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.