Shearing Force (SF)
When a section such as a beam is carrying a load there is a tendency for some parts to be pushed upwards and for other parts to move downwards, this tendency is termed Shearing.The Shear force at a point or station is the vertical force at that point. The shear force at a station may also defined as being the total load on either the left hand side or the right hand side of the station; load being defined as the difference between the down and the upward forces, or for a ship the weight would be the downward force and the buoyancy would be the upward thrust or force.
Bending Moment (BM)
The beam, which we have considered above, would also have a tendency to bend and the bending moment measures this tendency. Its size depends upon the amount of the load as well as how the load is placed together with the method of support. Bending moments are calculated in the same way as ordinary moments that is multiplying force by distance, and so they are expressed in weight – length units.
