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CoGripedia your encyclopedia of terms used in the industrial flooring industry.

Bending Moment


A bending moment is the reaction in a structural element when external forces cause the element to bend. It can be measured in kNm.

Technical Information

For a structure to remain in static equilibrium, the bending moments induced by external forces must not exceed the moment capacity of the elements upon which they act. 

A bending moment will cause both compressive and tensile stress in a cross section. Because plain concrete is much weaker in tension than it is in compression, it will tend to fail on its tension face when subjected to a bending moment. This is why tensile reinforcement is used in a lot of concrete structural elements.

A bending moment diagram is a useful way to visualise the distribution of bending moments in a structural element. It gives the magnitude of the bending moment at any given point in the element. 

In a horizontal member, such as a beam or floor, the following statements are true:

  • Bending moments which cause tension on the top of the member are known as hogging moments.
  • Bending moments which cause tension on the bottom of the member are known as sagging moments. 
  • Points at which there is no prevailing bending moment are known as points of contraflexure.

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