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ATLAS thermosiphon project
Piping design and seismic analysis framework
Délio Ramos EN/MME, 28.05.2010
Outline
• Piping layout
• Regulations and standards
• Strength analysis to EN 13480
• Seismic analysis– Calculation method
– Assumptions and requirements
– Seismic actions
– Load combination
• Conclusion
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
Regulations and standards
General Safety Instruction GSI-M2 - Standard Pressure
Equipment
European Directive 97/23/EC
CERN
Euro
pea
n r
egu
lati
on
s
Eurocode 8EN 1998-1 GeneralEN 1998-4 Silos, tanks and pipelines
EN 13480 – Metallic industrial piping
ATLAS Seismic requirements
Actions (from national regulations)
Piping Design
EN 13480 Strength analysis
Permanent mechanical loads
Occasional or exceptional loads
Thermal and variable loads
MA + MB obtained directly from the FE model. k=1.2 for seismic loads.
Applied moments and their combination
From Ansys 3D model Excel or Ansys post-processor
k=1
Criteria Allowable stresses
N<7000 cycles => U=1
Preliminary designD. Ramos, Piping analysis for the ATLAS thermosiphon project - Preliminary engineering analysis, EDMS 1064571, 2010-04-03
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Pipe DN25 Pipe DN50
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
Response spectrum analysis
Mode combination
Structure response
Eigenmode-eigenvalue analysisSpecified response spectrum
Combination of modal responses
• 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
Clause 4.3.3.3.2, EN 1998-1
Combination of X, Y, Z action’s effects
• SRSS combination
– Is the reference method (conservative)
– Yields the expected result if the modal contributions have been combined using the CQCrule
• 30% rule as an alternative
Clause 4.3.3.5.1, EN 1998-1
Easier implementation in Ansys
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