Flexural rigidity is defined as the force couple required to bend a fixed non-rigid structure by one unit of curvature, or as the resistance offered by a structure while undergoing bending.
generally result from external loads and may vary along the length of the beam or rod, the flexural rigidity (defined as
) is a property of the beam itself and is generally constant for prismatic members.
However, in cases of non-prismatic members, such as the case of the tapered beams or columns or notched stair stringers, the flexural rigidity will vary along the length of the beam as well.
The flexural rigidity, moment, and transverse displacement are related by the following equation along the length of the rod,
The flexural rigidity (stiffness) of the beam is therefore related to both
Flexural rigidity has SI units of Pa·m4 (which also equals N·m2).
In the study of geology, lithospheric flexure affects the thin lithospheric plates covering the surface of the Earth when a load or force is applied to them.
On a geological timescale, the lithosphere behaves elastically (in first approach) and can therefore bend under loading by mountain chains, volcanoes and other heavy objects.
Isostatic depression caused by the weight of ice sheets during the last glacial period is an example of the effects of such loading.
= Poisson's Ratio Flexural rigidity of a plate has units of Pa·m3, i.e. one dimension of length less than the same property for the rod, as it refers to the moment per unit length per unit of curvature, and not the total moment.