20.1 : 弯曲

Pure bending occurs when a prismatic member possesses a plane of symmetry and experiences couples of equal magnitudes acting within that plane. This type of bending occurs without the influence of direct forces.

For example, pure bending can be observed in the middle portion of a barbell being lifted by a weightlifter. Here, no direct forces are applied to the central part of the barbell. Instead, the weight at each end creates equal and opposite moments, resulting in bending.

When a person climbs a ladder, the ladder's rungs experience pure bending due to the moment generated by the person's weight.

Pure bending analysis is also used to examine beams or prismatic members subjected to transverse loads. In a cantilever beam supporting a concentrated load at its free end, the distribution of normal stresses can be obtained from the couple as if the beam were in pure bending.

It can also be used in studying stresses and deformations in composite members made of more than one material, such as reinforced concrete beams.