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DTD Handbook

Handbook for Damage Tolerant Design

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    • Sections
      • 1. Introduction
      • 2. Fundamentals of Damage Tolerance
      • 3. Damage Size Characterizations
      • 4. Residual Strength
        • 0. Residual Strength
        • 1. Introduction
        • 2. Failure Criteria
        • 3. Residual Strength Capability
        • 4. Single Load Path Structure
        • 5. Built-Up Structures
          • 0. Built-Up Structures
          • 1. Edge Stiffened Panel with a Central Crack
          • 2. Centrally and Edge Stiffened Panel with a Central Crack
          • 3. Analytical Methods
          • 4. Stiffener Failure
          • 5. Fastener Failure
          • 6. Methodology Basis for Stiffened Panel Example Problem
          • 7. Tearing Failure Analysis
          • 8. Summary
        • 6. References
      • 5. Analysis Of Damage Growth
      • 6. Examples of Damage Tolerant Analyses
      • 7. Damage Tolerance Testing
      • 8. Force Management and Sustainment Engineering
      • 9. Structural Repairs
      • 10. Guidelines for Damage Tolerance Design and Fracture Control Planning
      • 11. Summary of Stress Intensity Factor Information
    • Examples

Section 4.5.0. Built-Up Structures

The structural configuration essentially determines the complexity of the residual strength analysis.  Typical structural parameters which must be considered for skin-stiffened structure are:

·        Type of Construction

-        Monolithic (unreinforced/forgings)

-        Skin (longerons, stringer)

-        Integrally stiffened

-        Planked

-        Layered (honeycomb/laminated)

·        Panel Geometry

-        Planform

-        Curvature

-        Stiffener spacing and orientation

-        Attachments (spar caps, webs, frames, etc.)

·        Details of Construction

-        Stiffener geometry (hat, Z-channel, etc.)

-        Attachment details (bolted, riveted, welded, etc.)

-        Fastener flexibility

-        Eccentricity

 

Ideally, the residual strength analysis will take all these parameters into consideration.  In practice, many are treated empirically and others are not considered except in extremely detailed analyses.  This section provides details of the analysis methods used for built-up skin stringer structure and the effects of many of the structural parameters listed above.  In the order of their presentation, the subsections provide: overviews of the analysis for edge stiffened and for centrally stiffened skin structure, the analysis methods used to determine the stress-intensity factor in the skin structure and the loading transferred to the stringers, the analysis of stiffener failure, the analysis of fastener failure, the analysis methodology and an example.