Definition of Beams, Shear Force & Bending Moment Diagram

Beams belong to structural members and these are generally found in buildings. Beams contains various other applications concerning bridges, automobiles or in mechanical systems. Given below some useful tips for determining strength of a beam.

What is a Beam? In a beam transverse load operates and it is originated from the slabs to the column or walls. Beams are considered as the inherent part of building structure.

In order to make analysis, a beam is treated as a portion of the beam column system. It will help in finding out exterior load functioning on individual beams. Once it is detected, beam is segregated from beam column system for making analysis repeatedly.

Length of the beam is greater as compared to its lateral dimensions. Therefore, axial strain evolved in a beam is minor than shear strain, or strain caused because of bending.

So for design purpose of beams, Analysis of shear force and bending moment induced are the most vital factors for creating design of beams. Before sketching shear force and bending moment allocation on any beam, clear conception on shear force and bending moment is required.

Either shear force or bending moment is driven in beam for controlling exterior load operating on it.

Shear Force: Shear force refers to the inward resistance generated in beam cross sections, for controlling transverse external load functioning on beam. While inserting forces functioning on it, it should be in symmetry. Shear force is driven perfectly for this objective, to make the section symmetric in vertical direction. It is equivalent to cross section.

The value of shear force at a specific section is calculated by using force balance in vertical direction on the free body diagram. Given below, general sign convention of the shear force.

The identical concept can be used in various cross sections and it detects how shear force differentiates along the length of the beam.

Bending Moment: But balance of transverse forces solely can’t offer symmetry of a section. The rotation of beam can be occurred, if moment operating on it is not uniform. A bending moment will be evolved in cross section of beam, to capture this rotation. It is evolved as normal forces functioning on fiber cross section.

Outcomes of those forces are zero, but it will create a moment, to counter balance the exterior moment. The moment evolved can be computed at any cross section by adjusting the exterior moment functioning on the free body diagram.

Given below the example of sign convention of bending moment:-

This sign convention approach can be applied for easily supported beam. For cantilever case sign convention is perfectly contrary to this.

With the above theory, it becomes easier to compute allocation of shear force and bending moment toward the length of the beam.