Bentley Communities
Bentley Communities
  • Site
  • User
  • Site
  • Search
  • User
  • Welcome
  • Products
  • Support
  • About
  • More
  • Cancel
AutoPIPE
  • Product Communities
  • More
AutoPIPE
AutoPIPE Wiki 02. Comments about Seismic / Earthquake loads in AutoPIPE
    • Sign in
    • -Pipe and Vessel Stress Analysis - Wiki
      • +ADL PIPE
      • -Bentley AutoPIPE
        • ++Table Of Contents - AutoPIPE Wiki page
        • +- General Information about AutoPIPE
        • +-NEW User Guide - TIPs - FAQ AutoPIPE
        • +ATS, ITS, and Batch Processing - AutoPIPE
        • AutoPIPE QA&R program
        • Bentley AutoPIPE Basic User Accrediation
        • +Download - Install - Release Notes - AutoPIPE
        • +File / Model Management using AutoPIPE
        • +General - AutoPIPE
        • +Graphics - AutoPIPE
        • +Grids (Input & Results) - AutoPIPE
        • +Import and Export - AutoPIPE
        • +Known Issues in AutoPIPE (Enhancements, defects, etc..)
        • +Libraries - AutoPIPE
        • +License AutoPIPE -
        • -Loads and Load Sets - AutoPIPE
          • 01. Animate Load cases - AutoPIPE
          • 02a. Load Case Descriptions in AutoPIPE
          • +02b. Static Analysis in AutoPIPE
          • +02c. Dynamic Analysis in AutoPIPE
          • +02e. "Hydrotest" - AutoPIPE Load Case
          • -02f. "Static Earthquake" - AutoPIPE Load Case
            • 0. How to apply a Static Seismic load case in AutoPIPE?
            • 01. Can the seismic input be explained again in the new version of AutoPIPE V8i 09.06.xx.xx and higher?
            • 02. Comments about Seismic / Earthquake loads in AutoPIPE
            • 03. What is the recommended Seismic support spacing?
            • 04. How to add seismic "G factors" in an AutoPIPE model?
            • 05. Distributed load assigned to GR does appear to be applied to the Static Seismic results in AutoPIPE, why?
            • 06. Are seismic force applied on structural elements as well as pipe in an AutoPIPE analysis?
            • 07. Is it not conservative approach to apply static seismic force on structure in AutoPIPE as done in STAAD?
            • 08. What values of Rp can be input when using static seismic ASCE-7 2010 code in AutoPIPE?
            • 09. How to apply Seismic loads to part of model and not to complete model?
            • 10. Is it possible to combine S.A.M. load case (S1..S10) with a static seismic load case (E1..E30) in AutoPIPE?
          • +02g. "Wind" - AutoPIPE Load Case
          • +02h. "Snow Load" - AutoPIPE Load Case
          • 02i. "Thermal Bowing" - AutoPIPE Load Case
          • +02k. "Response / Force Spectrum Loads" - AutoPIPE Load Case
          • +02n. "Harmonic" - AutoPIPE Load case
          • 02p. "Time History" (M1-M50) - AutoPIPE Load Case
          • 02s. "Buoyancy" - AutoPIPE Load Case
          • +02t. "Wave" - AutoPIPE Load Case
          • +02u. "Fluid Transient" - AutoPIPE Load Case
          • 02v. "Steam Relief" - AutoPIPE Load Case
          • +02w. "Thermal Transient Analysis" (TTA) - AutoPIPE Load Case
          • +03a. "Gravity" - AutoPIPE Load Case
          • +03b. "Pressure" - AutoPIPE load case
          • 03c. "Temperature" - AutoPIPE load case
          • +03d. "SAM" (Seismic Anchor Analysis) - AutoPIPE load case
          • +03e. "Fatigue" - AutoPIPE load case
          • +03f. "Xtra Data" - AutoPIPE load case
          • +03g. "Occasional" - AutoPIPE load case
          • 03h. "Distributed Load" - AutoPIPE load case
          • 04. Results From Loads and Load Sets Not Answered By Piping Code Calculations
          • +05. Combination Load Cases (Tools> Combinations dialog)
          • +06. Non-linear Load Sequencing Explained
        • +Localization (Non-English Language) - AutoPIPE
        • +Modeling Approaches in AutoPIPE
        • +Modules (i.e. Flange Analysis, Spring Hanger Selection, Rotating Equip, TTA) in AutoPIPE
        • +Piping codes - AutoPIPE
        • +Post Processing - AutoPIPE
        • +Printing - AutoPIPE
        • +Reports - AutoPIPE
        • Security
        • +Settings - AutoPIPE
        • +Stress Isometrics - AutoPIPE
        • +Technology Productivity Capabilities
        • +Warnings, Errors, Crashed, Confirm, etc.. messages in AutoPIPE
        • +~ Technical Support - AutoPIPE
      • +Bentley AutoPIPE Nozzle (WinNOZL)
      • +Bentley AutoPIPE Vessel (powered by Microprotol)
      • +Bentley PlantFLOW
      • +Bentley PULS
    • Multi-lingual announcement from BENTLEY TECHNICAL SUPPORT.
    • Working at Home with AutoPIPE
    • +AutoPIPE Brand Learning Resources
    • +Attend a live meeting with an AutoPIPE Analyst

     
     Questions about this article, topic, or product? Click here. 

    02. Comments about Seismic / Earthquake loads in AutoPIPE

    Comment #1:

    A real world seismic response of the piping system  is probably somewhere between a linear and non-linear behavior since pipes may jump off supports and friction is no longer present

    So running a non-linear and a linear analysis then finding the maximum loads between the 2 results may yield the most real world results.

    Comment #2:

    When using "ASCE 2010" Seismic Static Load Generator, 

    The component response factor Rp is an important factor for calculating the seismic ground acceleration. 

    Rp = 12 is common for stress, but ASCE-2010 paragraph 13.4.1. states that for supports/structure reactions to use a value NOT higher than 6:

     

    One Recommendation is to run 2 sets of seismic cases

    Rp = 6.0 (Support & Anchor Reactions)
    Rp = 12.0 (Pipe stresses)

    Comment #3:

    Depending on your type of analysis (i.e. Linear or Non-linear) there are options for load case combinations:

    Linear Analysis:

    On the Combinations dialog, select the "Combination Options" button, and place a check mark next to "Add Negative Occasional Cases", From the online help:

    If this option is selected, the program will generate default Non-Code combinations for negative occasional load cases in addition to the default Non-Code combinations for positive occasional load cases of seismic and wind only, i.e. GRTP1+W1, GRTP1-W1, GRTP1+E1, GRTP1-E1, etc. The default state is unchecked. This option will be disabled (grayed out) if the "Add default Non-Code combination" option is unchecked or if the static analysis = non-linear.

    Some behaviors:

    • Disabled when 'Disable Auto Non-Code Combination' checked

    • Always Enabled for B31.8, B31.4 Offset, B31.8 Offset, CSA Z662 Offset

    • KHK (Enabled only for level 2)

    • All other codes (Enabled when one or more load sets are linear)

    Non-Linear analysis

    For static seismic cases we recommend a minimum of 8 cases as shown here which will provide the accurate non-linear support load combinations and occasional code stresses.

    Define minimum of 8 static seismic cases:

    +/- X +/- Y (4) and +/- Z +/- Y (4) where Y = Vertical

    Note: You would typically use OP1 as the initial state.  Seismic loads at the load case level e.g. E1, E2 etc are combined as load vectors algebraically to get a resultant loading.

    Horizontal X and Z seismic loads are typically not combined in the same load case.  Seismic guidelines recommend analyzing two non-concurrent horizontal seismic loadings. It is common to consider separate loadings for X and Z directions in different load cases E1 and E2 both with vertical Y component.

    So only cases SUS +E1 to SUS +E8 need to be considered for occasional stress compliance.

    Comment #4: 

    For most tall structures, the greater seismic accelerations occur at the top of the structure / building.

    We can use the AutoPIPE's Insert> Xtra Data>  "Member Static Earthquake factors" or "Point Static Earthquake factors" commands to model the increased seismic accelerations upward through the building / supporting steel structure.

    Note: 

    The Static G load can be varied at different locations by factoring.  To factor all the weight you must use both the member and the point Earthquake factors. 

       - Member Earthquake Factor (Insert > Xtra Data > Member Earthquake Factor) are applied to weights of pipe, pipe contents, pipe insulation etc...

       - Point Earthquake Factor (Insert > Xtra Data > Point Earthquake Factor) are applied to point loads: valve, flange, and added weight.

    Typically component amplification between 1 and 2.5

    Comment #5: 

    The static earthquake "g" force, or Seismic Coefficients, are dimensionless coefficients which represent the (maximum) earthquake acceleration as a fraction of the acceleration due to gravity. Typical values are in the range of 0.1 to 0.3. The static seismic gravity factor is multiplied by deadweight in the system to provide a lateral seismic loading typically in the X & Z directions applied to mass points or to the nodes points of the pipe, not the supports. This type of loading is classified as an occasional loading by the piping codes (301.5 Dynamic effects: 301.5.3: Earth quake. Piping shall be designed for earthquake-induced horizontal forces. The method of analysis may be described in ASCE 7).

    A full response spectrum analysis can also be performed. See AutoPIPE/ Help/ Contents/ Reference Information/ Analysis Considerations/ Response Spectrum Analysis

    See Also

    "Static Earthquake" Load Case

    Bentley AutoPIPE

    • Load Case
    • Point Static
    • AutoPIPE
    • Static Earthquake
    • Member Static
    • Share
    • History
    • More
    • Cancel
    • Mike Dattilio Created by Bentley Colleague Mike Dattilio
    • When: Mon, Dec 22 2014 6:32 PM
    • Mike Dattilio Last revision by Bentley Colleague Mike Dattilio
    • When: Tue, Apr 6 2021 12:59 PM
    • Revisions: 7
    • Comments: 0
    Recommended
    Related
    Communities
    • Home
    • Getting Started
    • Community Central
    • Products
    • Support
    • Secure File Upload
    • Feedback
    Support and Services
    • Home
    • Product Support
    • Downloads
    • Subscription Services Portal
    Training and Learning
    • Home
    • About Bentley Institute
    • My Learning History
    • Reference Books
    Social Media
    •    LinkedIn
    •    Facebook
    •    Twitter
    •    YouTube
    •    RSS Feed
    •    Email

    © 2021 Bentley Systems, Incorporated  |  Contact Us  |  Privacy |  Terms of Use  |  Cookies