts for it and for poisson ratio. In the case of a flexible joint, AutoPIPE does apply the cap force P x Pressure Area to properly get the extension at the joint. Item #4: How to find the pressure thrust on an anchor Answer: AutoPIPE calculates pressure extension under steady state not pipe cap end pressure thrust. Another words, if you add pressure to a pipe line the pipe is going to extended due to internal pressure (assuming that your had "Include Axial" and "Pcase in Sustained" checked on). We refer to this as pressure extension not pressure thrust. To include axial forces in AutoPIPE analysis, please consider the following settings, located under Tools Model Options Results "Include Axial, Pcase in Sustained" and / or "Include axial force". See the respective help section for more information on these options. The program only calculates a pressure thrust across an un-tied expansion joint or as a result of a fluid transient. As mentioned in FAQ #46 Note: AutoPIPE does not report the cap internal pressure load at an anchor unless it is unbalance thrust across a flexible joint with the pressure analysis option checked when performing a static analysis. See Also Bentley AutoPIPE External Links Bentley Technical Support KnowledgeBase Bentley LEARN Server Comments or Corrections? Bentley's Technical Support Group requests that you please submit any comments you have on this Wiki article to the "Comments" area below. THANK YOU!
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