The discoveries of gravitational waves linked to binary black holes coalescence have multiplied since 11 February2016. The formation of a resulting black hole from this cataclysmic event, concentrating in the final stage in a very small radius a colossal mass (50 solar masses and more), is sufficiently energetic to deform the space-time which then propagates without any attenuation during Billions of years, the associated gravitational waves. These were predicted by Einstein in his theory of general relativity a century ago. Their measurements, which are characterized by an infinitesimal DL / L deformation (10-21 , or 10-18 at the kilometer size of the interferometers), corresponds to the billionth of the size of an atom, today. The smallness of its deformations is the character trait of an extraordinarily great rigidity of space-time. We will show in this paper that the constant of proportionality κ between the curvature tensor Gμv and the stress energy tensor Tμv is a characterization of this very high rigidity. To do this we will make an analogy with the strength of materials via the theory of the beams to show it.