What is shear force in a beam and where is it maximum?

Shear force is the internal force acting perpendicular to the beam's longitudinal axis that resists transverse loads. It represents the algebraic sum of all vertical forces on either side of a section. Shear force is typically maximum at supports for simply supported beams and at the face of supports for continuous beams. Critical shear design is required where shear force is high to prevent diagonal tension failure.