Shear Force and Bending Moment

Hello friends , today I am going to share about the basic knowledge of shear force and  bending moment.
First start with what are shear force and bending moment.


Shear force and bending moments are generally develop on a beam when a beam subjected to lateral forces.

When a beam subjected to lateral force then some reaction are develop on the supports of the beam and internal forces are developed on the span or length of the beam. If we take any section of beam then for to beam in equilibrium  we apply a opposite force on to the beam which we call as a shear force of beam of that section. In other language shear force is a force which try to separate the beam into two half's . It may be also called the internal vertical force on a particular beam section. Shear force are generally positive (+) or negative (-) depending upon loading and support conditions.


A positive shear force is a force if left hand sight load is in  upward direction  and right hand sight force is in downward direction.

A negative shear force is a force if a left hand sight force is in downward direction and right hand sight force is in upward direction.

If a beam subjected to some lateral loads then there are internal  bending moment are developed in the beam due to these bending moment  beam tend to bend in the direction of loading. In a beam generally two type of bending moment develop, positive bending moment  (+)or sagging and negative bending moment (-)or hogging.

 These bending moment are generally calculated by taking an section where we have to find the bending moment and take algebraic sum of all moment according to their sign convention.

NOTE:- maximum bending moment always occur where shear force is zero

                     Because ,    dM/dx = v
                               If v= 0 Then  dm / dx will be max.


Why we calculate S.F & B.M:- Bending moment and shear force are the internal force in a loaded beam, If we plot these on a graph then these shows the overall behavior of the beam  how is  the distribution of shear force and bending moment each and every point of beam, these also helpful to understand the failure behavior of the structural elements.