ATLAS thermosiphon project Piping design and seismic analysis framework

1. ATLAS thermosiphon project Piping design and seismic analysis framework Délio Ramos EN/MME, 28.05.2010

2. Outline • Piping layout • Regulations and standards • Strength analysis to EN 13480 • Seismic analysis • Calculation method • Assumptions and requirements • Seismic actions • Load combination • Conclusion

3. Layout Design goal: A. Define supports layout in order to allow enough flexibility for thermal loads B. Provide sufficient piping restraints to limit static deflection and dynamic (seismic) load consequences From A. Bitadze

4. Regulations and standards CERN General Safety Instruction GSI-M2 - Standard Pressure Equipment ATLAS Seismic requirements European regulations European Directive 97/23/EC Eurocode 8 EN 1998-1 General EN 1998-4 Silos, tanks and pipelines EN 13480 – Metallic industrial piping Actions (from national regulations) Piping Design

5. EN 13480 Strength analysis Applied moments and their combination From Ansys 3D model Excel or Ansys post-processor Criteria Allowable stresses Permanent mechanical loads k=1 Occasional or exceptional loads MA + MB obtained directly from the FE model. k=1.2 for seismic loads. Thermal and variable loads N<7000 cycles => U=1

6. Preliminary design D. Ramos, Piping analysis for the ATLAS thermosiphon project - Preliminary engineering analysis, EDMS 1064571, 2010-04-03 Pipe DN25 Pipe DN50

7. Earthquake: Methods of analysis • Options provided by EN 1998-1 for the design of buildings: • Linear static analysis (“lateral force” method or “equivalent static”) • Modal response spectrum analysis • Non-linear static • Non-linear dynamic (time-history) Implemented in Ansys but requires post-processing to combine loads from X, Y and Z action spectrum

8. Response spectrum analysis Eigenmode-eigenvalue analysis Specified response spectrum Mode combination Structure response

9. Combination of modal responses Clause 4.3.3.3.2, EN 1998-1 • Sum of squares of modal responses (SRSS) • When all relevant modal responses may be regarded as independent of each other (Tj<=0.9Ti) • Complete quadratic combination (CQC) • If Tj<=0.9Ti not satisfied Both available in Ansys

10. Modelling requirements Clause 5.4.1, EN 1998-4 ! ! ok ok ok

11. Seismic actions specification Benincasa and Schmidt, 2000

12. Combination of X, Y, Z action’s effects Clause 4.3.3.5.1, EN 1998-1 • SRSS combination • Is the reference method (conservative) • Yields the expected result if the modal contributions have been combined using the CQC rule • 30% rule as an alternative Easier implementation in Ansys

13. Conclusion • Strength analysis of the piping to EN 13480 has been performed on a preliminary design and will be repeated once the layout has been completely approved. • The requested seismic analysis can be performed following the procedures of Eurocode 8 • Through a response spectrum analysis (linear) • CQC modal contribution combination + SRSS action combination • For specified X, Y and Z spectra applied to all supports • The seismic analysis will not take into account the • Effects of the supporting structure dynamics • Influence in the actions from the difference in elevation