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

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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

Modelling requirementsClause 5.4.1, EN 1998-4

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Seismic actions specificationBenincasa and Schmidt, 2000

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