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Design by Analysis:Present Future EN 13445-3 Direct Route

Design by Analysis. Pressure vessel design has been historically based on Design By Formula (DBF). Standard vessel configurations are sized using a series of simple formulae and chartsIn addition to the Design by Formula route, many national codes and standards for pressure vessel and boiler design do provide for a Design By Analysis (DBA) route.

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Design by Analysis:Present Future EN 13445-3 Direct Route

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    1. Design by Analysis:Present & Future EN 13445-3 Direct Route Jim Boyle, University of Strathclyde, Glasgow, Scotland

    2. Design by Analysis Pressure vessel design has been historically based on Design By Formula (DBF). Standard vessel configurations are sized using a series of simple formulae and charts In addition to the Design by Formula route, many national codes and standards for pressure vessel and boiler design do provide for a Design By Analysis (DBA) route

    3. Design by Analysis All these DBA routes in the major codes and standards in the pressure equipment field are based on the rules first proposed in the ASME Pressure Vessel and Boiler Code, which was formulated in the late 1950's before being released, originally for nuclear applications, in 1964

    4. Design by Analysis All these routes lead to the same well-known problems, especially the stress categorization problem, and all are out-of-step with the continuing development of computer hardware and software Further, all are focused on pressure, and possibly, and to a limited extent, temperature, treating other actions in an inflexible manner, giving them marginal attention only.

    5. EN 13445-3 The DBA direct route in CEN's unfired pressure vessel standard prEN 13445-3 tries to avoid these problems: by addressing the failure modes directly by allowing for non-linear constitutive models by applying a multiple safety factor format for the incorporation of actions other than pressure by specifying mainly the principal technical goals of the standard together with some application rules as possible methods for the fulfillment of these goals.

    6. Design by Analysis Direct Route (DBA-DR) Design Principles Application Rules Partial Safety Factors Non-linear Design Models Design Checks

    7. DBA-DR New Terminology! Action physical influence causing stress & strain Effect response of a component to a specific action Load Case a combination of coincident actions Characteristic Value representative value which takes account of the variation of an action

    8. DBA-DR New Terminology! Principle general statement, definition or requirement of a given failure mode Application Rule procedure to determine whether a principle is satisfied Design Check assessment of a component by means of an application rule

    9. DBA-DR New Terminology! Limit State structural condition beyond which the design performance requirements of a component are not met Resistance the limiting value for a given limit state of an action or effect

    10. DBA-DR Methodology Specify Failure Mode & Limit State Specify the Principle Select an appropriate Application Rule Carry out the Design Check If the Principle is not satisfied, repeat with amended loading, geometry or material

    11. (d) Design Checks Define the Load Case and specify Actions Determine the Characteristic Value and calculate the Design Value of each action Calculate the Effect of the actions Calculate the Resistance of the component Indicate whether or not the Principle is satisfied

    12. Design Models Geometric model Structural strains Material model Linear elastic ideal plastic Tresca yield & associated flow rule Deformation model First/second order theory Non-linear

    13. Structural Strain Defined as the strain in a stress concentration free model Idealized Design Model based on real geometry with exception of details which cause only local stress or strain concentration

    14. Design Checks Gross Plastic Deformation (GPD) Progressive Plastic Deformation (GPD) Fatigue (F) Instability (I) Static Equilibrium (SE)

    15. e.g. Design Check for GPD - 1 Specified Design Model Geometry to provide structural strains Linear elastic, ideal plastic Tresca yield condition & flow rule Design strength parameters First-order deformation theory Second-order for geometric weakening

    16. e.g. Design Check for GPD - 2 Principle: Design Actions shall be carried by Design Models for Proportional increase in actions Stress free initial state Limitation of maximum absolute value of principal structural strains

    17. Design by Analysis: The Future? The Direct Route is a major step forward in Design by Analysis Nevertheless Design By Formula remains the dominant approach In an increasingly technically sophisticated society, it may be asked why this should be the case?

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