What is Shear Force and Bending Moment Diagram | Types of Beam | Load Types

This article will guide you on what is share force and bending moment diagram. Shear force is an imbalanced vertical force exerted on the section’s right or left side. It’s also known as aligned forces, which push one part of the body in one way while the other section of the body moves in a different direction.

A parallel shear force occurring in a different direction at another place of the body might cause a crack to form in a body. Compressive forces are also known as Colinear forces.

The maximum absolute value of the shear force and the bending moment of the beams with regard to the relative load can be determined using the shear force and bending moment diagram in beams.

Before we can design the Shear force and bending moment diagram, we must first understand the various types of beams and loads, as well as the reaction forces acting on them.

According to the right or left of the section, the bending moment is the algebraic sum of all the moment of forces. It is the reaction that is induced in a structural element as a result of an external force or moment.

The moment caused by external forces is balanced in the equilibrium position by the couple induced by the internal load; this internal couple is known as a bending moment.

Type of Beams

• Cantilever Beam
• Simply Supported Beam
• Overhanging Beam
• Fixed Beam
• Continuous Beam

Type of Loads

The applied weight is normally vertical, whereas the beam is usually horizontal.

Concentrated or Point Load: Act at a point.

Uniformly Distributed Load: The load is evenly distributed along the length of the Beam.

Uniformly Varying Load: Load distribution along the length of the beam, and rate of varying loading from point to point.

Sign Convention of Shear Force:

Shear force is an imbalanced vertical force that causes one end of the beam to move forward or downward in relation to the other.

When the left-hand portion of a section tends to slide upward and the right-hand half tends to slide downward, the shear force is deemed positive.

When the left-hand portion of a section tends to slide downward, or the right-hand portion tends to slide upward, the shear force at that section is negative.

Sign Convention for Bending Moment:

When the bending moment at a section tends to bend the beam at a point to curvature with a concavity at the top, or when the moments are operating clockwise to the left or anti-clockwise to the right, we consider it positive.

On the other hand, the bending moment at a section is deemed negative when it tends to bend the beam at a point to curvature with convexity at the top or when moments are taken in an anti-clockwise or clockwise manner.

Positive bending moments are sometimes referred to as sagging moments, whereas negative bending moments are referred to as hogging moments.

Shear Force and Bending Moment Diagram Drawing Instructions

• The ordinates in SFD and BMD diagrams are shear force or bending moment, and the abscissa is the length of the beam.
• Take a look at the left or right side of the section.
• On one of the portions, add the forces (including reactions) normal to the beam.
• The force acting downhill is positive, whereas the force acting upwards is negative if the right portion of the section is chosen.
• The force acting downhill is negative, whereas the force acting upwards is positive if the Left component of the section is chosen.
• Shear force and Bending moment positive values are plotted above the baseline, while negative values are plotted below the baseline.
• The sheer force diagram will suddenly increase or decrease. I.e., at a segment where there is a vertical point load, by a vertical straight line.
• Between any two vertical weights, the shear force will be constant. As a result, the horizontal shear force between the two vertical loads will exist.
• At the two ends of a simply supported beam and at the free end of a cantilever, the bending moment will be zero.

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