Applies To Product(s): AutoPIPE, Version(s): 2004, XM, & V8i Environment: N/A Area: results Subarea: Original Author: Bentley Technical Support Group Comments, Questions, and Answers about dynamic support forces in AutoPIPE Items #1 Question: AutoPIPE: Dynamic Results Interpretation A. My question is how come the code compliance section does not include both the positive and negative dynamic results (ie GRTP# +/- R#)? Is there a way to do that? OR B. Also, I am confused about how to interpret the local and global forces for the combinations which contain the dynamic support load. Why are the local forces for the dynamic load given as +ve? TR Number: None Product: AutoPIPE Version: n/a Area: General Problem ID#: 74535 Keywords: R1 - R50 Response spectrum cases 1 to 50 H1 - H10 Harmonic cases 1 to 10 M1 - M50 Time history cases 1 to 50 F1 - F10 Force spectrum cases 1 to 10 S1 - S10 Seismic Anchor Movement cases 1 to 10 Answer : All dynamic results in AutoPIPE are positive. Since it is the maximum absolute value of the oscillating response. By reviewing all of AutoPIPE's dynamic results, the following load cases are reported as positive numbers: ...R1 - R50 Response spectrum cases 1 to 50 ...H1 - H10 Harmonic cases 1 to 10 ...M1 - M50 Time history cases 1 to 50 ...F1 - F10 Force spectrum cases 1 to 10 ...S1 - S10 Seismic Anchor Movement cases 1 to 10 For more details on this subject please see the following AutoPIPE help section: A. Help Contents Contents Tab Reference Information Results Interpretation Select the "Results Interpretation Overview" link, at the bottom of the listing select "Dynamic Support Forces" link, read the entire section for complete details and workaround. B. Help Contents Contents Tab Reference Information Analysis Considerations Modal Analysis Modal Analysis. Workaround: Crate additional User combinations using -1.0 Factor with the Dynamic load case. For example R1 is defined as shown below with respective displacement of vertical pipe anchored at the bottom: Create a new user combination as followed, NOTE: the -1.0 factor with respective displacement of same vertical pipe anchored at the bottom: Item #2 My structures have slightly different seismic displacements at different places on the same floor. I am designing a piping system spanning several independent structures which have different phases. It appears that the supports gaps are not recognized by the software. I have created a very simple model that should not fail because the line stop gaps are much larger than the imposed seismic displacements in he axial direction. 1. Are there various options/settings which I need to change to make the analysis work ? 2. Is there a work around ? Answer: AutoPIPE's SAM (Seismic Anchor Movement, S1..S10) analysis is a Dynamic analysis and is subjected to all restrictions of a dynamic analysis primarily being analyzed as a linear analysis. From the online help: A linear analysis ignores all defined support gaps and friction coefficients, and assumes a linear soil stiffness response (k2 is ignored). In addition, the initial soil stiffness (k1) is used for the horizontal and longitudinal directions, whereas the average of the up and down initial stiffnesses is used for the vertical direction. Unfortunately at this time there is no workaround for a S.A.M. analysis to consider a gaped support. 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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