Stressed skin

Sometimes the diagonal elements are flexible like wires, which are used to provide tension, or the elements can be rigid to resist compression, as with a Warren or Pratt truss; in either case, adding discrete diagonal members results in full frame structures in which the skin contributes very little or nothing to the structural rigidity.

In a monocoque design, the skin assumes all or most of the stress and the structure has fewer discrete framing elements, sometimes including only longitudinal or lateral members.

William Fairbairn documented the development of the Britannia and Conwy tubular bridges for the Chester and Holyhead Railway in 1849;[4] in it, Fairbairn describes how Robert Stephenson enlisted his aid to revise Stephenson's original concepts, which would route rail traffic inside riveted steel tubes, supported by chains, with a circular- or egg-shaped cross-section.

[6]: 8 The adoption of stressed-skin construction resulted in improved aircraft speed and range, accomplished by reduced drag through smoother surfaces, elimination of external bracing, and providing internal space for retractable landing gear.

The London Transport AEC Routemaster incorporated internal panels riveted to the frames which took most of the structure's shear load.

The Zeppelin-Lindau D.I had stressed skin fuselage and wings.
A rectangular box can be distorted with a small load (left), but adding a diagonal member to form a triangular truss results in a more rigid structure (right)
The square frame (black members) resist compression while the skin (translucent pink), which is fixed to the frame (blue rivets), resists in-plane shear that would distort the frame from square
Internals of stressed skin construction on Murphy Moose showing frames and supporting skin
Section from the original Britannia Bridge , showing top and bottom stressed-skin construction
Worker carrying partially finished Deperdussin Monocoque fuselage, c. 1912