Drawing Bending Moment & Shear Force for a Beam w/ Constant Moment

Click For Summary
SUMMARY

This discussion focuses on drawing bending moment and shear force diagrams for a beam subjected to a constant moment. The key takeaway is that a constant moment introduces a discontinuity in the bending moment diagram, similar to how loads affect the shear diagram. Specifically, when a clockwise moment is applied, it adds to the area under the shear force diagram, while a counterclockwise moment subtracts from it. The formula for bending moment, Mx = (Ay)(x) - (wx^2)/2 + constant moment, is confirmed for cases involving uniformly distributed loads.

PREREQUISITES
  • Understanding of shear force and bending moment diagrams
  • Familiarity with static equilibrium and reaction forces
  • Knowledge of uniformly distributed loads in structural analysis
  • Basic principles of mechanics of materials
NEXT STEPS
  • Study the effects of constant moments on bending moment diagrams
  • Learn about the relationship between shear force and bending moment using integration
  • Explore advanced topics in structural analysis, such as moment distribution method
  • Review examples of bending moment and shear force diagrams for various loading conditions
USEFUL FOR

Civil engineers, structural analysts, and students studying mechanics of materials will benefit from this discussion, particularly those focused on beam analysis and design.

frozen7
Messages
163
Reaction score
0
Can anyone draw me a correct Bending moment diagram and shear force diagram for this beam?
i have drawn the shear force diagram for this case but I do not know how to draw the bending moment disgram for this case because this question involve a constant moment. Normally the rule for bending moment is the value of bending moment at certain point is the area under shear force diagram from the starting point to that certain point. Can this rule applied on this question as well? I felt the bending moment diagram is quite strange if follow this rule for this question. Can anyone help me?
Thanks.
 

Attachments

  • beam.JPG
    beam.JPG
    29.8 KB · Views: 552
Physics news on Phys.org
Hello, the only thing a couple or moment does for the bending diagram is create a "discontinuity" (more like a derivative doesn't exist at said point), just like the loads do on the shear diagram. If the moment is clockwise it goes up (adds to the area [method]), and if its counterclockwise it goes down (substract to the area [method]).
 
Last edited:
Does it mean when there is a constant moment at point b, then we should either add or substract that value of constant moment in that point (either draw a straight line goes up or goes down)?
 
frozen7 said:
Does it mean when there is a constant moment at point b, then we should either add or substract that value of constant moment in that point (either draw a straight line goes up or goes down)?

exactly what i said above.
 
One more thing have to be confirmed.
For uniformly distributed load, Mx = (Ay)(x) - (wx^2)/2 (where x is the distance from staring point to x, Ay is the reaction force at the starting point and w is the force per unit length and Mx is the bending moment)
Let say if there is a constant moment which is 50N/m at point a ,then Mx become Mx = (Ay)(x) - (wx^2)/2 +50 ??
 
frozen7 said:
One more thing have to be confirmed.
For uniformly distributed load, Mx = (Ay)(x) - (wx^2)/2 (where x is the distance from staring point to x, Ay is the reaction force at the starting point and w is the force per unit length and Mx is the bending moment)
Let say if there is a constant moment which is 50N/m at point a ,then Mx become Mx = (Ay)(x) - (wx^2)/2 +50 ??

Yes +50 if its clockwise.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 16 ·
Replies
16
Views
4K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
4K
  • · Replies 3 ·
Replies
3
Views
2K