A- Moment and Bending moment B- What the Bending Moment does to the Beam C-Sign convention for bending moments D- WHY WE DRAW B.M.D (APPLICATIONS) E- Technique to find B.M.D F- S.F.D and B.M.D for cantilever beam

1. Basics of Bending
moment Diagrams

2. Contents:
• Moment and Bending moment
• What the Bending Moment does to the
Beam
• Sign convention for bending moments
• WHY WE DRAW BMD (APPLICATIONS)
• Technique to find BMD

3. Moment and Bending moment
• Moment: It is the product of force and
perpendicular distance between line of
action of the force and the point about
which moment is required to be calculated.
• Bending Moment (BM): The moment
which causes the bending effect on the
beam is called Bending Moment. It is
generally denoted by ‘M’ or ‘BM’.

4.  Causes compression on one face and tension on the
other
 Causes the beam to deflect
How much deflection?
How much
compressive stress?
How much
tensile stress?
What the Bending Moment does to the Beam

5. Sign convention for bending moments:
The bending moment is considered as Sagging
Bending Moment if it tends to bend the beam to a
curvature having convexity at the bottom as
shown in the Fig. given below. Sagging Bending
Moment is considered as positive bending
moment.
Fig. Sagging bending moment [Positive bending moment ]
Convexity

6. Sign convention for bending moments:
Similarly the bending moment is considered as
hogging bending moment if it tends to bend the
beam to a curvature having convexity at the top
as shown in the Fig. given below. Hogging
Bending Moment is considered as Negative
Bending Moment.
Fig. Hogging bending moment [Negative bending moment ]
Convexity

7. Bending Moment Diagram (BMD):
Bending Moment Diagram (BMD):
The diagram which shows the variation of
bending moment along the length of the
beam is called Bending Moment
Diagram (BMD).

8. These diagrams plot the internal
forces with respect to x along the
beam.
WHY WE DRAW BMD (APPLICATIONS)
They help engineers analyze
where the weak points will be in a
member

9. Technique to find BMD
• 1) Determine all reaction forces
• 2) Label x starting at left edge
• 3) Section the beam at points of
discontinuity of load
• 4) FBD each section showing V and M in
their positive sense
• 5) Find V(x), M(x)
• 6) Plot the two curves

10. General Technique
• Because the shear and
bending moment are
discontinuous near a
concentrated load, they
need to be analyzed in
segments between
discontinuities

11. Question with Application

12. S.F.D and B.M.D for cantilever beam

13. References:
• Google
• Dr.I.S.Gujral