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It is a known fact that beams and spheres have the ability to carry relatively high loads. Beams are seen in bridges and other structures even since the days of ancient roman architecture. Spheres have even more impressive abilities. Eggs, for instance, can deal with great compression loads without breaking while their shell is ridiculously thin. Pressure chambers also usually have domes at their ends - being able to resist much higher loads than plane surfaces.

I assume the trick is that there are almost no shear stresses - most of the stress is tensile due to the shapes geometry. Generally, materials can withstand loads more easily this way (bending is more destructing than stretching). Can someone shed some light about this mechanism? How the stresses are arranged in a tension-compression pattern? If find it quite challenging to visualize it.

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  • $\begingroup$ check out the construction of the Ariane rocket... $\endgroup$ – Solar Mike Jul 26 '18 at 16:00
  • $\begingroup$ You are not quite right. The important thing in thin structures is not so much the absence of shear stress, as the absence of tensile stress on one side of the structure when it bends. Most materials fail much more easily in tension than in compression. $\endgroup$ – alephzero Jul 26 '18 at 17:54
  • $\begingroup$ @alephzero Except where buckling can occur. Pressurized thin wall tanks are in tension. $\endgroup$ – Eric Shain Jul 26 '18 at 23:05
  • $\begingroup$ Does anyone have a good reference source for this subject? $\endgroup$ – Yaniv Ben David Aug 3 '18 at 7:28
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In the tension-compression pattern, normal stresses are evenly distributed over the cross-section of the shell, which means that the load-bearing is attributed to the whole cross-section. This is completely different from bending, when only the material fibres adjacent to the surface of the shell participate in the load bearing. This feature is heavily used in so-called "shallow" shells (low-curvature shells), which are used instead of planar slabs. Since you've asked for a reference, you will find a good example here: http://members.ozemail.com.au/~comecau/quad_shell_shallow_shell.htm

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