These moments will be clockwise to the left of the section and anticlockwise to the right of the section. 1(a) the bending moment is either M xor M’ x. The bending moment at a given section of a beam is defined as the resultant moment about that section of either all the forces to the left of the section or of all the forces to the right of the section. + F) if the tendency to shear is as shown in Fig. 1(b), the shearing force is regarded as positive (i.e. The shearing force is defined as the force transverse to the beam at any given section tending to cause it to shear at that section.īy convention, if the tendency is to shear as shown in Fig. The resultant force to the left of X and the resultant force to the right of X (forces or components of forces transverse to the beam) constitute a pair of forces tending to shear the beam at this section. Also the moments about X of the forces to the left must balance the moments about X of the forces to the right.Īlthough, for equilibrium, the forces and moments cancel each other, the magnitude and nature of these forces and moments are important as they determine both the stresses at X, and the beam curvature and deflection. 1(a) must balance the forces to the right of the section X. Beam Analysis – For equilibrium in a beam the forces to the left of any section such as X as shown in Fig.
