What is shear force and bending moment?

What is shear force and bending moment?

Shear force

Shear force is the force acting on a substance in a direction perpendicular to the extension of the substance, acting in a direction to a planar cross-section of a body. Shear force is the summation of the effect of shear stress over a surface and often results in shear strain. Shear force is an internal force in any material which is usually caused by any external force acting perpendicular to the material, or a force that has a component acting tangent to the material. Shearing forces are unaligned forces pushing one part of a body in one direction, and another part of the body in the opposite direction. When the forces are aligned into each other, they are called compression forces.

Bending moment
A bending moment is a force normally measured in a force x length (e.g. kNm). Bending moments occur when a force is applied at a given distance away from a point of reference; causing a bending effect. In the most simple terms, a bending moment is basically a force that causes something to bend. If the object is not well-restrained the bending force will cause the object to rotate about a certain point.

Shear and bending moment diagrams 
Shear and bending moment diagrams are analytical tools used in conjunction with structural analysis to help perform structural design by determining the value of shear force and bending moment at a given point of a structural element such as a beam. These diagrams can be used to easily determine the type, size, and material of a member in a structure so that a given set of loads can be supported without structural failure. Another application of shear and moment diagrams is that the deflection of a beam can be easily determined using either the moment area method or the conjugate beam method.

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